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How to create Junit testcases for lambda expression using Mockito Junit 5?

I want to create Junit TestCases of method, in which we are iterating List<Map<String,Object>> using forEach loop with lambda expresion. Now I want to mock statement objectMapper.writeValueAsString(recordObj.get("value")); but I am not understanding how to use recordObj.
public String apply(MyRequestWrapper requestWrapper) {
String resultStr=null;
final Map<String, List<PubSubEvent>> packagesEventList = AppUtilities.getPackagesEventsMappedList();
try {
logger.debug("Received Record:: " + requestWrapper.getBody().toString());
List<RecordProcessedResult> results = new ArrayList<>();
List<Map<String,Object>> recordMaps= string2List(objectMapper,requestWrapper.getBody().toString());
logger.debug("Parsed received payload ::: "+ LocalDateTime.now() + " batch size is ::: "+ recordMaps.size());
if(! ObjectUtils.isEmpty(recordMaps) && !recordMaps.isEmpty() ) {
recordMaps.forEach(recordObj ->{
ConsumerRecord record=objectMapper.convertValue(recordObj, ConsumerRecord.class);
String topicName = recordObj.get("topic").toString();
String key = null;
String value = null;
String offset = null;
String xTraceabilityId = ((Map<String, String>) recordObj.get("headers")).get(IdTypeConstants.XTRACEABILITYID);
String xCorrelationId = ((Map<String, String>) recordObj.get("headers")).get(IdTypeConstants.XCORRELATIONID);
MDC.put(IdTypeConstants.XTRACEABILITYID, xTraceabilityId);
MDC.put(IdTypeConstants.XCORRELATIONID, xCorrelationId);
try {
key = objectMapper.writeValueAsString(recordObj.get("key"));
value = objectMapper.writeValueAsString(recordObj.get("value"));
offset = objectMapper.writeValueAsString(recordObj.get("offset"));
MyEvent myEvent= objectMapper.readValue(value, MyEvent.class);
subscribedPackageProcessor.setInput(input);
subscribedPackageProcessor.setOutput(output);
subscribedPackageProcessor.setPackagesEventList(packagesEventList);
subscribedPackageProcessor.setRequesterType(requesterType); subscribedPackageProcessor.processSubscribedPackage(myEvent.getPackageId());
RecordProcessedResult rpr = new RecordProcessedResult(record, true, null, xTraceabilityId, xCorrelationId, key, System.currentTimeMillis());
results.add(rpr);
}
catch(Exception e) {
RecordProcessedResult rpr = new RecordProcessedResult(record, false, ExceptionUtils.getStackTrace(e), xTraceabilityId, xCorrelationId, key, System.currentTimeMillis());
results.add(rpr);
logger.info("Exception occured while processing fund data :::out ", e);
}
MDC.clear();
});
}
resultStr = objectMapper.writeValueAsString(results);
}catch (Exception e) {
logger.debug(e.getMessage());
}
return resultStr;
}
I have tried following testcases.
#Test void applyTest() throws Exception {
MyEvent myEvent = new MyEvent();
myEvent.setPackageId("test");
MyRequestWrapper flowRequestWrapper= getMyRequestWrapper();
List<Map<String, Object>> maps = string2List(objectMapper1, flowRequestWrapper.getBody().toString());
Map<String,Object> map = new HashMap<String, Object>();
Mockito.when(objectMapper.readValue(Mockito.anyString(), Mockito.any(TypeReference.class))).thenReturn(maps);
Mockito.when(objectMapper.writeValueAsString(Mockito.anyString())).thenReturn("test");
Mockito.when(objectMapper.readValue(Mockito.anyString(), Mockito.eq(MyEvent.class))).thenReturn(myEvent);
//doNothing().when(subscribedPackageProcessor).processSubscribedPackage("");
String response = processESignCompletedEventSvcFlow.apply(flowRequestWrapper);
Assertions.assertNotNull(response);
}
Please help, Thanks

