Java Servlet JSON Response in JSP using Gson

In Modern web application We get data from server in JSON format and display data in jsp or html page using Front end library or frameworks like Angular, React etc.

This is similar for mobile app development.

Here we will see how we can get JSON Response from servlet and show in jsp.

What is JSON ?

JavaScript Object Notation (JSON) is a lightweight format for interchange data.

JSON is a Good Human readable format
JSON is derived from JavaScript
JSON is text based format for representing structured data
JSON is key value pair data
JSON is language independent

These are features of JSON.

JSON can be used to interchange data between different platform.

Due to lightweight it is very fast to exchange information between different application i.e. web based applications.

So knowing how to use JSON with servlet will good

Creating Java web project in NetBeans

We already know how to create simple projects with netbeans see project creating with maven and creating simple web project in netbeans.

We created a Java Web project ServletJson to get Response from Servlet JSON

Project Explorer

In above project

Created Pojo for Studnet
Created Pojo for Address
Created Pojo for Subject
Created JsonResponse Servlet
created index.jsp

Creating Classes and Pages In Netbeans

index.jsp

This file contains a link on click that will goto url

localhost:8084/ServletJson/jsonResponse

<%@page contentType=”text/html” pageEncoding=”UTF-8″%>

        <a href="jsonResponse">Get Json response from server</a>

1	<a href="jsonResponse">Get Json response from server</a>

JsonResponse.java

Here we want to send json data response from servlet.
Here a link is available in jsp page on link click it is calling /jsonResponse url where JsonResponse’s doGet() method is get called.

How to set HttpServletResponse set body json

To generate json response we are setting response.setContentType("application/json"); that is used to set response as application/json.

Here response is reference variable of HttpServletResponse.

In servlet student object is created with name gender mobile number and three subjects marks. After creating object we are converting objects to json using gson library.

response.setContentType("application/json"); is used to send response as json.

response.setCharacterEncoding("utf-8"); is character encoding method.

We have created student object which contains students id,name,gender,address, mobileNo and set of subjects and address.

We send this data to jsp using Gson Object.

The method gson.toJson(student); is converting object to json string

then we are passing json data to PrintWriter object to write in browser

package ebhor.servlet;

import com.google.gson.Gson;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashSet;
import java.util.Set;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet(urlPatterns = {"/jsonResponse"})
public class JsonResponse extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("application/json");
        response.setCharacterEncoding("utf-8");
        Student student = new Student(12, "Ram Kumar", "Male", "1234565678");
        Subject subject1 = new Subject(1, "Computer Fundamentals");
        Subject subject2 = new Subject(2, "Computer Graphics");
        Subject subject3 = new Subject(3, "Data Structures");
        Set subjects = new HashSet();
        subjects.add(subject1);
        subjects.add(subject2);
        subjects.add(subject3);
        student.setSubjects(subjects);
        Address address = new Address(1, "Street 23 NN West ", "Bhilai", "Chhattisgarh", "India");
        student.setAddress(address);
        Gson gson = new Gson();
        String jsonData = gson.toJson(student);
        PrintWriter out = response.getWriter();
        try {
            out.println(jsonData);
        } finally {
            out.close();
        }

    }
}

package ebhor.servlet;

import com.google.gson.Gson;

import java.io.IOException;

import java.io.PrintWriter;

import java.util.HashSet;

import java.util.Set;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

@WebServlet(urlPatterns = {"/jsonResponse"})

public class JsonResponse extends HttpServlet {

@Override

protected void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

response.setContentType("application/json");

response.setCharacterEncoding("utf-8");

Student student = new Student(12, "Ram Kumar", "Male", "1234565678");

Subject subject1 = new Subject(1, "Computer Fundamentals");

Subject subject2 = new Subject(2, "Computer Graphics");

Subject subject3 = new Subject(3, "Data Structures");

Set subjects = new HashSet();

subjects.add(subject1);

subjects.add(subject2);

subjects.add(subject3);

student.setSubjects(subjects);

Address address = new Address(1, "Street 23 NN West ", "Bhilai", "Chhattisgarh", "India");

student.setAddress(address);

Gson gson = new Gson();

String jsonData = gson.toJson(student);

