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Jackson Change Property Name

By Arvind Rai, October 17, 2017
This page will walk through how to change property name using Jackson API. Jackson provides @JsonProperty annotation that is used to change property name in serialized JSON. @JsonProperty is annotated on class fields and we need to pass a value that will be used as property name for that field in serialized JSON. If we do not pass value to @JsonProperty then property name in serialized JSON will be same as class field name. If we do not use @JsonProperty annotation on class fields at all then property name will be same as class field name in serialized JSON. On this page we will create examples to covert Java object into JSON and also we will provide example to convert JSON into Java object. Our java bean will use @JsonProperty annotation to change property name in our examples.

Gradle to Resolve Jackson API

Find the Gradle file to resolve Jackson API.
build.gradle
apply plugin: 'java'
apply plugin: 'eclipse'
archivesBaseName = 'Concretepage'
version = '1' 
repositories {
    mavenCentral()
}
dependencies {
    compile group: 'com.fasterxml.jackson.core', name: 'jackson-core', version: '2.9.1'
    compile group: 'com.fasterxml.jackson.core', name: 'jackson-databind', version: '2.9.1'
    compile group: 'com.fasterxml.jackson.core', name: 'jackson-annotations', version: '2.9.1'
} 

@JsonProperty

Jackson provides @JsonProperty annotation that can be used to change property name while serializing Object to JSON. Let us understand step by step.
1. Find sample code.
public class Book {
  @JsonProperty("bookName")		
  private String name;
  @JsonProperty("bookCategory")		
  private String category;   
  ------
}
In the above code, class fields are using @JsonProperty annotation and we are assigning a value. When we serialize the object of Book class, we will get JSON whose properties name will be as defined by @JsonProperty values.
{
    "bookName" : "Learning Java",
    "bookCategory" : "Java"
}
2. If we use @JsonProperty annotation but do not provide value then the serialized JSON will contain property name as class field name. By default @JsonProperty has value (""). It indicates that field name will be used as property name while serializing JSON. Suppose we are using @JsonProperty as given below.
public class Book {
  @JsonProperty		
  private String name;
  @JsonProperty		
  private String category;   
  ------
} 
The output will be as following.
{
    "name" : "Learning Java",
    "category" : "Java"
} 
3. If we do not use @JsonProperty at all on the class fields then it will act as default behavior of @JsonProperty. It means the serialized JSON output will contain property name as class field name. Find the sample code.
public class Book {
  private String name;
  private String category;   
  ------
}
The output will be as following.
{
    "name" : "Learning Java",
    "category" : "Java"
}

Example 1: Convert Java Object to JSON

Find the example to convert Java Object to JSON using Jackson. In this example we will change property name using @JsonProperty.
Book.java
package com.concretepage;
import com.fasterxml.jackson.annotation.JsonProperty;
public class Book {
	@JsonProperty("bookName")		
	private String name;
	@JsonProperty("bookCategory")		
  	private String category;   
  	public Book(){}
  	public Book(String name, String category) {
  		this.name = name;
  		this.category = category;
  	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getCategory() {
		return category;
	}
	public void setCategory(String category) {
		this.category = category;
	}
} 
Writer.java
package com.concretepage;
import com.fasterxml.jackson.annotation.JsonProperty;
public class Writer {
	@JsonProperty("writerId")	
	private Integer id; 
	@JsonProperty("writerName")
	private String name;
	@JsonProperty("writerBook")	
	private Book book;
  	public Writer(){}
  	public Writer(Integer id, String name, Book book){
  		this.id = id;
  		this.name = name;
        this.book = book;
  	}
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Book getBook() {
		return book;
	}
	public void setBook(Book book) {
		this.book = book;
	}
} 
ObjectToJSON
package com.concretepage;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
public class ObjectToJSON {
  public static void main(String[] args) throws JsonProcessingException {
     ObjectMapper mapper = new ObjectMapper();
     Book book = new Book("Learning Java", "Java");
     Writer writer = new Writer(110, "Mohit", book);
     String jsonWriter = mapper.writerWithDefaultPrettyPrinter()
		 .writeValueAsString(writer);
     System.out.println(jsonWriter);
  }
} 
Output
{
  "writerId" : 110,
  "writerName" : "Mohit",
  "writerBook" : {
    "bookName" : "Learning Java",
    "bookCategory" : "Java"
  }
} 
In the above output we can observe that the property names are values defined by @JsonProperty annotated at class fields.
If we do not use @JsonProperty annotation on the fields of Book and Writer then serialized JSON output will contain property names as class field names as given below.
{
  "id" : 110,
  "name" : "Mohit",
  "book" : {
    "name" : "Learning Java",
    "category" : "Java"
  }
} 

Example 2: Convert JSON to Java Object

In this example we will convert JSON to Java Object using Jackson. @JsonProperty annotation is being used on the fields of Book and Writer classes. Find the example.
JSONToObject.java
package com.concretepage;
import java.io.IOException;
import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
public class JSONToObject {
	public static void main(String[] args) throws JsonParseException, JsonMappingException, IOException {
		 String jsonData = 
		    "{"
			  +"\"writerId\" : 111,"
			  +"\"writerName\" : \"Mahesh\","
			  +"\"writerBook\" : {"
			    +"\"bookName\" : \"Learning Spring\","
			    +"\"bookCategory\" : \"Spring\""
			  +"}"
		   +"}";
		 ObjectMapper mapper = new ObjectMapper();
		 Writer writer = mapper.readValue(jsonData, Writer.class);
		 System.out.println(writer.getId()+", "+ writer.getName());
		 Book book = writer.getBook();
		 System.out.println(book.getName()+", "+ book.getCategory());
	}
} 
Output
111, Mahesh
Learning Spring, Spring 

Reference

Annotation Type JsonProperty
POSTED BY
ARVIND RAI
ARVIND RAI
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