Android/Java：JSON HTTP 请求

Android/Java: JSON HTTP Request

提问by mergesort

How can I make a request to get/download http://coolsite.com/coolstuff.jsonin Java/Android

如何在 Java/Android 中请求获取/下载http://coolsite.com/coolstuff.json

回答by Tony the Pony

Android supports all the standard java.netclasses. The simplest way to retrieve content via HTTP is to call openStream()on your URL and read it:

Android 支持所有标准java.net类。通过 HTTP 检索内容的最简单方法是调用openStream()您的 URL 并读取它：

    URL url = new URL("http://coolsite.com/coolstuff.js");
    InputStream in = url.openStream();
    InputStreamReader reader = new InputStreamReader(in);
    // read the JSON data

There are libraries for reading JSON in Java (see http://json.org/java), but since the format is really simple, you can parse it easily.

有一些用于在 Java 中读取 JSON 的库（请参阅http://json.org/java），但由于格式非常简单，因此您可以轻松解析它。

回答by LocalPCGuy

From a cached copy of:

从缓存的副本：

How-to: Android as a RESTful Client

操作方法：Android 作为 RESTful 客户端

This is a how-to focused on creating a RESTful java object at Android. I've used HTTPClient, HTTPEntry, HTTPGet, HTTPResponse, JSONArray and JSONObject classes. I think it'll be useful if we need to use a web-service from client application.

这是一个专注于在 Android 上创建 RESTful java 对象的方法。我使用过 HTTPClient、HTTPEntry、HTTPGet、HTTPResponse、JSONArray 和 JSONObject 类。我认为如果我们需要使用来自客户端应用程序的 Web 服务会很有用。

I've implemented a simple Java Object called RestClient which connects to a given Rest-JSON service. After connection, this object prints response content. Using this content, a JSONObject created. Then, RestClient prints the JSONObject's content, parses all values of this object and prints them as well. And as a last job, RestClient pushes a sample value to the JSONObject.

我已经实现了一个名为 RestClient 的简单 Java 对象，它连接到给定的 Rest-JSON 服务。连接后，该对象打印响应内容。使用此内容，创建了一个 JSONObject。然后，RestClient 打印 JSONObject 的内容，解析该对象的所有值并打印它们。作为最后一项工作，RestClient 将示例值推送到 JSONObject。

I've uploaded RestClient. Hope it'll be useful.

我已经上传了 RestClient。希望它会很有用。

P.s: To get access to internet at Android, following field must be included to AndroidManifest.xml file of the project.

Ps：要在Android上访问互联网，项目的AndroidManifest.xml文件中必须包含以下字段。

<uses-permission android:name="android.permission.INTERNET"></uses-permission>

RestClient code:

休息客户端代码：

package praeda.muzikmekan;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.util.Log;

public class RestClient {

    private static String convertStreamToString(InputStream is) {
        /*
         * To convert the InputStream to String we use the BufferedReader.readLine()
         * method. We iterate until the BufferedReader return null which means
         * there's no more data to read. Each line will appended to a StringBuilder
         * and returned as String.
         */
        BufferedReader reader = new BufferedReader(new InputStreamReader(is));
        StringBuilder sb = new StringBuilder();

        String line = null;
        try {
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                is.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return sb.toString();
    }

    /* This is a test function which will connects to a given
     * rest service and prints it's response to Android Log with
     * labels "Praeda".
     */
    public static void connect(String url)
    {

        HttpClient httpclient = new DefaultHttpClient();

        // Prepare a request object
        HttpGet httpget = new HttpGet(url); 

        // Execute the request
        HttpResponse response;
        try {
            response = httpclient.execute(httpget);
            // Examine the response status
            Log.i("Praeda",response.getStatusLine().toString());

            // Get hold of the response entity
            HttpEntity entity = response.getEntity();
            // If the response does not enclose an entity, there is no need
            // to worry about connection release

            if (entity != null) {

                // A Simple JSON Response Read
                InputStream instream = entity.getContent();
                String result= convertStreamToString(instream);
                Log.i("Praeda",result);

                // A Simple JSONObject Creation
                JSONObject json=new JSONObject(result);
                Log.i("Praeda","<jsonobject>\n"+json.toString()+"\n</jsonobject>");

                // A Simple JSONObject Parsing
                JSONArray nameArray=json.names();
                JSONArray valArray=json.toJSONArray(nameArray);
                for(int i=0;i<valArray.length();i++)
                {
                    Log.i("Praeda","<jsonname"+i+">\n"+nameArray.getString(i)+"\n</jsonname"+i+">\n"
                            +"<jsonvalue"+i+">\n"+valArray.getString(i)+"\n</jsonvalue"+i+">");
                }

                // A Simple JSONObject Value Pushing
                json.put("sample key", "sample value");
                Log.i("Praeda","<jsonobject>\n"+json.toString()+"\n</jsonobject>");

                // Closing the input stream will trigger connection release
                instream.close();
            }


        } catch (ClientProtocolException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}