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How can JDBC URLs be parsed for extracting connection properties in mysql-connector-java 8.0? [duplicate]

I've got the URI like this:
https://google.com.ua/oauth/authorize?client_id=SS&response_type=code&scope=N_FULL&access_type=offline&redirect_uri=http://localhost/Callback
I need a collection with parsed elements:
NAME VALUE
------------------------
client_id SS
response_type code
scope N_FULL
access_type offline
redirect_uri http://localhost/Callback
To be exact, I need a Java equivalent for the C#/.NET HttpUtility.ParseQueryString method.

If you are looking for a way to achieve it without using an external library, the following code will help you.
public static Map<String, String> splitQuery(URL url) throws UnsupportedEncodingException {
Map<String, String> query_pairs = new LinkedHashMap<String, String>();
String query = url.getQuery();
String[] pairs = query.split("&");
for (String pair : pairs) {
int idx = pair.indexOf("=");
query_pairs.put(URLDecoder.decode(pair.substring(0, idx), "UTF-8"), URLDecoder.decode(pair.substring(idx + 1), "UTF-8"));
}
return query_pairs;
}
You can access the returned Map using <map>.get("client_id"), with the URL given in your question this would return "SS".
UPDATE URL-Decoding added
UPDATE As this answer is still quite popular, I made an improved version of the method above, which handles multiple parameters with the same key and parameters with no value as well.
public static Map<String, List<String>> splitQuery(URL url) throws UnsupportedEncodingException {
final Map<String, List<String>> query_pairs = new LinkedHashMap<String, List<String>>();
final String[] pairs = url.getQuery().split("&");
for (String pair : pairs) {
final int idx = pair.indexOf("=");
final String key = idx > 0 ? URLDecoder.decode(pair.substring(0, idx), "UTF-8") : pair;
if (!query_pairs.containsKey(key)) {
query_pairs.put(key, new LinkedList<String>());
}
final String value = idx > 0 && pair.length() > idx + 1 ? URLDecoder.decode(pair.substring(idx + 1), "UTF-8") : null;
query_pairs.get(key).add(value);
}
return query_pairs;
}
UPDATE Java8 version
public Map<String, List<String>> splitQuery(URL url) {
if (Strings.isNullOrEmpty(url.getQuery())) {
return Collections.emptyMap();
}
return Arrays.stream(url.getQuery().split("&"))
.map(this::splitQueryParameter)
.collect(Collectors.groupingBy(SimpleImmutableEntry::getKey, LinkedHashMap::new, mapping(Map.Entry::getValue, toList())));
}
public SimpleImmutableEntry<String, String> splitQueryParameter(String it) {
final int idx = it.indexOf("=");
final String key = idx > 0 ? it.substring(0, idx) : it;
final String value = idx > 0 && it.length() > idx + 1 ? it.substring(idx + 1) : null;
return new SimpleImmutableEntry<>(
URLDecoder.decode(key, StandardCharsets.UTF_8),
URLDecoder.decode(value, StandardCharsets.UTF_8)
);
}
Running the above method with the URL
https://stackoverflow.com?param1=value1&param2=&param3=value3&param3
returns this Map:
{param1=["value1"], param2=[null], param3=["value3", null]}

org.apache.http.client.utils.URLEncodedUtils
is a well known library that can do it for you
import org.apache.hc.client5.http.utils.URLEncodedUtils
String url = "http://www.example.com/something.html?one=1&two=2&three=3&three=3a";
List<NameValuePair> params = URLEncodedUtils.parse(new URI(url), Charset.forName("UTF-8"));
for (NameValuePair param : params) {
System.out.println(param.getName() + " : " + param.getValue());
}
Outputs
one : 1
two : 2
three : 3
three : 3a

If you are using Spring Framework:
public static void main(String[] args) {
String uri = "http://my.test.com/test?param1=ab&param2=cd&param2=ef";
MultiValueMap<String, String> parameters =
UriComponentsBuilder.fromUriString(uri).build().getQueryParams();
List<String> param1 = parameters.get("param1");
List<String> param2 = parameters.get("param2");
System.out.println("param1: " + param1.get(0));
System.out.println("param2: " + param2.get(0) + "," + param2.get(1));
}
You will get:
param1: ab
param2: cd,ef

use google Guava and do it in 2 lines:
import java.util.Map;
import com.google.common.base.Splitter;
public class Parser {
public static void main(String... args) {
String uri = "https://google.com.ua/oauth/authorize?client_id=SS&response_type=code&scope=N_FULL&access_type=offline&redirect_uri=http://localhost/Callback";
String query = uri.split("\\?")[1];
final Map<String, String> map = Splitter.on('&').trimResults().withKeyValueSeparator('=').split(query);
System.out.println(map);
}
}
which gives you
{client_id=SS, response_type=code, scope=N_FULL, access_type=offline, redirect_uri=http://localhost/Callback}

The shortest way I've found is this one:
MultiValueMap<String, String> queryParams =
UriComponentsBuilder.fromUriString(url).build().getQueryParams();
UPDATE: UriComponentsBuilder comes from Spring. Here the link.

For Android, if you are using OkHttp in your project. You might get a look at this. It simple and helpful.
final HttpUrl url = HttpUrl.parse(query);
if (url != null) {
final String target = url.queryParameter("target");
final String id = url.queryParameter("id");
}

PLAIN Java 11
Given the URL to analyse:
URL url = new URL("https://google.com.ua/oauth/authorize?client_id=SS&response_type=code&scope=N_FULL&access_type=offline&redirect_uri=http://localhost/Callback");
This solution collects a list of pairs:
List<Map.Entry<String, String>> list = Pattern.compile("&")
.splitAsStream(url.getQuery())
.map(s -> Arrays.copyOf(s.split("=", 2), 2))
.map(o -> Map.entry(decode(o[0]), decode(o[1])))
.collect(Collectors.toList());
This solution on the other hand collects a map (given that in a url there can be more parameters with same name but different values).
Map<String, List<String>> list = Pattern.compile("&")
.splitAsStream(url.getQuery())
.map(s -> Arrays.copyOf(s.split("=", 2), 2))
.collect(groupingBy(s -> decode(s[0]), mapping(s -> decode(s[1]), toList())));
Both the solutions must use an utility function to properly decode the parameters.
private static String decode(final String encoded) {
return Optional.ofNullable(encoded)
.map(e -> URLDecoder.decode(e, StandardCharsets.UTF_8))
.orElse(null);
}

On Android, there is a Uri class in package android.net . Note that Uri is part of android.net, whereas URI is part of java.net .
Uri class has many functions to extract key-value pairs from a query.
Following function returns key-value pairs in the form of HashMap.
In Java:
Map<String, String> getQueryKeyValueMap(Uri uri){
HashMap<String, String> keyValueMap = new HashMap();
String key;
String value;
Set<String> keyNamesList = uri.getQueryParameterNames();
Iterator iterator = keyNamesList.iterator();
while (iterator.hasNext()){
key = (String) iterator.next();
value = uri.getQueryParameter(key);
keyValueMap.put(key, value);
}
return keyValueMap;
}
In Kotlin:
fun getQueryKeyValueMap(uri: Uri): HashMap<String, String> {
val keyValueMap = HashMap<String, String>()
var key: String
var value: String
val keyNamesList = uri.queryParameterNames
val iterator = keyNamesList.iterator()
while (iterator.hasNext()) {
key = iterator.next() as String
value = uri.getQueryParameter(key) as String
keyValueMap.put(key, value)
}
return keyValueMap
}

If you are using servlet doGet try this
request.getParameterMap()
Returns a java.util.Map of the parameters of this request.
Returns:
an immutable java.util.Map containing parameter names as keys and parameter values as map values. The keys in the parameter map are of type String. The values in the parameter map are of type String array.
(Java doc)

