Question

Java Web 怎样修改request的参数值

Answer 1

用过滤器就可以实现，现在web.xml文件中配置好过滤器，自定义个一个过滤器，实现Filter接口，在doFilter中实现自己的过滤逻辑，我这里有个设置所有请求中的字符编码，你可以参考一下：

Java code

web.xml配置如下：
<filter>
<!--过滤器名称，随便定义-->
        <filter-name>UrlFilter</filter-name>
<!--filter-class指向自定义的过滤器，完整的包名+类名-->
        <filter-class>
            com.wgh.common.SetCharacterEncodingFilter
        </filter-class>
<!--过滤器中的默认参数，默认的字符编码是GBK-->
        <init-param>
            <param-name>defaultEncoding</param-name>
            <param-value>GBK</param-value>
        </init-param>
    </filter>
<!--filter和filter-mapping是成对出现的-->
    <filter-mapping>
<!--过滤器名称，一定要和上面的一样，-->
        <filter-name>UrlFilter</filter-name>
<!--表示拦截所有的请求-->
        <url-pattern>/*</url-pattern>
    </filter-mapping>
 
SetCharacterEncodingFilter过滤器类：
 
package com.wgh.common;
 
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Enumeration;
import java.util.List;
 
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;
 
 
public class SetCharacterEncodingFilter implements Filter {
 
 
    
    private static String log = "ksURL_log";
    private static String web_xml_url;
 
    
    protected static String defaultEncoding = null;
    protected FilterConfig filterConfig = null;
    protected boolean ignore = true;
    
    public void destroy() {
        this.defaultEncoding = null;
        this.filterConfig = null;
        this.web_xml_url = null;
 
    }
 
 
    public void doFilter(ServletRequest request, ServletResponse response,
                         FilterChain chain) throws IOException, ServletException {
        if (ignore || (request.getCharacterEncoding() == null)) {
            String defaultEncoding = selectEncoding(request);
             
            HttpServletRequest req = (HttpServletRequest) request;
            if (defaultEncoding != null){
                String uri = req.getRequestURI();
                String url_suffix = uri.substring(uri.lastIndexOf("/")+1);
                 
                    request.setCharacterEncoding(defaultEncoding);
 
            } 
        }
    }
 
    public void init(FilterConfig filterConfig) throws ServletException {
 
        this.filterConfig = filterConfig;
        this.defaultEncoding = filterConfig.getInitParameter("defaultEncoding");
        String value = filterConfig.getInitParameter("ignore");
        if (value == null)
            this.ignore = true;
        else if (value.equalsIgnoreCase("true"))
            this.ignore = true;
        else if (value.equalsIgnoreCase("yes"))
            this.ignore = true;
        else
            this.ignore = false;
 
    }
 
    protected String selectEncoding(ServletRequest request) {
        return (this.defaultEncoding);
    }
     
}