Filter

1.定义自己的过滤器，Myfilter 实现Filter接口

public class MyFilter implements Filter {
FilterConfig filterConfig = null;

public void init(FilterConfig filterConfig) throws ServletException {
this.filterConfig = filterConfig;
}

public void destroy() {
}

public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)
throws IOException, ServletException {
servletResponse.setContentType("text/html");

PrintWriter out = servletResponse.getWriter();
out.println("my-param (InitParameter): " + filterConfig.getInitParameter("name"));
out.println("<br/><br/>Parameters:<br/>");
Enumeration<String> parameterNames = servletRequest.getParameterNames();

if (parameterNames.hasMoreElements()) {
while (parameterNames.hasMoreElements()) {
String name = parameterNames.nextElement();
String value = servletRequest.getParameter(name);
out.println("name:" + name + ", value: " + value + "<br/>");
}
} else {
out.println("---None---<br/>");
}
out.println("<br/>Start Regular Content:<br/><hr/>");
filterChain.doFilter(servletRequest, servletResponse);
out.println("<br/><hr/>End Regular Content:<br/>");

}

}

2. 设计Servlet

public class Aservlet extends HttpServlet {

private static final long serialVersionUID = 1L;

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
performTask(request, response);
}

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException,
IOException {
performTask(request, response);
}

private void performTask(HttpServletRequest request, HttpServletResponse response) throws ServletException,
IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("TestServlet says hi"+request.getProtocol());

}
}

3.web.xml中配置

<?xml version="1.0" encoding="ISO-8859-1"?>
<web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

<filter>
<filter-name>myFilter</filter-name>
<filter-class>com.donghua.filter.MyFilter</filter-class>
<init-param>
<param-name>name</param-name>
<param-value>my-filter</param-value>
</init-param>

</filter>

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

<servlet>
<servlet-name>myServlet</servlet-name>
<servlet-class>com.donghua.filter.Aservlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>myServlet</servlet-name>
<url-pattern>/test</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>

</web-app>