Netty also provides a nice query string parser called QueryStringDecoder.
In one line of code, it can parse the URL in the question.
I like because it doesn't require catching or throwing java.net.MalformedURLException.
In one line:
Map<String, List<String>> parameters = new QueryStringDecoder(url).parameters();
See javadocs here: https://netty.io/4.1/api/io/netty/handler/codec/http/QueryStringDecoder.html
Here is a short, self contained, correct example:
import io.netty.handler.codec.http.QueryStringDecoder;
import org.apache.commons.lang3.StringUtils;
import java.util.List;
import java.util.Map;
public class UrlParse {
public static void main(String... args) {
String url = "https://google.com.ua/oauth/authorize?client_id=SS&response_type=code&scope=N_FULL&access_type=offline&redirect_uri=http://localhost/Callback";
QueryStringDecoder decoder = new QueryStringDecoder(url);
Map<String, List<String>> parameters = decoder.parameters();
print(parameters);
}
private static void print(final Map<String, List<String>> parameters) {
System.out.println("NAME VALUE");
System.out.println("------------------------");
parameters.forEach((key, values) ->
values.forEach(val ->
System.out.println(StringUtils.rightPad(key, 19) + val)));
}
}
which generates
NAME VALUE
------------------------
client_id SS
response_type code
scope N_FULL
access_type offline
redirect_uri http://localhost/Callback

If you're using Java 8 and you're willing to write a few reusable methods, you can do it in one line.
private Map<String, List<String>> parse(final String query) {
return Arrays.asList(query.split("&")).stream().map(p -> p.split("=")).collect(Collectors.toMap(s -> decode(index(s, 0)), s -> Arrays.asList(decode(index(s, 1))), this::mergeLists));
}
private <T> List<T> mergeLists(final List<T> l1, final List<T> l2) {
List<T> list = new ArrayList<>();
list.addAll(l1);
list.addAll(l2);
return list;
}
private static <T> T index(final T[] array, final int index) {
return index >= array.length ? null : array[index];
}
private static String decode(final String encoded) {
try {
return encoded == null ? null : URLDecoder.decode(encoded, "UTF-8");
} catch(final UnsupportedEncodingException e) {
throw new RuntimeException("Impossible: UTF-8 is a required encoding", e);
}
}
But that's a pretty brutal line.

There a new version of Apache HTTP client - org.apache.httpcomponents.client5 - where URLEncodedUtils is now deprecated. URIBuilder should be used instead:
import org.apache.hc.core5.http.NameValuePair;
import org.apache.hc.core5.net.URIBuilder;
private static Map<String, String> getQueryParameters(final String url) throws URISyntaxException {
return new URIBuilder(new URI(url), StandardCharsets.UTF_8).getQueryParams()
.stream()
.collect(Collectors.toMap(NameValuePair::getName,
nameValuePair -> URLDecoder.decode(nameValuePair.getValue(), StandardCharsets.UTF_8)));
}

A ready-to-use solution for decoding of URI query part (incl. decoding and multi parameter values)
Comments
I wasn't happy with the code provided by #Pr0gr4mm3r in https://stackoverflow.com/a/13592567/1211082 . The Stream-based solution does not do URLDecoding, the mutable version clumpsy.
Thus I elaborated a solution that
Can decompose a URI query part into a Map<String, List<Optional<String>>>
Can handle multiple values for the same parameter name
Can represent parameters without a value properly (Optional.empty() instead of null)
Decodes parameter names and values correctly via URLdecode
Is based on Java 8 Streams
Is directly usable (see code including imports below)
Allows for proper error handling (here via turning a checked exception UnsupportedEncodingExceptioninto a runtime exception RuntimeUnsupportedEncodingException that allows interplay with stream. (Wrapping regular function into functions throwing checked exceptions is a pain. And Scala Try is not available in the Java language default.)
Java Code
import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.util.*;
import static java.util.stream.Collectors.*;
public class URIParameterDecode {
/**
* Decode parameters in query part of a URI into a map from parameter name to its parameter values.
* For parameters that occur multiple times each value is collected.
* Proper decoding of the parameters is performed.
*
* Example
* <pre>a=1&b=2&c=&a=4</pre>
* is converted into
* <pre>{a=[Optional[1], Optional[4]], b=[Optional[2]], c=[Optional.empty]}</pre>
* #param query the query part of an URI
* #return map of parameters names into a list of their values.
*
*/
public static Map<String, List<Optional<String>>> splitQuery(String query) {
if (query == null || query.isEmpty()) {
return Collections.emptyMap();
}
return Arrays.stream(query.split("&"))
.map(p -> splitQueryParameter(p))
.collect(groupingBy(e -> e.get0(), // group by parameter name
mapping(e -> e.get1(), toList())));// keep parameter values and assemble into list
}
public static Pair<String, Optional<String>> splitQueryParameter(String parameter) {
final String enc = "UTF-8";
List<String> keyValue = Arrays.stream(parameter.split("="))
.map(e -> {
try {
return URLDecoder.decode(e, enc);
} catch (UnsupportedEncodingException ex) {
throw new RuntimeUnsupportedEncodingException(ex);
}
}).collect(toList());
if (keyValue.size() == 2) {
return new Pair(keyValue.get(0), Optional.of(keyValue.get(1)));
} else {
return new Pair(keyValue.get(0), Optional.empty());
}
}
/** Runtime exception (instead of checked exception) to denote unsupported enconding */
public static class RuntimeUnsupportedEncodingException extends RuntimeException {
public RuntimeUnsupportedEncodingException(Throwable cause) {
super(cause);
}
}
/**
* A simple pair of two elements
* #param <U> first element
* #param <V> second element
*/
public static class Pair<U, V> {
U a;
V b;
public Pair(U u, V v) {
this.a = u;
this.b = v;
}
public U get0() {
return a;
}
public V get1() {
return b;
}
}
}
Scala Code
... and for the sake of completeness I can not resist to provide the solution in Scala that dominates by brevity and beauty
import java.net.URLDecoder
object Decode {
def main(args: Array[String]): Unit = {
val input = "a=1&b=2&c=&a=4";
println(separate(input))
}
def separate(input: String) : Map[String, List[Option[String]]] = {
case class Parameter(key: String, value: Option[String])
def separateParameter(parameter: String) : Parameter =
parameter.split("=")
.map(e => URLDecoder.decode(e, "UTF-8")) match {
case Array(key, value) => Parameter(key, Some(value))
case Array(key) => Parameter(key, None)
}
input.split("&").toList
.map(p => separateParameter(p))
.groupBy(p => p.key)
.mapValues(vs => vs.map(p => p.value))
}
}

Using above mentioned comments and solutions, I am storing all the query parameters using Map<String, Object> where Objects either can be string or Set<String>. The solution is given below. It is recommended to use some kind of url validator to validate the url first and then call convertQueryStringToMap method.
private static final String DEFAULT_ENCODING_SCHEME = "UTF-8";
public static Map<String, Object> convertQueryStringToMap(String url) throws UnsupportedEncodingException, URISyntaxException {
List<NameValuePair> params = URLEncodedUtils.parse(new URI(url), DEFAULT_ENCODING_SCHEME);
Map<String, Object> queryStringMap = new HashMap<>();
for(NameValuePair param : params){
queryStringMap.put(param.getName(), handleMultiValuedQueryParam(queryStringMap, param.getName(), param.getValue()));
}
return queryStringMap;
}
private static Object handleMultiValuedQueryParam(Map responseMap, String key, String value) {
if (!responseMap.containsKey(key)) {
return value.contains(",") ? new HashSet<String>(Arrays.asList(value.split(","))) : value;
} else {
Set<String> queryValueSet = responseMap.get(key) instanceof Set ? (Set<String>) responseMap.get(key) : new HashSet<String>();
if (value.contains(",")) {
queryValueSet.addAll(Arrays.asList(value.split(",")));
} else {
queryValueSet.add(value);
}
return queryValueSet;
}
}

