Tomcat+MySql+Struts中文问题绝妙的解决方案

开发Web应用程序时，无论是用什么样的框架技术来开发，一碰从数据库存取涉及到中文的数据，就要面对中文乱码或者是各种编码方式不匹配的异常，今天晚上终于搞定了Tomcat+MySql+Struts的中文问题，用到了很简单的方法，很快就能搞定。

    在做以下工作之前，所有的HTML/jsp的charset都设为charset=gb2312。

    第一个要解决的是表单提交乱码问题。在使用Struts提供的ActionForm过程中，无论表单采用的是Struts标签还是Html标签，都可以用ActionForm的Get/Set来获取和设置表单的元素值（它们的作用效果与request.getParameter()方法一样），但提取出来的数据不经过处理的话就是乱码，主要的原因是1.Tomcat的J2EE实现对表单提交即Post方法提交时，处理参数采用默认的ISO8859_1来处理2.Tomcat对Get方法提交的请求在query-string处理时采用了和Post方法不一样的处理方式。所以如果要正确地显示和获取中文数据采用的解决方案：（1）对于Post方法提交的表单通过编写一个过滤器（filer）的方法解决，过滤器在用户提交的数据被处理之前被调用，可以通过这个Java代码改变参数的编码方式（目标编码方式可以通过Web.xml文件里面的参数指定）。过滤器的代码如下：

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;

/**
 * <p>Example filter that sets the character encoding to be used in parsing the
 * incoming request, either unconditionally or only if the client did not
 * specify a character encoding.  Configuration of this filter is based on
 * the following initialization parameters:</p>
 * <ul>
 * <li><strong>encoding</strong> - The character encoding to be configured
 *     for this request, either conditionally or unconditionally based on
 *     the <code>ignore</code> initialization parameter.  This parameter
 *     is required, so there is no default.</li>
 * <li><strong>ignore</strong> - If set to "true", any character encoding
 *     specified by the client is ignored, and the value returned by the
 *     <code>selectEncoding()</code> method is set.  If set to "false,
 *     <code>selectEncoding()</code> is called <strong>only</strong> if the
 *     client has not already specified an encoding.  By default, this
 *     parameter is set to "true".</li>
 * </ul>
 *
 * <p>Although this filter can be used unchanged, it is also easy to
 * subclass it and make the <code>selectEncoding()</code> method more
 * intelligent about what encoding to choose, based on characteristics of
 * the incoming request (such as the values of the <code>Accept-Language</code>
 * and <code>User-Agent</code> headers, or a value stashed in the current
 * user's session.</p>
 *
 * @author Craig McClanahan
 * @version $Revision: 1.2 $ $Date: 2004/03/18 16:40:33 $
 */

public class SetCharacterEncodingFilter implements Filter {

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

    /**
     * The default character encoding to set for requests that pass through
     * this filter.
     */
    protected String encoding = null;

    /**
     * The filter configuration object we are associated with.  If this value
     * is null, this filter instance is not currently configured.
     */
    protected FilterConfig filterConfig = null;

    /**
     * Should a character encoding specified by the client be ignored?
     */
    protected boolean ignore = true;

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