Your method is way too complex to be unit tested. For example it declares dependencies by calling methods in the same class. You cannot mock those and it makes the testing many times more complicated.
List<Map<String,Object>> recordMaps =
string2List(objectMapper,requestWrapper.getBody().toString());
You need to extract the string2List method into a standalone class (with it's own unit tests) that is injected into your class as a dependency.
Then you can just mock the string2List class and when you do that, you control the creation of recordObj instances from your unit test for this method.
Your second "sin" is abusing lambdas by creating one that is longer than two lines. Lambdas should be short. If it spans more than a few lines, it must be extracted into a standalone class that can be unit tested separately. And again, when you have extracted this lambda into a standalone class and unit tested it, you can't just go "new RecordObjConsumer(results)" in your method, as that creates a hard-coded dependency that you again cannot mock. You need to design the consumer so that it can be injected into your class as an external dependency.

TestNG data provider convert object 2d array to Hashtable - throws MethodMatcherException

I have Data provider defined to get the data from excel sheet and passing it to the test method of testing. I am able to get and read data from excel but when passing it to the testing method under test it throws MethodMatcherException
Code from dataProvider
#DataProvider(name = "testdatasupply")
public Object[][] ReadDetails() throws IOException {
HashMap<String,String> rowdata=new HashMap<String,String>();
File file=new File("src/main/resources/TestData.xlsx");
FileInputStream fis=new FileInputStream(file);
XSSFWorkbook wb= new XSSFWorkbook(fis);
XSSFSheet sheet=wb.getSheet("API");
Row key=sheet.getRow(0);
int rowcount=sheet.getPhysicalNumberOfRows();
int columncount=key.getLastCellNum();
Object[][] data1 =new Object[rowcount][columncount];
for(int i=0;i<sheet.getPhysicalNumberOfRows()-1;i++) {
Row row = sheet.getRow(i+1);
if(row.getCell(2).getStringCellValue().equalsIgnoreCase("Yes")){
for (int j = 0; j < row.getLastCellNum(); j++) {
rowdata.put(key.getCell(j).getStringCellValue(), row.getCell(j).getStringCellValue());
}
data1[i][0]=rowdata;
System.out.println(data1[i][0]);
}
}
return data1;
}
And my testing class under test .
#Test(dataProvider = "testdatasupply",dataProviderClass = TestData.ReadData.class)
public void APITesting(Hashtable<String,String> data){
System.out.println(data);
String API= data.get("API Name");
switch (API.toLowerCase()){
case "petstore/get":
System.out.println(data.get("ID"));
case "petstore/post":
System.out.println(data.get("ID")+"from secnd");
}
}
When I run above code, I am getting org.testng.internal.reflect.MethodMatcherException: which shows return type is not matching as expected. Since I have more columns , getting it as individual string is not helping as I have to create more number of variables.
[public void TestRunner.main.testrunner.APITesting(java.util.Hashtable)] has no parameters defined but was found to be using a data provider (either explicitly specified or inherited from class level annotation).
Data provider mismatch
Method: APITesting([Parameter{index=0, type=java.util.Hashtable, declaredAnnotations=[]}])
Can anyone suggest best way to get this as Hashtable or what I am doing wrong here?

Your dataprovider returns a HashMap for each test, while your test method expects a parameter of type Hashtable. These two are different data types. But both have a common interface Map.
So, in your test method, change as below:
public void APITesting(Map<String,String> data)
In your data provider change as: (not required, but recommended):
Map<String,String> rowdata=new HashMap<String,String>();
Also, your code dataprovider code has some issues - The same map, rowdata is being used inside the loop, So for every test run the data passed to the test method would be the same since you are doing data1[i][0]=rowdata; within the i loop.
I assume you should be doing:
for(int i=0;i<sheet.getPhysicalNumberOfRows()-1;i++) {
Row row = sheet.getRow(i+1);
// initialize the map here.
Map<String,String> rowdata=new HashMap<String,String>();
if(row.getCell(2).getStringCellValue().equalsIgnoreCase("Yes")){
for (int j = 0; j < row.getLastCellNum(); j++) {
rowdata.put(key.getCell(j).getStringCellValue(), row.getCell(j).getStringCellValue());
}
data1[i][0]=rowdata;
System.out.println(data1[i][0]);
}
}

