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How to parse JSON in Java
(36 answers)
Closed 5 years ago.
I have a Java String that contains a json object and I do not know how to get this json object from it?
My string is like this:
String myString = "[1,\"{\\\"Status\\\":0,\\\"InstanceNumber\\\":9}\"]";
How can i get the json object from this String?
I would recommend simple plain org.json library. Pass the string in JSONArray and then get the JSONObject. For example something like below :
String myString = "[1,\"{\\\"Status\\\":0,\\\"InstanceNumber\\\":9}\"]";
JSONArray js = new JSONArray(myString);
System.out.println(js);
JSONObject obj = new JSONObject(js.getString(1));
System.out.println(obj);
Output :
[1,"{\"Status\":0,\"InstanceNumber\":9}"]
{"Status":0,"InstanceNumber":9}
Downloadable jar: http://mvnrepository.com/artifact/org.json/json
For sure that you need to use a library lie Jackson or Gson.
I work mostly with gson when I don't have complicated stuff.
So here the output of what you are asking for. I suppose that you don't have the type that you want to convert to (for that I am taking Object).
Here is the code:
import com.google.gson.Gson;
public class Json {
public static void main(String[] args) {
Gson g = new Gson();
String myString = "[1,\"{\\\"Status\\\":0,\\\"InstanceNumber\\\":9}\"]";
Object p = g.fromJson(myString, Object.class);
System.out.println(p.toString());
}
}
And here is the output :
run:
[1.0, {"Status":0,"InstanceNumber":9}]
BUILD SUCCESSFUL (total time: 0 seconds)
You may wanting to manipulate the output object as you wish (I just printed it out).
NOTE: Don't forget to add gson jar to you classpath.
You can use any Json mapping framework to deserialise the String into Java object. Below example shows how to do it with Jackson:
String myString = "[1,\"{\\\"Status\\\":0,\\\"InstanceNumber\\\":9}\"]";
ObjectMapper mapper = new ObjectMapper();
List<Object> value = mapper.readValue(myString, new TypeReference<List<Object>>() {});
Map<String, Object> map = mapper.readValue(value.get(1).toString(), new TypeReference<Map<String, Object>>() {});
System.out.println(map);
Here's the documentation.
Related
I am using objectmapper to convert the class into json.
Following is the code:
JSONParser parser = new JSONParser();
ObjectMapper mapper = new ObjectMapper();
String obj = mapper.writeValueAsString(myClass);
JSONObject jsonObject = (JSONObject)parser.perse(obj);
now line number 4 where I get the jsobObject reshuffles the order of class member.
See the attached image, before it converting to jsonobject "authorisation" was first element then signatries.
But at line 4 it becomes 2nd ..... why ?
I want order to be preserved, that is the requirement of my project.
Please help !
You can configure the ordering this way :
#JsonPropertyOrder({ "authorisation", "signatoryDetails", "requestedLimits" })
public class MyClass { ... }
I tried to convert following JSON string into Array and got following error:
Exception in thread "AWT-EventQueue-0" java.lang.NoClassDefFoundError:
org/apache/commons/logging/LogFactory at
net.sf.json.AbstractJSON.(AbstractJSON.java:54) at
net.sf.json.util.CycleDetectionStrategy.(CycleDetect‌​ionStrategy.java:36)
at net.sf.json.JsonConfig.(JsonConfig.java:65) at
net.sf.json.JSONSerializer.toJSON(JSONSerializer.java:84)
JSON:
[
{
"file_name":"1.xml",
"file_ext":"application/octet-stream",
"sr_no":"0.1",
"status":"Checked ",
"rev":"1",
"locking":"0"
},
{
"file_name":"2.xml",
"file_ext":"json/octet-stream",
"sr_no":"0.2",
"status":"Not Checked ",
"rev":"2",
"locking":"1"
},
{
"file_name":"3.xml",
"file_ext":"application/json-stream",
"sr_no":"0.3",
"status":"Checked ",
"rev":"1",
"locking":"3"
},
{
"file_name":"4.xml",
"file_ext":"application/octet-stream",
"sr_no":"0.4",
"status":"Checked ",
"rev":"0.4",
"locking":"4"
}
]
Code:
JSONArray nameArray = (JSONArray) JSONSerializer.toJSON(output);
System.out.println(nameArray.size());
for(Object js : nameArray)
{
JSONObject json = (JSONObject) js;
System.out.println("File_Name :" +json.get("file_name"));
}
I know the question is about converting JSON String to Java Array, but I would like to also answer about how to convert the JSON String to an ArrayList using the Gson Library.
Since I spend a good amount of time in solving this, I hope my solution may help others.
My JSON string looks similar to this one -
I had an object named StockHistory, and I wanted to convert this JSON into an ArrayList of StockHistory.
