To parse JSON responses easily using Java 11’s HttpClient, you can use libraries like Jackson or Gson that help in converting a JSON string to Java objects (POJOs) without hassle.
Here’s a step-by-step guide:
Step 1: Create a Java 11 HttpClient request
- Use Java’s
HttpClientto make an HTTP request and get the JSON response as a string. - Use
HttpRequestorHttpResponseas part of the Java 11HttpClientAPI.
Step 2: Add Jackson or Gson to Parse JSON
- Jackson: Add the dependency to your
pom.xml(for Maven):<dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-databind</artifactId> <version>2.15.2</version> </dependency> - Gson: Add this dependency:
<dependency> <groupId>com.google.code.gson</groupId> <artifactId>gson</artifactId> <version>2.10.1</version> </dependency>
Step 3: Example Using Jackson
package org.kodejava.net.http;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.net.URI;
public class HttpClientJacksonExample {
public static void main(String[] args) throws Exception {
// 1. Create an HttpClient
HttpClient client = HttpClient.newHttpClient();
// 2. Create an HttpRequest
HttpRequest request = HttpRequest.newBuilder()
.uri(new URI("https://jsonplaceholder.typicode.com/posts/1")) // Example URL
.GET()
.build();
// 3. Send the HttpRequest and get an HttpResponse
HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());
// 4. Parse JSON String Response to a Java Object using Jackson
ObjectMapper mapper = new ObjectMapper();
Post post = mapper.readValue(response.body(), Post.class);
// 5. Use the parsed object
System.out.println("Post Title: " + post.getTitle());
}
// Sample POJO to match the JSON structure
public static class Post {
private int userId;
private int id;
private String title;
private String body;
// Getters and Setters
public int getUserId() {
return userId;
}
public void setUserId(int userId) {
this.userId = userId;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getBody() {
return body;
}
public void setBody(String body) {
this.body = body;
}
}
}
Step 4: Example Using Gson
package org.kodejava.net.http;
import com.google.gson.Gson;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.net.URI;
public class HttpClientGsonExample {
public static void main(String[] args) throws Exception {
// 1. Create HttpClient
HttpClient client = HttpClient.newHttpClient();
// 2. Create HttpRequest
HttpRequest request = HttpRequest.newBuilder()
.uri(new URI("https://jsonplaceholder.typicode.com/posts/1")) // Example URL
.GET()
.build();
// 3. Send HttpRequest and get HttpResponse
HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());
// 4. Parse JSON String response to Java Object using Gson
Gson gson = new Gson();
Post post = gson.fromJson(response.body(), Post.class);
// 5. Use the parsed object
System.out.println("Post Title: " + post.getTitle());
}
// Sample POJO class to match the JSON structure
public static class Post {
private int userId;
private int id;
private String title;
private String body;
// Getters and Setters
public int getUserId() {
return userId;
}
public void setUserId(int userId) {
this.userId = userId;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getBody() {
return body;
}
public void setBody(String body) {
this.body = body;
}
}
}
Key Points:
- Serialization and Deserialization: POJO structure must match your JSON’s keys.
- Why Jackson or Gson?
They are robust and simplify working with JSON (and even converting nested structures).
