Java의 필터에 대한 자세한 설명

public void init(FilterConfig filterConfig) throws ServletException;//初始化

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException;//拦截请求

public void destroy();//销毁

String getFilterName();//得到filter的名称。 String getInitParameter(String name);//返回在部署描述中指定名称的初始化参数的值。如果不存在返回null. Enumeration getInitParameterNames();//返回过滤器的所有初始化参数的名字的枚举集合。 public ServletContext getServletContext();//返回Servlet上下文对象的引用。

<filter>
    <filter-name>SessionFilter</filter-name>
    <filter-class>com.action.login.SessionFilter</filter-class>
    <init-param>
        <param-name>logonStrings</param-name><!-- 对登录页面不进行过滤 -->
        <param-value>/project/index.jsp;login.do</param-value>
    </init-param>
    <init-param>
        <param-name>includeStrings</param-name><!-- 只对指定过滤参数后缀进行过滤 -->
        <param-value>.do;.jsp</param-value>
    </init-param>
    <init-param>
        <param-name>redirectPath</param-name><!-- 未通过跳转到登录界面 -->
        <param-value>/index.jsp</param-value>
    </init-param>
    <init-param>
        <param-name>disabletestfilter</param-name><!-- Y:过滤无效 -->
        <param-value>N</param-value>
    </init-param></filter><filter-mapping>
    <filter-name>SessionFilter</filter-name>
    <url-pattern>/*</url-pattern></filter-mapping>

package com.action.login;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.HttpServletResponse;import javax.servlet.http.HttpServletResponseWrapper;/**
 *    判断用户是否登录,未登录则退出系统
 */public class SessionFilter implements Filter {    public FilterConfig config;    public void destroy() {        this.config = null;
    }    public static boolean isContains(String container, String[] regx) {        boolean result = false;        for (int i = 0; i < regx.length; i++) {            if (container.indexOf(regx[i]) != -1) {                return true;
            }
        }        return result;
    }    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest hrequest = (HttpServletRequest)request;
        HttpServletResponseWrapper wrapper = new HttpServletResponseWrapper((HttpServletResponse) response);

        String logonStrings = config.getInitParameter("logonStrings");        // 登录登陆页面
        String includeStrings = config.getInitParameter("includeStrings");    // 过滤资源后缀参数
        String redirectPath = hrequest.getContextPath() + config.getInitParameter("redirectPath");// 没有登陆转向页面
        String disabletestfilter = config.getInitParameter("disabletestfilter");// 过滤器是否有效

        if (disabletestfilter.toUpperCase().equals("Y")) {    // 过滤无效
            chain.doFilter(request, response);            return;
        }
        String[] logonList = logonStrings.split(";");
        String[] includeList = includeStrings.split(";");        if (!this.isContains(hrequest.getRequestURI(), includeList)) {// 只对指定过滤参数后缀进行过滤
            chain.doFilter(request, response);            return;
        }        if (this.isContains(hrequest.getRequestURI(), logonList)) {// 对登录页面不进行过滤
            chain.doFilter(request, response);            return;
        }

        String user = ( String ) hrequest.getSession().getAttribute("useronly");//判断用户是否登录
        if (user == null) {
            wrapper.sendRedirect(redirectPath);            return;
        }else {
            chain.doFilter(request, response);            return;
        }
    }    public void init(FilterConfig filterConfig) throws ServletException {
        config = filterConfig;
    }
}

<filter>
    <filter-name>encoding</filter-name>
    <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
    <init-param>
        <param-name>encoding</param-name><!--用来指定一个具体的字符集-->
        <param-value>UTF-8</param-value>
    </init-param>
    <init-param>
        <param-name>forceEncoding</param-name><!--true：无论request是否指定了字符集，都是用encoding；false：如果request已指定一个字符集，则不使用encoding-->
        <param-value>false</param-value>
    </init-param></filter><filter-mapping>
    <filter-name>encoding</filter-name>
    <url-pattern>/*</url-pattern></filter-mapping>

<filter><!-- lazy loading enabled in spring -->
    <filter-name>OpenSessionInViewFilter</filter-name>
    <filter-class>org.springframework.orm.hibernate3.support.OpenSessionInViewFilter</filter-class>
    <init-param>
        <param-name>sessionFactoryBeanName</param-name><!-- 可缺省。默认是从spring容器中找id为sessionFactory的bean，如果id不为sessionFactory，则需要配置如下，此处SessionFactory为spring容器中的bean。 -->
        <param-value>sessionFactory</param-value>
    </init-param>
    <init-param>
        <param-name>singleSession</param-name><!-- singleSession默认为true,若设为false则等于没用OpenSessionInView -->
        <param-value>true</param-value>
    </init-param></filter><filter-mapping>
    <filter-name>OpenSessionInViewFilter</filter-name>
    <url-pattern>*.do</url-pattern></filter-mapping>

<!-- struts 2.x filter --><filter>
    <filter-name>struts2</filter-name>
    <filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class></filter><filter-mapping>
    <filter-name>struts2</filter-name>
    <url-pattern>*.do</url-pattern></filter-mapping>