I had a go at a Kotlin version seeing how this is the top result in Google.
#Throws(UnsupportedEncodingException::class)
fun splitQuery(url: URL): Map<String, List<String>> {
val queryPairs = LinkedHashMap<String, ArrayList<String>>()
url.query.split("&".toRegex())
.dropLastWhile { it.isEmpty() }
.map { it.split('=') }
.map { it.getOrEmpty(0).decodeToUTF8() to it.getOrEmpty(1).decodeToUTF8() }
.forEach { (key, value) ->
if (!queryPairs.containsKey(key)) {
queryPairs[key] = arrayListOf(value)
} else {
if(!queryPairs[key]!!.contains(value)) {
queryPairs[key]!!.add(value)
}
}
}
return queryPairs
}
And the extension methods
fun List<String>.getOrEmpty(index: Int) : String {
return getOrElse(index) {""}
}
fun String.decodeToUTF8(): String {
URLDecoder.decode(this, "UTF-8")
}

Also, I would recommend regex based implementation of URLParser
import java.util.regex.Matcher;
import java.util.regex.Pattern;
class URLParser {
private final String query;
public URLParser(String query) {
this.query = query;
}
public String get(String name) {
String regex = "(?:^|\\?|&)" + name + "=(.*?)(?:&|$)";
Pattern pattern = Pattern.compile(regex);
Matcher matcher = pattern.matcher(this.query);
if (matcher.find()) {
return matcher.group(1);
}
return "";
}
}
This class is easy to use. It just needs the URL or the query string on initialization and parses value by given key.
class Main {
public static void main(String[] args) {
URLParser parser = new URLParser("https://www.google.com/search?q=java+parse+url+params&oq=java+parse+url+params&aqs=chrome..69i57j0i10.18908j0j7&sourceid=chrome&ie=UTF-8");
System.out.println(parser.get("q")); // java+parse+url+params
System.out.println(parser.get("sourceid")); // chrome
System.out.println(parser.get("ie")); // UTF-8
}
}

Kotlin's Answer with initial reference from https://stackoverflow.com/a/51024552/3286489, but with improved version by tidying up codes and provides 2 versions of it, and use immutable collection operations
Use java.net.URI to extract the Query. Then use the below provided extension functions
Assuming you only want the last value of query i.e. page2&page3 will get {page=3}, use the below extension function
fun URI.getQueryMap(): Map<String, String> {
if (query == null) return emptyMap()
return query.split("&")
.mapNotNull { element -> element.split("=")
.takeIf { it.size == 2 && it.none { it.isBlank() } } }
.associateBy({ it[0].decodeUTF8() }, { it[1].decodeUTF8() })
}
private fun String.decodeUTF8() = URLDecoder.decode(this, "UTF-8") // decode page=%22ABC%22 to page="ABC"
Assuming you want a list of all value for the query i.e. page2&page3 will get {page=[2, 3]}
fun URI.getQueryMapList(): Map<String, List<String>> {
if (query == null) return emptyMap()
return query.split("&")
.distinct()
.mapNotNull { element -> element.split("=")
.takeIf { it.size == 2 && it.none { it.isBlank() } } }
.groupBy({ it[0].decodeUTF8() }, { it[1].decodeUTF8() })
}
private fun String.decodeUTF8() = URLDecoder.decode(this, "UTF-8") // decode page=%22ABC%22 to page="ABC"
The way to use it as below
val uri = URI("schema://host/path/?page=&page=2&page=2&page=3")
println(uri.getQueryMapList()) // Result is {page=[2, 3]}
println(uri.getQueryMap()) // Result is {page=3}

There are plenty of answers which work for your query as you've indicated when it has single parameter definitions. In some applications it may be useful to handle a few extra query parameter edge cases such as:
list of parameter values such as param1&param1=value&param1= meaning param1 is set to List.of("", "value", "")
invalid permutations such as querypath?&=&&=noparamname&.
use empty string not null in maps a= means "a" is List.of("") to match web servlet handling
This uses a Stream with filters and groupingBy to collect to Map<String, List<String>>:
public static Map<String, List<String>> getParameterValues(URL url) {
return Arrays.stream(url.getQuery().split("&"))
.map(s -> s.split("="))
// filter out empty parameter names (as in Tomcat) "?&=&&=value&":
.filter(arr -> arr.length > 0 && arr[0].length() > 0)
.collect(Collectors.groupingBy(arr -> URLDecoder.decode(arr[0], StandardCharsets.UTF_8),
// drop this line for not-name definition order Map:
LinkedHashMap::new,
Collectors.mapping(arr -> arr.length < 2 ? "" : URLDecoder.decode(arr[1], StandardCharsets.UTF_8), Collectors.toList())));
}

If you are using Spring, add an argument of type #RequestParam Map<String,String> to your controller method, and Spring will construct the map for you!

Just an update to the Java 8 version
public Map<String, List<String>> splitQuery(URL url) {
if (Strings.isNullOrEmpty(url.getQuery())) {
return Collections.emptyMap();
}
return Arrays.stream(url.getQuery().split("&"))
.map(this::splitQueryParameter)
.collect(Collectors.groupingBy(SimpleImmutableEntry::getKey, LinkedHashMap::new, **Collectors**.mapping(Map.Entry::getValue, **Collectors**.toList())));
}
mapping and toList() methods have to be used with Collectors which was not mentioned in the top answer. Otherwise it would throw compilation error in IDE

Answering here because this is a popular thread. This is a clean solution in Kotlin that uses the recommended UrlQuerySanitizer api. See the official documentation. I have added a string builder to concatenate and display the params.
var myURL: String? = null
if (intent.hasExtra("my_value")) {
myURL = intent.extras.getString("my_value")
} else {
myURL = intent.dataString
}
val sanitizer = UrlQuerySanitizer(myURL)
// We don't want to manually define every expected query *key*, so we set this to true
sanitizer.allowUnregisteredParamaters = true
val parameterNamesToValues: List<UrlQuerySanitizer.ParameterValuePair> = sanitizer.parameterList
val parameterIterator: Iterator<UrlQuerySanitizer.ParameterValuePair> = parameterNamesToValues.iterator()
// Helper simply so we can display all values on screen
val stringBuilder = StringBuilder()
while (parameterIterator.hasNext()) {
val parameterValuePair: UrlQuerySanitizer.ParameterValuePair = parameterIterator.next()
val parameterName: String = parameterValuePair.mParameter
val parameterValue: String = parameterValuePair.mValue
// Append string to display all key value pairs
stringBuilder.append("Key: $parameterName\nValue: $parameterValue\n\n")
}
// Set a textView's text to display the string
val paramListString = stringBuilder.toString()
val textView: TextView = findViewById(R.id.activity_title) as TextView
textView.text = "Paramlist is \n\n$paramListString"
// to check if the url has specific keys
if (sanitizer.hasParameter("type")) {
val type = sanitizer.getValue("type")
println("sanitizer has type param $type")
}

Here is my solution with reduce and Optional:
private Optional<SimpleImmutableEntry<String, String>> splitKeyValue(String text) {
String[] v = text.split("=");
if (v.length == 1 || v.length == 2) {
String key = URLDecoder.decode(v[0], StandardCharsets.UTF_8);
String value = v.length == 2 ? URLDecoder.decode(v[1], StandardCharsets.UTF_8) : null;
return Optional.of(new SimpleImmutableEntry<String, String>(key, value));
} else
return Optional.empty();
}
private HashMap<String, String> parseQuery(URI uri) {
HashMap<String, String> params = Arrays.stream(uri.getQuery()
.split("&"))
.map(this::splitKeyValue)
.filter(Optional::isPresent)
.map(Optional::get)
.reduce(
// initial value
new HashMap<String, String>(),
// accumulator
(map, kv) -> {
map.put(kv.getKey(), kv.getValue());
return map;
},
// combiner
(a, b) -> {
a.putAll(b);
return a;
});
return params;
}
I ignore duplicate parameters (I take the last one).
I use Optional<SimpleImmutableEntry<String, String>> to ignore garbage later
The reduction start with an empty map, then populate it on each SimpleImmutableEntry
In case you ask, reduce requires this weird combiner in the last parameter, which is only used in parallel streams. Its goal is to merge two intermediate results (here HashMap).

If you happen to have cxf-core on the classpath and you know you have no repeated query params, you may want to use UrlUtils.parseQueryString.

