JAVA SERVLETJSP DAY08
1 过滤器——过滤敏感词汇
1.1 问题
针对用户输入的评论内容进行敏感词汇的过滤，如果包含“damn”字样，则提示用户评论已关闭。
1.2 方案
在评论内容到达处理Servlet之前，由过滤器拦截后先进行内容的过滤，如果包含敏感词汇则直接返回给客户端相应提示，不包含敏感词汇则可以将此请求传递给下一个过滤器或用于处理的Servlet。
1.3 步骤
步骤一：新建comment.jsp页面
comment.jsp页面用于收集用户评论信息，显示效果及页面源码如下：
图– 1
图 - 2
步骤二：新建CommentServlet.java文件
创建处理评论及显示的Servlet。并部署工程，测试评论是否能够正确发布。
图– 3
web.xml文件配置如下：
图 - 4
步骤三：新建CommentFilter类
图 - 5
步骤四：配置CommentFilter过滤器
图 - 6
步骤五：部署应用，输入评论查看结果
图 - 7
图 - 8
1.4 完整代码
comment.jsp页面的代码：
<%@ page contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <html> <head> <title>评论</title> </head> <body> <form action="comment" method="post"> <fieldset> <legend>评论</legend> 请输入评论：<textarea name="comment" style="vertical-align:middle; width:140px;height:55px"></textarea><Br> <input type="submit" value="发表评论" /> </fieldset> </form> </body> </html>
CommentServlet.java文件代码：
package web;
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 CommentServlet extends HttpServlet {
public void service(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
//获取评论内容
String str = request.getParameter("comment");
//显示评论内容
out.println("<h3>评论内容：" + str + "</h3>");
out.close();
}
}
CommentFilter1.java文件代码：
package web;
import java.io.IOException;
import java.io.PrintWriter;
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;
public class CommentFilter1 implements Filter{
private String illegalWord;
/**
* 容器删除过滤器实例之前调用，只执行一次
*/
public void destroy() {
}
/**
* 用于处理请求的主要方法
*/
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest req = (HttpServletRequest)request;
HttpServletResponse resp = (HttpServletResponse)response;
req.setCharacterEncoding("UTF-8");
resp.setContentType("text/html;charset=UTF-8");
PrintWriter out = resp.getWriter();
String comment = req.getParameter("comment");
if(comment.indexOf("damn")!=-1){
//有敏感词汇
out.print("<h3>评论内容已关闭</h3>");
}else{
//没有敏感词汇则向后处理，交给其他过滤器或Servlet
chain.doFilter(req, resp);
}
}
/**
* 容器启动之后，创建过滤器实例
* 然后调用init方法，只会调用一次
* 容器会将已经创建好的FilterConfig对象作为参数传入
* 可以从该参数中获取初始化的配置信息
*/
public void init(FilterConfig filterConfig) throws ServletException {
illegalWord = filterConfig.getInitParameter("illegalWord");
System.out.println("Filter1:init is runnming... " + illegalWord);
}
}
web.xml文件代码：
<?xml version="1.0" encoding="UTF-8"?> <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"> <display-name></display-name> <!-- 过滤器 --> <filter> <filter-name>filter1</filter-name> <filter-class>web.CommentFilter1</filter-class> </filter> <filter-mapping> <filter-name>filter1</filter-name> <url-pattern>/comment</url-pattern> </filter-mapping> <!-- Servlet --> <servlet> <servlet-name>CommentServlet</servlet-name> <servlet-class>web.CommentServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>CommentServlet</servlet-name> <url-pattern>/comment</url-pattern> </servlet-mapping> </web-app>
2 过滤器——多个过滤器
2.1 问题
在进行过滤评论时，如果发布内容多过20个字，则不允许发布，并出现相应提示。
2.2 方案
增加过滤器，用于检查评论内容的长度。
2.3 步骤
步骤一：新建CommentFilter2.java文件
图 - 9
步骤二：配置CommentFilter过滤器
图 - 10
步骤三：运行查看结果
图 - 11
图 - 12
图 - 13
图– 14
从运行结果中的，如果有多个过滤器存在，则执行顺序按<filter-mapping>的顺序执行。谁在前面，谁先执行。
2.4 完整代码
CommentFilter.java文件代码：
package web;
import java.io.IOException;
import java.io.PrintWriter;
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;
public class CommentFilter2 implements Filter {
public void destroy() {
}
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest req = (HttpServletRequest)request;
HttpServletResponse resp = (HttpServletResponse)response;
req.setCharacterEncoding("UTF-8");
resp.setContentType("text/html;charset=UTF-8");
PrintWriter out = resp.getWriter();
String str = req.getParameter("comment");
if(str.length()>20){
