web.xml
<context-param>
<param-name>username</param-name>
<param-value>tom</param-value>
</context-param>
<context-param>
<param-name>password</param-name>
<param-value>123123</param-value>
</context-param>
package com.Greatest.Filter;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
/**
* Servlet Filter implementation class UsernameFilter
*/
@WebFilter("/hello.jsp")
public class UsernameFilter implements Filter {
private FilterConfig f;
/**
* Default constructor.
*/
public UsernameFilter() {
// TODO Auto-generated constructor stub
}
/**
* @see Filter#destroy()
*/
public void destroy() {
// TODO Auto-generated method stub
}
/**
* @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
*/
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
String name = f.getServletContext().getInitParameter("username");
String name1 = request.getParameter("username");
if (!(name.equals(name1))) {
request.setAttribute("message", "對不起，您輸入的名字不正確！");
request.getRequestDispatcher("/login.jsp").forward(request, response);
return;
}
chain.doFilter(request, response);
}
/**
* @see Filter#init(FilterConfig)
*/
public void init(FilterConfig fConfig) throws ServletException {
this.f = fConfig;
}
}
package com.Greatest.Filter;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
/**
* Servlet Filter implementation class PasswordFilter
*/
@WebFilter("/hello.jsp")
public class PasswordFilter implements Filter {
private FilterConfig f;
/**
* Default constructor.
*/
public PasswordFilter() {
// TODO Auto-generated constructor stub
}
/**
* @see Filter#destroy()
*/
public void destroy() {
// TODO Auto-generated method stub
}
/**
* @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
*/
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
String password=f.getServletContext().getInitParameter("password");
String password1=request.getParameter("password");
if(!(password.equals(password1))){
request.setAttribute("message", "對不起，您輸入的密碼不正確！");
request.getRequestDispatcher("/login.jsp").forward(request, response);
return;
}
chain.doFilter(request, response);
}
/**
* @see Filter#init(FilterConfig)
*/
public void init(FilterConfig fConfig) throws ServletException {
this.f=fConfig;
}
}
hello.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
Hello: ${param.username }
</body>
</html>
login.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<font color="red">${message }</font>
<br><br>
<form action="hello.jsp" method="post">
username: <input type="text" name="username" value="${param.username }"/>
password: <input type="password" name="password"/>
<input type="submit" value="Submit"/>
</form>
</body>
</html>