字符过滤器+在web.xml中的配置

import javax.servlet.*;
import java.io.IOException;

/**
* 字符过滤器
* 
* @author 大有软件
*/
public class SetCharacterEncodingFilter implements Filter {

    protected String encoding = "GBK";

    protected FilterConfig filterConfig = null;

    protected boolean ignore = true;

    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;
    }

    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);
    }

    protected String selectEncoding(ServletRequest request) {
        return (this.encoding);
    }

    public void destroy() {
        this.encoding = null;
        this.filterConfig = null;
    }
}

注意问题：粗斜体的参数部分必须和过滤器中的属性要一样，否则过滤器可能不起作用。

<!-- 字符过滤器 -->
    <filter>
        <filter-name>encodeFilter</filter-name>
        <filter-class>
            com.dayou.util.SetCharacterEncodingFilter
        </filter-class>
        <init-param>
            <param-name>encoding</param-name>
            <param-value>GBK</param-value>
        </init-param>
        <init-param>
            <param-name>ignore</param-name>
            <param-value>true</param-value>
        </init-param>
    </filter>

    <filter-mapping>
        <filter-name>encodeFilter</filter-name>
        <url-pattern>*.jsp</url-pattern>
    </filter-mapping>
    <filter-mapping>
        <filter-name>encodeFilter</filter-name>
        <url-pattern>*.do</url-pattern>
    </filter-mapping>

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