利用filter 过滤掉html标签

web.xml配置文件:

<filter>

<filter-name>HtmlFilter</filter-name>

<filter-class>com.itheima.filter.HtmlFilter</filter-class>

</filter>

<filter-mapping>

<filter-name>HtmlFilter</filter-name>

<url-pattern>/*</url-pattern>

</filter-mapping>

java代码:

public class HtmlFilter implements Filter {

public void init(FilterConfig filterConfig) throws ServletException {

}

public void doFilter(ServletRequest req, ServletResponse res,

FilterChain chain) throws IOException, ServletException {

HttpServletRequest request;

HttpServletResponse response;

try {

request = (HttpServletRequest) req;

response = (HttpServletResponse) res;

} catch (ClassCastException e) {

throw new ServletException("non-HTTP request or response");

}

HtmlHttpServletRequest hrequest = new HtmlHttpServletRequest(request);

chain.doFilter(hrequest, response);

}

public void destroy() {

// TODO Auto-generated method stub

}

}

class HtmlHttpServletRequest extends HttpServletRequestWrapper{

public HtmlHttpServletRequest(HttpServletRequest request) {

super(request);

}

public String getParameter(String name) {

String value = super.getParameter(name);

if(value==null)

return value;

value = filter(value);

return value;

}

private String filter(String message) {

if (message == null)

           return (null);

       char content[] = new char[message.length()];

       message.getChars(0, message.length(), content, 0);

       StringBuffer result = new StringBuffer(content.length + 50);

       for (int i = 0; i < content.length; i++) {

           switch (content[i]) {

           case '<':

               result.append("&lt;");

               break;

           case '>':

               result.append("&gt;");

               break;

           case '&':

               result.append("&amp;");

               break;

           case '"':

               result.append("&quot;");

               break;

           default:

               result.append(content[i]);

           }

       }

       return (result.toString());

}