The Eclipse Jersey REST framework supports this through UriComponent. Example:
import org.glassfish.jersey.uri.UriComponent;
String uri = "https://google.com.ua/oauth/authorize?client_id=SS&response_type=code&scope=N_FULL&access_type=offline&redirect_uri=http://localhost/Callback";
MultivaluedMap<String, String> params = UriComponent.decodeQuery(URI.create(uri), true);
for (String key : params.keySet()) {
System.out.println(key + ": " + params.getFirst(key));
}

If just want the parameters after the URL from a String. Then the following code will work. I am just assuming the simple Url. I mean no hard and fast checking and decoding. Like in one of my test case I got the Url and I know I just need the value of the paramaters. The url was simple. No encoding decoding needed.
String location = "https://google.com.ua/oauth/authorize?client_id=SS&response_type=code&scope=N_FULL&access_type=offline&redirect_uri=http://localhost/Callback";
String location1 = "https://stackoverflow.com?param1=value1&param2=value2&param3=value3";
String location2 = "https://stackoverflow.com?param1=value1&param2=&param3=value3&param3";
Map<String, String> paramsMap = Stream.of(location)
.filter(l -> l.indexOf("?") != -1)
.map(l -> l.substring(l.indexOf("?") + 1, l.length()))
.flatMap(q -> Pattern.compile("&").splitAsStream(q))
.map(s -> s.split("="))
.filter(a -> a.length == 2)
.collect(Collectors.toMap(
a -> a[0],
a -> a[1],
(existing, replacement) -> existing + ", " + replacement,
LinkedHashMap::new
));
System.out.println(paramsMap);
Thanks

That seems tidy to me the best way:
static Map<String, String> decomposeQueryString(String query, Charset charset) {
return Arrays.stream(query.split("&"))
.map(pair -> pair.split("=", 2))
.collect(Collectors.toMap(
pair -> URLDecoder.decode(pair[0], charset),
pair -> pair.length > 1 ? URLDecoder.decode(pair[1], charset) : null)
);
}
The prerequisite is that your query syntax does not allow repeated parameters.

The Hutool framework supports this through HttpUtil. Example:
import cn.hutool.http.HttpUtil;
String url ="https://google.com.ua/oauth/authorize?client_id=SS&response_type=code&scope=N_FULL&access_type=offline&redirect_uri=http://localhost/Callback";
Map<String, List<String>> stringListMap = HttpUtil.decodeParams(url, "UTF-8");
System.out.println("decodeParams：" + stringListMap);
You will get:
decodeParams：{client_id=[SS], response_type=[code], scope=[N_FULL], access_type=[offline], redirect_uri=[http://localhost/Callback]}

A kotlin version
of the answer Answer by matthias provided
fun decomposeQueryString(query: String, charset: Charset): Map<String, String?> {
return if (query.split("?").size <= 1)
emptyMap()
else {
query.split("?")[1]
.split("&")
.map { it.split(Pattern.compile("="), 2) }
.associate {
Pair(
URLDecoder.decode(it[0], charset.name()),
if (it.size > 1) URLDecoder.decode(it[1], charset.name()) else null
)
}
}
}
This takes of the first parameter after the question mark '?' as well.

Plain Java, No Special Libraries, Nothing Fancy
// assumes you are parsing a line that looks like:
// /path/resource?key=value&parameter=value
// which you got from a request header line that looks like:
// GET /path/resource?key=value&parameter=value HTTP/1.1
public HashMap<String, String> parseQuery(String path){
if(path == null || path.isEmpty()){ //basic sanity check
return null;
}
int indexOfQ = path.indexOf("?"); //where the query string starts
if(indexOfQ == -1){return null;} //check query exists
String queryString = path.substring(indexOfQ + 1);
String[] queryStringArray = queryString.split("&");
Map<String, String> kvMap = new HashMap<>();
for(String kvString : queryStringArray){
int indexOfE = kvString.indexOf("="); //check query is formed correctly
if(indexOfE == -1 || indexOfE == 0){return null;}
String[] kvPairArray = kvString.split("=");
kvMap.put(kvPairArray[0], kvPairArray[1]);
}
return kvMap;
}

org.keycloak.common.util.UriUtils
I had to parse URIs and Query Parameters in a Keycloak extension and found this utility classes very useful:
org.keycloak.common.util.UriUtils:
static MultivaluedHashMap<String,String> decodeQueryString(String queryString)
There is also a useful method to delete one query parameter:
static String stripQueryParam(String url, String name)
And to parse the URL there is
org.keycloak.common.util.KeycloakUriBuilder:
KeycloakUriBuilder uri(String uriTemplate)
String getQuery()
and lots of other goodies.

Getting URL parameter in java and extract a specific text from that URL

I have a URL and I need to get the value of v from this URL.
Here is my URL: http://www.youtube.com/watch?v=_RCIP6OrQrE
How can I do that?

I think the one of the easiest ways out would be to parse the string returned by URL.getQuery() as
public static Map<String, String> getQueryMap(String query) {
String[] params = query.split("&");
Map<String, String> map = new HashMap<String, String>();
for (String param : params) {
String name = param.split("=")[0];
String value = param.split("=")[1];
map.put(name, value);
}
return map;
}
You can use the map returned by this function to retrieve the value keying in the parameter name.

If you're on Android, you can do this:
Uri uri = Uri.parse(url);
String v = uri.getQueryParameter("v");

I have something like this:
import org.apache.http.NameValuePair;
import org.apache.http.client.utils.URIBuilder;
private String getParamValue(String link, String paramName) throws URISyntaxException {
List<NameValuePair> queryParams = new URIBuilder(link).getQueryParams();
return queryParams.stream()
.filter(param -> param.getName().equalsIgnoreCase(paramName))
.map(NameValuePair::getValue)
.findFirst()
.orElse("");
}

I wrote this last month for Joomla Module when implementing youtube videos (with the Gdata API). I've since converted it to java.
Import These Libraries
import java.net.URL;
import java.util.regex.*;
Copy/Paste this function
public String getVideoId( String videoId ) throws Exception {
String pattern = "^(https?|ftp|file)://[-a-zA-Z0-9+&##/%?=~_|!:,.;]*[-a-zA-Z0-9+&##/%=~_|]";
Pattern p = Pattern.compile(pattern);
Matcher m = p.matcher(videoId);
int youtu = videoId.indexOf("youtu");
if(m.matches() && youtu != -1){
int ytu = videoId.indexOf("http://youtu.be/");
if(ytu != -1) {
String[] split = videoId.split(".be/");
return split[1];
}
URL youtube = new URL(videoId);
String[] split = youtube.getQuery().split("=");
int query = split[1].indexOf("&");
if(query != -1){
String[] nSplit = split[1].split("&");
return nSplit[0];
} else return split[1];
}
return null; //throw something or return what you want
}
URL's it will work with
http://www.youtube.com/watch?v=k0BWlvnBmIE (General URL)
http://youtu.be/k0BWlvnBmIE (Share URL)
http://www.youtube.com/watch?v=UWb5Qc-fBvk&list=FLzH5IF4Lwgv-DM3CupM3Zog&index=2 (Playlist URL)

Import these libraries
import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
Similar to the verisimilitude, but with the capabilities of handling multivalue parameters. Note: I've seen HTTP GET requests without a value, in this case the value will be null.
public static List<NameValuePair> getQueryMap(String query)
{
List<NameValuePair> queryMap = new ArrayList<NameValuePair>();
String[] params = query.split(Pattern.quote("&"));
for (String param : params)
{
String[] chunks = param.split(Pattern.quote("="));
String name = chunks[0], value = null;
if(chunks.length > 1) {
value = chunks[1];
}
queryMap.add(new BasicNameValuePair(name, value));
}
return queryMap;
}
Example:
GET /bottom.gif?e235c08=1509896923&%49%6E%...

