Servlet Filter 過濾器訪問基礎實驗程式碼-1

阿新 • • 發佈：2019-01-19

index.jsp 程式碼：

<%@ 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>人數統計</title>
</head>
<body>
<h2>
歡迎光臨，<br>
您是本站的第【
<%=application.getAttribute("count") %>
】位訪客！
</h2>
</body>
</html>

--------------------------------

CountFilter.java 程式碼：

package com.lyq;

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
/**
* ͳ�ƹ��
* @author Li YongQiang
*/
public class CountFilter implements Filter {
// ��
private int count;

@Override
public void init(FilterConfig filterConfig) throws ServletException {
// ��ȡ��ʼ��
String param = filterConfig.getInitParameter("count");
// ��ַ��ת��Ϊint
count = Integer.valueOf(param);
}

@Override
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
// ��
count ++;
// ��ServletRequestת��HttpServletRequest
HttpServletRequest req = (HttpServletRequest) request;
// ��ȡServletContext
ServletContext context = req.getSession().getServletContext();
// ��ֵ��뵽ServletContext��
context.setAttribute("count", count);
// ��´��ݹ��
chain.doFilter(request, response);
}

@Override
public void destroy() {

}
}

-------------------------------

ServletFilter.java 程式碼：

package com.lyq;

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;

/**
* Servlet Filter implementation class ServletFilter
*/
@WebFilter("/ServletFilter")
public class ServletFilter implements Filter {

private String name;
public ServletFilter() {
// 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 {
// TODO Auto-generated method stub
// place your code here

// pass the request along the filter chain

HttpServletRequest req = (HttpServletRequest) request;
String reqname = req.getParameter("name");
System.out.println("reqname:+"+reqname);
if(name.equals(reqname))
{
chain.doFilter(request, response);
}

}

/**
* @see Filter#init(FilterConfig)
*/
public void init(FilterConfig fConfig) throws ServletException {
name = fConfig.getInitParameter("name");

}

}

-------------------------------------

RunServlet.java 程式碼：

package com.lyq;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
* Servlet implementation class servletservser
*/
@WebServlet("/servletservser")
public class RunServlet extends HttpServlet {
private static final long serialVersionUID = 1L;

/**
* @see HttpServlet#HttpServlet()
*/
public RunServlet() {
super();
// TODO Auto-generated constructor stub
}

/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
//response.getWriter().append("Served at: ").append(request.getContextPath());

System.out.println("servlet is running");
}

/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}

}

-------------------------------

web 程式碼：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>testFilter</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>
<filter>
<filter-name>CountFilter</filter-name>
<filter-class>com.lyq.CountFilter</filter-class>
<init-param>
<param-name>count</param-name>
<param-value>5000</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>CountFilter</filter-name>
<url-pattern>/index.jsp</url-pattern>
</filter-mapping>


<filter>
<filter-name>ServletFilter</filter-name>
<filter-class>com.lyq.ServletFilter</filter-class>
<init-param>
<param-name>name</param-name>
<param-value>22</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>ServletFilter</filter-name>
<url-pattern>/RunServlet</url-pattern>
</filter-mapping>

<servlet>
<servlet-name>RunServlet</servlet-name>
<servlet-class>com.lyq.RunServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>RunServlet</servlet-name>
<url-pattern>/RunServlet</url-pattern>
</servlet-mapping>

</web-app>

個人經驗：上面的程式碼測試成功。突破點：自己設定一個過濾 servlet的 Filter 哈哈哈。你要是感興趣可以測試改進程式碼

=========================================================

相關參考網址：

https://blog.csdn.net/u010902721/article/details/51673760 https://blog.csdn.net/lip009/article/details/1337730

=======================================================

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