java如何解决用户注销的过滤查询

Question

我有这段代码用于过滤缓存页，但在编译时遇到了一些问题：

package bean.log.filter;
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.HttpSession;
//import javax.servlet.annotation.WebFilter;

public class LoginFilter implements Filter
    {
    @Override

        public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException
        {  
        try
        {


        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) res; 
        HttpSession session = request.getSession(false); 
        if (session == null || session.getAttribute("userHash") == null)
            { 
            response.sendRedirect("/scape/applicationservices/fileshare/vm/login/login.jsp"); // No logged-in user found, so redirect to login page.
            response.setHeader("Cache-Control", "no-cache, no-store, must-revalidate"); // HTTP 1.1. 
            response.setHeader("Pragma", "no-cache"); // HTTP 1.0.
            response.setDateHeader("Expires", 0);
            }
            else
                { 
                chain.doFilter(req, res); // Logged-in user found, so just continue request.
                }
            }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }

}

在编译相同的代码后，我得到以下错误：

D:\programs\MyPackage\bean\log\filter>javac LoginFilter.java
LoginFilter.java:14: bean.log.filter.LoginFilter is not abstract and does not ov
erride abstract method destroy() in javax.servlet.Filter
public class LoginFilter implements Filter
       ^
1 error

所以我对我的代码做了如下修改，然后进行编译，但没有得到预期的结果。我所做的改变是： 我在评论中加入了@Override和implements Filter，并添加了public void init和public void destroy方法

package bean.log.filter;
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.HttpSession;
//import javax.servlet.annotation.WebFilter;

public class LoginFilter // implements Filter
    {
    //@Override
        public void init( ) 
        {   
        }

        public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException
        {  
        try
        {


        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) res; 
        HttpSession session = request.getSession(false); 
        if (session == null || session.getAttribute("userHash") == null)
            { 
            response.sendRedirect("/timescape/applicationservices/fileshare/vm/login/login.jsp"); // No logged-in user found, so redirect to login page.
            response.setHeader("Cache-Control", "no-cache, no-store, must-revalidate"); // HTTP 1.1. 
            response.setHeader("Pragma", "no-cache"); // HTTP 1.0.
            response.setDateHeader("Expires", 0);
            }
            else
                { 
                chain.doFilter(req, res); // Logged-in user found, so just continue request.
                }
            }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }

    public void destroy( ) 
        {   
        }

}

如何在web中配置过滤器。xml

我的配置如下

<web-app>


    <welcome-file-list>
        <welcome-file>/WEB-INF/index.jsp</welcome-file>
    </welcome-file-list>

    <filter>     
        <filter-name>noCacheFilter</filter-name>     
        <filter-class>bean.log.filter.LoginFilter</filter-class> 
    </filter> 
    <filter-mapping>     
        <filter-name>noCacheFilter</filter-name>     
        <url-pattern>/scape/applicationservices/fileshare/vm/apps/*</url-pattern> 
    </filter-mapping>



</web-app>

我希望此筛选器限制用户在注销后返回到我的apps目录中的前一个缓存页，因此我使用该url-pattern。 如何实现这个过滤器的工作

Answer 1

JavaEE过滤器必须实现上面提到的接口：javax.servlet.Filter。问题不在于Filter本身，而在于Java的使用。在这种语言中，当一些非抽象类实现接口时，它或它的父类必须实现所有声明的方法。这意味着，当接口声明方法init()、doFilter()和destroy()时，即使实现应该是空的，您的类也必须实现所有这些方法。这意味着您必须将两种解决方案结合起来：

1. 取消注释implements Filter
2. 让未注释的方法init()和destroy()
3. 如果您使用的是Java 6或更高版本，可能会取消注释@Override

在这之后，你的过滤器应该是好的，至少应该在web容器处理web.xml映射中指定的一些页面匹配URL时执行

无论如何，我猜注销URL通常不是那么复杂，所以我希望映射URL类似于/logout。正如我已经提到的，只对与URL匹配的页面执行过滤器