Using pure Java 8
Assumming you want to extract param "v" from url:
String paramV = Stream.of(url.split("?")[1].split("&"))
.map(kv -> kv.split("="))
.filter(kv -> "v".equalsIgnoreCase(kv[0]))
.map(kv -> kv[1])
.findFirst()
.orElse("");

Assuming the URL syntax will always be http://www.youtube.com/watch?v= ...
String v = "http://www.youtube.com/watch?v=_RCIP6OrQrE".substring(31);
or disregarding the prefix syntax:
String url = "http://www.youtube.com/watch?v=_RCIP6OrQrE";
String v = url.substring(url.indexOf("v=") + 2);

I believe we have a better approach to answer this question.
1: Define a function that returns Map values.
Here we go.
public Map<String, String> getUrlValues(String url) throws UnsupportedEncodingException {
int i = url.indexOf("?");
Map<String, String> paramsMap = new HashMap<>();
if (i > -1) {
String searchURL = url.substring(url.indexOf("?") + 1);
String params[] = searchURL.split("&");
for (String param : params) {
String temp[] = param.split("=");
paramsMap.put(temp[0], java.net.URLDecoder.decode(temp[1], "UTF-8"));
}
}
return paramsMap;
}
2: Call your function surrounding with a try catch block
Here we go
try {
Map<String, String> values = getUrlValues("https://example.com/index.php?form_id=9&page=1&view_id=78");
String formId = values.get("form_id");
String page = values.get("page");
String viewId = values.get("view_id");
Log.d("FormID", formId);
Log.d("Page", page);
Log.d("ViewID", viewId);
} catch (UnsupportedEncodingException e) {
Log.e("Error", e.getMessage());
}

If you are using Jersey (which I was, my server component needs to make outbound HTTP requests) it contains the following public method:
var multiValueMap = UriComponent.decodeQuery(uri, true);
It is part of org.glassfish.jersey.uri.UriComponent, and the javadoc is here. Whilst you may not want all of Jersey, it is part of the Jersey common package which isn't too bad on dependencies...

I solved the problem like this
public static String getUrlParameterValue(String url, String paramName) {
String value = "";
List<NameValuePair> result = null;
try {
result = URLEncodedUtils.parse(new URI(url), UTF_8);
value = result.stream().filter(pair -> pair.getName().equals(paramName)).findFirst().get().getValue();
System.out.println("--------------> \n" + paramName + " : " + value + "\n");
} catch (URISyntaxException e) {
e.printStackTrace();
}
return value;
}

this will work for all sort of youtube url :
if url could be
youtube.com/?v=_RCIP6OrQrE
youtube.com/v/_RCIP6OrQrE
youtube.com/watch?v=_RCIP6OrQrE
youtube.com/watch?v=_RCIP6OrQrE&feature=whatever&this=that
Pattern p = Pattern.compile("http.*\\?v=([a-zA-Z0-9_\\-]+)(?:&.)*");
String url = "http://www.youtube.com/watch?v=_RCIP6OrQrE";
Matcher m = p.matcher(url.trim()); //trim to remove leading and trailing space if any
if (m.matches()) {
url = m.group(1);
}
System.out.println(url);
this will extract video id from your url
further reference

My solution mayble not good
String url = "https://www.youtube.com/watch?param=test&v=XcHJMiSy_1c&lis=test";
int start = url.indexOf("v=")+2;
// int start = url.indexOf("list=")+5; **5 is length of ("list=")**
int end = url.indexOf("&", start);
end = (end == -1 ? url.length() : end);
System.out.println(url.substring(start, end));
// result: XcHJMiSy_1c
work fine with:
https://www.youtube.com/watch?param=test&v=XcHJMiSy_1c&lis=test
https://www.youtube.com/watch?v=XcHJMiSy_1c

public static String getQueryMap(String query) {
String[] params = query.split("&");
for (String param : params) {
String name = param.split("=")[0];
if ("YourParam".equals(name)) {
return param.split("=")[1];
}
}
return null;
}

Simplest way to strip an int out of a URL in Java?

I have a String containing a URL. I want to get just one piece of data out of it: an int that should be showing up in the query string.
So if the url is:
http://domain.tld/page.html?iVar=123
I want to get "123" into an int.
What's the most elegant way you know to do this?

You could try matching just that parameter in the URL string:
public static Integer getIVarParamValue(String urlStr) {
Pattern p = Pattern.compile("iVar=(\\d+)");
Matcher m = p.matcher(urlStr);
if (m.find()) {
return Integer.parseInt(m.group(1));
}
return null;
}

It seems you want to obtain get parameters and parse them. I have this method here (got it from somewhere on SO, I guess):
public static Map<String, List<String>> getQueryParams(String url) {
try {
Map<String, List<String>> params = new HashMap<String, List<String>>();
String[] urlParts = url.split("\\?");
if (urlParts.length > 1) {
String query = urlParts[1];
for (String param : query.split("&")) {
String[] pair = param.split("=");
String key = URLDecoder.decode(pair[0], "UTF-8");
String value = "";
if (pair.length > 1) {
value = URLDecoder.decode(pair[1], "UTF-8");
}
List<String> values = params.get(key);
if (values == null) {
values = new ArrayList<String>();
params.put(key, values);
}
values.add(value);
}
}
return params;
} catch (UnsupportedEncodingException ex) {
throw new AssertionError(ex);
}
}
So:
String var = WebUtils.getQueryParams(url).get("iVar");
int intVar = Integer.parseInt(var);

You can use the URL class.
i.e.:
URL myUrl = new URL("http://domain.tld/page.html?iVar=123");
String query = myUrl.getQuery(); //this will return iVar=123
//at this point you can either parse it manually (i.e. use some of the regexp in the other suggestions, or use something like:
String[] parts = query.split();
String variable = parts[0];
String value = parts[1];
This will work only for this case though and won't work if you have additional params or no params.
There are a number of solution that will split it into a param map online, you can see some here.

If it's really as simple as you describe: There is only 1 int in your URL and all you want is that int, I'd go for a regular expression. If it is actually more complicated see the other answers.
Pattern p = Pattern.compile("[0-9]+");
Matcher m = p.matcher("http://domain.tld/page.html?iVar=123");
if (m.find())
System.out.println(m.group());

This also could do the work :
public static int getIntParam(HttpServletRequest request, String name, int defaultValue) {
String value = request.getParameter(name);
try {
if (value != null) {
return Integer.valueOf(value);
}
} catch (NumberFormatException e) {
}
return defaultValue;
}
Hope it helps!

If the query string part of the URL is always the same (so if it was always iVar) you could use urlAsString.indexOf("iVar=") to find iVar= and then knowing the number is after that, extract the number. That is admittedly not the least brittle approach.
But if you're looking for all the query strings then Bozho's answer is much better.

Query String Manipulation in Java

Does anyone have, or know of, a java class that I can use to manipulate query strings?
Essentially I'd like a class that I can simply give a query string to and then delete, add and modify query string KVP's.
Thanks in advance.
EDIT
In response to a comment made to this question, the query string will look something like this;
N=123+456+112&Ntt=koala&D=abc
So I'd like to pass this class the query string and say something like;
String[] N = queryStringClass.getParameter("N");
and then maybe
queryStringClass.setParameter("N", N);
and maybe queryStringClass.removeParameter("N");
Or something to that effect.

SOmething like this
public static Map<String, String> getQueryMap(String query)
{
String[] params = query.split("&");
Map<String, String> map = new HashMap<String, String>();
for (String param : params)
{
String name = param.split("=")[0];
String value = param.split("=")[1];
map.put(name, value);
}
return map;
}
To iterate the map simply:
String query = url.getQuery();
Map<String, String> map = getQueryMap(query);
Set<String> keys = map.keySet();
for (String key : keys)
{
System.out.println("Name=" + key);
System.out.println("Value=" + map.get(key));
}

You can also use Google Guava's Splitter.
String queryString = "variableA=89&variableB=100";
Map<String,String> queryParameters = Splitter
.on("&")
.withKeyValueSeparator("=")
.split(queryString);
System.out.println(queryParameters.get("variableA"));
prints out
89
This I think is a very readable alternative to parsing it yourself.
Edit: As #raulk pointed out, this solution does not account for escaped characters. However, this may not be an issue because before you URL-Decode, the query string is guaranteed to not have any escaped characters that conflict with '=' and '&'. You can use this to your advantage in the following way.
Say that you must decode the following query string:
a=%26%23%25!)%23(%40!&b=%23%24(%40)%24%40%40))%24%23%5E*%26
which is URL encoded, then you are guaranteed that the '&' and '=' are specifically used for separating pairs and key from value, respectively, at which point you can use the Guava splitter to get:
a = %26%23%25!)%23(%40!
b = %23%24(%40)%24%40%40))%24%23%5E*%26
Once you have obtained the key-value pairs, then you can URL decode them separately.
a = &#%!)#(#!
b = #$(#)$##))$#^*&
That should cover all cases.

