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

2022-08-25 13:05:26

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：

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：

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

MainActivity.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");
}
}

码农公寓

一、HttpClient介绍

二、服务器端代码

三、Android客户端代码

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