如何为一个特定的 servlet 应用过滤器？

Posted 2023-02-26

【中文标题】如何为一个特定的 servlet 应用过滤器？

【英文标题】：How to apply filter for one particular servlet?

【发布时间】：2012-11-10 15:19:27

【问题描述】：

在聊天中，我的应用程序有五个 servlet。我需要为单个 servlet 应用过滤器。

我的过滤器是，

package com.tps.flexchat.action;

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;

/**
 * Servlet Filter implementation class EncodingFilter
 */
public class EncodingFilter implements Filter 
    private String encoding = "UTF-8";
    private FilterConfig filterConfig;
    /**
     * @see javax.servlet.Filter#init(javax.servlet.FilterConfig)
     */
    public void init(FilterConfig filterConfig) throws ServletException 
        this.filterConfig = filterConfig;
    

    /**
     * @see javax.servlet.Filter#doFilter(javax.servlet.ServletRequest, javax.servlet.ServletResponse, javax.servlet.FilterChain)
     */
    public void doFilter(ServletRequest req, ServletResponse resp,FilterChain chain) throws IOException, ServletException 

        resp.setCharacterEncoding("encoding");
        resp.setContentType("encoding");
                    req.setCharacterEncoding(encoding);
        chain.doFilter(req, resp);

        System.out.println("filter -------> :"+encoding );
    

    /**
     * @see javax.servlet.Filter#destroy()
     */
    public void destroy() 
    

web.xml 中的映射将是

<filter>
    <display-name>EncodingFilter</display-name>
    <filter-name>EncodingFilter</filter-name>
    <filter-class>com.tps.flexchat.action.EncodingFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>EncodingFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

我只需要将 EncodingFilter 过滤器应用于此 SendMessageAction servlet，

package com.tps.flexchat.action;

import java.io.IOException;
import java.io.PrintWriter;
import java.net.URLDecoder;
import java.net.URLEncoder;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.genesyslab.platform.webmedia.protocol.FlexChatProtocol;
import com.tps.flexchat.Request.SendMessage;
import com.tps.flexchat.info.ApplicationInfo;
import com.tps.flexchat.info.CustomerInfo;

public class SendMessageAction extends HttpServlet 
    private static final long serialVersionUID = 1L;

    private String msg;
    private String seckey;
    private String uid;
    private String sessionId;
    private int counter;
    private FlexChatProtocol protocol = null; 
    private SendMessage message;


    public SendMessageAction() 
        super();
    

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 

            msg = request.getParameter("message");
            seckey = request.getParameter("securekey");
            uid = request.getParameter("userId");
            sessionId = request.getParameter("sessionId");
            counter = 1;
            protocol = ApplicationInfo.flexProtocol;

            message = new SendMessage();
            message.send(msg, seckey, uid, sessionId, counter, protocol);

            CustomerInfo customer = ApplicationInfo.customerDetails.get(uid);

            out.print(customer.getMessage());

        

    

提前谢谢....

【问题讨论】：

为什么不将相同的路径应用于您的过滤器作为您的 Servlet ？

感谢您的回复...你能给我密码吗？

您的 servlet 路径将在 web.xml 中，类似于：Servlet/path/-pattern>

这是对的兄弟吗？ /SendMessageAction ?

/SendMessageAction/ ?

【参考方案1】：

您还可以通过引用 servlet 名称而不是 url 模式将过滤器应用于特定的 servlet。如果你的 servlet 是这样声明的：

<servlet>
    <servlet-name>SendMessageAction</servlet-name>
    <servlet-class>com.tps.flexchat.action.SendMessageAction</servlet-class>
</servlet>

您应该能够使用以下过滤器映射：

<filter-mapping>
    <filter-name>EncodingFilter</filter-name>
    <servlet-name>SendMessageAction</servlet-name>
</filter-mapping>

【讨论】：

很好，我不知道！

我喜欢这种方法，因为它更直接。

【参考方案2】：

您可以更改过滤器路径：

将<url-pattern> 更改为与您的servlet 相同的路径

<filter>
    <display-name>EncodingFilter</display-name>
    <filter-name>EncodingFilter</filter-name>
    <filter-class>com.tps.flexchat.action.EncodingFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>EncodingFilter</filter-name>
    <url-pattern>/SendMessageAction/</url-pattern>
</filter-mapping>