If you are using J2EE, you can use ServletRequest.getParameterValues().
Otherwise, I don't think Java has any common classes for query string handling. Writing your own shouldn't be too hard, though there are certain tricky edge cases, such as realizing that technically the same key may appear more than once in the query string.
One implementation might look like:
import java.util.*;
import java.net.URLEncoder;
import java.net.URLDecoder;
public class QueryParams {
private static class KVP {
final String key;
final String value;
KVP (String key, String value) {
this.key = key;
this.value = value;
}
}
List<KVP> query = new ArrayList<KVP>();
public QueryParams(String queryString) {
parse(queryString);
}
public QueryParams() {
}
public void addParam(String key, String value) {
if (key == null || value == null)
throw new NullPointerException("null parameter key or value");
query.add(new KVP(key, value));
}
private void parse(String queryString) {
for (String pair : queryString.split("&")) {
int eq = pair.indexOf("=");
if (eq < 0) {
// key with no value
addParam(URLDecoder.decode(pair), "");
} else {
// key=value
String key = URLDecoder.decode(pair.substring(0, eq));
String value = URLDecoder.decode(pair.substring(eq + 1));
query.add(new KVP(key, value));
}
}
}
public String toQueryString() {
StringBuilder sb = new StringBuilder();
for (KVP kvp : query) {
if (sb.length() > 0) {
sb.append('&');
}
sb.append(URLEncoder.encode(kvp.key));
if (!kvp.value.equals("")) {
sb.append('=');
sb.append(URLEncoder.encode(kvp.value));
}
}
return sb.toString();
}
public String getParameter(String key) {
for (KVP kvp : query) {
if (kvp.key.equals(key)) {
return kvp.value;
}
}
return null;
}
public List<String> getParameterValues(String key) {
List<String> list = new LinkedList<String>();
for (KVP kvp : query) {
if (kvp.key.equals(key)) {
list.add(kvp.value);
}
}
return list;
}
public static void main(String[] args) {
QueryParams qp = new QueryParams("k1=v1&k2&k3=v3&k1=v4&k1&k5=hello+%22world");
System.out.println("getParameter:");
String[] keys = new String[] { "k1", "k2", "k3", "k5" };
for (String key : keys) {
System.out.println(key + ": " + qp.getParameter(key));
}
System.out.println("getParameters(k1): " + qp.getParameterValues("k1"));
}
}

Another way is to use apache http-components. It's a bit hacky, but at least you leverage all the parsing corner cases:
List<NameValuePair> params =
URLEncodedUtils.parse("http://example.com/?" + queryString, Charset.forName("UTF-8"));
That'll give you a List of NameValuePair objects that should be easy to work with.

You can create a util method and use regular expression to parse it. A pattern like "[;&]" should suffice.

Named placeholders in string formatting

In Python, when formatting string, I can fill placeholders by name rather than by position, like that:
print "There's an incorrect value '%(value)s' in column # %(column)d" % \
{ 'value': x, 'column': y }
I wonder if that is possible in Java (hopefully, without external libraries)?

StrSubstitutor of jakarta commons lang is a light weight way of doing this provided your values are already formatted correctly.
http://commons.apache.org/proper/commons-lang/javadocs/api-3.1/org/apache/commons/lang3/text/StrSubstitutor.html
Map<String, String> values = new HashMap<String, String>();
values.put("value", x);
values.put("column", y);
StrSubstitutor sub = new StrSubstitutor(values, "%(", ")");
String result = sub.replace("There's an incorrect value '%(value)' in column # %(column)");
The above results in:
"There's an incorrect value '1' in column # 2"
When using Maven you can add this dependency to your pom.xml:
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.4</version>
</dependency>

not quite, but you can use MessageFormat to reference one value multiple times:
MessageFormat.format("There's an incorrect value \"{0}\" in column # {1}", x, y);
The above can be done with String.format() as well, but I find messageFormat syntax cleaner if you need to build complex expressions, plus you dont need to care about the type of the object you are putting into the string

Another example of Apache Common StringSubstitutor for simple named placeholder.
String template = "Welcome to {theWorld}. My name is {myName}.";
Map<String, String> values = new HashMap<>();
values.put("theWorld", "Stackoverflow");
values.put("myName", "Thanos");
String message = StringSubstitutor.replace(template, values, "{", "}");
System.out.println(message);
// Welcome to Stackoverflow. My name is Thanos.

You can use StringTemplate library, it offers what you want and much more.
import org.antlr.stringtemplate.*;
final StringTemplate hello = new StringTemplate("Hello, $name$");
hello.setAttribute("name", "World");
System.out.println(hello.toString());

public static String format(String format, Map<String, Object> values) {
StringBuilder formatter = new StringBuilder(format);
List<Object> valueList = new ArrayList<Object>();
Matcher matcher = Pattern.compile("\\$\\{(\\w+)}").matcher(format);
while (matcher.find()) {
String key = matcher.group(1);
String formatKey = String.format("${%s}", key);
int index = formatter.indexOf(formatKey);
if (index != -1) {
formatter.replace(index, index + formatKey.length(), "%s");
valueList.add(values.get(key));
}
}
return String.format(formatter.toString(), valueList.toArray());
}
Example:
String format = "My name is ${1}. ${0} ${1}.";
Map<String, Object> values = new HashMap<String, Object>();
values.put("0", "James");
values.put("1", "Bond");
System.out.println(format(format, values)); // My name is Bond. James Bond.

Thanks for all your help! Using all your clues, I've written routine to do exactly what I want -- python-like string formatting using dictionary. Since I'm Java newbie, any hints are appreciated.
public static String dictFormat(String format, Hashtable<String, Object> values) {
StringBuilder convFormat = new StringBuilder(format);
Enumeration<String> keys = values.keys();
ArrayList valueList = new ArrayList();
int currentPos = 1;
while (keys.hasMoreElements()) {
String key = keys.nextElement(),
formatKey = "%(" + key + ")",
formatPos = "%" + Integer.toString(currentPos) + "$";
int index = -1;
while ((index = convFormat.indexOf(formatKey, index)) != -1) {
convFormat.replace(index, index + formatKey.length(), formatPos);
index += formatPos.length();
}
valueList.add(values.get(key));
++currentPos;
}
return String.format(convFormat.toString(), valueList.toArray());
}

This is an old thread, but just for the record, you could also use Java 8 style, like this:
public static String replaceParams(Map<String, String> hashMap, String template) {
return hashMap.entrySet().stream().reduce(template, (s, e) -> s.replace("%(" + e.getKey() + ")", e.getValue()),
(s, s2) -> s);
}
Usage:
public static void main(String[] args) {
final HashMap<String, String> hashMap = new HashMap<String, String>() {
{
put("foo", "foo1");
put("bar", "bar1");
put("car", "BMW");
put("truck", "MAN");
}
};
String res = replaceParams(hashMap, "This is '%(foo)' and '%(foo)', but also '%(bar)' '%(bar)' indeed.");
System.out.println(res);
System.out.println(replaceParams(hashMap, "This is '%(car)' and '%(foo)', but also '%(bar)' '%(bar)' indeed."));
System.out.println(replaceParams(hashMap, "This is '%(car)' and '%(truck)', but also '%(foo)' '%(bar)' + '%(truck)' indeed."));
}
The output will be:
This is 'foo1' and 'foo1', but also 'bar1' 'bar1' indeed.
This is 'BMW' and 'foo1', but also 'bar1' 'bar1' indeed.
This is 'BMW' and 'MAN', but also 'foo1' 'bar1' + 'MAN' indeed.

