3、过滤器细节：
1、web.xml配置
<filter>
<filter-name>test1</filter-name>
<filter-class>com.example.web.filter.FilterDemo1</filter-class>
</filter>
<filter-mapping>
<filter-name>test1</filter-name>
<!--拦截路径-->
<url-pattern>/*</url-pattern>
</filter-mapping>
2、过滤器执行流程
1. 执行过滤器
2. 执行放行后的资源
3. 回来执行过滤器放行代码下边的代码
3、过滤器声明周期方法
1. init:在服务器启动后，会创建Filter对象，然后调用init方法。只执行一次。用于加载资源
2. doFilter:每一次请求被拦截资源时，会执行。执行多次
3. destroy:在服务器关闭后，Filter对象被销毁。如果服务器是正常关闭，则会执行destroy方法。只执行一次。用于释放资源
4、过滤器配置详解
5、过滤器链（配置多个过滤器）
1.web.xml配置
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0">
<filter>
<filter-name>test1</filter-name>
<filter-class>com.example.web.filter.FilterDemo1</filter-class>
</filter>
<filter-mapping>
<filter-name>test1</filter-name>
<!--拦截路径-->
<url-pattern>/*</url-pattern>
</filter-mapping>
</web-app>
实现
/**
* 过滤器快熟入门
*/
public class FilterDemo1 implements Filter { @Override public void init(FilterConfig filterConfig) throws ServletException { Filter.super.init(filterConfig); } @Override public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { System.out.println("被执行了。。。"); //放行 filterChain.doFilter(servletRequest, servletResponse); } @Override public void destroy() { Filter.super.destroy(); } }
2.过滤器执行流程
@WebFilter("/*")
public class FilterDemo2 implements Filter {
public void init(FilterConfig config) throws ServletException {
}
public void destroy() {
}
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException, IOException {
System.out.println("FilterDemo2跑了...");
//放行
chain.doFilter(request, response);
System.out.println("FilterDemo2又回来了");
}
}
<%@ page contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" %>
<!DOCTYPE html>
<html>
<head>
<title>JSP - Hello World</title>
</head>
<body>
index.jsp...
<%
System.out.println("index.jsp...");
%>
</body>
</html>
3.过滤器声明周期方法
@WebFilter("/*")
public class FilterDemo3 implements Filter {
/**
* 在服务器启动后，创建Filter对象，然后用init方法，只执行一次
* @param config
* @throws ServletException
*/
public void init(FilterConfig config) throws ServletException {
System.out.println("init...");
}
/**
* 在服务器关闭后，filter对象被销毁，如果服务器是正常关闭，则会执行destroy方法，只执行一次，用于释放资源
*/
public void destroy() {
System.out.println("destroy...");
}
/**
* 每一次被请求拦截资源时，会执行多次
* @param request
* @param response
* @param chain
* @throws ServletException
* @throws IOException
*/
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException, IOException {
System.out.println("doFilter...");
//放行
chain.doFilter(request, response);
}
}
标签：xml,web,ServletException,void,public,Filter,过滤器,throws From： https://www.cnblogs.com/agzq/p/17136426.html