Maybe some time for any special use case we need to keep JSON object properties in some specific order. This can be done in two ways in Java.
1- Just write a method to return JSON string in that order or you can override toString() the the the the method with JSON string in order properties.
2- Use Jackson library and @JsonPropetyOrder class attribute.
3- Using LinkedHashMap will serialize in inserted order and TreeMap will serialize in sorted key order
Example of Jackson Property order
import com.fasterxml.jackson.annotation.JsonPropertyOrder;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.sun.istack.NotNull;
import java.io.IOException;
import java.util.UUID;
@JsonPropertyOrder({ "id", "password", "name", "email", "enabled" })
public class UserResource {
private UUID id;
@NotNull
private String name;
@NotNull
private String email;
private boolean enabled;
private String password;
public UserResource(UUID id, String name, String email, boolean enabled, String password) {
this.id = id;
this.name = name;
this.email = email;
this.enabled = enabled;
this.password = password;
}
public UUID getId() {
return id;
}
public void setId(UUID id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public boolean isEnabled() {
return enabled;
}
public void setEnabled(boolean enabled) {
this.enabled = enabled;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public static void main(String args[]){
ObjectMapper mapper = new ObjectMapper();
try {
UserResource student = new UserResource(UUID.randomUUID(), "sheel", "sheel@c4c.com",true, "$$$$$$%%##^^$DSGHHH");
String jsonString = mapper
.writerWithDefaultPrettyPrinter()
.writeValueAsString(student);
System.out.println(jsonString);
}
catch (IOException e) {
e.printStackTrace();
}
}
}
Output is given below
{
"id" : "fbfcd21d-731e-4acb-9fec-90a499e47cc9",
"password" : "$$$$$$%%##^^$DSGHHH",
"name" : "sheel",
"email" : "sheel@c4c.com",
"enabled" : true
}
Example of Ordered Serialization in JSON using LinkedHashMap and TreeMap
public static void main(String args[]){
ObjectMapper mapper = new ObjectMapper();
Map<String, String> itemObj = new LinkedHashMap<>();
itemObj.put("s91","Value1");
itemObj.put("s2","Value2");
itemObj.put("s3","Value3");
itemObj.put("s4","Value4");
try {
String jsonString = mapper
.writerWithDefaultPrettyPrinter()
.writeValueAsString(itemObj);
System.out.println(jsonString);
}
catch (IOException e) {
e.printStackTrace();
}
}
Output
{
"s91" : "Value1",
"s2" : "Value2",
"s3" : "Value3",
"s4" : "Value4"
}
Using TreeSet
public static void main(String args[]){
ObjectMapper mapper = new ObjectMapper();
Map itemObj = new LinkedHashMap<>();
itemObj.put(“s91″,”Value1”);
itemObj.put(“s2″,”Value2”);
itemObj.put(“s3″,”Value3”);
itemObj.put(“s4″,”Value4”);
try {
public static void main(String args[]){
ObjectMapper mapper = new ObjectMapper();
Map<String, String> itemObj = new TreeMap<>();
itemObj.put("s91","Value1");
itemObj.put("s2","Value2");
itemObj.put("s3","Value3");
itemObj.put("s4","Value4");
try {
String jsonString = mapper
.writerWithDefaultPrettyPrinter()
.writeValueAsString(itemObj);
System.out.println(jsonString);
}
catch (IOException e) {
e.printStackTrace();
}
}
Output
{
"s2" : "Value2",
"s3" : "Value3",
"s4" : "Value4",
"s91" : "Value1"
}