FirstFilter.java

	@Override
	public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2)
			throws IOException, ServletException {
		System.out.println("Start.....doFilter----FirstFilter");
		// arg2.doFilter(arg0, arg1);
		HttpServletRequest req = (HttpServletRequest) arg0;
		HttpServletResponse response2 = (HttpServletResponse) arg1;
		// 重定向
		response2.sendRedirect(req.getContextPath() + "/main.jsp");
		System.out.println("End.....doFilter----FirstFilter");
	}
	
	

web.xml

<welcome-file-list>

<welcome-file>index.jsp</welcome-file>

</welcome-file-list>

<filter>

<filter-name>FirstFilter</filter-name>

<filter-class>com.filter.FirstFilter</filter-class>

</filter>

<filter-mapping>

<filter-name>FirstFilter</filter-name>

<url-pattern>/index.jsp</url-pattern>

</filter-mapping>

<filter-mapping>

<filter-name>FirstFilter</filter-name>

<url-pattern>/main.jsp</url-pattern>

<dispatcher>FORWARD</dispatcher>

</filter-mapping>

index.jsp

一个打印输出语句

<%

System.out.println("index.jsp");

%>

main.jsp

一个打印输出语句

<%

System.out.println("main.jsp");

%>

访问工程下面的index.jsp，控制台输出的结果是

Start.....doFilter----FirstFilter

End.....doFilter----FirstFilter

main.jsp

为什么不是先

main.jsp

后输出

End.....doFilter----FirstFilter