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JSON

JSON Properties Order Change (Jackson)

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@JsonPropertyOrder annotation use to define the order of JSON properties while serialization from Java to JSON. This annotation always use on class level.

@JsonPropertyOrder on Class Level

@JsonPropertyOrder({"firstName","lastName","rollNumber"})
public class StudentDetail
{	
		@JsonProperty(value = "id")
		private int rollNumber;
		
		@JsonProperty(value = "firstName")
		private String first_name;
		
		@JsonProperty(value = "lastName")
		private String last_name;
}

Here you will see complete example of JSON properties name change and define order of  JSON  propertis.

Complete Example

@JsonPropertyOrder({"firstName","lastName","rollNumber"})
public class StudentDetail
{	
		@JsonProperty(value = "id")
		private int rollNumber;
		
		@JsonProperty(value = "firstName")
		private String first_name;
		
		@JsonProperty(value = "middleName")
		private String middle_name;
		
		@JsonProperty(value = "lastName", index=1)
		private String last_name;

		public StudentDetail()
		{
			
		}
		//Getter and Setter

                //toString() method
}

Code to convert  Java object to JSON.

public class JsonPropertiesOrder {
	public static void main(String [] args)
	{
	StudentDetail student=new StudentDetail();
	student.setFirst_name("Saurabh");
	student.setRollNumber(25);
	student.setLast_name("Gupta");
	System.out.println(student);
	try {

		// ObjectMapper new instance
		ObjectMapper objectMapper = new ObjectMapper();

		// configure Object mapper for pretty print
		objectMapper.configure(SerializationFeature.INDENT_OUTPUT, true);

		// writing to console, can write to any output stream such as file
		String json =objectMapper.writeValueAsString(student);
		System.out.println(json);

	} catch (JsonMappingException ex) {
		ex.printStackTrace();
	} catch (JsonGenerationException ex) {
		ex.printStackTrace();
	} catch (IOException ex) {
		ex.printStackTrace();
	}
	}
}

Output


StudentDetail [rollNumber=25, firstName=Saurabh, lastName=Gupta]
{
  "firstName" : "Saurabh",
  "lastName" : "Gupta",
  "id" : 25
}

References

https://github.com/FasterXML/jackson-annotations

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Follow below link to learn more on JSON and  JSON issues solutions:

JSON

How to do JSON pretty formatting and Null Serialization (GSON/GsonBuilder)

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In previous example use GSON comes with simple JAVA API’s to convert JAVA object to/from JSON and here I will use GsonBuilder to print format JSON and serialize null object values also.

How to convert Java object to / from JSON by (GSON)

Pre-Requisite:

  • JAVA 8
  • Maven 3
  • GSON Jar as below.

GSON Dependency:

 <dependency>
    <groupId>com.google.code.gson</groupId>
    <artifactId>gson</artifactId>
    <version>2.8.2</version>
 </dependency>

Convert JAVA object to/from JSON

package gsonexamples;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

import model.Employee;

public class GsonConvertJavaToJSON {

	public static void main(String[] args) {
		//Create GSON Object
		//Gson gson = new Gson();
Gson gson = new GsonBuilder().setPrettyPrinting().serializeNulls().create();
		Employee employee=getJavaObject();
		String json=gson.toJson(employee);

        System.out.println("Convert Java Object To JSON");
		System.out.println(json);

		System.out.println("Convert JSON To Java Object");
		employee=gson.fromJson(json,Employee.class);
		System.out.println(employee);

	}
	public static  Employee getJavaObject()
	{
		Employee employee=new Employee("C123","Saurabh" ,"Kumar","Gupta","Tech Lead",50000,"Alpharetta,GA","Dallas, TX","1231231230",null,null);
		return employee;
	}

