Develop Reference

Failed to read JSON file in new IDE

I have an Eclipse project with the following code:
import org.json.*;
import org.json.simple.JSONObject;
import java.io.*;
import java.util.Iterator;
(...)
public static void main( String[] args )
{
String resourceName = "C:\\Users\\Snail_Sniffer\\Desktop\\books.json";
String jsonData = readFile(resourceName);
JSONObject jobj = new JSONObject(jsonData);
(...)
It produces no errors and works as intended, but when I reuse the same code in IntelliJ, it produces following errors:
Error:java: constructor JSONObject in class org.json.simple.JSONObject
cannot be applied to given types;
required: no arguments
found: java.lang.String
reason: actual and formal argument lists differ in length
Error:java: cannot find symbol
symbol: method getString(java.lang.String)
location: variable jobj of type org.json.simple.JSONObject
What is causing the issue and how to workaround it?

I'm not sure which library you are using in eclipse, but org.json.simple.JSONObject does not have constructor with String argument. It has only no argument constructor
public JSONObject()
If you want to parse json string using org.json.simple library you need JSONParser
JSONParser parser = new JSONParser();
JSONObject jsonObject = (JSONObject) parser.parse(jsonData);

Read JSON file with JSONParser not available in the jarfile

I am trying to read a json file and convert it to the jsonObject and when I searched on how to do it, I came across the method to user
JSONParser parser= new JSONParse();
But the version of org.json I am using in the code is "20180803". It does not contain JSONParser. Has it been removed from the org.json package? If so what is the new class or method that I could use to read a json file and convert it to a json object.
My dependency is given below :
<dependency>
<groupId>org.json</groupId>
<artifactId>json</artifactId>
<version>20180813</version>
</dependency>

Hi you can use simple JSON. You just need to add in your pom.xml file:
<dependency>
<groupId>com.googlecode.json-simple</groupId>
<artifactId>json-simple</artifactId>
</dependency>
Sample code
public static JSONObject convertJsonStingToJson(String jsonString) {
JSONParser parser = new JSONParser();
return json = (JSONObject) parser.parse(jsonString);
}

org.json library has very simple API which does not have JSONParser but has JSONTokener. We can construct JSONObject or JSONArray directly from String:
import org.json.JSONArray;
import org.json.JSONObject;
public class JsonApp {
public static void main(String[] args) {
// JSON Object
String object = "{\"p1\":\"v1\", \"p2\":2}";
JSONObject jsonObject = new JSONObject(object);
System.out.println(jsonObject);
// JSON Array
String array = "[{\"p1\":\"v1\", \"p2\":2}]";
JSONArray jsonArray = new JSONArray(array);
System.out.println(jsonArray);
}
}
Above code prints:
{"p1":"v1", "p2":2}
[{"p1":"v1","p2":2}]
You need to notice that it depends from JSON payload which class to use: if JSON starts from { use JSONObject, if from [ - use JSONArray. In other case JSON payload is invalid.
As it mentioned in other answers, if you can you should definitely use Jackson or Gson

Add following dependency in build file
//json processing
implementation("com.fasterxml.jackson.core:jackson-core:2.9.8")
implementation("com.fasterxml.jackson.core:jackson-annotations:2.9.8")
implementation("com.fasterxml.jackson.core:jackson-databind:2.9.8")
a.json file
{
"a": "b"
}
code:
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.FileInputStream;
import java.io.InputStream;
public class App {
public static void main(String[] args) throws Exception {
ObjectMapper objectMapper = new ObjectMapper();
InputStream input = new FileInputStream("a.json");
JsonNode obj = objectMapper.readTree(input);
System.out.println(obj.get("a")); // "b"
}
}

The short answer to your question is: No, it was not removed, because it never existed.
I think you are mentioning a library, and trying to use another one. Anyway, if you really want to use org.json, you can find how here
JSONObject jsonObject = new JSONObject(instanceOfClass1);
String myJson = jsonObject.toString();

How do I parse JSON objects from a JSONArray?

I have a very large JSON file in the following format:
[{"fullname": "name1", "id": "123"}, {"fullname": "name2", "id": "245"}, {"fullname": "name3", "id": "256"}]
It looks like a JSONArray. All the records are written in the same line.
Can you help me how can I parse this file using Java. I want to read each JSON object and display all the fullname and ids. Below is my attempt, but my code is not working:
import org.apache.commons.lang3.StringEscapeUtils;
import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import org.json.simple.parser.ParseException;
public class JSONFileReaderDriver {
public static void main(String[] args) throws FileNotFoundException,
IOException, ParseException
{
String filename="Aarau";
String src="C:\\"+filename+".json";
JSONParser parser = new JSONParser();
JSONObject obj;
try
{
BufferedReader br=new BufferedReader (new FileReader(src));
obj = (JSONObject) new JSONParser().parse(row);
String fullname=obj.get("fullname");
String id=obj.get("id");
System.out.println ("fullname: "+fullname+" id: "+id);
}catch(Exception e)
{e.printStackTrace();}
br.close();
}
}