Apache Commons StringSubstitutor can be used. Note that StrSubstitutor is deprecated.
import org.apache.commons.text.StringSubstitutor;
// ...
Map<String, String> values = new HashMap<>();
values.put("animal", "quick brown fox");
values.put("target", "lazy dog");
StringSubstitutor sub = new StringSubstitutor(values);
String result = sub.replace("The ${animal} jumped over the ${target}.");
// "The quick brown fox jumped over the lazy dog."
This class supports providing default values for variables.
String result = sub.replace("The number is ${undefined.property:-42}.");
// "The number is 42."
To use recursive variable replacement, call setEnableSubstitutionInVariables(true);.
Map<String, String> values = new HashMap<>();
values.put("b", "c");
values.put("ac", "Test");
StringSubstitutor sub = new StringSubstitutor(values);
sub.setEnableSubstitutionInVariables(true);
String result = sub.replace("${a${b}}");
// "Test"

I am the author of a small library that does exactly what you want:
Student student = new Student("Andrei", 30, "Male");
String studStr = template("#{id}\tName: #{st.getName}, Age: #{st.getAge}, Gender: #{st.getGender}")
.arg("id", 10)
.arg("st", student)
.format();
System.out.println(studStr);
Or you can chain the arguments:
String result = template("#{x} + #{y} = #{z}")
.args("x", 5, "y", 10, "z", 15)
.format();
System.out.println(result);
// Output: "5 + 10 = 15"

There is nothing built into Java at the moment of writing this. I would suggest writing your own implementation. My preference is for a simple fluent builder interface instead of creating a map and passing it to function -- you end up with a nice contiguous chunk of code, for example:
String result = new TemplatedStringBuilder("My name is {{name}} and I from {{town}}")
.replace("name", "John Doe")
.replace("town", "Sydney")
.finish();
Here is a simple implementation:
class TemplatedStringBuilder {
private final static String TEMPLATE_START_TOKEN = "{{";
private final static String TEMPLATE_CLOSE_TOKEN = "}}";
private final String template;
private final Map<String, String> parameters = new HashMap<>();
public TemplatedStringBuilder(String template) {
if (template == null) throw new NullPointerException();
this.template = template;
}
public TemplatedStringBuilder replace(String key, String value){
parameters.put(key, value);
return this;
}
public String finish(){
StringBuilder result = new StringBuilder();
int startIndex = 0;
while (startIndex < template.length()){
int openIndex = template.indexOf(TEMPLATE_START_TOKEN, startIndex);
if (openIndex < 0){
result.append(template.substring(startIndex));
break;
}
int closeIndex = template.indexOf(TEMPLATE_CLOSE_TOKEN, openIndex);
if(closeIndex < 0){
result.append(template.substring(startIndex));
break;
}
String key = template.substring(openIndex + TEMPLATE_START_TOKEN.length(), closeIndex);
if (!parameters.containsKey(key)) throw new RuntimeException("missing value for key: " + key);
result.append(template.substring(startIndex, openIndex));
result.append(parameters.get(key));
startIndex = closeIndex + TEMPLATE_CLOSE_TOKEN.length();
}
return result.toString();
}
}

Apache Commons Lang's replaceEach method may come in handy dependeding on your specific needs. You can easily use it to replace placeholders by name with this single method call:
StringUtils.replaceEach("There's an incorrect value '%(value)' in column # %(column)",
new String[] { "%(value)", "%(column)" }, new String[] { x, y });
Given some input text, this will replace all occurrences of the placeholders in the first string array with the corresponding values in the second one.

You should have a look at the official ICU4J library. It provides a MessageFormat class similar to the one available with the JDK but this former supports named placeholders.
Unlike other solutions provided on this page. ICU4j is part of the ICU project that is maintained by IBM and regularly updated. In addition, it supports advanced use cases such as pluralization and much more.
Here is a code example:
MessageFormat messageFormat =
new MessageFormat("Publication written by {author}.");
Map<String, String> args = Map.of("author", "John Doe");
System.out.println(messageFormat.format(args));

As of 2022 the up-to-date solution is Apache Commons Text StringSubstitutor
From the doc:
// Build map
Map<String, String> valuesMap = new HashMap<>();
valuesMap.put("animal", "quick brown fox");
valuesMap.put("target", "lazy dog");
String templateString = "The ${animal} jumped over the ${target} ${undefined.number:-1234567890} times.";
// Build StringSubstitutor
StringSubstitutor sub = new StringSubstitutor(valuesMap);
// Replace
String resolvedString = sub.replace(templateString)
;

You could have something like this on a string helper class
/**
* An interpreter for strings with named placeholders.
*
* For example given the string "hello %(myName)" and the map <code>
* <p>Map<String, Object> map = new HashMap<String, Object>();</p>
* <p>map.put("myName", "world");</p>
* </code>
*
* the call {#code format("hello %(myName)", map)} returns "hello world"
*
* It replaces every occurrence of a named placeholder with its given value
* in the map. If there is a named place holder which is not found in the
* map then the string will retain that placeholder. Likewise, if there is
* an entry in the map that does not have its respective placeholder, it is
* ignored.
*
* #param str
* string to format
* #param values
* to replace
* #return formatted string
*/
public static String format(String str, Map<String, Object> values) {
StringBuilder builder = new StringBuilder(str);
for (Entry<String, Object> entry : values.entrySet()) {
int start;
String pattern = "%(" + entry.getKey() + ")";
String value = entry.getValue().toString();
// Replace every occurence of %(key) with value
while ((start = builder.indexOf(pattern)) != -1) {
builder.replace(start, start + pattern.length(), value);
}
}
return builder.toString();
}

Based on the answer I created MapBuilder class:
public class MapBuilder {
public static Map<String, Object> build(Object... data) {
Map<String, Object> result = new LinkedHashMap<>();
if (data.length % 2 != 0) {
throw new IllegalArgumentException("Odd number of arguments");
}
String key = null;
Integer step = -1;
for (Object value : data) {
step++;
switch (step % 2) {
case 0:
if (value == null) {
throw new IllegalArgumentException("Null key value");
}
key = (String) value;
continue;
case 1:
result.put(key, value);
break;
}
}
return result;
}
}
then I created class StringFormat for String formatting:
public final class StringFormat {
public static String format(String format, Object... args) {
Map<String, Object> values = MapBuilder.build(args);
for (Map.Entry<String, Object> entry : values.entrySet()) {
String key = entry.getKey();
Object value = entry.getValue();
format = format.replace("$" + key, value.toString());
}
return format;
}
}
which you could use like that:
String bookingDate = StringFormat.format("From $startDate to $endDate"),
"$startDate", formattedStartDate,
"$endDate", formattedEndDate
);

