Web.xml过滤器配置及执行顺序概念

Posted 2020-11-03 你从哪里来？要到哪里去？我又在哪里？

第一个过滤器

@Override
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
Boolean b1 = false;
if (b1 = true) {
// 继续此次请求，如果有多个过滤器，进入下一个过滤器
chain.doFilter(request, response);
} else {
// 重定向此请求
((HttpServletResponse) response).sendRedirect("/xxxx");
}
System.out.println("UrlFilter_1         doFilter...");

}


-----------------------------------------------------------------------------------

第二个过滤器

@Override
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
Boolean b2 = false;
if (b2 = true) {
// 继续此次请求，如果有多个过滤器，进入下一个过滤器
chain.doFilter(request, response);
} else {
// 重定向此请求
((HttpServletResponse) response).sendRedirect("/xxxx");
}
System.out.println("UrlFilter_1         doFilter...");

}

-----------------------------------------------------------------------------------

第三个过滤器

@Override
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
Boolean b3 = false;
if (b3 = true) {
// 继续此次请求，如果有多个过滤器，进入下一个过滤器
chain.doFilter(request, response);
} else {
// 重定向此请求
((HttpServletResponse) response).sendRedirect("/xxxx");
}
System.out.println("UrlFilter_1         doFilter...");

}  

--------------------------------------------------------------------------------------------

Web,xml配置如下

<filter>
<filter-name>url_1</filter-name>
<filter-class>com.boya.filters.UrlFilter_1</filter-class>
</filter>

<filter>
<filter-name>url_3</filter-name>
<filter-class>com.boya.filters.UrlFilter_3</filter-class>
</filter>
<filter>
<filter-name>url_2</filter-name>
<filter-class>com.boya.filters.UrlFilter_2</filter-class>
</filter>


<filter-mapping>
<filter-name>url_3</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<filter-mapping>
<filter-name>url_1</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<filter-mapping>
<filter-name>url_2</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

--------------------------------------------------------------------------------------
执行结果为

UrlFilter_1         初始化...
UrlFilter_3        初始化...
UrlFilter_2        初始化...
2013-9-29 13:38:40 org.apache.coyote.AbstractProtocol start
信息: Starting ProtocolHandler ["http-bio-8080"]
2013-9-29 13:38:40 org.apache.coyote.AbstractProtocol start
信息: Starting ProtocolHandler ["ajp-bio-8009"]
2013-9-29 13:38:40 org.apache.catalina.startup.Catalina start
信息: Server startup in 596 ms
UrlFilter_2         doFilter...
UrlFilter_1         doFilter...
UrlFilter_3         doFilter...

-------------------------------------------------------------------------------------

分析结果：

1.
  chain.doFilter(request, response);
  为继续此次请求，如果有下一个过滤器就进去下一个过滤器，没有就直接跳转到请求的链接里。

2.
  过滤器的执行顺序与xml里面的
<filter-mapping>
<filter-name>xxx</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
有关系，顺序为xml 配置的顺序由下至上 执行。