Analyze the serialization and data generic binding of objects in Java's Jackson library

Jackson Object Serialization
Here we will introduce serializing Java objects to a JSON file, and then reading the JSON file to obtain and convert it into an object. In this example, the Student class is created. Create a student.json file that will have student objects represented as JSON.

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 results

Use javac compiles the following class:

C:\Jackson_WORKSPACE>javac JacksonTester.java

Now run jacksonTester to see the result:

C:\Jackson_WORKSPACE>java JacksonTester

Verify the output result

Student [ name: Mahesh, age: 10 ]

Jackson data binding generics
In simple data In binding, we use String as the key object and as a value object mapping class. Instead, we can use concrete Java objects and typecast to JSON for use.

#Consider the following example using a class UserData to save user-specific data.

Create a file named JacksonTester in the Java class file directory C:\>Jackson_WORKSPACE.

File name: JacksonTester.java

import java.io.File;
import java.io.IOException;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
 
import org.codehaus.jackson.JsonGenerationException;
import org.codehaus.jackson.JsonParseException;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.type.TypeReference;
 
public class JacksonTester {
  public static void main(String args[]){
   JacksonTester tester = new JacksonTester();
     try {
      ObjectMapper mapper = new ObjectMapper();
 
      Map userDataMap = new HashMap();
      UserData studentData = new UserData(); 
      int[] marks = {1,2,3};
 
      Student student = new Student();
      student.setAge(10);
      student.setName("Mahesh");
      // JAVA Object
      studentData.setStudent(student);
      // JAVA String
      studentData.setName("Mahesh Kumar");
      // JAVA Boolean
      studentData.setVerified(Boolean.FALSE);
      // Array
      studentData.setMarks(marks);
      TypeReference ref = new TypeReference>() { };
      userDataMap.put("studentData1", studentData);
      mapper.writeValue(new File("student.json"), userDataMap);
      //{
      //  "studentData1":
      // {
      // "student":
      // {
      //  "name":"Mahesh",
      //  "age":10
      //   },
      //   "name":"Mahesh Kumar",
      //   "verified":false,
      //   "marks":[1,2,3]
      //  }
      //}
      userDataMap = mapper.readValue(new File("student.json"), ref);
 
      System.out.println(userDataMap.get("studentData1").getStudent());
      System.out.println(userDataMap.get("studentData1").getName());
      System.out.println(userDataMap.get("studentData1").getVerified());
      System.out.println(Arrays.toString(userDataMap.get("studentData1").getMarks()));
   } catch (JsonParseException e) {
     e.printStackTrace();
   } catch (JsonMappingException e) {
     e.printStackTrace();
   } catch (IOException e) {
      e.printStackTrace();
   }
  }
}
 
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+ " ]";
  } 
}
 
class UserData {
  private Student student;
  private String name;
  private Boolean verified;
  private int[] marks;
 
  public UserData(){}
 
  public Student getStudent() {
   return student;
  }
  public void setStudent(Student student) {
   this.student = student;
  }
  public String getName() {
   return name;
  }
  public void setName(String name) {
   this.name = name;
  }
  public Boolean getVerified() {
   return verified;
  }
  public void setVerified(Boolean verified) {
   this.verified = verified;
  }
  public int[] getMarks() {
   return marks;
  }
  public void setMarks(int[] marks) {
   this.marks = marks;
  } 
}

Verification output

Use javac to compile the following class:

C:\Jackson_WORKSPACE>javac JacksonTester.java

Now run jacksonTester to see the results:

C:\Jackson_WORKSPACE>java JacksonTester

Verification output

Student [ name: Mahesh, age: 10 ]
Mahesh Kumar
false
[1, 2, 3]

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