}
  • GsonBuilder().setPrettyPrinting() :  This api is to generate pretty formatted JSON string.
  • GsonBuilder().searializeNulls() :  This api is to serialize null values in object.
  • GsonBuilder().create(): This api is to create GSON object to Java object to/from JSON.
package model;

import java.util.List;
import java.util.Set;

public class Employee {
private String employeeId;
private String firstName;
private String middleName;
private String lastName;
private String designation;
private int salary;
private String permanentAddress;
private String mailingAddress;
private String mobile;
private Set<Education> educationDetail;
private List<Experience> expericeDetail;

@Override
public String toString() {
	return "Employee [employeeId=" + employeeId + ", firstName=" + firstName + ", middleName=" + middleName
			+ ", lastName=" + lastName + ", designation=" + designation + ", salary=" + salary + ", permanentAddress="
			+ permanentAddress + ", mailingAddress=" + mailingAddress + ", mobile=" + mobile + ", educationDetail="
			+ educationDetail + ", expericeDetail=" + expericeDetail + "]";
}
public Employee(String employeeId, String firstName, String middleName, String lastName, String designation, int salary,
		String permanentAddress, String mailingAddress, String mobile, Set<Education> educationDetail,
		List<Experience> expericeDetail) {
	super();
	this.employeeId = employeeId;
	this.firstName = firstName;
	this.middleName = middleName;
	this.lastName = lastName;
	this.designation = designation;
	this.salary = salary;
	this.permanentAddress = permanentAddress;
	this.mailingAddress = mailingAddress;
	this.mobile = mobile;
	this.educationDetail = educationDetail;
	this.expericeDetail = expericeDetail;
}
//Getter and Setter
}


package model;

public class Education {
private String schoolOrCollegeName;
private String standard;
private String stream;
private double percentage;

@Override
public String toString() {
	return "Education [schoolOrCollegeName=" + schoolOrCollegeName + ", standard=" + standard + ", stream=" + stream
			+ ", percentage=" + percentage + "]";
}
public Education(String schoolOrCollegeName, String standard, String stream, double percentage) {
	super();
	this.schoolOrCollegeName = schoolOrCollegeName;
	this.standard = standard;
	this.stream = stream;
	this.percentage = percentage;
}
//getter and setter
}

package model;

import java.util.Date;

public class Experience {
private String companyName;
private String designation;
private Date startDate;
private Date endDate;
private double salary;
public Experience(String companyName, String designation, Date startDate, Date endDate, double salary) {
	super();
	this.companyName = companyName;
	this.designation = designation;
	this.startDate = startDate;
	this.endDate = endDate;
	this.salary = salary;
}
@Override
public String toString() {
	return "Experience [companyName=" + companyName + ", designation=" + designation + ", startDate=" + startDate
			+ ", endDate=" + endDate + ", salary=" + salary + "]";
}
//getter and setter
}

Output:

Convert Java Object To JSON
{
  "employeeId": "C123",
  "firstName": "Saurabh",
  "middleName": "Kumar",
  "lastName": "Gupta",
  "designation": "Tech Lead",
  "salary": 50000,
  "permanentAddress": "Alpharetta,GA",
  "mailingAddress": "Dallas, TX",
  "mobile": "1231231230",
  "educationDetail": null,
  "expericeDetail": null
}
<span 				data-mce-type="bookmark" 				id="mce_SELREST_start" 				data-mce-style="overflow:hidden;line-height:0" 				style="overflow:hidden;line-height:0" 			></span>
Convert JSON To Java Object
Employee [employeeId=C123, firstName=Saurabh, middleName=Kumar, lastName=Gupta, designation=Tech Lead, salary=50000, permanentAddress=Alpharetta,GA, mailingAddress=Dallas, TX, mobile=1231231230, educationDetail=null, expericeDetail=null]

In above JSON output is pretty formatted properly and  serialize null objects for education and experience. In next blog will explain about how to exclude fields while serializing/deserializing to/from JSON by GsonBuilder.

How to exclude fields from JSON while parsing by GSON/GsonBuilder?