Your code seems incorrect and you can do the following things:
1). First Solution:
a) #Test method cannot have public void APITesting(Hashtable<String,String> data) try to replace it with public void APITesting(String API, String ID)
b) In the data provider try to return the ID and API. You need to parse data before returning it. In the dataprovider method you need to get the API and ID and then pass it to the #test method.
data1[i][0]=APIData;
data1[i][1]=ID;
Code:
#Test(dataProvider = "testdatasupply",dataProviderClass = TestData.ReadData.class)
public void APITesting(String API, String ID) {
switch (API.toLowerCase()) {
case "petstore/get":
System.out.println(ID);
case "petstore/post":
System.out.println(ID + "from secnd");
}
}
2) Second Solution:
As you cannot pass the public void APITesting(Hashtable<String,String> data) try to again replace it with public void APITesting(String data) and then convert the string to hashtable again.
Code:
#Test(dataProvider = "testdatasupply",dataProviderClass = TestData.ReadData.class)
public void APITesting(String data) {
String a = data.toString();
a = a.replaceAll("[{}]","");
System.out.println(a);
// New HashTable obj
Hashtable<String, String> hashTable
= new Hashtable<String, String>();
// split the String by a comma
String parts[] = a.split(",");
// iterate the parts and add them to a HashTable
for (String part : parts) {
String subData[] = part.split("=");
String api = subData[0].trim();
String id = subData[1].trim();
// Add to hashTable
hashTable.put(api, id);
}
System.out.println("String to HashTable: " + hashTable);
System.out.println(hashTable.get("API"));
System.out.println(hashTable.get("id"));
String API= hashTable.get("API Name");
switch (API.toLowerCase()){
case "petstore/get":
System.out.println(hashTable.get("ID"));
case "petstore/post":
System.out.println(hashTable.get("ID")+"from secnd");
}
}

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.

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.

Parsing query strings on Android

Java EE has ServletRequest.getParameterValues().
On non-EE platforms, URL.getQuery() simply returns a string.
What's the normal way to properly parse the query string in a URL when not on Java EE?
It is popular in the answers to try and make your own parser. This is very interesting and exciting micro-coding project, but I cannot say that it is a good idea.
The code snippets below are generally flawed or broken. Breaking them is an interesting exercise for the reader. And to the hackers attacking the websites that use them.
Parsing query strings is a well defined problem but reading the spec and understanding the nuances is non-trivial. It is far better to let some platform library coder do the hard work, and do the fixing, for you!

On Android:
import android.net.Uri;
[...]
Uri uri=Uri.parse(url_string);
uri.getQueryParameter("para1");

Since Android M things have got more complicated. The answer of android.net.URI.getQueryParameter() has a bug which breaks spaces before JellyBean.
Apache URLEncodedUtils.parse() worked, but was deprecated in L, and removed in M.
So the best answer now is UrlQuerySanitizer. This has existed since API level 1 and still exists. It also makes you think about the tricky issues like how do you handle special characters, or repeated values.
The simplest code is
UrlQuerySanitizer.ValueSanitizer sanitizer = UrlQuerySanitizer.getAllButNullLegal();
// remember to decide if you want the first or last parameter with the same name
// If you want the first call setPreferFirstRepeatedParameter(true);
sanitizer.parseUrl(url);
String value = sanitizer.getValue("paramName");
If you are happy with the default parsing behavior you can do:
new UrlQuerySanitizer(url).getValue("paramName")
but you should make sure you understand what the default parsing behavor is, as it might not be what you want.

