简单的Filter实现

1.在xml文件配置过滤器

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
<display-name>Filter</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
<welcome-file>default.html</welcome-file>
<welcome-file>default.htm</welcome-file>
<welcome-file>default.jsp</welcome-file>
</welcome-file-list>

<error-page>
<error-code>404</error-code>
<location>/error.jsp</location>
</error-page>
<error-page>
<error-code>500</error-code>
<location>/error.jsp</location>
</error-page>
<filter>
<filter-name>CharsetFilter</filter-name>
<filter-class>com.test.filter.CharsetFilter</filter-class>
<init-param>
<param-name>charset</param-name>
<param-value>UTF-8</param-value>
</init-param>
</filter>
<filter>
<filter-name>LoginFilter</filter-name>
<filter-class>com.test.filter.LoginFilter</filter-class>
<init-param>
<param-name>noLoginPath</param-name>
<param-value>login.jsp;error.jsp;index.jsp</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>LoginFilter</filter-name>
<url-pattern>/*</url-pattern>
<dispatcher>REQUEST</dispatcher>
</filter-mapping>
<filter>
<filter-name>ErrorFilter</filter-name>
<filter-class>com.test.filter.ErrorFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>ErrorFilter</filter-name>
<url-pattern>/error.jsp</url-pattern>
<dispatcher>ERROR</dispatcher>
</filter-mapping>
<filter-mapping>
<filter-name>CharsetFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

</web-app>

2.建立java类实现Filter接口

package com.test.filter;

import java.io.IOExcepti
4000
on;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class CharsetFilter implements Filter{
private FilterConfig config;
@Override
public void destroy() {
// TODO Auto-generated method stub

}

@Override
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
String charset = config.getInitParameter("charset");
if(charset == null || charset.equals("")){
charset = "UTF-8";
}
request.setCharacterEncoding(charset);
response.setCharacterEncoding(charset);
chain.doFilter(request, response);
}

@Override
public void init(FilterConfig arg0) throws ServletException {
config = arg0;
}

}

package com.test.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;

public class ErrorFilter implements Filter{

@Override
public void destroy() {
// TODO Auto-generated method stub

}

@Override
public void doFilter(ServletRequest arg0, ServletResponse arg1,
FilterChain chain) throws IOException, ServletException {
System.out.println("error!!!!");
chain.doFilter(arg0, arg1);

}

@Override
public void init(FilterConfig arg0) throws ServletException {
// TODO Auto-generated method stub

}

}

package com.test.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.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class LoginFilter implements Filter{
private FilterConfig config;
@Override
public void destroy() {

}

@Override
public void doFilter(ServletRequest arg0, ServletResponse arg1,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest request = (HttpServletRequest)arg0;
HttpServletResponse response = (HttpServletResponse)arg1;
HttpSession session = request.getSession();

//获取不用过滤的路径
String noLoginPath = config.getInitParameter("noLoginPath");
//对于不用过滤的路径直接放行
if(noLoginPath != null){
String[] strArray = noLoginPath.split(";");

for(String str:strArray){
if(str == null || str.equals(""))   continue;
if(request.getRequestURI().indexOf(str) != -1){
chain.doFilter(arg0, arg1);
return;
}
}
}
//如果session中没有用户信息就跳转到登陆界面，否则放行
if(session.getAttribute("user") == null){
response.sendRedirect("login.jsp");
}else{
chain.doFilter(arg0, arg1);
}
}

@Override
public void init(FilterConfig arg0) throws ServletException {
// TODO Auto-generated method stub
config = arg0;
}

}

3.建立过滤后显示的页面

package com.test.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;

public class CharsetFilter implements Filter{
private FilterConfig config;
@Override
public void destroy() {
// TODO Auto-generated method stub

}

@Override
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
String charset = config.getInitParameter("charset");
if(charset == null || charset.equals("")){
charset = "UTF-8";
}
request.setCharacterEncoding(charset);
response.setCharacterEncoding(charset);
chain.doFilter(request, response);
}

@Override
public void init(FilterConfig arg0) throws ServletException {
config = arg0;
}

}

<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">

<title>My JSP 'error.jsp' starting page</title>

<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->

</head>

<body>
This is my error page. <br>
</body>
</html>

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">

<title>My JSP 'success.jsp' starting page</title>

<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->

</head>

<body>
<span><%=request.getParameter("userName") %></span>
<%System.out.println("userName is "+request.getParameter("userName")); %>
<span><%=request.getParameter("password") %></span>
<%System.out.println("pssword is "+request.getParameter("password")); %>
</body>
</html>