out.print("评论太长，请重试");
}else{
chain.doFilter(request, response);
}
}
public void init(FilterConfig filterConfig) throws ServletException {
}
}
web.xml文件代码：
<?xml version="1.0" encoding="UTF-8"?> <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"> <display-name></display-name> <!-- 过滤器 --> <filter> <filter-name>filter1</filter-name> <filter-class>web.CommentFilter1</filter-class> </filter> <filter> <filter-name>filter2</filter-name> <filter-class>web.CommentFilter2</filter-class> </filter> <filter-mapping> <filter-name>filter2</filter-name> <url-pattern>/comment</url-pattern> </filter-mapping> <filter-mapping> <filter-name>filter1</filter-name> <url-pattern>/comment</url-pattern> </filter-mapping> <!-- Servlet --> <servlet> <servlet-name>CommentServlet</servlet-name> <servlet-class>web.CommentServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>CommentServlet</servlet-name> <url-pattern>/comment</url-pattern> </servlet-mapping> </web-app>
3 过滤器——过滤器的初始化参数
3.1 问题
动态设置敏感词汇及所限制的评论长度
3.2 方案
使用过滤器的初始化参数，在web.xml文件设定敏感的词汇及限制的评论长度。需要修改时，只需要使用记事本修改web.xml即可
3.3 步骤
步骤一：修改web.xml文件
图 - 15
步骤二：修改CommentFilter1类、CommentFitlter2类读取初始化参数
图 - 16
图 - 17
图 - 18
步骤三：运行，查看是否能正确输出获取到的初始化参数
图 - 19
3.4 完整代码
web.xml文件代码：
<?xml version="1.0" encoding="UTF-8"?> <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"> <display-name></display-name> <!-- 过滤器 --> <filter> <filter-name>filter1</filter-name> <filter-class>web.CommentFilter1</filter-class> <!-- 初始化参数 --> <init-param> <param-name>illegalWord</param-name> <param-value>damn</param-value> </init-param> </filter> <filter> <filter-name>filter2</filter-name> <filter-class>web.CommentFilter2</filter-class> <!-- 初始化参数 --> <init-param> <param-name>illegalLength</param-name> <param-value>30</param-value> </init-param> </filter> <filter-mapping> <filter-name>filter2</filter-name> <url-pattern>/comment</url-pattern> </filter-mapping> <filter-mapping> <filter-name>filter1</filter-name> <url-pattern>/comment</url-pattern> </filter-mapping> <!-- Servlet --> <servlet> <servlet-name>CommentServlet</servlet-name> <servlet-class>web.CommentServlet</servlet-class> </servlet> </servlet> <servlet-mapping> <servlet-name>CommentServlet</servlet-name> <url-pattern>/comment</url-pattern> </servlet-mapping> </web-app>
CommentFilter1.java文件代码：
package web;
import java.io.IOException;
import java.io.PrintWriter;
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;
public class CommentFilter1 implements Filter{
private String illegalWord;
/**
* 容器删除过滤器实例之前调用，只执行一次
*/
public void destroy() {
}
/**
* 用于处理请求的主要方法
*/
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest req = (HttpServletRequest)request;
HttpServletResponse resp = (HttpServletResponse)response;
request.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
String comment = request.getParameter("comment");
if(comment.indexOf(illegalWord)!=-1){
//有敏感词汇
out.print("<h3>评论内容已关闭</h3>");
}else{
//没有敏感词汇则向后处理，交给其他过滤器或Servlet
chain.doFilter(request, response);
}
}
/**
* 容器启动之后，创建过滤器实例
* 然后调用init方法，只会调用一次
* 容器会将已经创建好的FilterConfig对象作为参数传入
* 可以从该参数中获取初始化的配置信息
*/
public void init(FilterConfig filterConfig) throws ServletException {
illegalWord = filterConfig.getInitParameter("illegalWord");
System.out.println("Filter1:init is runnming... " + illegalWord);
}
}
CommentFilter2.java文件代码：
package web;
import java.io.IOException;
import java.io.PrintWriter;
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;
public class CommentFilter2 implements Filter {
private int length;
public void destroy() {
}
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest req = (HttpServletRequest)request;