On Android, the Apache libraries provide a Query parser:
http://developer.android.com/reference/org/apache/http/client/utils/URLEncodedUtils.html and http://hc.apache.org/httpcomponents-client-ga/httpclient/apidocs/org/apache/http/client/utils/URLEncodedUtils.html

public static Map<String, List<String>> getUrlParameters(String url)
throws UnsupportedEncodingException {
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("=", 2);
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;
}

If you have jetty (server or client) libs on your classpath you can use the jetty util classes (see javadoc), e.g.:
import org.eclipse.jetty.util.*;
URL url = new URL("www.example.com/index.php?foo=bar&bla=blub");
MultiMap<String> params = new MultiMap<String>();
UrlEncoded.decodeTo(url.getQuery(), params, "UTF-8");
assert params.getString("foo").equals("bar");
assert params.getString("bla").equals("blub");

If you're using Spring 3.1 or greater (yikes, was hoping that support went back further), you can use the UriComponents and UriComponentsBuilder:
UriComponents components = UriComponentsBuilder.fromUri(uri).build();
List<String> myParam = components.getQueryParams().get("myParam");
components.getQueryParams() returns a MultiValueMap<String, String>
Here's some more documentation.

I have methods to achieve this:
1):
public static String getQueryString(String url, String tag) {
String[] params = url.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);
}
Set<String> keys = map.keySet();
for (String key : keys) {
if(key.equals(tag)){
return map.get(key);
}
System.out.println("Name=" + key);
System.out.println("Value=" + map.get(key));
}
return "";
}
2) and the easiest way to do this Using Uri class:
public static String getQueryString(String url, String tag) {
try {
Uri uri=Uri.parse(url);
return uri.getQueryParameter(tag);
}catch(Exception e){
Log.e(TAG,"getQueryString() " + e.getMessage());
}
return "";
}
and this is an example of how to use either of two methods:
String url = "http://www.jorgesys.com/advertisements/publicidadmobile.htm?position=x46&site=reform&awidth=800&aheight=120";
String tagValue = getQueryString(url,"awidth");
the value of tagValue is 800

For a servlet or a JSP page you can get querystring key/value pairs by using request.getParameter("paramname")
String name = request.getParameter("name");
There are other ways of doing it but that's the way I do it in all the servlets and jsp pages that I create.

On Android, I tried using #diyism answer but I encountered the space character issue raised by #rpetrich, for example:
I fill out a form where username = "us+us" and password = "pw pw" causing a URL string to look like:
http://somewhere?username=us%2Bus&password=pw+pw
However, #diyism code returns "us+us" and "pw+pw", i.e. it doesn't detect the space character. If the URL was rewritten with %20 the space character gets identified:
http://somewhere?username=us%2Bus&password=pw%20pw
This leads to the following fix:
Uri uri = Uri.parse(url_string.replace("+", "%20"));
uri.getQueryParameter("para1");

Parsing the query string is a bit more complicated than it seems, depending on how forgiving you want to be.
First, the query string is ascii bytes. You read in these bytes one at a time and convert them to characters. If the character is ? or & then it signals the start of a parameter name. If the character is = then it signals the start of a paramter value. If the character is % then it signals the start of an encoded byte. Here is where it gets tricky.
When you read in a % char you have to read the next two bytes and interpret them as hex digits. That means the next two bytes will be 0-9, a-f or A-F. Glue these two hex digits together to get your byte value. But remember, bytes are not characters. You have to know what encoding was used to encode the characters. The character é does not encode the same in UTF-8 as it does in ISO-8859-1. In general it's impossible to know what encoding was used for a given character set. I always use UTF-8 because my web site is configured to always serve everything using UTF-8 but in practice you can't be certain. Some user-agents will tell you the character encoding in the request; you can try to read that if you have a full HTTP request. If you just have a url in isolation, good luck.
Anyway, assuming you are using UTF-8 or some other multi-byte character encoding, now that you've decoded one encoded byte you have to set it aside until you capture the next byte. You need all the encoded bytes that are together because you can't url-decode properly one byte at a time. Set aside all the bytes that are together then decode them all at once to reconstruct your character.
Plus it gets more fun if you want to be lenient and account for user-agents that mangle urls. For example, some webmail clients double-encode things. Or double up the ?&= chars (for example: http://yoursite.com/blah??p1==v1&&p2==v2). If you want to try to gracefully deal with this, you will need to add more logic to your parser.

