Servlet中filter的执行顺序以及urlPatterns和servletNames之间的关系

servlet3.0以前

用web.xml中的<filter-mapping>顺序决定filter的执行顺序

<span style="white-space:pre"></span><filter><filter-name>firstfilter</filter-name><filter-class>filter.FirstFilter</filter-class></filter><filter><filter-name>secondfilter</filter-name><filter-class>filter.SecondFilter</filter-class></filter><filter-mapping><filter-name>firstfilter</filter-name><url-pattern>/*</url-pattern></filter-mapping><filter-mapping><filter-name>secondfilter</filter-name><url-pattern>/*</url-pattern></filter-mapping>

执行结果

servlet3.0以后

通过注解配置filter时，没有专门的指令来配置filter执行的先后。确定filter执行的先后是根据filter类名的字母表顺序

声明filter

@WebFilter(filterName = "second", urlPatterns = { "/*" })public class SecondFilter implements Filter {}@WebFilter(filterName = "first", urlPatterns = { "/*" })public class FirstFilter implements Filter {}

执行结果

@WebFilter(filterName = "second", urlPatterns = { "/*" })public class SecondFilter implements Filter {}@WebFilter(filterName = "first", urlPatterns = { "/*" })public class ZFirstFilter implements Filter {}

执行结果

可以在web.xml中单独写入<filter-mapping>配置filter顺序。

<span style="white-space:pre"></span><filter-mapping><filter-name>firstfilter</filter-name></filter-mapping><filter-mapping><filter-name>secondfilter</filter-name></filter-mapping>

另urlPatterns和servletNames之间的关系

Configuring a Chain of Filters

WebLogic Server creates a chain of filters by creating a list of all the filter mappings that match an incoming HTTP request. The ordering of the list is determined by the following sequence:

Filters where the filter-mapping element contains a url-pattern that matches the request are added to the chain in the order they appear in the web.xml deployment descriptor.
Filters where the filter-mapping element contains a servlet-name that matches the request are added to the chain after the filters that match a URL pattern.
The last item in the chain is always the originally requested resource.

In your filter class, use the FilterChain.doFilter() method to invoke the next item in the chain.