android中Post方式发送HTTP请求

Post方式比Get方式要复杂一点，因为该方式需要将请求的参数放在http请求的正文中，所以需要构造请求体。

步骤：

1.构造URL

URL url = new URL(PATH);

2.设置连接

HttpURLConnection connection = (HttpURLConnection) url.openConnection();
      connection.setConnectTimeout(3000);
      connection.setDoInput(true);//表示从服务器获取数据
      connection.setDoOutput(true);//表示向服务器写数据
      //获得上传信息的字节大小以及长度
     
      connection.setRequestMethod("POST");
      //是否使用缓存
      connection.setUseCaches(false);
      //表示设置请求体的类型是文本类型
      connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
      
      connection.setRequestProperty("Content-Length", String.valueOf(mydata.length));
      connection.connect();   

　　3.写入请求正文

Map<String, String> params = new HashMap<String, String>();
params.put("username", "lili");
params.put("password", "123");
StringBuffer buffer = new StringBuffer();
try {//把请求的主体写入正文！！
 if(params != null&&!params.isEmpty()){
//迭代器
  for(Map.Entry<String, String> entry : params.entrySet()){
  buffer.append(entry.getKey()).append("=").
  append(URLEncoder.encode(entry.getValue(),encode)).
  append("&");
  }
}
//   System.out.println(buffer.toString());
  //删除最后一个字符&，多了一个;主体设置完毕
  buffer.deleteCharAt(buffer.length()-1);
  byte[] mydata = buffer.toString().getBytes(); 
//获得输出流，向服务器输出数据
      OutputStream outputStream = connection.getOutputStream();
           outputStream.write(mydata,0,mydata.length);

　　4.读取返回数据，关闭连接

//通常叫做内存流，写在内存中的
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
byte[] data = new byte[1024];
int len = 0;
String result = "";
if(inputStream != null){
try {
while((len = inputStream.read(data))!=-1){
data.toString();

outputStream.write(data, 0, len);
}
//result是在服务器端设置的doPost函数中的
result = new String(outputStream.toByteArray(),encode);
outputStream.flush();

　　下面上代码：一个简单的Demo访问一个自建的Servlet:

package com.http.post;  
  
import java.io.ByteArrayOutputStream;  
import java.io.IOException;  
import java.io.InputStream;  
import java.io.OutputStream;  
import java.io.UnsupportedEncodingException;  
import java.net.HttpURLConnection;  
import java.net.MalformedURLException;  
import java.net.URL;  
import java.net.URLEncoder;  
import java.util.HashMap;  
import java.util.Map;  
  
public class HttpUtils {  
  
    private static String PATH = "http://172.24.87.47:8088/myhttp/servlet/LoginAction";  
    private static URL url;  
    public HttpUtils() {  
        // TODO Auto-generated constructor stub  
    }  
  
    static{  
        try {  
            url = new URL(PATH);  
        } catch (MalformedURLException e) {  
            // TODO Auto-generated catch block  
            e.printStackTrace();  
        }  
    }  
    /** 
     * @param params 填写的url的参数 
     * @param encode 字节编码 
     * @return 
     */  
    public static String sendPostMessage(Map<String, String> params,String encode){  
        StringBuffer buffer = new StringBuffer();  
        try {//把请求的主体写入正文！！  
             if(params != null&&!params.isEmpty()){  
                //迭代器  
              for(Map.Entry<String, String> entry : params.entrySet()){  
                  buffer.append(entry.getKey()).append("=").  
                  append(URLEncoder.encode(entry.getValue(),encode)).  
                  append("&");  
              }  
            }  
//            System.out.println(buffer.toString());  
              //删除最后一个字符&，多了一个;主体设置完毕  
              buffer.deleteCharAt(buffer.length()-1);  
              byte[] mydata = buffer.toString().getBytes();   
              HttpURLConnection connection = (HttpURLConnection) url.openConnection();  
              connection.setConnectTimeout(3000);  
              connection.setDoInput(true);//表示从服务器获取数据  
              connection.setDoOutput(true);//表示向服务器写数据  
              //获得上传信息的字节大小以及长度  
               
              connection.setRequestMethod("POST");  
              //是否使用缓存  
              connection.setUseCaches(false);  
              //表示设置请求体的类型是文本类型  
              connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");  
                
              connection.setRequestProperty("Content-Length", String.valueOf(mydata.length));  
              connection.connect();   //连接，不写也可以。。？？有待了解  
             
