java,web项目中的过滤器filter使用示例,登录操作中的过滤器例子

java,web项目中的过滤器filter的用法。

package com.web.filter;

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.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;

/**
 * 过滤器
 * @title MyFilter.java
 */
//@WebFilter(urlPatterns="/*")//过滤器的注解
public class MyFilter implements Filter {
	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
		System.out.println("MyFilter init()");
	}

	@Override
	public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain)
			throws IOException, ServletException {
		System.out.println("------------");
		// 所有的请求都放行
		//chain.doFilter(request, response);
		
		// 只要是.jsp结尾都放行
		HttpServletRequest request = (HttpServletRequest) req;
		String requestURI = request.getRequestURI();//uri为项目名称后的路径;url为网址协议包括http及后面的路径。如下所示：uri=/study-web/login  url=http://localhost:8888/study-web/login
		System.out.println(requestURI);
		
		if (requestURI.endsWith(".jsp")) {
			// 如果是以.jsp结尾，就通过
			chain.doFilter(req, resp);
		}
		
		//StringBuffer requestURL = request.getRequestURL();
		//System.out.println(requestURL.toString());
		
	}

	@Override
	public void destroy() {
		System.out.println("MyFilter destroy()");
	}
}
           

以上项目的uri和url如下所示：

uri=/study-web/login

url=http://localhost:8888/study-web/login

登录操作中的过滤器

package com.web.filter;

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.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import com.bean.User;

/**
 * 过滤登录操作
 * @title LoginFilter.java
 */
@WebFilter(urlPatterns="/*")
public class LoginFilter implements Filter {

	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
		System.out.println("LoginFilter init()");
	}

	@Override
	public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain)
			throws IOException, ServletException {
		HttpServletRequest request = (HttpServletRequest) req;
		HttpServletResponse response = (HttpServletResponse) resp;
		
		HttpSession session = request.getSession(false);
		User user = (User) session.getAttribute("user");
		
		String uri = request.getRequestURI();
		if (uri.endsWith(".js") || uri.endsWith(".css") || 
				uri.endsWith(".jpg") || uri.endsWith(".gif") || 
				uri.endsWith(".png") || uri.endsWith("login.jsp") || 
				uri.endsWith("valicode") || uri.endsWith("login")) {
			// 如果是一些静态资源就直接可以访问
			// 如果是登录页面也直接可以访问
			// 如果是请求验证码也可以直接访问
			// 如果是处理登录的也可以直接访问
			chain.doFilter(req, resp);
		} else {
			if (user == null) {
				// 如果没有登录就返回登录页面
				response.sendRedirect(request.getContextPath() + "/login.jsp");
			} else {
				// 如果登录了就直接可以访问目标
				chain.doFilter(req, resp);
			}
		}
	}

	@Override
	public void destroy() {
		System.out.println("LoginFilter destroy()");
	}
}