Servlet3.0新特性WebFilter（Annotation Filter）详解

摘要：

Servlet3.0作为J2EE 6规范一部分，并随J2EE6一起发布，WeFilter是过滤器注解，是Servlet3.0的新特性，不需要在web.xml进行配置，简化了配置。

Name	Type	Required	Description
filterName	String	Optional	Name of the filter.
value or urlPatterns	String[]	Required	Specify one or more URL patterns to which the filter applies. Either of attribute can be used, but not both.
dispatcherTypes	DispatcherType[]	Optional	Specify types of dispatcher to which the filter applies. Default isjavax.servlet.DispatcherType.REQUEST
servletNames	String[]	Optional	Specify names of servlets to which the filter applies.
displayName	String	Optional	Display name of the filter.
description	String	Optional	Description of the filter.
asyncSupported	boolean	Optional	Specify whether the filter supports asynchronous operation mode. Default is false.
initParams	WebInitParam[]	Optional	Specify one or more initialization parameters of the filter. Each parameter is specified by@WebInitParamannotation type.
smallIcon	String	Optional	Specify name of the small icon of the filter.
largeIcon	String	Optional	Specify name of the large icon of the filter.

OneFilter：

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package com.what21.servlet.webfilter;   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;   @WebFilter("/*") public class OneFilter implements Filter {       @Override     public void init(FilterConfig config) throws ServletException {       }       @Override     public void doFilter(ServletRequest request, ServletResponse response,             FilterChain chain) throws IOException, ServletException {         System.out.println("OneFilter doFilter()");         chain.doFilter(request, response);     }       @Override     public void destroy() {       }   }

TwoFilter：

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package com.what21.servlet.webfilter;   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;   @WebFilter(servletNames = "MyFourServlet") public class TwoFilter implements Filter {       @Override     public void init(FilterConfig config) throws ServletException {       }       @Override     public void doFilter(ServletRequest request, ServletResponse response,             FilterChain chain) throws IOException, ServletException {         System.out.println("TwoFilter doFilter()");         chain.doFilter(request, response);     }       @Override     public void destroy() {       }   }

ThreeFilter：

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package com.what21.servlet.webfilter;   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;   @WebFilter(servletNames = {"MyFourServlet", "MyFiveServlet"}) public class ThreeFilter implements Filter {       @Override     public void init(FilterConfig config) throws ServletException {       }       @Override     public void doFilter(ServletRequest request, ServletResponse response,             FilterChain chain) throws IOException, ServletException {         System.out.println("ThreeFilter doFilter()");         chain.doFilter(request, response);     }       @Override     public void destroy() {       }   }

FourFilter：

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package com.what21.servlet.webfilter;   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;   @WebFilter({"/one","/two"}) public class FourFilter implements Filter {       @Override     public void init(FilterConfig config) throws ServletException {       }       @Override     public void doFilter(ServletRequest request, ServletResponse response,             FilterChain chain) throws IOException, ServletException {         System.out.println("FourFilter doFilter()");         chain.doFilter(request, response);     }       @Override     public void destroy() {       }   }

FiveFilter：

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package com.what21.servlet.webfilter;   import java.io.IOException;   import javax.servlet.DispatcherType; 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.annotation.WebInitParam;   @WebFilter(     urlPatterns = "/five",     filterName = "FiveFilter",     initParams = {         @WebInitParam(name = "name", value = "username"),         @WebInitParam(name = "value", value = "password")     },     description = "MyFiveFilter",     dispatcherTypes = {DispatcherType.REQUEST, DispatcherType.FORWARD} ) public class FiveFilter implements Filter {       @Override     public void init(FilterConfig config) throws ServletException {         String name = config.getInitParameter("name");         String value = config.getInitParameter("value");         System.out.println("name = " + name);         System.out.println("value = " + value);         System.out.println("init().....");     }       @Override     public void doFilter(ServletRequest request, ServletResponse response,             FilterChain chain) throws IOException, ServletException {         System.out.println("FiveFilter doFilter()");     }       @Override     public void destroy() {       }   }