I have looked at several other questions, but I still don't fully understand this. I want to POST a JSON string to a remote address and then retrieve the values from the JSON response. I am using the Apache libraries for Java.
public HttpResponse http(String url, String body) throws IOException {
try (CloseableHttpClient httpClient = HttpClientBuilder.create().build()) {
HttpPost request = new HttpPost(url);
StringEntity params = new StringEntity(body);
request.addHeader("content-type", "application/json");
request.setEntity(params);
//httpClient.execute(request);
HttpResponse result = httpClient.execute(request);
} catch (IOException ex) {
}
return null;
}
And as body, I would pass the following (an example):
{"example":1,"fr":"lol"}
I have absolutely no idea about how to retrieve the JSON values from the response, either.
The simplest way is using libraries like google-http-java-client but if you want parse the JSON response by yourself you can do that in a multiple ways, you can use org.json, json-simple, Gson, minimal-json, jackson-mapper-asl (from 1.x)... etc
A set of simple examples:
Using Gson:
import java.io.IOException;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.util.EntityUtils;
public class Gson {
public static void main(String[] args) {
}
public HttpResponse http(String url, String body) {
try (CloseableHttpClient httpClient = HttpClientBuilder.create().build()) {
HttpPost request = new HttpPost(url);
StringEntity params = new StringEntity(body);
request.addHeader("content-type", "application/json");
request.setEntity(params);
HttpResponse result = httpClient.execute(request);
String json = EntityUtils.toString(result.getEntity(), "UTF-8");
com.google.gson.Gson gson = new com.google.gson.Gson();
Response respuesta = gson.fromJson(json, Response.class);
System.out.println(respuesta.getExample());
System.out.println(respuesta.getFr());
} catch (IOException ex) {
}
return null;
}
public class Response{
private String example;
private String fr;
public String getExample() {
return example;
}
public void setExample(String example) {
this.example = example;
}
public String getFr() {
return fr;
}
public void setFr(String fr) {
this.fr = fr;
}
}
}
Using json-simple:
import java.io.IOException;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.util.EntityUtils;
import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
public class JsonSimple {
public static void main(String[] args) {
}
public HttpResponse http(String url, String body) {
try (CloseableHttpClient httpClient = HttpClientBuilder.create().build()) {
HttpPost request = new HttpPost(url);
StringEntity params = new StringEntity(body);
request.addHeader("content-type", "application/json");
request.setEntity(params);
HttpResponse result = httpClient.execute(request);
String json = EntityUtils.toString(result.getEntity(), "UTF-8");
try {
JSONParser parser = new JSONParser();
Object resultObject = parser.parse(json);
if (resultObject instanceof JSONArray) {
JSONArray array=(JSONArray)resultObject;
for (Object object : array) {
JSONObject obj =(JSONObject)object;
System.out.println(obj.get("example"));
System.out.println(obj.get("fr"));
}
}else if (resultObject instanceof JSONObject) {
JSONObject obj =(JSONObject)resultObject;
System.out.println(obj.get("example"));
System.out.println(obj.get("fr"));
}
} catch (Exception e) {
// TODO: handle exception
}
} catch (IOException ex) {
}
return null;
}
}
etc...