class DelegatingFilterProxy

/**
 * Proxy for a standard Servlet Filter, delegating to a Spring-managed bean that
 * implements the Filter interface. Supports a "targetBeanName" filter init-param
 * in {@code web.xml}, specifying the name of the target bean in the Spring
 * application context.
 *
 * <p>{@code web.xml} will usually contain a {@code DelegatingFilterProxy} definition,
 * with the specified {@code filter-name} corresponding to a bean name in
 * Spring's root application context. All calls to the filter proxy will then
 * be delegated to that bean in the Spring context, which is required to implement
 * the standard Servlet Filter interface.
 *
 * <p>This approach is particularly useful for Filter implementation with complex
 * setup needs, allowing to apply the full Spring bean definition machinery to
 * Filter instances. Alternatively, consider standard Filter setup in combination
 * with looking up service beans from the Spring root application context.
 *
 * <p><b>NOTE:</b> The lifecycle methods defined by the Servlet Filter interface
 * will by default <i>not</i> be delegated to the target bean, relying on the
 * Spring application context to manage the lifecycle of that bean. Specifying
 * the "targetFilterLifecycle" filter init-param as "true" will enforce invocation
 * of the {@code Filter.init} and {@code Filter.destroy} lifecycle methods
 * on the target bean, letting the servlet container manage the filter lifecycle.
 *
 */

1. 这是一个过滤器代理 <filter-name>shiroFilter</filter-name> 的值会传递给 targetBeanName ，

targetBeanName = "shiroFilter";

shiroFilter 是由Spring管理的bean，并实现了Filter 接口。

2. 所有的请求会被转发给shiroFilter

3. 当过滤器配置复杂的时候，这个代理非常有用

4. 通过指定 targetFilterLifecycle = "true"; 来强制调用过滤器的初始化方法和销毁方法，从而被servlet 纳入管理

实例：

web.xml 部分代码

    <filter>
        <filter-name>shiroFilter</filter-name>
        <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
        <init-param>
            <param-name>targetFilterLifecycle</param-name>
            <param-value>true</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>shiroFilter</filter-name>
        <url-pattern>/*</url-pattern>
        <dispatcher>FORWARD</dispatcher>
        <dispatcher>INCLUDE</dispatcher>
        <dispatcher>REQUEST</dispatcher>
        <dispatcher>ERROR</dispatcher>
    </filter-mapping>

applicationContext-Shiro.xml  代码片段

    <bean id="shiroFilter" class="org.apache.shiro.spring.web.ShiroFilterFactoryBean">
        <property name="securityManager" ref="webSecurityManager" />
    </bean>