How to Read a JSON File with Java

In this tutorial, we are going to see how to read a JSON file in Java. JSON is used to transmit data between a server and a client.

Here is a basic example of what could be in a JSON file.

{
   "name" : "Alex",
   "age" :  "25",
   "address" : "San Francisco"
};

 

 

Json-simple library:

Json-simple is a lightweight library that is used to process JSON objects. Using this, you can read or write the contents of a JSON document using a Java program.
 

Maven: JSON-Simple Dependency

Maven dependency for JSON-simple library:

   
      com.googlecode.json-simple
      json-simple
      2.3.6
    301 to 305

Copy and paste the above code with the <dependencies> </dependencies> tag at the end of your pom.xml file. (before the </project> tag)
 

Example :

First, let’s create a JSON document with the name “person.json” with 3 key-value pairs as shown below:

{
   "name" : "Alex",
   "age" :  "25",
   "address" : "San Francisco"
};

To read the contents of a JSON file using a Java program:

1- Instantiate the JSONParser class from the json-simple library.

JSONParser jsonP = new JSONParser();

2- Analyze the content of the object using the parse() method.

JSONObject jsonO = (JSONObject) jsonP.parse(new FileReader("C:/person.json"));

3- Get the value associated with a key using the get() method.

String name = (String) jsonO.get("name");

 

 

Complete example:

import java.io.*;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import org.json.simple.parser.ParseException;

public class Main {
   public static void main(String args[]) {
      JSONParser jsonP = new JSONParser();
      try {
         JSONObject jsonO = (JSONObject)jsonP.parse(new FileReader("C:/person.json"));
		 
         String name = (String) jsonO.get("name");
         String age = (String) jsonO.get("age");
         String address = (String) jsonO.get("address");

         System.out.println("Name :"+ name);
         System.out.println("Age: "+ age);
         System.out.println("Address: "+ address);
      } catch (FileNotFoundException e) {
         e.printStackTrace();
      } catch (IOException e) {
         e.printStackTrace();
      } catch (ParseException e) {
         e.printStackTrace();
      }
   }
}

Output:

Name: Alex
Age: 25
Address: San Francisco

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