Java Http请求JSON和响应处理

Question

我已经看过其他几个问题，但我仍然不完全理解这一点。我想将JSON字符串POST到远程地址，然后从JSON响应中检索值。我正在使用Apache的Java库。

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;
}

作为正文，我将通过以下（示例）：

{"example":1,"fr":"lol"}

我完全不知道如何从响应中检索JSON值。

Answer 1

最简单的方法是使用像google-http-java-client这样的库，但是如果你想自己解析JSON响应你可以用多种方式解决，你可以使用org.json，json-simple，Gson，minimal-json，jackson-mapper-asl（来自1.x）......等等

一组简单的例子：

使用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;
        }
    }
}

使用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;
    }
}

等等...