This is how my StockHistory class looked -
class StockHistory {
Date date;
Double open;
Double high;
Double low;
Double close;
Double adjClose;
Double volume;
}
The code that I used to convert the JSON Array to the ArrayList of StockHistory is as follows -
Gson gson = new Gson();
Type listType = new TypeToken< ArrayList<StockHistory> >(){}.getType();
List<StockHistory> history = gson.fromJson(reader, listType);
Now if you are reading your JSON from a file, the reader's initialization would be -
Reader reader = new FileReader(fileName);
and if you are just converting a string to JSON object then, the reader's initialization would simply be -
String reader = "{ // json String }";
Hope that helps. Cheers!!!
You can create a java class with entities are: file_name, file_ext, sr_no, status, rev, locking in string type.
public class TestJson {
private String file_name, file_ext, sr_no, status, rev, locking;
//get & set
}
}
Then you call:
public static void main(String[] args) {
String json = your json string;
TestJson[] respone = new Gson().fromJson(json, TestJson[].class);
for (TestJson s : respone) {
System.out.println("File name: " + s.getFile_name());
}
}
So, you have a list of object you want.
Firstly I have to say your question is quite "ugly" and next time please improve your question's quality.
Answer:
Try to use com.fasterxml.jackson.databind.ObjectMapper
If you have a java class to describe your items in the list:
final ObjectMapper mapper = new ObjectMapper();
YourClass[] yourClasses = mapper.readValue(YourString, YourClass[].class);
Then convert the array to a List.
If you don't have a java class, just you LinkedHashMap instead.
I have tried with gson and Jackson parsers unfortunately I couldn't achieve what I wanted to.
{
"rateName": "My Special Rate",
"adjustments": [
{
"adjustmentType": "LOAN_AMOUNT_GREATER_THAN_550K",
"rate": 0.75
},
{
"adjustmentType": "AMORTIZATION_TERM_LESS_THAN_30_YEARS",
"rate": -0.2
}
],
"errorTypes": [],
"premiumTaxs": [],
"renewalPremiums": [],
"totalInitialRate": 1.95,
"optimumPricing": false,
"miPricingVO": null,
"rateCardId": "BALS_NR",
"ratingInfoBaseRate": 1.4
}
Above is the Json I want to parse. I want to create generic methods using which I can access a value by name easily. For example:
getName(rateName) - Should return 'My Special Rate'
getNameFromArray(adjustmentType, adjustments) - Should return
'LOAN_AMOUNT_GREATER_THAN_550K'
Is there a way to do this? It should be generic so that this can be applied on any Json file.
Additional info: I tried using Gson, but this parses the whole file and throws an error if it finds an array.
JsonReader j = new JsonReader(new FileReader("Path of Json"));
j.beginObject();
while (j.hasNext()) {
String name = j.nextName();
if (name.equals("rateName")) {
System.out.println(j.nextString());
}
System.out.println(name);
}
I tried with jackson and encountered the same as Gson.
JsonFactory jfactory = new JsonFactory();
JsonParser jParser = jfactory.createJsonParser("Path of Json");
while (jParser.nextToken() != JsonToken.END_OBJECT) {
System.out.println(jParser.getCurrentName());;
}
If you mean standard library when you say generic, then org.json would be that library.
Altough not as intuitive as GSON or Jackson, it is easy to use it:
JSONObject jsonData = new JSONObject(jsonString);
String rateName= jsonData.getString("rateName");//My Special Rate
To parse array you need to loop:
JSONArray adjustments = jsonData.getJSONArray("adjustments");
for(int i = 0; i < adjustments.length(); i++){
JSONObject adjustment = adjustments.getJSONObject(i);
String adjustmentType = adjustment.getString("adjustmentType");
}
Hi You can use JASON READER , it readers the JSON and map the data into a MAP .
Below is the URL to Download the JAR JASON READER.
https://drive.google.com/open?id=0BwyOcFBoJ5pueXdadFFMS2tjLVU
Below is the example -
package com;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
import com.JasonReader;
public class Test {
public static void main(String[] args) {
String request ="{\"rateName\": \"My Special Rate\",\"adjustments\":[{\"adjustmentType\": \"LOAN_AMOUNT_GREATER_THAN_550K\",\"rate\": 0.75},{\"adjustmentType\": \"AMORTIZATION_TERM_LESS_THAN_30_YEARS\",\"rate\": -0.2}],\"errorTypes\": [],\"premiumTaxs\": [],\"renewalPremiums\": [],\"totalInitialRate\": 1.95,\"optimumPricing\": false,\"miPricingVO\": null,\"rateCardId\": \"BALS_NR\",\"ratingInfoBaseRate\": 1.}";
//
Map<String,String> map =new HashMap<String,String>();
map=JasonReader.readJason(request,map);
//System.out.println(map);
for (Entry<String, String> entry : map.entrySet()) {
System.out.println(entry.getKey()+ "=" +entry.getValue());
}
}
}
OUTPUT -
rateCardId=BALS_NR
adjustments|rate1=-0.2
miPricingVO=null
adjustments|adjustmentType=LOAN_AMOUNT_GREATER_THAN_550K
adjustments|adjustmentType1=AMORTIZATION_TERM_LESS_THAN_30_YEARS
adjustments|rate=0.75
optimumPricing=false
totalInitialRate=1.95
rateName=My Special Rate
ratingInfoBaseRate=1.
