特定于请求参数的Java过滤器URL模式

Question

我们有一种情况,我们想对包含一些特定请求参数的URL使用过滤器,例如:

http://mydomain.com/?id=78&formtype=simple_form&.......    
http://mydomain.com/?id=788&formtype=special_form&.......    

等等,id都是在运行时牵强,我想在设置过滤器web.xml仅当formtype=special_form.应该如何实现解决方案？可以使用正则表达式模式配置过滤器吗？

Answer 1

据我所知,没有解决方案可以直接在查询字符串中将请求与过滤器匹配web.xml.因此,您可以在web.xml使用init-params中注册过滤器,以使过滤器可配置,并void init(FilterConfig filterConfig)在您的javax.servlet.Filter实现中设置模式.

package mypackage;

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;

public class MyFilter implements Filter {

    private String pattern;

    @Override
    public void destroy() {
        // TODO Auto-generated method stub
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        // check whether we have a httpServletRequest and a pattern
        if (this.pattern != null && request instanceof HttpServletRequest) {
            // resolve the query string from the httpServletRequest
            String queryString = ((HttpServletRequest) request).getQueryString();
            // check whether a query string exists and matches the given pattern
            if (queryString != null && queryString.matches(pattern)) {
                // TODO do someting special
            }
        }
        chain.doFilter(request, response);
    }

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        this.pattern = filterConfig.getInitParameter("pattern");
    }

}

您的web.xml中的配置如下所示:

<!-- MyFilter -->
<filter>
    <filter-name>myFilter</filter-name>
    <filter-class>mypackage.MyFilter</filter-class>
    <init-param>
        <param-name>pattern</param-name>
        <param-value>{{PATTERN HERE}}</param-value>
    </init-param>
</filter>

<filter-mapping>
    <filter-name>myFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

进一步阅读:http:
//java.sun.com/javaee/5/docs/api/javax/servlet/Filter.html