使用过滤器(Filter)解决JSP/Servlet中的中文(编码)问题

时间： 2007-12-18

仅仅对于中文问题，我们可以在获取参数的时候指明：
String myparam = new String(request.getParameter("myparam").getBytes("ISO8859_1"),"GB2312");

如果一个应用里有多个地方要获得参数并且每个地方都要用这样的方式来解决编码问题，那肯定会很有意思；如果以后不仅仅是中文问题还有其他字符问题，那肯定更有意思。

其实可以在数据进/出的时候就将他们处理，以获得和设置正确的编码信息，这需要用到过滤器(Filter)，以下是使用过滤器的方法：


1、编写过滤器SetCharacterEncodingFilter.java:

package cn.net.badboy.jane.tools;

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.UnavailableException;


public class SetCharacterEncodingFilter implements Filter {


    // ----------------------------------------------------- Instance Variables



    protected String encoding = null;



    protected FilterConfig filterConfig = null;



    protected boolean ignore = true;


    // --------------------------------------------------------- Public Methods



    public void destroy() {

        this.encoding = null;
        this.filterConfig = null;

    }



    public void doFilter(ServletRequest request, ServletResponse response,
                         FilterChain chain)
 throws IOException, ServletException {

        // Conditionally select and set the character encoding to be used
        if (ignore || (request.getCharacterEncoding() == null)) {
            String encoding = selectEncoding(request);
            if (encoding != null)
                request.setCharacterEncoding(encoding);
        }

 // Pass control on to the next filter
        chain.doFilter(request, response);

    }



    public void init(FilterConfig filterConfig) throws ServletException {

 this.filterConfig = filterConfig;
        this.encoding = filterConfig.getInitParameter("encoding");
        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 Methods



    protected String selectEncoding(ServletRequest request) {

        return (this.encoding);

    }

}

2、配置web.xml，在web-app元素内增加：

<filter>
  <filter-name>CharacterEncoding</filter-name>
  <filter-class>cn.net.badboy.jane.tools.SetCharacterEncodingFilter</filter-class>
  <init-param>
   <param-name>encoding</param-name>
   <param-value>utf-8</param-value>
  </init-param>
 </filter>
 <filter-mapping>
  <filter-name>CharacterEncoding</filter-name>
  <url-pattern>/*</url-pattern>
 </filter-mapping>