请问tomcat如何实现访问限制

<filter>
		<filter-name>TestFile</filter-name>
		<filter-class>top.afternoontea.frame.filter.TestFile</filter-class>
		<init-param>
			<param-name>ips</param-name>
			<param-value>127.0.21.0,125.152.154.2</param-value>
		</init-param>
	</filter>
	<filter-mapping>
		<filter-name>TestFile</filter-name>
		<url-pattern>/test.jsp</url-pattern>
	</filter-mapping>

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

public class TestFilter implements javax.servlet.Filter {
	
	private String ips;

	public void destroy() {

	}

	@SuppressWarnings("unchecked")
	public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse,
			FilterChain chain) throws IOException, ServletException {
		/*你应该知道怎么做了*/
	}

	public void init(FilterConfig config) throws ServletException {
		this.ips = config.getInitParameter("ips");
	}

}