              //获得输出流，向服务器输出数据  
              OutputStream outputStream = connection.getOutputStream();  
                   outputStream.write(mydata,0,mydata.length);  
                   //获得服务器响应的结果和状态码  
              int responseCode = connection.getResponseCode();   
              if(responseCode == HttpURLConnection.HTTP_OK){  
                 return changeInputeStream(connection.getInputStream(),encode);  
                    
              }  
        } catch (UnsupportedEncodingException e) {  
            // TODO Auto-generated catch block  
            e.printStackTrace();  
        } catch (IOException e) {  
            // TODO Auto-generated catch block  
            e.printStackTrace();  
        }  
          
        return "";  
    }  
   /** 
    * 将一个输入流转换成字符串 
    * @param inputStream 
    * @param encode 
    * @return 
    */  
    private static String changeInputeStream(InputStream inputStream,String encode) {  
        //通常叫做内存流，写在内存中的  
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();  
        byte[] data = new byte[1024];  
        int len = 0;  
        String result = "";  
        if(inputStream != null){  
            try {  
                while((len = inputStream.read(data))!=-1){  
                    data.toString();  
                      
                    outputStream.write(data, 0, len);  
                }  
                //result是在服务器端设置的doPost函数中的  
                result = new String(outputStream.toByteArray(),encode);  
                outputStream.flush();  
            } catch (IOException e) {  
                // TODO Auto-generated catch block  
                e.printStackTrace();  
            }  
        }  
        return result;  
    }  
  
    public static void main(String[] arsg){  
        Map<String, String> params = new HashMap<String, String>();  
        params.put("username", "lili");  
        params.put("password", "123");  
        String result = sendPostMessage(params,"utf-8");  
        System.out.println("result->"+result);  
    }  
}  

　　下边是服务端的Servlet代码：

package com.login.manager;  
  
import java.io.ByteArrayOutputStream;  
import java.io.IOException;  
import java.io.InputStream;  
import java.io.InputStreamReader;  
import java.io.PrintWriter;  
  
import javax.servlet.ServletException;  
import javax.servlet.http.HttpServlet;  
import javax.servlet.http.HttpServletRequest;  
import javax.servlet.http.HttpServletResponse;  
  
public class LoginAction extends HttpServlet {  
  
    /** 
     * Constructor of the object. 
     */  
    public LoginAction() {  
        super();  
    }  
  
    /** 
     * Destruction of the servlet. <br> 
     */  
    public void destroy() {  
        super.destroy(); // Just puts "destroy" string in log  
        // Put your code here  
    }  
  
    public void doGet(HttpServletRequest request, HttpServletResponse response)  
            throws ServletException, IOException {  
  
        this.doPost(request, response);  
      
    }  
  
    /** 
     * The doPost method of the servlet. <br> 
     * 
     * This method is called when a form has its tag value method equals to post. 
     *  
     * @param request the request send by the client to the server 
     * @param response the response send by the server to the client 
     * @throws ServletException if an error occurred 
     * @throws IOException if an error occurred 
     */  
    public void doPost(HttpServletRequest request, HttpServletResponse response)  
            throws ServletException, IOException {  
  
        response.setContentType("text/html;charset=utf-8");  
        request.setCharacterEncoding("utf-8");  
        response.setCharacterEncoding("utf-8");  
        PrintWriter out = response.getWriter();  
        String username = request.getParameter("username");  //传过来的内容是：password=123&username=lili
        System.out.println("username:"+username);  
        String pswd = request.getParameter("password");  
        System.out.println("password:"+pswd);  
        if(username.equals("张三")&&pswd.equals("123")){  
            //表示服务器端返回的结果  
            out.print("login is success!!!!");  
        }else{  
            out.print("login is fail!!!");  
        }  
      
        out.flush();  
        out.close();  
    }  
  
    /** 
     * Initialization of the servlet. <br> 
     * 
     * @throws ServletException if an error occurs 
     */  
    public void init() throws ServletException {  
        // Put your code here  
    }  
  
}  

　　服务端代码使用servlet搭建的。。。

这是运行结果：

服务端的：

 在服务端接收的内容是：password=123&username=lili  被它解析啦。。