简单使用URLConnection、HttpURLConnection和HttpClient访问网络资源

URL的openConnection方法将返回一个URLConnection，该对象表示应用程序和URL之间的通信连接。程序可以通过它的实例向该URL发送请求，读取URL引用的资源。

下面通过一个简单示例来演示：

Activity：

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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; 
  
    @Override
    protected 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); 
    } 
  
    @Override
    public void onClick(View v) { 
        if (v == urlConnectionBtn) { 
            try { 
                // 直接使用URLConnection对象进行连接  
                URL url = new URL("http://192.168.1.100:8080/myweb/hello.jsp"); 
                // 得到URLConnection对象  
                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对象进行连接  
            try { 
                URL url = new URL( 
                        "http://192.168.1.100:8080/myweb/hello.jsp?username=abc"); 
                // 得到HttpURLConnection对象  
                HttpURLConnection connection = (HttpURLConnection) url 
                        .openConnection(); 
                // 设置为GET方式  
                connection.setRequestMethod("GET"); 
                if (connection.getResponseCode() == HttpURLConnection.HTTP_OK) { 
                    // 得到响应消息  
                    String message = connection.getResponseMessage(); 
                    showTextView.setText(message); 
                } 
            } catch (Exception e) { 
                e.printStackTrace(); 
            } 
        } 
        if (v == httpClientBtn) { 
            try { 
                // 使用ApacheHttp客户端进行连接(重要方法)  
                HttpClient client = new DefaultHttpClient(); 
  
                // 如果是Get提交则创建HttpGet对象，否则创建HttpPost对象  
                // POST提交的方式  
                HttpPost httpPost = new HttpPost( 
                        "http://192.168.1.100:8080/myweb/hello.jsp"); 
                // 如果是Post提交可以将参数封装到集合中传递  
                List dataList = new ArrayList(); 
                dataList.add(new BasicNameValuePair("username", "abc")); 
                dataList.add(new BasicNameValuePair("pwd", "123")); 
                // UrlEncodedFormEntity用于将集合转换为Entity对象  
                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");  
  
                // 获取相应消息  
                HttpResponse httpResponse = client.execute(httpPost); 
                // 获取消息内容  
                HttpEntity entity = httpResponse.getEntity(); 
                // 把消息对象直接转换为字符串  
                String content = EntityUtils.toString(entity); 
                // 显示在TextView中  
                // showTextView.setText(content);  
  
                // 通过webview来解析网页  
                webView.loadDataWithBaseURL(null, content, "text/html", 
                        "utf-8", null); 
                // 直接根据url来进行解析  
                // webView.loadUrl(url);  
            } catch (ClientProtocolException e) { 
                e.printStackTrace(); 
            } catch (IOException e) { 
                e.printStackTrace(); 
            } 
        } 
    } 
  
} 
 
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;
 
 @Override
 protected 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);
 }
 
 @Override
 public void onClick(View v) {
  if (v == urlConnectionBtn) {
   try {
    // 直接使用URLConnection对象进行连接
    URL url = new URL("http://192.168.1.100:8080/myweb/hello.jsp");
    // 得到URLConnection对象
    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对象进行连接
   try {
    URL url = new URL(
      "http://192.168.1.100:8080/myweb/hello.jsp?username=abc");
    // 得到HttpURLConnection对象
    HttpURLConnection connection = (HttpURLConnection) url
      .openConnection();
    // 设置为GET方式
    connection.setRequestMethod("GET");
    if (connection.getResponseCode() == HttpURLConnection.HTTP_OK) {
     // 得到响应消息
     String message = connection.getResponseMessage();
     showTextView.setText(message);
    }
   } catch (Exception e) {
    e.printStackTrace();
   }
  }
  if (v == httpClientBtn) {
   try {
    // 使用ApacheHttp客户端进行连接(重要方法)
    HttpClient client = new DefaultHttpClient();
 
    // 如果是Get提交则创建HttpGet对象，否则创建HttpPost对象
    // POST提交的方式
    HttpPost httpPost = new HttpPost(
      "http://192.168.1.100:8080/myweb/hello.jsp");
    // 如果是Post提交可以将参数封装到集合中传递
    List dataList = new ArrayList();
    dataList.add(new BasicNameValuePair("username", "abc"));
    dataList.add(new BasicNameValuePair("pwd", "123"));
    // UrlEncodedFormEntity用于将集合转换为Entity对象
    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");
 
    // 获取相应消息
    HttpResponse httpResponse = client.execute(httpPost);
    // 获取消息内容
    HttpEntity entity = httpResponse.getEntity();
    // 把消息对象直接转换为字符串
    String content = EntityUtils.toString(entity);
    // 显示在TextView中
    // showTextView.setText(content);
 
    // 通过webview来解析网页
    webView.loadDataWithBaseURL(null, content, "text/html",
      "utf-8", null);
    // 直接根据url来进行解析
    // webView.loadUrl(url);
   } catch (ClientProtocolException e) {
    e.printStackTrace();
   } catch (IOException e) {
    e.printStackTrace();
   }
  }
 }
 
}

上面使用到的url是部署在笔者本机的web应用，这里不再给出，大家可以换成自己的web应用即可。
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连接" /> 
  
    <Button
        android:id="@+id/test_url_main_btn_httpurlconnection"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="使用HttpURLConnection连接" /> 
  
    <Button
        android:id="@+id/test_url_main_btn_httpclient"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="使用Apache客户端连接" /> 
  
    <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> 
 
<?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连接" />
 
    <Button
        android:id="@+id/test_url_main_btn_httpurlconnection"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="使用HttpURLConnection连接" />
 
    <Button
        android:id="@+id/test_url_main_btn_httpclient"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="使用Apache客户端连接" />
 
    <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>

权限：

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

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原文地址：https://www.cnblogs.com/AceIsSunshineRain/p/5095114.html