jsp---Filter的使用

struts2中的攔截器可以攔截action，但是無法攔截頁面的請求，但是有些頁面需要有權限纔可以訪問，不可以直接訪問，有一種解決的辦法就是使用Filter

1、創建Filter類，需要實現Filter接口：

package filter;

import java.io.IOException;
import java.util.Map;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import model.Admin;


public class LoginFilter implements Filter {
	//private Map session;
	public void destroy() {
	}
	public void doFilter(ServletRequest req, ServletResponse resp,
			FilterChain chain) throws IOException, ServletException {
		HttpServletRequest request = (HttpServletRequest) req;
		HttpServletResponse response = (HttpServletResponse) resp;
		HttpSession session = request.getSession();
		
		Admin admin = (Admin) session.getAttribute("nowUser");
System.out.println(admin);
		if(admin == null){
			response.sendRedirect("login.html");
		}
		chain.doFilter(request, response);
	}

	public void init(FilterConfig arg0) throws ServletException {
		
	}
}

在doFilter中實現過濾功能，這裏主要是驗證用戶請求index.html頁面時是否登錄，如果登錄則繼續運行，否則返回到登錄頁面

還需要配置web.xml：添加下面的代碼

<filter>
  	<filter-name>loginFilter</filter-name>
  	<filter-class>filter.LoginFilter</filter-class>
  </filter>
  <filter-mapping>
  	<filter-name>loginFilter</filter-name>
  	<url-pattern>/index.html</url-pattern>
  </filter-mapping>

配置文件的幾種不同的情況：

1、過濾所有的請求：

<filter-mapping>

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

    <url-pattern>/*</url-pattern>

</filter-mapping>

2、過濾制定類型的請求：只過濾“.html”的文件

filter-mapping>

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

    <url-pattern>*.html</url-pattern>

</filter-mapping>

3、過濾多種類型的：需要配置兩個<filter-mapping>

<filter-mapping>

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

    <url-pattern>*.html</url-pattern>

</filter-mapping>

<filter-mapping>

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

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

</filter-mapping>

4、過濾指定文件：就是剛纔的情況，注意加“/”

<filter-mapping>
  	<filter-name>loginFilter</filter-name>
  	<url-pattern>/index.html</url-pattern>
  </filter-mapping>