You can use the standard JsonParser which is part of the javax.json package. This parser is part of Java EE since version 7 and you can use this parser without any additional library.
The parser allows you to navigate through a JSON structure using the so called 'pull parsing programming model'
JsonParser parser = Json.createParser(myJSON);
Event event = parser.next(); // START_OBJECT
event = parser.next(); // KEY_NAME
String key = parser.getString(); // 'rateName'
event = parser.next(); // STRING_VALUE
String value=parser.getString(); // 'My Special Rate'
event = parser.next(); // START_ARRAY
....
But of course you need to navigate through your json data structure
Or you can just use Jodd JSON parser. You just need to deserialize the input string and the result will be collected in regular Map and List.
JsonParser jsonParser = new JsonParser();
Map<String, Object> map = jsonParser.parse(input);
Simple as that - and the result is the most generic as it can be. Then just call map.get("rateName") to get your value and so on.
But notice that for adjustments you can get the way you want without some util method that would iterate elements and search for the right one. If you can, change the JSON so that you dont have an array of adjustments, but a map.
If you need specific results, just pass the type with the input string. See more about parsing features.
I have the following string
["xyz#live.com","abc#live.com"]
I am using String.split(",") to get String[]. But array contents consist of '[' and '"'.
I need to get the actual strings with out quotes. Is there a library or method with which I can do it?
At present I am doing like this.
recipients = recipients.replace("\"", "");
recipients = recipients.replace("[", "");
recipients = recipients.replace("]", "");
String[] totalRecipients = recipients.split(",");
De-serialize the json string to java object using boon or jackson 3rd party library.
Boon Example -
ObjectMapper mapper = JsonFactory.create();
String[] recipientArray = mapper.readValue(recipients , String[].class, String.class);
Find Java Boon vs jackson json - Benchmarks - here
Source : Link
I suggest you to use json library to solve it.
http://jackson.codehaus.org/
String s = "[\"xyz#live.com\",\"abc#live.com\"]";
ObjectMapper mapper = new ObjectMapper();
JsonNode node = mapper.readValue(s);
for(JsonNode n : node){
.......
}
you can use of google's gson and to decode your json to String[] you can simply use this line of code
Gson gson = new Gson();
String[] myArray = gson.fromJson(yourjson,String[].class);
I have JSON string which is in a standalone Java project:
{"MsgType":"AB","TID":"1","ItemID":"34532136","TransactTime":1389260033223}
I want to extract MsgType from this which is AB
Which is the best way to do it?
You can use Gson library for this.
String json="{MsgType:AB,TID:1,ItemID:34532136,TransactTime:1389260033223}";
Map jsonJavaRootObject = new Gson().fromJson(json, Map.class);
System.out.println(jsonJavaRootObject.get("MsgType"));
where the jsonJavaRootObject will contain a map of keyvalues like this
{MsgType=AB, TID=1.0, ItemID=3.4532136E7, TransactTime=1.389260033223E12}
I use JSONObject under android but from Oracle docs I see its also available under javax.json package:
http://docs.oracle.com/javaee/7/api/javax/json/package-summary.html
If you want Gson then your code should look like below (sorry not compiled/tested):
/*
{"MsgType":"AB","TID":"1","ItemID":"34532136","TransactTime":1389260033223}
*/
Gson gson = new Gson();
static class Data{
String MsgType;
String TID;
String ItemID;
int TransactTime;
}
Data data = gson.fromJson(yourJsonString, Data.class);
I have an example with json-simple:
JSONParser parser = new JSONParser();
JSONObject jsonObject = (JSONObject) parser.parse(yourString);
String msgType = (String) jsonObject.get("MsgType");
Check this link for a complete example.
JsonPath
For parsing simple JSON use JsonPath
JsonPath is to JSON what XPATH is to XML, a simple way to extract parts of a given document.
Example code
String json = "{\"MsgType\":\"AB\",\"TID\":\"1\",\"ItemID\":\"34532136\",\"TransactTime\":1389260033223}";
String author = JsonPath.read(json, "$.MsgType");
System.out.println(author);
Result
AB
Dependency
'com.jayway.jsonpath:json-path:0.9.1'