簡單使用URLConnection、HttpURLConnection和HttpClient訪問網路資源

URL的openConnection方法將返回一個URLConnection，該對象表示應用程式和URL之間的通訊串連。程式可以通過它的執行個體向該URL發送請求，讀取URL引用的資源。

下面通過一個簡單樣本來示範：

Activity：

package com.home.urlconnection;import java.io.IOException;import java.io.InputStream;import java.net.HttpURLConnection;import java.net.URL;import java.net.URLConnection;import java.util.ArrayList;import java.util.List;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.entity.UrlEncodedFormEntity;import org.apache.http.client.methods.HttpPost;import org.apache.http.impl.client.DefaultHttpClient;import org.apache.http.message.BasicNameValuePair;import org.apache.http.util.EntityUtils;import android.app.Activity;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.webkit.WebView;import android.widget.Button;import android.widget.TextView;public class MainActivity extends Activity implements OnClickListener {private Button urlConnectionBtn;private Button httpUrlConnectionBtn;private Button httpClientBtn;private TextView showTextView;private WebView webView;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);init();}private void init() {urlConnectionBtn = (Button) findViewById(R.id.test_url_main_btn_urlconnection);httpUrlConnectionBtn = (Button) findViewById(R.id.test_url_main_btn_httpurlconnection);httpClientBtn = (Button) findViewById(R.id.test_url_main_btn_httpclient);showTextView = (TextView) findViewById(R.id.test_url_main_tv_show);webView = (WebView) findViewById(R.id.test_url_main_wv);urlConnectionBtn.setOnClickListener(this);httpUrlConnectionBtn.setOnClickListener(this);httpClientBtn.setOnClickListener(this);}@Overridepublic void onClick(View v) {if (v == urlConnectionBtn) {try {// 直接使用URLConnection對象進行串連URL url = new URL("http://192.168.1.100:8080/myweb/hello.jsp");// 得到URLConnection對象URLConnection connection = url.openConnection();InputStream is = connection.getInputStream();byte[] bs = new byte[1024];int len = 0;StringBuffer sb = new StringBuffer();while ((len = is.read(bs)) != -1) {String str = new String(bs, 0, len);sb.append(str);}showTextView.setText(sb.toString());} catch (Exception e) {e.printStackTrace();}}if (v == httpUrlConnectionBtn) {// 直接使用HttpURLConnection對象進行串連try {URL url = new URL("http://192.168.1.100:8080/myweb/hello.jsp?username=abc");// 得到HttpURLConnection對象HttpURLConnection connection = (HttpURLConnection) url.openConnection();// 設定為GET方式connection.setRequestMethod("GET");if (connection.getResponseCode() == HttpURLConnection.HTTP_OK) {// 得到響應訊息String message = connection.getResponseMessage();showTextView.setText(message);}} catch (Exception e) {e.printStackTrace();}}if (v == httpClientBtn) {try {// 使用ApacheHttp用戶端進行串連(重要方法)HttpClient client = new DefaultHttpClient();// 如果是Get提交則建立HttpGet對象，否則建立HttpPost對象// POST提交的方式HttpPost httpPost = new HttpPost("http://192.168.1.100:8080/myweb/hello.jsp");// 如果是Post提交可以將參數封裝到集合中傳遞List dataList = new ArrayList();dataList.add(new BasicNameValuePair("username", "abc"));dataList.add(new BasicNameValuePair("pwd", "123"));// UrlEncodedFormEntity用於將集合轉換為Entity對象httpPost.setEntity(new UrlEncodedFormEntity(dataList));// GET提交的方式// HttpGet httpGet = new// HttpGet("http://192.168.1.100:8080/myweb/hello.jsp?username=abc&pwd=321");// 擷取相應訊息HttpResponse httpResponse = client.execute(httpPost);// 擷取訊息內容HttpEntity entity = httpResponse.getEntity();// 把訊息對象直接轉換為字串String content = EntityUtils.toString(entity);// 顯示在TextView中// showTextView.setText(content);// 通過webview來解析網頁webView.loadDataWithBaseURL(null, content, "text/html","utf-8", null);// 直接根據url來進行解析// webView.loadUrl(url);} catch (ClientProtocolException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}}}}

上面使用到的url是部署在筆者原生web應用，這裡不再給出，大家可以換成自己的web應用即可。
布局XML：

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical" >    <Button        android:id="@+id/test_url_main_btn_urlconnection"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="使用URLConnection串連" />    <Button        android:id="@+id/test_url_main_btn_httpurlconnection"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="使用HttpURLConnection串連" />    <Button        android:id="@+id/test_url_main_btn_httpclient"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="使用Apache用戶端串連" />    <TextView        android:id="@+id/test_url_main_tv_show"        android:layout_width="wrap_content"        android:layout_height="wrap_content" />    <WebView        android:id="@+id/test_url_main_wv"        android:layout_width="match_parent"        android:layout_height="match_parent" /></LinearLayout>

許可權：

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