Make your life easy and use an ObjectMapper.
This way you simply define a Pojo with the same properties as you json object.
In you case you need a Pojo that looks like this:
public class Person{
private String fullname;
private int id;
public Person(String fullname, int id) {
this.fullname = fullname;
this.id = id;
}
public String getFullname() {
return fullname;
}
public int getId() {
return id;
}
}
With that you only need to do:
ObjectMapper objectMapper = new ObjectMapper();
List<Person> persons = objectMapper.readValue(myInputStream, TypeFactory.defaultInstance().constructCollectionType(List.class, Person.class));
This is a hassle free and type safe approach.
Dependencies needed:
https://github.com/FasterXML/jackson-databind
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
</dependency>

you can use Json.simple java api , below is code that can helpful to you
byte[] bFile = Files.readAllBytes(new File("C:/xyz.json").toPath());
JSONArray root = (JSONArray) JSONValue.parseWithException(bFile);
JSONObject rootObj = (JSONObject) root.get(0);
You can get values from JSONObject based on key , it also depends on format of your json as there could be nested json data. So you have to extract data accordingly . Apart from this you can use jackson parser api or GSON as well.

Okay folks...just solved my problem. I am posting the solution in case someone runs into the same issue again, can use my solution. My solution is partly motivated by Rahul Rabhadiya. Thanks, dude.
try{
row=br.readLine();
JSONArray root = (JSONArray) JSONValue.parseWithException(row);
for (int i=0;i<root.size();i++)
{
JSONObject rootObj = (JSONObject) root.get(i);
String fullname=(String) rootObj.get("fullname");
System.out.println (fullname);
}
}catch(Exception e)
{
e.printStackTrace();
}

Your json is a JSONArray, so when you are parsing it, you need to parse it as a JSONArray.
JSONParser jsonParser = new JSONParser();
JSONArray a = (JSONArray) jsonParser.parse(new FileReader(src));
for (Object o : a) {
// access your object here.
}

I would suggest going with Jackson, in particular the Jackson Streaming API which is perfect for parsing large arrays like this.
See this answer: https://stackoverflow.com/a/24838392/3765428

URL issue with JSONObject

I've the following code, but when I am saving below JSON in database its giving me wrong url like {"#url#":"https:\/\/www.test.com\/test"}
import org.json.simple.JSONObject;
public class DemoURL {
private static String url = "https://www.test.com/test";
public static void main(String[] args) {
JSONObject msgJson = new JSONObject();
msgJson.put("#url#", url);
System.out.println(msgJson.toString());
}
}
I want url like {"#url#":"https://www.test.com/test"}
Please suggest how to fix it?

Here is the solution:
public class App{
private static String url = "https://www.test.com/test";
public static void main(String[] args) {
JSONObject msgJson = new JSONObject();
msgJson.put("#url#", url);
System.out.println(getCleanURL(msgJson.toString()));
}
private static String getCleanURL(String url){
return url.replaceAll("\\\\", "").trim();
}
}
This gives correct output, simply run this code. This will store exact value in the database.
{"#url#":"https://www.test.com/test"}

You are using org.json.simple JSON library. JSON-Simple escapes char from String.
You can't change this thing, as its not configurable.
But you can use org.json JSON library, this will not escape String, and good part is, you don't have to change your code, existing syntax will work fine.
e.g.
import org.json.JSONObject;
public class DemoURL {
private static String url = "https://www.test.com/test";
public static void main(String[] args) {
JSONObject msgJson = new JSONObject();
msgJson.put("#url#", url);
System.out.println(msgJson.toString());
}
}
output : {"#url#":"https://www.test.com/test"}

Try replacing slash(/) with unicode character \u2215 before passing it to JSON object.

try to quote the string with single quotes, something like this
JSONObject msgJson = new JSONObject();
msgJson.put("#url#", "\'"+url+"\'");
System.out.println(msgJson.toString());

How to drop keys from string json in java?

I have a json string like this:
{"a":"vala", "b":"valb", "c":"valc"}
I want to convert the above string to a JSONObject so that I can do something like:
testObject.remove("b");
testObject.remove("c");
So that I can easily print out the json string of:
{"a":"vala"}
What is the simplest way for me to do this?

org-json-java can do the things you want
import org.json.JSONException;
import org.json.JSONObject;
public class JsonTest {
public static void main(String[] args) {
try {
JSONObject testObject = new JSONObject("{\"a\":\"vala\", \"b\":\"valb\", \"c\":\"valc\"}");
testObject.remove("b");
testObject.remove("c");
System.out.println(testObject.toString()); // This prints out the json string
} catch (JSONException e) {
e.printStackTrace();
}
}
}
The execution result is
{"a":"vala"}
Make sure you've downloaded and imported org.json-YYYYMMDD.jar from here before you run the above code.

Firstly I think you need change title of question.
Secondly, If you want change from String to Json just using org.json library
JSONObject jsonObj = new JSONObject("{\"a\":\"valuea\",\"b\":\"valueb\"}");
Are you tried remove. http://www.json.org/javadoc/org/json/JSONObject.html#remove(java.lang.String)
Json.remove(key)