從Url-空值返回解析Json數據-Java

Question

我正在使用Eclipse IDE從URl解析Json數據，但是每當我運行此代碼時，它都會返回空值。

這是來自URL的json數據

{
  "userId": 1,
  "id": 1,
  "title": "sunt aut facere repellat provident occaecati excepturi optio reprehenderit",
  "body": "quia et suscipit\nsuscipit recusandae consequuntur expedita et cum\nreprehenderit molestiae ut ut quas totam\nnostrum rerum est autem sunt rem eveniet architecto"
}

這是POJO類

package com.beto.test.json;

public class Data {
    private String id;

    private String body;

    private String title;

    private String userId;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getBody() {
        return body;
    }

    public void setBody(String body) {
        this.body = body;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getUserId() {
        return userId;
    }

    public void setUserId(String userId) {
        this.userId = userId;
    }

    @Override
    public String toString() {
        return "ClassPojo [id = " + id + ", body = " + body + ", title = " + title + ", userId = " + userId + "]";
    }
}

JsonParserUrl.java類

package com.beto.test.json;

import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.List;
import java.util.Objects;

/**
 * Created by BeytullahC on 23.03.2015.
 */
public class JsonParserFromUrl {
    public static void main(String[] args) {
        DefaultHttpClient httpClient = null;
        try {
            httpClient = new DefaultHttpClient();
            HttpResponse response = getResponse("http://jsonplaceholder.typicode.com/posts", httpClient);
            String outPut = readData(response);
            System.out.println(outPut);
            Gson gson = new Gson();
            List<Data> fromJson = gson.fromJson(outPut, new TypeToken<List<Data>>(){}.getType());
            System.out.println("DATA SIZE : "+fromJson.size());
            System.out.println("GET FIRST DATA : "+fromJson.get(0));
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            httpClient.getConnectionManager().shutdown();
        }

    }

    public static HttpResponse getResponse(String url, DefaultHttpClient httpClient) throws IOException {
        try {

            HttpGet httpGet = new HttpGet(url);
            httpGet.addHeader("accept", "application/json");
            HttpResponse response = httpClient.execute(httpGet);
            return response;
        } catch (IOException e) {
            throw e;
        }
    }

    public static String readData(HttpResponse response) throws Exception {
        BufferedReader reader = null;
        try {


            reader = new BufferedReader(new InputStreamReader(
                    response.getEntity().getContent()));
            StringBuffer data = new StringBuffer();
            char[] dataLength = new char[1024];
            int read;
            while (((read = reader.read(dataLength)) != -1)) {
                data.append(dataLength, 0, read);
            }
            return data.toString();
        } finally {
            if (reader != null)
                reader.close();
        }
    }
}

TestRunner.java類

package com.beto.test.json;

    public class TestRunner {

        public static void main(String[] args) {
            // TODO Auto-generated method stub

            try{

          Data data = JsonParserfromUrl.getData("http://jsonplaceholder.typicode.com/posts/1");
            System.out.println("result:\n" +data);
        }
            catch(Exception e)
            {
                System.out.println("error");
            }

    }}

自由主義者增加了：

 - gson-2.3.1.jar
 - httpclient-4.5.jar
 - commons-logging-1.1.1.jar
 - httpclient-cache-4.4.jar
 - httpmime-4.0.jar
 - commons-codec-1.1.jar
 - httpcore-4.4.jar

輸出值

ClassPojo [id = " null ", body = " null ", title = " null ", userId ="null"]

請解決此問題，它不應返回空值。

Answer 1

首先，您應該獲取JSON字符串，然后將其解析為Data類。

String yourJsonString = readUrl("http://jsonplaceholder.typicode.com/posts/1");

Gson gson = new Gson();        
Data data = gson.fromJson(yourJsonString, Data.class);