On Android its simple as the code below:
UrlQuerySanitizer sanitzer = new UrlQuerySanitizer(url);
String value = sanitzer.getValue("your_get_parameter");
Also if you don't want to register each expected query key use:
sanitzer.setAllowUnregisteredParamaters(true)
Before calling:
sanitzer.parseUrl(yourUrl)

On Android, you can use the Uri.parse static method of the android.net.Uri class to do the heavy lifting. If you're doing anything with URIs and Intents you'll want to use it anyways.

Just for reference, this is what I've ended up with (based on URLEncodedUtils, and returning a Map).
Features:
it accepts the query string part of the url (you can use request.getQueryString())
an empty query string will produce an empty Map
a parameter without a value (?test) will be mapped to an empty List<String>
Code:
public static Map<String, List<String>> getParameterMapOfLists(String queryString) {
Map<String, List<String>> mapOfLists = new HashMap<String, List<String>>();
if (queryString == null || queryString.length() == 0) {
return mapOfLists;
}
List<NameValuePair> list = URLEncodedUtils.parse(URI.create("http://localhost/?" + queryString), "UTF-8");
for (NameValuePair pair : list) {
List<String> values = mapOfLists.get(pair.getName());
if (values == null) {
values = new ArrayList<String>();
mapOfLists.put(pair.getName(), values);
}
if (pair.getValue() != null) {
values.add(pair.getValue());
}
}
return mapOfLists;
}
A compatibility helper (values are stored in a String array just as in ServletRequest.getParameterMap()):
public static Map<String, String[]> getParameterMap(String queryString) {
Map<String, List<String>> mapOfLists = getParameterMapOfLists(queryString);
Map<String, String[]> mapOfArrays = new HashMap<String, String[]>();
for (String key : mapOfLists.keySet()) {
mapOfArrays.put(key, mapOfLists.get(key).toArray(new String[] {}));
}
return mapOfArrays;
}

This works for me..
I'm not sure why every one was after a Map, List>
All I needed was a simple name value Map.
To keep things simple I used the build in URI.getQuery();
public static Map<String, String> getUrlParameters(URI uri)
throws UnsupportedEncodingException {
Map<String, String> params = new HashMap<String, String>();
for (String param : uri.getQuery().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");
}
params.put(new String(key), new String(value));
}
return params;
}

Guava's Multimap is better suited for this. Here is a short clean version:
Multimap<String, String> getUrlParameters(String url) {
try {
Multimap<String, String> ret = ArrayListMultimap.create();
for (NameValuePair param : URLEncodedUtils.parse(new URI(url), "UTF-8")) {
ret.put(param.getName(), param.getValue());
}
return ret;
} catch (URISyntaxException e) {
throw new RuntimeException(e);
}
}

Origanally answered here
On Android, there is Uri class in package android.net . Note that Uri is part of android.net, while URI is part of java.net .
Uri class has many functions to extract query key-value pairs.
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
}

Apache AXIS2 has a self-contained implementation of QueryStringParser.java. If you are not using Axis2, just download the sourcecode and test case from here -
http://svn.apache.org/repos/asf/axis/axis2/java/core/trunk/modules/kernel/src/org/apache/axis2/transport/http/util/QueryStringParser.java
http://svn.apache.org/repos/asf/axis/axis2/java/core/trunk/modules/kernel/test/org/apache/axis2/transport/http/util/QueryStringParserTest.java

if (queryString != null)
{
final String[] arrParameters = queryString.split("&");
for (final String tempParameterString : arrParameters)
{
final String[] arrTempParameter = tempParameterString.split("=");
if (arrTempParameter.length >= 2)
{
final String parameterKey = arrTempParameter[0];
final String parameterValue = arrTempParameter[1];
//do something with the parameters
}
}
}