PrintWriter out = response.getWriter();

try {

out.println(jsonData);

} finally {

out.close();

}

Student.java

This class contains student data like id, name , gender ,address, mobile number and multiple subjects mark.

package ebhor.servlet;

import java.io.Serializable;
import java.util.Set;
import java.util.HashSet;

public class Student implements Serializable {

    private long id;
    private String name;
    private String gender;
    private Address address;
    private Set subjects = new HashSet(0);
    private String mobileNo;

    public Student() {
    }

    public Student(long id, String name, String gender, String mobileNo) {
        this.id = id;
        this.name = name;
        this.gender = gender;
        this.mobileNo = mobileNo;
    }

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public Address getAddress() {
        return address;
    }

    public void setAddress(Address address) {
        this.address = address;
    }

    public Set getSubjects() {
        return subjects;
    }

    public void setSubjects(Set subjects) {
        this.subjects = subjects;
    }

    public String getMobileNo() {
        return mobileNo;
    }

    public void setMobileNo(String mobileNo) {
        this.mobileNo = mobileNo;
    }

}

package ebhor.servlet;

import java.io.Serializable;

import java.util.Set;

import java.util.HashSet;

public class Student implements Serializable {

private long id;

private String name;

private String gender;

private Address address;

private Set subjects = new HashSet(0);

private String mobileNo;

public Student() {

}

public Student(long id, String name, String gender, String mobileNo) {

this.id = id;

this.name = name;

this.gender = gender;

this.mobileNo = mobileNo;

}

public long getId() {

return id;

}

public void setId(long id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public String getGender() {

return gender;

}

public void setGender(String gender) {

this.gender = gender;

}

public Address getAddress() {

return address;

}

public void setAddress(Address address) {

this.address = address;

}

public Set getSubjects() {

return subjects;

}

public void setSubjects(Set subjects) {

this.subjects = subjects;

}

public String getMobileNo() {

return mobileNo;

}

public void setMobileNo(String mobileNo) {

this.mobileNo = mobileNo;

}

Subject.java

contains id and name of subject.

package ebhor.servlet;

import java.io.Serializable;

public class Subject implements Serializable {

    private long id;
    private String name;

    public Subject() {
    }

    public Subject(long id, String name) {
        this.id = id;
        this.name = name;
    }

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

}

package ebhor.servlet;

import java.io.Serializable;

public class Subject implements Serializable {

private long id;

private String name;

public Subject() {

}

public Subject(long id, String name) {

this.id = id;

this.name = name;

}

public long getId() {

return id;

}

public void setId(long id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

Address

contain address fields id , street, city,state and country fields

package ebhor.servlet;

import java.io.Serializable;

public class Address implements Serializable{

    private long id;
    private String street;
    private String city;
    private String state;
    private String country;

    public Address() {
    }

    public Address(long id, String street, String city, String state, String country) {
        this.id = id;
        this.street = street;
        this.city = city;
        this.state = state;
        this.country = country;
    }

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public String getStreet() {
        return street;
    }

    public void setStreet(String street) {
        this.street = street;
    }

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public String getState() {
        return state;
    }

    public void setState(String state) {
        this.state = state;
    }

    public String getCountry() {
        return country;
    }

    public void setCountry(String country) {
        this.country = country;
    }

}

package ebhor.servlet;

import java.io.Serializable;

public class Address implements Serializable{

private long id;

private String street;

private String city;

private String state;

private String country;

public Address() {

}

public Address(long id, String street, String city, String state, String country) {

this.id = id;

this.street = street;

this.city = city;

this.state = state;

this.country = country;

}

public long getId() {

return id;

}

public void setId(long id) {

this.id = id;

}

public String getStreet() {

return street;

}

public void setStreet(String street) {

this.street = street;

}

public String getCity() {

return city;

}

public void setCity(String city) {

this.city = city;

}

public String getState() {

return state;

}

public void setState(String state) {

this.state = state;

}

public String getCountry() {

return country;

}

public void setCountry(String country) {

this.country = country;

}

Result

This is index.jsp page after running the project on click on link it will show json data in browser

Jsp Page to generate JSON Response

JSON Response In JSP page from Servlet

Above java servlet return JSON response.

Downlaod above program from here