JSP Filter

web.xml中定义Filter

<!-- 定义Filter -->
<filter>
<filter-name>log</filter-name>
<filter-class>zcw.LogFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>log</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>


<!-- authority -->
<filter>
<filter-name>authority</filter-name>
<filter-class>zcw.AuthorityFilter</filter-class>
<init-param>
<param-name>encoding</param-name>
<param-value>GBK</param-value>
</init-param>
<init-param>
<param-name>loginPage</param-name>
<param-value>/login.jsp</param-value>
</init-param>
<init-param>
<param-name>proLogin</param-name>
<param-value>/proLogin.jsp</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>authority</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

对应的java代码

package zcw;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;

public class LogFilter implements Filter{

private FilterConfig config;
public void destroy() {
this.config = null;
}

public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
//----------对用户请求进行预处理----------
//获取ServletContext对象，用于记录日志
ServletContext context = this.config.getServletContext();
long before = System.currentTimeMillis();
System.out.println("开始过滤");
//请求转换成HttpServletRequest
HttpServletRequest hrequest = (HttpServletRequest)request;
//记录日志
context.log("Filter拦截的请求地址"+hrequest.getServletPath());
//Filter只是链式处理请求依然放入目的地址
chain.doFilter(request, response);
//-----------对服务器响应后处理-----------
long after = System.currentTimeMillis();
//记录日志
context.log("过滤结束");
//在此记录
context.log("请求被定位到"+hrequest.getRequestURI()+"所花时间"+(after-before));

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

}
--------------------------------------------------------------------------------------------

package zcw;

import java.io.IOException;

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.HttpServletRequest;
import javax.servlet.http.HttpSession;

public class AuthorityFilter implements Filter {

private FilterConfig config;
public void destroy() {
this.config = null;

}

public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
//获取Filter的配置参数
String encoding = config.getInitParameter("encoding");
String loginPage = config.getInitParameter("loginPage");
String proLogin = config.getInitParameter("proLogin");
//设置request的编码字符集
request.setCharacterEncoding(encoding);
HttpServletRequest requ = (HttpServletRequest) request;
HttpSession session = requ.getSession(true);
//获取客户请求的页面
String requestPath = requ.getServletPath();
if(session.getAttribute("user") == null
&& !requestPath.endsWith(loginPage)
&& !requestPath.endsWith(proLogin)
)
{
//forward都登陆页面
request.setAttribute("tip", "您还没登录");
request.getRequestDispatcher(loginPage)
.forward(request, response);
}else{
chain.doFilter(request, response);
}
}

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

第一个filter对所有的jsp文件都有过滤作用
第二个过滤器可以对用户是否登录做出响应响应