I don't think there is one in JRE. You can find similar functions in other packages like Apache HttpClient. If you don't use any other packages, you just have to write your own. It's not that hard. Here is what I use,
public class QueryString {
private Map<String, List<String>> parameters;
public QueryString(String qs) {
parameters = new TreeMap<String, List<String>>();
// Parse query string
String pairs[] = qs.split("&");
for (String pair : pairs) {
String name;
String value;
int pos = pair.indexOf('=');
// for "n=", the value is "", for "n", the value is null
if (pos == -1) {
name = pair;
value = null;
} else {
try {
name = URLDecoder.decode(pair.substring(0, pos), "UTF-8");
value = URLDecoder.decode(pair.substring(pos+1, pair.length()), "UTF-8");
} catch (UnsupportedEncodingException e) {
// Not really possible, throw unchecked
throw new IllegalStateException("No UTF-8");
}
}
List<String> list = parameters.get(name);
if (list == null) {
list = new ArrayList<String>();
parameters.put(name, list);
}
list.add(value);
}
}
public String getParameter(String name) {
List<String> values = parameters.get(name);
if (values == null)
return null;
if (values.size() == 0)
return "";
return values.get(0);
}
public String[] getParameterValues(String name) {
List<String> values = parameters.get(name);
if (values == null)
return null;
return (String[])values.toArray(new String[values.size()]);
}
public Enumeration<String> getParameterNames() {
return Collections.enumeration(parameters.keySet());
}
public Map<String, String[]> getParameterMap() {
Map<String, String[]> map = new TreeMap<String, String[]>();
for (Map.Entry<String, List<String>> entry : parameters.entrySet()) {
List<String> list = entry.getValue();
String[] values;
if (list == null)
values = null;
else
values = (String[]) list.toArray(new String[list.size()]);
map.put(entry.getKey(), values);
}
return map;
}
}

public static Map <String, String> parseQueryString (final URL url)
throws UnsupportedEncodingException
{
final Map <String, String> qps = new TreeMap <String, String> ();
final StringTokenizer pairs = new StringTokenizer (url.getQuery (), "&");
while (pairs.hasMoreTokens ())
{
final String pair = pairs.nextToken ();
final StringTokenizer parts = new StringTokenizer (pair, "=");
final String name = URLDecoder.decode (parts.nextToken (), "ISO-8859-1");
final String value = URLDecoder.decode (parts.nextToken (), "ISO-8859-1");
qps.put (name, value);
}
return qps;
}

Use Apache HttpComponents and wire it up with some collection code to access params by value: http://www.joelgerard.com/2012/09/14/parsing-query-strings-in-java-and-accessing-values-by-key/

using Guava:
Multimap<String,String> parseQueryString(String queryString, String encoding) {
LinkedListMultimap<String, String> result = LinkedListMultimap.create();
for(String entry : Splitter.on("&").omitEmptyStrings().split(queryString)) {
String pair [] = entry.split("=", 2);
try {
result.put(URLDecoder.decode(pair[0], encoding), pair.length == 2 ? URLDecoder.decode(pair[1], encoding) : null);
} catch (UnsupportedEncodingException e) {
throw new RuntimeException(e);
}
}
return result;
}

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 the url is sent from a different activity where you set it to a value
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")
}

this method takes the uri and return map of par name and par value
public static Map<String, String> getQueryMap(String uri) {
String queryParms[] = uri.split("\\?");
Map<String, String> map = new HashMap<>();//
if (queryParms == null || queryParms.length == 0) return map;
String[] params = queryParms[1].split("&");
for (String param : params) {
String name = param.split("=")[0];
String value = param.split("=")[1];
map.put(name, value);
}
return map;
}

You say "Java" but "not Java EE". Do you mean you are using JSP and/or servlets but not a full Java EE stack? If that's the case, then you should still have request.getParameter() available to you.
If you mean you are writing Java but you are not writing JSPs nor servlets, or that you're just using Java as your reference point but you're on some other platform that doesn't have built-in parameter parsing ... Wow, that just sounds like an unlikely question, but if so, the principle would be:
xparm=0
word=""
loop
get next char
if no char
exit loop
if char=='='
param_name[xparm]=word
word=""
else if char=='&'
param_value[xparm]=word
word=""
xparm=xparm+1
else if char=='%'
read next two chars
word=word+interpret the chars as hex digits to make a byte
else
word=word+char
(I could write Java code but that would be pointless, because if you have Java available, you can just use request.getParameters.)