使用 Apache HttpClient

爲了更好的處理向web站點的請求,包括處理Session ,Cookie等細節問題,Apache 開源組織提供了一個 HttpClient項目.它是一個簡單的HTTP客戶端(並不是瀏覽器),可以用於發送HTTP請求,接受HTTP響應,.但不會緩存服務器的響應,不能執行HTML頁面中嵌入的JavaScript代碼,也不會對頁面內容進行任何解析,處理.

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使用 HttpClient 發送請求,接受響應. 需要如下幾步:

1. 創建 HttpClient 對象.
2. 如需要發送GET 請求,則創建 HttpGet對象.如發動POST請求,則創建HttpPost對象.
3. 如果需要發送請求參數,可調用 HttpGet,HttpPost共同的 setParams(HttpParams params) 方法來添加請求參數; 對於 HttpPost 對象而言, 也可調用setEntity(HttpEntity entity)方法來設置請求參數.
4. 調用 HttpClient 對象的execute(HttpUriRequest request) 發送請求執行該方法返回一個HttpResponse.
5. 調用 HttpResponse 的getAllHeaders(), getHeaders(String name),等方法獲取服務器的響應頭; 調用 HttpResponse 的getEntity()方法可獲取 HttpEntity 對象,該對象包裝了服務器的響應內容.程序可通過該對象獲取服務器的響應內容.

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package com.net.httpclient;

import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.protocol.HTTP;
import org.apache.http.util.EntityUtils;

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

/**
 * 使用 Apache HttpClient
 * org.apache.http.client.HttpClient
 */
public class HttpClientActivity extends AppCompatActivity {
    TextView respone;
    Button assess, login;
    HttpClient httpClient;

    Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            if(msg.what == 0x1234)
            {
                // 使用response文本框顯示服務器響應
                respone.append(msg.obj.toString() + "\n");
            }
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_http_client);

        //創建 DefaultHttpClient 對象
        httpClient = new DefaultHttpClient();
        respone = (TextView) findViewById(R.id.response);

        assess = (Button) findViewById(R.id.accessSecret);
        login = (Button) findViewById(R.id.showLogin);

        initListener();
    }

    private void initListener() {
        assess.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                new Thread() {
                    @Override
                    public void run() {
                        super.run();

                        //創建一個 HttpGet 對象
                        HttpGet get = new HttpGet("http://169.254.214.117:8080/foo/secret.jsp");

                        try {
                            //發送 get 請求
                            HttpResponse httpResponse = httpClient.execute(get);

                            HttpEntity entity = httpResponse.getEntity();

                            if (entity == null) {
                                //讀取服務器響應
                                BufferedReader br = new BufferedReader(new InputStreamReader(entity.getContent()));

                                String line = null;
                                while ((line = br.readLine()) != null) {

                                    Message msg = Message.obtain();
                                    msg.what = 0x1234;
                                    msg.obj = line;

                                    mHandler.sendMessage(msg);
                                }
                            }
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }
                }.start();
            }
        });

        login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //加載登錄界面
                final View loginDialog = getLayoutInflater().inflate(R.layout.login, null);

                //使用對話框供用戶登錄
                new AlertDialog.Builder(HttpClientActivity.this)
                        .setTitle("登錄系統")
                        .setView(loginDialog)
                        .setPositiveButton("登錄", new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialog, int which) {

                                //獲取用戶輸入的用戶名, 密碼
                                final String name = ((EditText) loginDialog.findViewById(R.id.name)).getText().toString();
                                final String pass = ((EditText) loginDialog.findViewById(R.id.pass)).getText().toString();


                                //開啓子線程
                                new Thread() {
                                    @Override
                                    public void run() {
                                        try {
                                            HttpPost post = new HttpPost("http://169.254.214.117:8080/foo/login.jsp");

                                            //如果傳遞參數個數比較多,可以對傳遞的多個參數進行封裝
                                            List<NameValuePair> params = new ArrayList<NameValuePair>();

                                            params.add(new BasicNameValuePair("name", name));
                                            params.add(new BasicNameValuePair("pass", pass));

                                            //設置請求參數
                                            post.setEntity(new UrlEncodedFormEntity(params, HTTP.UTF_8));

                                            //發送 post請求
                                            HttpResponse response =httpClient.execute(post);

                                            //如果服務器成功的 返回響應
                                            if (response.getStatusLine().getStatusCode()==200){
                                                String msg = EntityUtils.toString(response.getEntity());

                                                Looper.prepare();

                                                //提示登錄成功
                                                Toast.makeText(HttpClientActivity.this, msg, Toast.LENGTH_SHORT).show();

                                                Looper.loop();
                                            }

                                        } catch (Exception e) {
                                            e.printStackTrace();
                                        }
                                    }
                                }.start();

                            }
                        }).setNegativeButton("取消",null).show();
            }
        });
    }
}