本文内容：使用java标准接口，实现http用post方式提交数据。
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程序组成部分：
1.客户端用eclipse HttpUtils.java 标准java接口，实现http用post方式提交数据。 （用post方式提交 username 和 password）
2.服务器端用myeclipse+tomcat 对客户端请求进行相应。(若用户名密码正确，则返回字符串"login is success !" ,不正确则返回字符串“login is fail !”)
重点注意点：
1. public static String sendPostMessage(Map<String,String> params , String encode)
目的: 在客户端向服务器端发送 数据 params , 最终获取从服务器返回的输入流，最终将该输入流转换成字符串。注意使用标准java接口如何实现http的post请求，成功与服务器连接，并且获得从服务器端响应返回的数据。
2. public String String changInputStream(InputStream inputStream , String encode)
目的: 将一个输入流按照指定编码方式转变成一个字符串。(本例中是指，将从服务器端返回的输入流InputStream转变成一个字符串String，编码方式是encode方式)
3. Map<String ,String> 的实例化方法及迭代方法
Map 的实例化方法：
Map<String, String> params = new HashMap<String, String>();
params.put("username", "admin");
params.put("password", "123");
Map 的迭代方法：
StringBuffer stringBuffer = new StringBuffer();
for (Map.Entry<String, String> entry : params.entrySet()) {
try {
stringBuffer
.append(entry.getKey())
.append("=")
.append(URLEncoder.encode(entry.getValue(), encode))
.append("&");
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
// 删掉最后一个 & 字符
stringBuffer.deleteCharAt(stringBuffer.length() - 1);
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程序思路：
1. 客户端建立http链接httpURLConnection，使用OutputStream向服务器传入数据
2. 获得从服务器端返回的输入流InputStream
3. 将InputStream转换成字符串String
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程序运行效果：
1.客户端运行效果
2. 服务器端运行结果
关键代码：
1. 客户端 HttpUtils.java
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 {
// 表示服务器端的url
private static String PATH = "http://192.168.0.100:8080/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();
}
}
/*
* params 填写的URL的参数 encode 字节编码
*/
public static String sendPostMessage(Map<String, String> params,
String encode) {
StringBuffer stringBuffer = new StringBuffer();
if (params != null && !params.isEmpty()) {
for (Map.Entry<String, String> entry : params.entrySet()) {
try {
stringBuffer
.append(entry.getKey())
.append("=")
.append(URLEncoder.encode(entry.getValue(), encode))
.append("&");
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
// 删掉最后一个 & 字符
stringBuffer.deleteCharAt(stringBuffer.length() - 1);
System.out.println("-->>" + stringBuffer.toString());
try {
HttpURLConnection httpURLConnection = (HttpURLConnection) url
.openConnection();
httpURLConnection.setConnectTimeout(3000);
httpURLConnection.setDoInput(true);// 从服务器获取数据
httpURLConnection.setDoOutput(true);// 向服务器写入数据
// 获得上传信息的字节大小及长度
byte[] mydata = stringBuffer.toString().getBytes();
// 设置请求体的类型
httpURLConnection.setRequestProperty("Content-Type",
"application/x-www-form-urlencoded");
httpURLConnection.setRequestProperty("Content-Lenth",
String.valueOf(mydata.length));
// 获得输出流，向服务器输出数据
OutputStream outputStream = (OutputStream) httpURLConnection
.getOutputStream();
outputStream.write(mydata);
// 获得服务器响应的结果和状态码
int responseCode = httpURLConnection.getResponseCode();
if (responseCode == 200) {
// 获得输入流，从服务器端获得数据
InputStream inputStream = (InputStream) httpURLConnection
.getInputStream();
return (changeInputStream(inputStream, encode));
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return "";
}
/*
* // 把从输入流InputStream按指定编码格式encode变成字符串String
*/
public static String changeInputStream(InputStream inputStream,
String encode) {
// ByteArrayOutputStream 一般叫做内存流
ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
byte[] data = new byte[1024];
int len = 0;
String result = "";
if (inputStream != null) {
try {
while ((len = inputStream.read(data)) != -1) {
byteArrayOutputStream.write(data, 0, len);
}
result = new String(byteArrayOutputStream.toByteArray(), encode);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return result;
}
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Map<String, String> params = new HashMap<String, String>();
params.put("username", "admin");
params.put("password", "123");
String result = sendPostMessage(params, "utf-8");
System.out.println("-result->>" + result);
}
}
服务器端servlet: LoginAction.java
package com.login.manager;
import java.io.IOException;
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
}
/**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @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 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");
//客户端 HttpUtils并没有写request方法是post ,但服务器端可自动识别
String method = request.getMethod();
System.out.println("request method :"+method);
PrintWriter out = response.getWriter();
String username = request.getParameter("username");
System.out.println("-username->>"+username);
String password = request.getParameter("password");
System.out.println("-password->>"+password);
if (username.equals("admin") && password.equals("123")) {
// 表示服务器段返回的结果
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
}
}