I created also a util/helper class (using jdk 8) which can format a string an replaces occurrences of variables.
For this purpose I used the Matchers "appendReplacement" method which does all the substitution and loops only over the affected parts of a format string.
The helper class isn't currently well javadoc documented. I will changes this in the future ;)
Anyway I commented the most important lines (I hope).
public class FormatHelper {
//Prefix and suffix for the enclosing variable name in the format string.
//Replace the default values with any you need.
public static final String DEFAULT_PREFIX = "${";
public static final String DEFAULT_SUFFIX = "}";
//Define dynamic function what happens if a key is not found.
//Replace the defualt exception with any "unchecked" exception type you need or any other behavior.
public static final BiFunction<String, String, String> DEFAULT_NO_KEY_FUNCTION =
(fullMatch, variableName) -> {
throw new RuntimeException(String.format("Key: %s for variable %s not found.",
variableName,
fullMatch));
};
private final Pattern variablePattern;
private final Map<String, String> values;
private final BiFunction<String, String, String> noKeyFunction;
private final String prefix;
private final String suffix;
public FormatHelper(Map<String, String> values) {
this(DEFAULT_NO_KEY_FUNCTION, values);
}
public FormatHelper(
BiFunction<String, String, String> noKeyFunction, Map<String, String> values) {
this(DEFAULT_PREFIX, DEFAULT_SUFFIX, noKeyFunction, values);
}
public FormatHelper(String prefix, String suffix, Map<String, String> values) {
this(prefix, suffix, DEFAULT_NO_KEY_FUNCTION, values);
}
public FormatHelper(
String prefix,
String suffix,
BiFunction<String, String, String> noKeyFunction,
Map<String, String> values) {
this.prefix = prefix;
this.suffix = suffix;
this.values = values;
this.noKeyFunction = noKeyFunction;
//Create the Pattern and quote the prefix and suffix so that the regex don't interpret special chars.
//The variable name is a "\w+" in an extra capture group.
variablePattern = Pattern.compile(Pattern.quote(prefix) + "(\\w+)" + Pattern.quote(suffix));
}
public static String format(CharSequence format, Map<String, String> values) {
return new FormatHelper(values).format(format);
}
public static String format(
CharSequence format,
BiFunction<String, String, String> noKeyFunction,
Map<String, String> values) {
return new FormatHelper(noKeyFunction, values).format(format);
}
public static String format(
String prefix, String suffix, CharSequence format, Map<String, String> values) {
return new FormatHelper(prefix, suffix, values).format(format);
}
public static String format(
String prefix,
String suffix,
BiFunction<String, String, String> noKeyFunction,
CharSequence format,
Map<String, String> values) {
return new FormatHelper(prefix, suffix, noKeyFunction, values).format(format);
}
public String format(CharSequence format) {
//Create matcher based on the init pattern for variable names.
Matcher matcher = variablePattern.matcher(format);
//This buffer will hold all parts of the formatted finished string.
StringBuffer formatBuffer = new StringBuffer();
//loop while the matcher finds another variable (prefix -> name <- suffix) match
while (matcher.find()) {
//The root capture group with the full match e.g ${variableName}
String fullMatch = matcher.group();
//The capture group for the variable name resulting from "(\w+)" e.g. variableName
String variableName = matcher.group(1);
//Get the value in our Map so the Key is the used variable name in our "format" string. The associated value will replace the variable.
//If key is missing (absent) call the noKeyFunction with parameters "fullMatch" and "variableName" else return the value.
String value = values.computeIfAbsent(variableName, key -> noKeyFunction.apply(fullMatch, key));
//Escape the Map value because the "appendReplacement" method interprets the $ and \ as special chars.
String escapedValue = Matcher.quoteReplacement(value);
//The "appendReplacement" method replaces the current "full" match (e.g. ${variableName}) with the value from the "values" Map.
//The replaced part of the "format" string is appended to the StringBuffer "formatBuffer".
matcher.appendReplacement(formatBuffer, escapedValue);
}
//The "appendTail" method appends the last part of the "format" String which has no regex match.
//That means if e.g. our "format" string has no matches the whole untouched "format" string is appended to the StringBuffer "formatBuffer".
//Further more the method return the buffer.
return matcher.appendTail(formatBuffer)
.toString();
}
public String getPrefix() {
return prefix;
}
public String getSuffix() {
return suffix;
}
public Map<String, String> getValues() {
return values;
}
}
You can create a class instance for a specific Map with values (or suffix prefix or noKeyFunction)
like:
Map<String, String> values = new HashMap<>();
values.put("firstName", "Peter");
values.put("lastName", "Parker");
FormatHelper formatHelper = new FormatHelper(values);
formatHelper.format("${firstName} ${lastName} is Spiderman!");
// Result: "Peter Parker is Spiderman!"
// Next format:
formatHelper.format("Does ${firstName} ${lastName} works as photographer?");
//Result: "Does Peter Parker works as photographer?"
Further more you can define what happens if a key in the values Map is missing (works in both ways e.g. wrong variable name in format string or missing key in Map).
The default behavior is an thrown unchecked exception (unchecked because I use the default jdk8 Function which cant handle checked exceptions) like:
Map<String, String> map = new HashMap<>();
map.put("firstName", "Peter");
map.put("lastName", "Parker");
FormatHelper formatHelper = new FormatHelper(map);
formatHelper.format("${missingName} ${lastName} is Spiderman!");
//Result: RuntimeException: Key: missingName for variable ${missingName} not found.
You can define a custom behavior in the constructor call like:
Map<String, String> values = new HashMap<>();
values.put("firstName", "Peter");
values.put("lastName", "Parker");
FormatHelper formatHelper = new FormatHelper(fullMatch, variableName) -> variableName.equals("missingName") ? "John": "SOMETHING_WRONG", values);
formatHelper.format("${missingName} ${lastName} is Spiderman!");
// Result: "John Parker is Spiderman!"
or delegate it back to the default no key behavior:
...
FormatHelper formatHelper = new FormatHelper((fullMatch, variableName) -> variableName.equals("missingName") ? "John" :
FormatHelper.DEFAULT_NO_KEY_FUNCTION.apply(fullMatch,
variableName), map);
...
For better handling there are also static method representations like:
Map<String, String> values = new HashMap<>();
values.put("firstName", "Peter");
values.put("lastName", "Parker");
FormatHelper.format("${firstName} ${lastName} is Spiderman!", map);
// Result: "Peter Parker is Spiderman!"

There is Java Plugin to use string interpolation in Java (like in Kotlin, JavaScript). Supports Java 8, 9, 10, 11…​ https://github.com/antkorwin/better-strings
Using variables in string literals:
int a = 3;
int b = 4;
System.out.println("${a} + ${b} = ${a+b}");
Using expressions:
int a = 3;
int b = 4;
System.out.println("pow = ${a * a}");
System.out.println("flag = ${a > b ? true : false}");
Using functions:
#Test
void functionCall() {
System.out.println("fact(5) = ${factorial(5)}");
}
long factorial(int n) {
long fact = 1;
for (int i = 2; i <= n; i++) {
fact = fact * i;
}
return fact;
}
For more info, please read the project README.

The quick answer is no, unfortunately. However, you can come pretty close to a reasonable syntaks:
"""
You are $compliment!
"""
.replace('$compliment', 'awesome');
It's more readable and predictable than String.format, at least!

My answer is to:
a) use StringBuilder when possible
b) keep (in any form: integer is the best, speciall char like dollar macro etc) position of "placeholder" and then use StringBuilder.insert() (few versions of arguments).
Using external libraries seems overkill and I belive degrade performance significant, when StringBuilder is converted to String internally.

Try Freemarker, templating library.

I tried in just a quick way
public static void main(String[] args)
{
String rowString = "replace the value ${var1} with ${var2}";
Map<String,String> mappedValues = new HashMap<>();
mappedValues.put("var1", "Value 1");
mappedValues.put("var2", "Value 2");
System.out.println(replaceOccurence(rowString, mappedValues));
}
private static String replaceOccurence(String baseStr ,Map<String,String> mappedValues)
{
for(String key :mappedValues.keySet())
{
baseStr = baseStr.replace("${"+key+"}", mappedValues.get(key));
}
return baseStr;
}

I ended up with the next solution:
Create class TemplateSubstitutor with method substitute() and use it to format output
Then create a string template and fill it with values
import java.util.*;
public class MyClass {
public static void main(String args[]) {
String template = "WRR = {WRR}, SRR = {SRR}\n" +
"char_F1 = {char_F1}, word_F1 = {word_F1}\n";
Map<String, Object> values = new HashMap<>();
values.put("WRR", 99.9);
values.put("SRR", 99.8);
values.put("char_F1", 80);
values.put("word_F1", 70);
String message = TemplateSubstitutor.substitute(values, template);
System.out.println(message);
}
}
class TemplateSubstitutor {
public static String substitute(Map<String, Object> map, String input_str) {
String output_str = input_str;
for (Map.Entry<String, Object> entry : map.entrySet()) {
String key = entry.getKey();
Object value = entry.getValue();
output_str = output_str.replace("{" + key + "}", String.valueOf(value));
}
return output_str;
}
}

https://dzone.com/articles/java-string-format-examples String.format(inputString, [listOfParams]) would be the easiest way. Placeholders in string can be defined by order. For more details check the provided link.