最基本的servlet

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第一个Servlet示例

准备条件：安装eclipse及myeclipse，建立webproject.
1 页面部分index.jsp
<%@ page contentType="text/html;charset=UTF-8" isErrorPage="true" %>
<html>
<head>
<title></title>
</head>
<body>
<!—-对应web.xml的url-pattern-->
<FORM action="helloworld" method="post">
<input type="text" name="username">
<input type="submit">
</FORM>
</body>
</html>

2 web.xml文件配置
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<servlet>
<servlet-name>helloworld</servlet-name><!—-servlet类名-->
<servlet-class>first.HelloWorld</servlet-class><!—-类文件位置-->
</servlet>

<servlet-mapping>
    <servlet-name>helloworld</servlet-name> <!—-servlet类名-->
    <url-pattern>/helloworld</url-pattern> <!—-页面action的路径-->
</servlet-mapping>

</web-app>

3 servlet类的编写

package first;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class HelloWorld extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
  // 页面get方式同样也执行post
  this.doPost(request, response);
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
  request.setCharacterEncoding("UTF-8");
  String frontpage = request.getParameter("username");
  System.out.println(frontpage);

  // 转发到一个页面
  this.getServletContext().getRequestDispatcher("/finish.jsp")
  .forward(request, response);

  // 重定向到一个页面
response.sendRedirect("finish.jsp");
}
}

4 返回页面的编写finish.jsp
<%@ page contentType="text/html;charset=UTF-8" isErrorPage="true" %>
<html>
<head>
<title></title>
</head>
<body>
OK！
<FORM action="helloworld" method="post">
<input type="text" name="username">
<input type="submit">
</FORM>
</body>
</html>