servlet自定义过滤器

web.xml

<!-- 编码过滤器 -->  
    <filter>  
        <filter-name>setCharacterEncoding</filter-name>  
        <filter-class>com.company.strutstudy.web.servletstudy.filter.EncodingFilter</filter-class>  
        <init-param>  
            <param-name>encoding</param-name>  
            <param-value>utf-8</param-value>  
        </init-param>  
    </filter>  
    <filter-mapping>  
        <filter-name>setCharacterEncoding</filter-name>  
        <url-pattern>/*</url-pattern>  
    </filter-mapping>  

<!-- 请求url日志记录过滤器 -->  
    <filter>  
        <filter-name>logfilter</filter-name>  
        <filter-class>com.company.strutstudy.web.servletstudy.filter.LogFilter</filter-class>  
    </filter>  
    <filter-mapping>  
        <filter-name>logfilter</filter-name>  
        <url-pattern>/*</url-pattern>  
    </filter-mapping>  

编码过滤器

public class EncodingFilter implements Filter {  
    private String encoding;  
    private Map<String, String> params = new HashMap<String, String>();  
    // 项目结束时就已经进行销毁  
    public void destroy() {  
        System.out.println("end do the encoding filter!");  
        params=null;  
        encoding=null;  
    }  
    public void doFilter(ServletRequest req, ServletResponse resp,  
            FilterChain chain) throws IOException, ServletException {  
        //UtilTimerStack.push("EncodingFilter_doFilter:");  
        System.out.println("before encoding " + encoding + " filter！");  
        req.setCharacterEncoding(encoding);  
        // resp.setCharacterEncoding(encoding);  
        // resp.setContentType("text/html;charset="+encoding);  
        chain.doFilter(req, resp);        
        System.out.println("after encoding " + encoding + " filter！");  
        System.err.println("----------------------------------------");  
        //UtilTimerStack.pop("EncodingFilter_doFilter:");  
    }  

    // 项目启动时就已经进行读取  
    public void init(FilterConfig config) throws ServletException {  
        System.out.println("begin do the encoding filter!");  
        encoding = config.getInitParameter("encoding");  
        for (Enumeration e = config.getInitParameterNames(); e  
                .hasMoreElements();) {  
            String name = (String) e.nextElement();  
            String value = config.getInitParameter(name);  
            params.put(name, value);  
        }  
    }  
 }  

日志过滤器

public class LogFilter implements Filter {  
    FilterConfig config;  

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

    public void doFilter(ServletRequest req, ServletResponse res,  
            FilterChain chain) throws IOException, ServletException {  
        // 获取ServletContext 对象，用于记录日志  
        ServletContext context = this.config.getServletContext();  
        //long before = System.currentTimeMillis();  
        System.out.println("before the log filter!");  
        //context.log("开始过滤");  
        // 将请求转换成HttpServletRequest 请求  
        HttpServletRequest hreq = (HttpServletRequest) req;  
        // 记录日志  
        System.out.println("Log Filter已经截获到用户的请求的地址:"+hreq.getServletPath() );  
        //context.log("Filter已经截获到用户的请求的地址: " + hreq.getServletPath());  
        try {  
            // Filter 只是链式处理，请求依然转发到目的地址。  
            chain.doFilter(req, res);  
        } catch (Exception e) {  
            e.printStackTrace();  
        }  
        System.out.println("after the log filter!");  
        //long after = System.currentTimeMillis();  
        // 记录日志  
        //context.log("过滤结束");  
        // 再次记录日志  
        //context.log(" 请求被定位到" + ((HttpServletRequest) req).getRequestURI()  
        //      + "所花的时间为: " + (after - before));  
    }  

    public void init(FilterConfig config) throws ServletException {  
        System.out.println("begin do the log filter!");  
        this.config = config;  
    }  

 }