Httpclient in java send a POST request

Question

I want to make an API caller with all CRUD methods using java
I want to be able to get all the data with json then parse it and only get data with it's unique id

The thing that I can't figure out is how do I send data using an API. I get that I can use an id but what if I need to modify not one but 2 or more fields how do I do it then while Parsing a json?

So I have implemented the GET method but I can't think of how to implement the POST one

Here is the code from my methods class where I have all the methods

I'm using Jackson to parse json and Java's Httpclient

import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.annotation.JsonPOJOBuilder;
import java.io.IOException;
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.time.Duration;
import java.util.Collections;
import java.util.List;
import java.util.Map;
public class methods extends link{
 private final ObjectMapper mapper = new ObjectMapper();
 private final String url = "https://jsonplaceholder.typicode.com/todos";
 public List<dataGettingBack> getAllMethod() throws IOException, InterruptedException {
 HttpClient httpClientGet = HttpClient.newBuilder().connectTimeout(Duration.ofSeconds(10)).build();
 HttpRequest httpGetReq = HttpRequest
 .newBuilder(URI.create(url))
 .header("Content-Type", "application/json")
 .GET()
 .build();
 HttpResponse<String> res = httpClientGet.send(httpGetReq, HttpResponse.BodyHandlers.ofString());
 return mapper.readValue(res.body(), new TypeReference<List<dataGettingBack>>(){});
 }
 public List<dataGettingBack> getOne(int id) throws IOException, InterruptedException, error {
 HttpClient httpGetOne = HttpClient.newBuilder().connectTimeout(Duration.ofSeconds(10)).build();
 HttpRequest httpOne = HttpRequest
 .newBuilder(URI.create(url + "/"+ id))
 .header("Content-Type","application/json")
 .GET()
 .build();
 HttpResponse<String> responce = httpGetOne.send(httpOne, HttpResponse.BodyHandlers.ofString());
 if (responce.statusCode() == 404) { throw new error("Not found "+ responce.statusCode()); }
 return Collections.singletonList(mapper.readValue(responce.body(), dataGettingBack.class));
 }
 public void putMethod(int id) throws IOException, InterruptedException, error
 {
 HttpClient httpClientPut = HttpClient.newBuilder().connectTimeout(Duration.ofSeconds(10)).build();
 HttpRequest httpPutReq = HttpRequest
 .newBuilder(URI.create(url+ "/" +id))
 .PUT(HttpRequest.BodyPublishers.ofString(url))
 .header("Content-Type", "application/json")
 .build();
 HttpResponse<String> response = httpClientPut.send(httpPutReq, HttpResponse.BodyHandlers.ofString());
 
 }
 public void postMethod() {
 HttpClient httpClientPost = HttpClient.newBuilder().connectTimeout(Duration.ofSeconds(10)).build();
 HttpRequest httpPostReq = HttpRequest
 .newBuilder(URI.create(url))
 //.POST()
 .header("Content-Type", "application/json")
 .build();
 }
 public void deleteMethod(int id)
 {
 HttpClient httpClientDelete = HttpClient.newBuilder().connectTimeout(Duration.ofSeconds(10)).build();
 HttpRequest httpDelReq = HttpRequest
 .newBuilder(URI.create(url))
 .DELETE()
 .header("Content-Type", "application/json")
 .build();
 }
}

Here is how I get my data back

public record dataGettingBack(Integer userId, Integer id, String title, boolean completed) {}

That's the output when I run it all

[dataGettingBack[userId=1, id=10, title=illo est ratione doloremque quia maiores aut, completed=true]]

I also have an error class

public class error extends Throwable
{ public error(String massege) { super(massege); } }

as well as link class

abstract class link
{
 public String url;
}

That's what I have in main

public static void main(String[] args) throws Exception, error
{
 methods methods = new methods();
 List<dataGettingBack> getAll = methods.getAllMethod();
 List<dataGettingBack> one = methods.getOne(10);
 System.out.println(one);
}

I started my programming classes a few months ago and that's my first project on my own

• user207421: You don't have to 'think' it: you have to consult the documentation.
• Slaw: Is your problem on the client side or the server side? Have you created the server as well? Which specific part of your code is wrong?
• g00se: I'm glad you got it sorted out but for goodness' sake, you need to get your naming right or your code is difficult and unpleasant to read

Answer 1

You can implement the POST request like below:

 import java.net.URI;
 import java.net.http.HttpRequest;
 import java.net.http.HttpRequest.BodyPublishers;
 String requestBody = "{\"key\":\"value\"}"; // Example JSON body
 HttpRequest request = HttpRequest.newBuilder()
 .uri(URI.create(url))
 .header("Content-Type", "application/json") // Set appropriate Content-Type
 .POST(BodyPublishers.ofString(requestBody)) // Specify POST method and body
 .build();

• Dmitrii Fedorov: Thanks, a couple more guides and I have done what I wanted to do dataGettingBack body = new dataGettingBack(3, 1,"test-test",true); return gson.toJson(body)

Answer 2

I used gson library to convert the data to json when sending it

public String putMethod(int id) throws IOException, InterruptedException, error
{
 HttpClient httpClientPut = HttpClient.newBuilder().connectTimeout(Duration.ofSeconds(10)).build();
 HttpRequest httpPutReq = HttpRequest
 .newBuilder(URI.create(url+ "/" +id))
 .PUT(HttpRequest.BodyPublishers.ofString(""))
 .header("Content-Type", "application/json")
 .build();
 HttpResponse<String> response = httpClientPut.send(httpPutReq, HttpResponse.BodyHandlers.ofString());
 dataGettingBack body = new dataGettingBack(3, 1,"test-test",true);
 return gson.toJson(body);
}

• VGR: I very much doubt HttpRequest.BodyPublishers.ofString("") addresses the question. There probably is an object that needs to be serialized using Jackson.
• Dmitrii Fedorov: Thanks I didn't notice that at first when it started working I used Jackson this time and it worked as well String jsonBody = mapper.writeValueAsString(body); .PUT(HttpRequest.BodyPublishers.ofString(jsonBody))