JSON.simple – How to parse JSON

In this tutorial, we will show you how to parse JSON with JSON.simple

Note
You may have interest to read – How to parse JSON with Jackson or Gson
JSON.simple short history
This project was formerly JSON.simple 1.x from a Google code project by Yidong, now maintaining by Clifton Labs, read this JSON.simple history

P.S Tested with json-simple 3.1.0

1. Download JSON.simple

pom.xml

	<dependency>
		<groupId>com.github.cliftonlabs</groupId>
		<artifactId>json-simple</artifactId>
		<version>3.1.0</version>
	</dependency>

2. POJO + Jsonable

2.1 To convert Java objects to/from JSON, The JSON.simple requires POJO to implement Jsonable, and override toJson()

Staff.java

package com.mkyong;

import com.github.cliftonlabs.json_simple.JsonObject;
import com.github.cliftonlabs.json_simple.Jsonable;

import java.io.IOException;
import java.io.StringWriter;
import java.io.Writer;
import java.math.BigDecimal;
import java.util.Arrays;
import java.util.List;
import java.util.Map;

public class Staff implements Jsonable {

    private String name;
    private int age;
    private String[] position;
    private List<String> skills;
    private Map<String, BigDecimal> salary;

    //..getters setters

    @Override
    public String toJson() {
        final StringWriter writable = new StringWriter();
        try {
            this.toJson(writable);
        } catch (final IOException e) {
        }
        return writable.toString();
    }

    @Override
    public void toJson(Writer writer) throws IOException {

        final JsonObject json = new JsonObject();
        json.put("name", this.getName());
        json.put("age", this.getAge());
        json.put("position", this.getPosition());
        json.put("skills", this.getSkills());
        json.put("salary", this.getSalary());
        json.toJson(writer);

    }
}

3. Java objects to JSON

3.1 Convert a Java object to JSON string and save as .json file.

JsonSimple1.java

package com.mkyong;

import com.github.cliftonlabs.json_simple.Jsoner;

import java.io.FileWriter;
import java.io.IOException;
import java.math.BigDecimal;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

public class JsonSimple1 {

    public static void main(String[] args) throws IOException {

        Staff staff = createStaff();

        // Java objects to JSON String
        String json = Jsoner.serialize(staff);

        // pretty print
        json = Jsoner.prettyPrint(json);

        System.out.println(json);

        // Java objects to JSON file
        try (FileWriter fileWriter = new FileWriter("C:\\projects\\user3.json")) {
            Jsoner.serialize(staff, fileWriter);
        }

    }

    private static Staff createStaff() {

        Staff staff = new Staff();

        staff.setName("mkyong");
        staff.setAge(38);
        staff.setPosition(new String[]{"Founder", "CTO", "Writer"});
        Map<String, BigDecimal> salary = new HashMap() {{
            put("2010", new BigDecimal(10000));
            put("2012", new BigDecimal(12000));
            put("2018", new BigDecimal(14000));
        }};
        staff.setSalary(salary);
        staff.setSkills(Arrays.asList("java", "python", "node", "kotlin"));

        return staff;

    }

}

Output

Terminal

{
	"skills":[
		"java",
		"python",
		"node",
		"kotlin"
	],
	"name":"mkyong",
	"position":[
		"Founder",
		"CTO",
		"Writer"
	],
	"salary":{
		"2018":14000,
		"2012":12000,
		"2010":10000
	},
	"age":38
}
C:\\projects\\user3.json

{"skills":["java","python","node","kotlin"],"name":"mkyong","position":["Founder","CTO","Writer"],"salary":{"2018":14000,"2012":12000,"2010":10000},"age":38}

3.2 Convert list of objects to JSON array and save as .json file.


	Staff staff = createStaff();

	List<Staff> list = Arrays.asList(createStaff(), createStaff());

	// list of Java objects to JSON file 
	try (FileWriter fileWriter = new FileWriter("C:\\projects\\user4.json")) {
		Jsoner.serialize(list, fileWriter);
	}

Output

C:\\projects\\user4.json

[
{"skills":["java","python","node","kotlin"],"name":"mkyong","position":["Founder","CTO","Writer"],"salary":{"2018":14000,"2012":12000,"2010":10000},"age":38},
{"skills":["java","python","node","kotlin"],"name":"mkyong","position":["Founder","CTO","Writer"],"salary":{"2018":14000,"2012":12000,"2010":10000},"age":38}
]

4. JSON to Java objects

4.1 To convert JSON back to Java objects, we need help from dozer third party library to copy the object properties.

pom.xml

	<dependency>
		<groupId>net.sf.dozer</groupId>
		<artifactId>dozer</artifactId>
		<version>5.5.1</version>
	</dependency>

4.2 JSON string to Java object.

JsonSimple2.java

package com.mkyong;

import com.github.cliftonlabs.json_simple.JsonException;
import com.github.cliftonlabs.json_simple.JsonObject;
import com.github.cliftonlabs.json_simple.Jsoner;
import org.dozer.DozerBeanMapper;
import org.dozer.Mapper;

import java.io.FileReader;
import java.io.IOException;

public class JsonSimple2 {

    public static void main(String[] args) throws IOException, JsonException {

		// The file `user3.json` is generated from above example 3.1 
        try (FileReader fileReader = new FileReader(("C:\\projects\\user3.json"))) {

            JsonObject deserialize = (JsonObject) Jsoner.deserialize(fileReader);
			
			// need dozer to copy object to staff, json_simple no api for this?
            Mapper mapper = new DozerBeanMapper();
			
			// JSON to object
            Staff staff = mapper.map(deserialize, Staff.class);
			
            System.out.println(staff);

        }

    }

}

Output


Staff{name='mkyong', age=38, position=[Founder, CTO, Writer], 
	skills=[java, python, node, kotlin], salary={2018=14000, 2012=12000, 2010=10000}}

4.3 JSON array to Java object.

JsonSimple3.java

package com.mkyong;

import com.github.cliftonlabs.json_simple.JsonArray;
import com.github.cliftonlabs.json_simple.JsonException;
import com.github.cliftonlabs.json_simple.Jsoner;
import org.dozer.DozerBeanMapper;
import org.dozer.Mapper;

import java.io.FileReader;
import java.io.IOException;
import java.util.List;
import java.util.stream.Collectors;

public class JsonSimple3 {

    public static void main(String[] args) throws IOException, JsonException {

		// The file `user4.json` is generated from above example 3.2
        try (FileReader fileReader = new FileReader(("C:\\projects\\user4.json"))) {

            JsonArray objects = Jsoner.deserializeMany(fileReader);

            Mapper mapper = new DozerBeanMapper();

            JsonArray o = (JsonArray) objects.get(0);
            List<Staff> collect = o.stream()
				.map(x -> mapper.map(x, Staff.class)).collect(Collectors.toList());
            collect.forEach(x -> System.out.println(x));

        }

    }

}

Output


Staff{name='mkyong', age=38, position=[Founder, CTO, Writer], skills=[java, python, node, kotlin], salary={2018=14000, 2012=12000, 2010=10000}}
Staff{name='mkyong', age=38, position=[Founder, CTO, Writer], skills=[java, python, node, kotlin], salary={2018=14000, 2012=12000, 2010=10000}}

References

About the Author

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mkyong
Founder of Mkyong.com, love Java and open source stuff. Follow him on Twitter. If you like my tutorials, consider make a donation to these charities.

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Rahul Surabhi Recent comment authors
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Rahul Surabhi
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Rahul Surabhi

Hello, not really relevant but can you correct a typo in your references.
Gson – How to arse JSON