Jackson - Object Serialization

To understand object serialization in detail, let us serialize a Java object to a JSON file and then read that JSON file to get the object back.

Object Serialization Example

In the following example, we will create a Student class. Thereafter we will create a student.json file which will have a JSON representation of Student object.
First of all, create a Java class file named JacksonTester in C:\>Jackson_WORKSPACE.

File: JacksonTester.java

import java.io.File;
import java.io.IOException;

import org.codehaus.jackson.JsonGenerationException;
import org.codehaus.jackson.JsonParseException;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;

public class JacksonTester {
   public static void main(String args[]){
      JacksonTester tester = new JacksonTester();
  
      try {
         Student student = new Student();
         student.setAge(10);
         student.setName("Mahesh");
         tester.writeJSON(student);

         Student student1 = tester.readJSON();
         System.out.println(student1);

      } 
      catch (JsonParseException e) { e.printStackTrace(); }
      catch (JsonMappingException e) { e.printStackTrace(); }
      catch (IOException e) { e.printStackTrace(); }
   }

   private void writeJSON(Student student) throws JsonGenerationException, JsonMappingException, IOException{
      ObjectMapper mapper = new ObjectMapper(); 
      mapper.writeValue(new File("student.json"), student);
   }

   private Student readJSON() throws JsonParseException, JsonMappingException, IOException{
      ObjectMapper mapper = new ObjectMapper();
      Student student = mapper.readValue(new File("student.json"), Student.class);
      return student;
   }
}

class Student {
   private String name;
   private int age;
 
   public Student(){}
 
   public String getName() {
      return name;
   }
 
   public void setName(String name) {
      this.name = name;
   }
 
   public int getAge() {
      return age;
   }
 
   public void setAge(int age) {
      this.age = age;
   }
 
   public String toString(){
      return "Student [ name: "+name+", age: "+ age+ " ]";
   } 
}

Verify the result

Compile the classes using javac compiler as follows −

C:\Jackson_WORKSPACE>javac JacksonTester.java

Now run the jacksonTester to see the result.

C:\Jackson_WORKSPACE>java JacksonTester

Verify the Output −

Student [ name: Mahesh, age: 10 ]