在Android开发中,Android SDK附带了Apache的HttpClient,它是一个完善的客户端。它提供了对HTTP协议的全面支持,可以使用HttpClient的对象来执行HTTP GET和HTTP POST调用。
HTTP工作原理:
1.客户端(一般是指浏览器,这里是指自己写的程序)与服务器建立连接
2.建立连接后,客户端向服务器发送请求
3.服务器接收到请求后,向客户端发送响应信息
4.客户端与服务器断开连接
HttpClient的一般使用步骤:
1.使用DefaultHttpClient类实例化HttpClient对象
2.创建HttpGet或HttpPost对象,将要请求的URL通过构造方法传入HttpGet或HttpPost对象。
3.调用execute方法发送HTTP GET或HTTP POST请求,并返回HttpResponse对象。
4.通过HttpResponse接口的getEntity方法返回响应信息,并进行相应的处理。
最后记得要在AndroidManifest.xml文件添加网络权限
<uses-permission android:name="android.permission.INTERNET" />
下面是具体的例子:
1.使用HttpClient来执行GET调用
在LogCat窗口就能看到输出的信息
- package com.lingdududu.http;
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import java.io.InputStream;
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import org.apache.http.HttpResponse;
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import org.apache.http.HttpStatus;
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import org.apache.http.client.HttpClient;
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import org.apache.http.client.methods.HttpGet;
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import org.apache.http.impl.client.DefaultHttpClient;
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import android.app.Activity;
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import android.os.Bundle;
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import android.util.Log;
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public class HttpGetActivity extends Activity {
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String uri = "http://developer.android.com/";
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final String TAG_STRING = "TAG";
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@Override
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public void onCreate(Bundle savedInstanceState) {
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super.onCreate(savedInstanceState);
- setContentView(R.layout.main);
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try {
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HttpClient getClient = new DefaultHttpClient();
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HttpGet request = new HttpGet(uri);
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- HttpResponse response = getClient.execute(request);
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if(response.getStatusLine().getStatusCode()==HttpStatus.SC_OK){
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Log.i(TAG_STRING, "请求服务器端成功");
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- InputStream inStrem = response.getEntity().getContent();
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int result = inStrem.read();
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while (result != -1){
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System.out.print((char)result);
- result = inStrem.read();
- }
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- inStrem.close();
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}else {
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Log.i(TAG_STRING, "请求服务器端失败");
- }
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} catch (Exception e) {
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- e.printStackTrace();
- }
- }
- }
使用HTTP GET调用有一个缺点就是,请求的参数作为URL一部分来传递,以这种方式传递的时候,URL的长度应该在2048个字符之内。如果超出这个这范围,就要使用到HTTP POST调用。
2.使用HttpClient来执行POST调用
使用POST调用进行参数传递时,需要使用NameValuePair来保存要传递的参数。NameValuePair封装了一个键/值组合。另外,还需要设置所使用的字符集。
- package com.androidbook.services.httppost;
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import java.io.BufferedReader;
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import java.io.IOException;
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import java.io.InputStreamReader;
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import java.util.ArrayList;
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import java.util.List;
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import org.apache.http.HttpResponse;
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import org.apache.http.NameValuePair;
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import org.apache.http.client.HttpClient;
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import org.apache.http.client.entity.UrlEncodedFormEntity;
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import org.apache.http.client.methods.HttpPost;
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import org.apache.http.impl.client.DefaultHttpClient;
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import org.apache.http.message.BasicNameValuePair;
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import android.app.Activity;
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import android.os.Bundle;
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public class HttpPostActivity extends Activity {
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String uri = "http://developer.android.com/";
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@Override
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public void onCreate(Bundle savedInstanceState) {
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super.onCreate(savedInstanceState);
- setContentView(R.layout.main);
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BufferedReader in = null;
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try {
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HttpClient client = new DefaultHttpClient();
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HttpPost request = new HttpPost("http://code.google.com/android/");
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List<NameValuePair> postParameters = new ArrayList<NameValuePair>();
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postParameters.add(new BasicNameValuePair("id", "12345"));
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postParameters.add(new BasicNameValuePair("username", "dave"));
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UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(
- postParameters);
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- request.setEntity(formEntity);
- HttpResponse response = client.execute(request);
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in = new BufferedReader(
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new InputStreamReader(
- response.getEntity().getContent()));
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StringBuffer string = new StringBuffer("");
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String lineStr = "";
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while ((lineStr = in.readLine()) != null) {
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string.append(lineStr + "\n");
- }
- in.close();
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- String resultStr = string.toString();
- System.out.println(resultStr);
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} catch(Exception e) {
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} finally {
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if (in != null) {
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try {
- in.close();
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} catch (IOException e) {
- e.printStackTrace();
- }
- }
- }
- }
- }
本文转自 lingdududu 51CTO博客,原文链接:
http://blog.51cto.com/liangruijun/803097