Javaweb中过滤器的使用，并实现留言板的功能
前端编写：index.jsp message.jsp
index.jsp编写:
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>管理界面</title>
<link href="form.css" rel="stylesheet" type="text/css"/>
</head>
<body>
<%
String flag = request.getParameter("flag");
%>
<script type="text/javascript">
var flag = <%= flag%>;
if(flag == "404")
{
alert("请先登录后操作！");
}
</script>
<form action="login.jsp" method="post" class="smart-green">
<h1>系统管理</h1>
<label>
<span>用户名：</span>
<input type="text" placeholder="请输入用户名" name="username"/>
</label>
<label>
<span>密码：</span>
<input type="password" placeholder="请输入密码" name="password"/>
</label>
<input value="点击登录" type="submit" />
</form>
</body>
</html>
基础验证这边不实现验证功能，只判断是否为空：
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%
//进行账号密码的验证
String username = request.getParameter("username");
String password = request.getParameter("password");
request.getSession().setAttribute("loginName", username);
response.sendRedirect(request.getContextPath()+"/message.jsp");//进行页面的跳转，request.getContextPath()获取本地地址；
%>
message.jsp编写：
<%@page import="model.message"%>
<%@page import="java.util.List"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>留言板使用</title>
<link href="form.css" rel="stylesheet" type="text/css" />
<link href="table.css" rel="stylesheet" type="text/css"/>
</head>
<body>
<%
String userName = (String)session.getAttribute("loginName");
String subFlag = request.getParameter("subFlag");
List<message> messages = (List<message>)session.getAttribute("message");
%>
<script type="text/javascript">
var flag = '<%= subFlag%>';
if(flag == "1")
{
alert("留言成功！");
}
</script>
<form action="/FilterDemo/messageServlet" method="get" class="smart-green">
<h1>留言板的编写</h1>
<label>
<span>留言人：</span>
<input type="text" placeholder="请输入标题" value="<%=userName %>" name="name"/>
</label>
<label>
<span>标题：</span>
<input type="text" placeholder="请输入标题" name="title"/>
</label>
<label>
<span>内容:</span>
<textarea name="content"></textarea>
</label>
<input type="submit" value="提交留言"/>
</form>
<br/>
<table id="table-3" width="85%" align="center">
<tr>
<th width="15％">留言人</th>
<th width="15%">标题</th>
<th width="70%">内容</th>
</tr>
<%
if(messages != null)
{
for(message ms : messages)
{
%>
<tr>
<td><%=userName %></td>
<td><%=ms.getTitle() %></td>
<td><%=ms.getContent() %></td>
</tr>
<%
}
}
%>
</table>
</body>
</html>
模块化数据，进行调用：
package model;
public class message {
//用来封装数据
private String title;
private String content;
public message(String title, String content) {
super();
this.title = title;
this.content = content;
}
public message() {
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getContent() {
return content;
}
public void setContent(String content) {
this.content = content;
}
}
留言板进行基本的数据处理：
package cn.java.servlet;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import model.message;
/**
* Servlet implementation class messageServlet
*/
@WebServlet("/messageServlet")
public class messageServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String title = request.getParameter("title");
String content = request.getParameter("content");
message ms = new message();
ms.setTitle(title);
ms.setContent(content);
List<message> list = (List<message>)request.getSession().getAttribute("message");
if(list == null)
{
list = new ArrayList<message>();
request.getSession().setAttribute("message", list);
}
list.add(ms);
response.sendRedirect(request.getContextPath()+"/message.jsp?subFlag=1");//重定向跳转地址；
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
css编写：省略；
关于过滤器的编写：进行全局过滤器测试：
Fileter编写
package cn.java.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;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebFilter("/Fileter")
//实例化接口
public class Fileter implements Filter {
private FilterConfig config;
public Fileter() {
}
public void destroy() {
//过滤器使用操作，最后一次使用，最后面做清除操作
System.out.println("characterEncodigFilter destroy....");
}
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
//过滤器的方法，进行过滤器的操作
//获取对象的时候做一些基本操作
System.out.println("characterEncodigFilter doFilter..");//获取对象时候被使用，第二次操作，每次刷新都执行
//1.注册过滤器需要在web.xml文件里面注册
String sysName = config.getInitParameter("systemName");
String version = config.getInitParameter("version");
System.out.println(sysName);
System.out.println(version);
//这边可以设置网页的编码格式
request.setCharacterEncoding(config.getInitParameter("encoding"));
//2.拦截映射配置
chain.doFilter(request, response);
}
public void init(FilterConfig Config) throws ServletException {
//获取配置对象；
System.out.println("characterEncodigFilter init...");//只有第一次调用的时候被使用，启动时第一步操作
this.config = Config;
}
public FilterConfig getConfig() {
return config;
}
public void setConfig(FilterConfig config) {
this.config = config;
}
}
进行web.xml配置
<?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>FilterDemo</display-name>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
<!-- 注册过滤器 -->
<filter>
<filter-name>FileterEncodig</filter-name>
<filter-class>cn.java.filter.Fileter</filter-class>
<init-param>
<param-name>systemName</param-name>
<param-value>filterEncodig</param-value>
</init-param>
<init-param>
<param-name>version</param-name>
<param-value>1.0</param-value>
</init-param>
<init-param>
<param-name>encoding</param-name>
<param-value>UTF-8</param-value>
</init-param>
</filter>
<!-- 做本地过滤器映射 -->
<filter-mapping>
<filter-name>FileterEncodig</filter-name>
<url-pattern>/*
可以获取版本，编码格式，等操作；
进行基本的是否登录验证：利用过滤器：
package cn.java.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;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebFilter("/SessionFileter")
public class SessionFileter implements Filter {
public void destroy() {
}
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
//进行是否登录验证,不一定需要过滤器来验证，也可以用其他方式
HttpServletRequest hrequest = (HttpServletRequest)request;
HttpServletResponse hresponse = (HttpServletResponse)response;
String userLogin = (String)hrequest.getSession().getAttribute("loginName");
if(userLogin == null)
{
hresponse.sendRedirect(hrequest.getContextPath()+"/index.jsp?flag=404");
return;
}else {
chain.doFilter(request, response);
return;
}
}
public void init(FilterConfig fConfig) throws ServletException {
//这里面用来初始化配置
}
}
也需要进行web.xml配置：
<!-- 用于做用户是否登录的过滤器验证 -->
<filter>
<filter-name>sessionFilter</filter-name>
<filter-class>cn.java.filter.SessionFileter</filter-class>
</filter>
<filter-mapping>
<filter-name>sessionFilter</filter-name>
<url-pattern>/message.jsp</url-pattern><!-- 用于配置是否使用在哪个页面 -->
</filter-mapping>
最后实现效果：
就可以实现这些功能了，过滤器可以进行一些基本的过滤操作，基本验证，后面讲解监听器，可以实现目前在线用户的数量，访问量统计，防止用户重复登录等操作！