spring DelegatingFilterProxy 过滤器 的原理及运用

DelegatingFilterProxy的原理及使用

DelegatingFilterProxy就是一个对于servlet filter的代理，用这个类的好处主要是通过spring容器来管理servlet
filter的生命周期，还有就是如果filter中需要一些Spring容器的实例，可以通过spring直接注入，另外读取一些配置文件这些便利的操作都可以通过Spring来配置实现。

DelegatingFilterProxy的使用方法，

首先在web.xml中配置：

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<filter> < filter-name>myFilter</filter-name> < filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class> </filter> <filter-mapping> < filter-name>myFilter</filter-name> < url-pattern>/*</url-pattern> </filter-mapping>

<filter>
< filter-name>myFilter</filter-name>
< filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
</filter>
<filter-mapping>
< filter-name>myFilter</filter-name>
< url-pattern>/*</url-pattern>
</filter-mapping>

然后在Spring的配置文件中，配置具体的Filter类的实例。

<bean name="myFilter" class="com.*.MyFilter"></bean>

在Spring中配置的bean的name要和web.xml中的<filter-name>一样

或者在DelegatingFilterProxy的filter配置中配置初始参数：targetBeanName，对应到Spring配置中的beanname

如果要保留Filter原有的init，destroy方法的调用，还需要配置初始化参数targetFilterLifecycle为true，该参数默认为false

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<filter> <filter-name>DelegatingFilterProxy</filter-name> <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class> <init-param> <param-name>ignoreUrls</param-name> <param-value>/caClient.jsp,/403.jsp,/login.html*,/j_spring_security_check,/accounts/**,/secure/logout,/js/**,/app/**,/images/**,/icons/**,/lib/**,/resource/**,/secure/changepassword</param-value> </init-param> <init-param> <param-name>targetBeanName</param-name> <param-value>commonWebFilter</param-value> </init-param> <init-param> <param-name>targetFilterLifecycle</param-name> <param-value>true</param-value> </init-param> </filter> <filter-mapping> <filter-name>DelegatingFilterProxy</filter-name> <url-pattern>/*</url-pattern> </filter-mapping>

<filter>
<filter-name>DelegatingFilterProxy</filter-name>
<filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
<init-param>
<param-name>ignoreUrls</param-name>
<param-value>/caClient.jsp,/403.jsp,/login.html*,/j_spring_security_check,/accounts/**,/secure/logout,/js/**,/app/**,/images/**,/icons/**,/lib/**,/resource/**,/secure/changepassword</param-value>
</init-param>
<init-param>
<param-name>targetBeanName</param-name>
<param-value>commonWebFilter</param-value>
</init-param>
<init-param>
<param-name>targetFilterLifecycle</param-name>
<param-value>true</param-value>
</init-param>
</filter>

<filter-mapping>
<filter-name>DelegatingFilterProxy</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

applicationContext.xml

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<bean id="commonWebFilter" class="com.wonders.LoginFilter"/>

<bean id="commonWebFilter" class="com.wonders.LoginFilter"/>