HttpServletResponse resp = (HttpServletResponse)response;
req.setCharacterEncoding("UTF-8");
resp.setContentType("text/html;charset=UTF-8");
PrintWriter out = resp.getWriter();
String str = req.getParameter("comment");
if(str.length()>length){
out.print("评论太长，请重试");
}else{
chain.doFilter(request, response);
}
}
public void init(FilterConfig filterConfig) throws ServletException {
length = Integer.parseInt(filterConfig.getInitParameter("illegalLength"));
System.out.println("Filter2:init is runnming... " + length);
}
}
4 监听器——统计在线人数
4.1 问题
实现对当前在线人数的统计。
4.2 方案
通过监听session的创建动作，修改存储在线总人数的计数器。这个计数器保存在Servlet上下文中。
4.3 步骤
步骤一：新建CountListener类
图 - 20
步骤二：配置监听器
图- 21
步骤三：添加index.jsp页面
图– 22
步骤四：添加LogoutServlet类
图 - 23
步骤四：配置LogoutServlet
图 - 24
步骤五：运行查看结果
图– 25
由于Chrome浏览器再打开选项卡也是与第一个窗口共用sessionId，所以使用火狐浏览器来模拟第二个上线的用户，运行效果如图-26
图– 26
回到Chrome浏览器，点击刷新，查看结果如图-27
图 - 27
点击火狐浏览器中的登出，然后回到Chrome浏览器刷新页面，查看结果与图-25结果一样。
4.4 完整代码
CountListener.java文件代码：
package web;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
public class CountListener implements HttpSessionListener {
private int count = 0;
public void sessionCreated(HttpSessionEvent se) {
count++;
HttpSession session = se.getSession();
ServletContext sct = session.getServletContext();
sct.setAttribute("count", count);
}
public void sessionDestroyed(HttpSessionEvent se) {
count--;
HttpSession session = se.getSession();
ServletContext sct = session.getServletContext();
sct.setAttribute("count", count);
}
}
web.xml文件代码如下：
<?xml version="1.0" encoding="UTF-8"?> <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"> <display-name></display-name> <!-- 全局初始化参数 --> <context-param> <param-name>count</param-name> <param-value>1000</param-value> </context-param> <!-- 监听器 --> <listener> <listener-class>web.CountListener</listener-class> </listener> <!-- 过滤器 --> <filter> <filter-name>filter1</filter-name> <filter-class>web.CommentFilter1</filter-class> <!-- 初始化参数 --> <init-param> <param-name>illegalWord</param-name> <param-value>damn</param-value> </init-param> </filter> <filter> <filter-name>filter2</filter-name> <filter-class>web.CommentFilter2</filter-class> <!-- 初始化参数 --> <init-param> <param-name>illegalLength</param-name> <param-value>30</param-value> </init-param> </filter> <filter-mapping> <filter-name>filter2</filter-name> <url-pattern>/comment</url-pattern> </filter-mapping> <filter-mapping> <filter-name>filter1</filter-name> <url-pattern>/comment</url-pattern> </filter-mapping> <!-- Servlet --> <servlet> <servlet-name>CommentServlet</servlet-name> <servlet-class>web.CommentServlet</servlet-class> </servlet> <servlet> <servlet-name>LogoutServlet</servlet-name> <servlet-class>web.LogoutServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>CommentServlet</servlet-name> <url-pattern>/comment</url-pattern> </servlet-mapping> <servlet-mapping> <servlet-name>LogoutServlet</servlet-name> <url-pattern>/logout</url-pattern> </servlet-mapping> </web-app>
index.jsp文件代码如下：
<%@ page contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<html>
<head>
<title></title>
</head>
<body>
当前共有<%=application.getAttribute("count").toString()%>人在线<br>
<a href="logout">登出</a>
</body>
</html>
LogoutServlet.java文件代码：
package web;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
public class LogoutServlet extends HttpServlet {
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.setCharacterEncoding("utf-8");
resp.setContentType("text/html; charset=utf-8");
/*
* 因为监听器是通过监听 session 的创建与销毁来计算 count，因此登出的请求应该是在此处进行 session 的注销，
* 这样就能实现登出人数-1的效果。
*/
HttpSession session = req.getSession();
session.invalidate();// session 无效化
}
}