Servlet3.0之七：@WebFilter申明该类为过滤器

Servlet3.0作为J2EE 6规范一部分，并随J2EE6一起发布，@WebFilter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。

一、Filter介绍

二、@WebFilter用法

在servlet3.0以后，我们可以不用再web.xml里面配置Filter，只需要加上@WebFilter注解就可以实现。

下面是@WebFilter的属性列表。

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.

示例：

package com.dxz.demo.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
import javax.servlet.annotation.WebInitParam;

@WebFilter(filterName = "oneFilter", //不指定name的情况下，name默认值为类全路径，即com.dxz.demo.filter.oneFilter
urlPatterns="/filter/*",
description="注解声明filter",
initParams={//以下都是druid数据源状态监控的参数
        @WebInitParam(name="allow",value=""),// IP白名单 (没有配置或者为空，则允许所有访问)
        @WebInitParam(name="deny",value=""),// IP黑名单 (存在共同时，deny优先于allow)
        @WebInitParam(name="loginUsername",value="dev"),// 用户名
        @WebInitParam(name="loginPassword",value="123456"),// 密码
        @WebInitParam(name="resetEnable",value="false")// 禁用HTML页面上的“Reset All”功能
        })
public class OneFilter implements Filter {

    @Override
    public void init(FilterConfig config) throws ServletException {
        System.out.println("OneFilter init()");
        System.out.println(config.getInitParameter("loginUsername"));
        System.out.println(config.getInitParameter("loginPassword"));
    }

    @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() {

    }

}

结果：

注意：

1、Filter类使用@WebFilter注解；

2、Spring boot的启动类需要增加@ServletComponentScan用于扫描加载Filter类；