Android入门：用HttpClient模拟HTTP的GET和POST请求

一、HttpClient介绍

HttpClient是用来模拟HTTP请求的，其实实质就是把HTTP请求模拟后发给Web服务器；

Android已经集成了HttpClient，因此可以直接使用；

注：此处HttpClient代码不只可以适用于Android，也可适用于一般的Java程序；

HTTP GET核心代码：

(1)DefaultHttpClient client = new DefaultHttpClient();

(2)HttpGet get = new HttpGet(String url);//此处的URL为http://..../path?arg1=value&....argn=value

(3)HttpResponse response = client.execute(get); //模拟请求

(4)int code = response.getStatusLine().getStatusCode();//返回响应码

(5)InputStream in = response.getEntity().getContent();//服务器返回的数据

HTTP POST核心代码：

(1)DefaultHttpClient client = new DefaultHttpClient();

(2)BasicNameValuePair pair = new BasicNameValuePair(String name,String value);//创建一个请求头的字段，比如content-type,text/plain

(3)UrlEncodedFormEntity entity = new UrlEncodedFormEntity(List<NameValuePair> list,String encoding);//对自定义请求头进行URL编码

(4)HttpPost post = new HttpPost(String url);//此处的URL为http://..../path

(5)post.setEntity(entity);

(6)HttpResponse response = client.execute(post);

(7)int code = response.getStatusLine().getStatusCode();

(8)InputStream in = response.getEntity().getContent();//服务器返回的数据

二、服务器端代码

服务器端代码和通过URLConnection发出请求的代码不变：

[java]

package org.xiazdong.servlet;

import java.io.IOException;

import java.io.OutputStream;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

@WebServlet("/Servlet1")

public class Servlet1 extends HttpServlet {

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

String nameParameter = request.getParameter("name");

String ageParameter = request.getParameter("age");

String name = new String(nameParameter.getBytes("ISO-8859-1"),"UTF-8");

String age = new String(ageParameter.getBytes("ISO-8859-1"),"UTF-8");

System.out.println("GET");

System.out.println("name="+name);

System.out.println("age="+age);

response.setCharacterEncoding("UTF-8");

OutputStream out = response.getOutputStream();//返回数据

out.write("GET请求成功!".getBytes("UTF-8"));

out.close();

}

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

request.setCharacterEncoding("UTF-8");

String name = request.getParameter("name");

String age = request.getParameter("age");

System.out.println("POST");

System.out.println("name="+name);

System.out.println("age="+age);

response.setCharacterEncoding("UTF-8");

OutputStream out = response.getOutputStream();

out.write("POST请求成功!".getBytes("UTF-8"));

out.close();

}

}

三、Android客户端代码

效果如下：



在AndroidManifest.xml加入：

[html]

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

MainActivity.java

[java]

package org.xiazdong.network.httpclient;

import java.io.ByteArrayOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.net.URLEncoder;

import java.util.ArrayList;

import java.util.List;

import org.apache.http.HttpResponse;

import org.apache.http.NameValuePair;

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 android.app.Activity;

import android.os.Bundle;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.EditText;

import android.widget.Toast;

public class MainActivity extends Activity {

private EditText name, age;

private Button getbutton, postbutton;

private OnClickListener listener = new OnClickListener() {

@Override

public void onClick(View v) {

try{

if(postbutton==v){

/*

* NameValuePair代表一个HEADER，List<NameValuePair>存储全部的头字段

* UrlEncodedFormEntity类似于URLEncoder语句进行URL编码

* HttpPost类似于HTTP的POST请求

* client.execute()类似于发出请求，并返回Response

*/

DefaultHttpClient client = new DefaultHttpClient();

List<NameValuePair> list = new ArrayList<NameValuePair>();

NameValuePair pair1 = new BasicNameValuePair("name", name.getText().toString());

NameValuePair pair2 = new BasicNameValuePair("age", age.getText().toString());

list.add(pair1);

list.add(pair2);

UrlEncodedFormEntity entity = new UrlEncodedFormEntity(list,"UTF-8");

HttpPost post = new HttpPost("http://192.168.0.103:8080/Server/Servlet1");

post.setEntity(entity);

HttpResponse response = client.execute(post);

if(response.getStatusLine().getStatusCode()==200){

InputStream in = response.getEntity().getContent();//接收服务器的数据，并在Toast上显示

String str = readString(in);

Toast.makeText(MainActivity.this, str, Toast.LENGTH_SHORT).show();

}

else Toast.makeText(MainActivity.this, "POST提交失败", Toast.LENGTH_SHORT).show();

}

if(getbutton==v){

DefaultHttpClient client = new DefaultHttpClient();

StringBuilder buf = new StringBuilder("http://192.168.0.103:8080/Server/Servlet1");

buf.append("?");

buf.append("name="+URLEncoder.encode(name.getText().toString(),"UTF-8")+"&");

buf.append("age="+URLEncoder.encode(age.getText().toString(),"UTF-8"));

HttpGet get = new HttpGet(buf.toString());

HttpResponse response = client.execute(get);

if(response.getStatusLine().getStatusCode()==200){

InputStream in = response.getEntity().getContent();

String str = readString(in);

Toast.makeText(MainActivity.this, str, Toast.LENGTH_SHORT).show();

}

else Toast.makeText(MainActivity.this, "GET提交失败", Toast.LENGTH_SHORT).show();

}

}

catch(Exception e){}

}

};

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

name = (EditText) this.findViewById(R.id.name);

age = (EditText) this.findViewById(R.id.age);

getbutton = (Button) this.findViewById(R.id.getbutton);

postbutton = (Button) this.findViewById(R.id.postbutton);

getbutton.setOnClickListener(listener);

postbutton.setOnClickListener(listener);

}

protected String readString(InputStream in) throws Exception {

byte[]data = new byte[1024];

int length = 0;

ByteArrayOutputStream bout = new ByteArrayOutputStream();

while((length=in.read(data))!=-1){

bout.write(data,0,length);

}

return new String(bout.toByteArray(),"UTF-8");

}

}

作者：xiazdong