servlet实现登录过滤

控制层：

package com.product.dbutil.login.action;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.product.dbutil.login.dao.LoginDao;
import com.product.dbutil.login.service.LoginService;
/**
 * MVC模式 一个控制层action 一个数据访问层dao，一个接口service
 * 接口定义一个登录功能规范， dao层实现对数据库的访问
 * action层获得客户端提交的表单信息，调用dao层访问数据库，若有返回真在做界面跳转。
 * @author yqq
 *
 */
public class LoginAction extends HttpServlet {

	private LoginService service;//接口

	/**
	 * Constructor of the object.
	 */
	public LoginAction() {
		super();
	}

	/**
	 * Destruction of the servlet. <br>
	 */
	public void destroy() {
		super.destroy(); // Just puts "destroy" string in log
		// Put your code here
	}

	/**
	 * The doGet method of the servlet. <br>
	 *
	 * This method is called when a form has its tag value method equals to get.
	 *
	 * @param request
	 *            the request send by the client to the server
	 * @param response
	 *            the response send by the server to the client
	 * @throws ServletException
	 *             if an error occurred
	 * @throws IOException
	 *             if an error occurred
	 */
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		this.doPost(request, response);
	}

	/**
	 * The doPost method of the servlet. <br>
	 *
	 * This method is called when a form has its tag value method equals to
	 * post.
	 *
	 * @param request
	 *            the request send by the client to the server
	 * @param response
	 *            the response send by the server to the client
	 * @throws ServletException
	 *             if an error occurred
	 * @throws IOException
	 *             if an error occurred
	 */
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		String path = request.getContextPath();
		//设置编码方式和客户端表单的编码方式相同
		response.setContentType("text/html;charset=utf-8");
		PrintWriter out = response.getWriter();
		//获取表单的值
		String username = request.getParameter("username");
		String pswd = request.getParameter("pswd");
		List<Object> params = new ArrayList<Object>();
		params.add(username);
		params.add(pswd);
		//查询数据库的内容若有则返回true
		boolean flag = service.login(params);
		////////////////
		if (flag) {
			//登录界面（获得Session并设置属性在登录成功后才可以）
			request.getSession().setAttribute("username", username);
			response.sendRedirect(path + "/main.jsp");
		}
		out.flush();
		out.close();
	}

	/**
	 * Initialization of the servlet. <br>
	 *
	 * @throws ServletException
	 *             if an error occurs
	 */
	public void init() throws ServletException {
		// Put your code here
		service = new LoginDao();
	}

}

服务层：

接口定义中，方法默认是公有抽象的，不指明也可以。

package com.product.dbutil.login.service;

import java.util.List;

public interface LoginService {

	public boolean login(List<Object> params);
}

dao层：

package com.product.dbutil.login.dao;

import java.util.List;
import java.util.Map;

import com.product.dbutil.jdbc.JdbcUtils;
import com.product.dbutil.login.service.LoginService;

public class LoginDao implements LoginService {

	private JdbcUtils jdbcUtils = null;

	public LoginDao() {
		// TODO Auto-generated constructor stub
		jdbcUtils = new JdbcUtils();
	}

	public boolean login(List<Object> params) {
		// TODO Auto-generated method stub
		boolean flag = false;
		String sql = "select * from userinfo where username=? and pswd=?";
		try {
			jdbcUtils.getConnection();
			Map<String, Object> map = jdbcUtils.findSimpleResult(sql, params);
			flag = !map.isEmpty() ? true : false;
		} catch (Exception e) {
			// TODO: handle exception
			e.printStackTrace();
		} finally {
			jdbcUtils.releaseConn();
		}
		return flag;
	}

}

过滤器：

package com.product.dbutil.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.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
 * web.xml配置中url-pattern配置为/*全过滤，配置为谁过滤谁
 * @author yqq_coder
 *
 */
public class MyFilter implements Filter {

	public MyFilter() {
		// TODO Auto-generated constructor stub
	}

	public void destroy() {
		// TODO Auto-generated method stub

	}

	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		// TODO Auto-generated method stub
		// 过滤用户的请求，判断是否登录
		//先做类型转换
		HttpServletRequest httpServletRequest = (HttpServletRequest) request;
		HttpServletResponse httpServletResponse = (HttpServletResponse) response;
		//获得从定向路径
		String path = httpServletRequest.getContextPath();
		//设置请求和响应的编码
		httpServletRequest.setCharacterEncoding("utf-8");
		httpServletResponse.setCharacterEncoding("utf-8");
		//从请求中获得Session值,为空跳转
		String username = (String)httpServletRequest.getSession().getAttribute("username");

		if (username==null) {
			httpServletResponse.sendRedirect(path + "/index.jsp");
		}
		///////
		chain.doFilter(httpServletRequest, httpServletResponse);
	}

	public void init(FilterConfig arg0) throws ServletException {
		// TODO Auto-generated method stub

	}

}

web.xml配置

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
	xmlns="http://java.sun.com/xml/ns/javaee"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
	http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>RegisterAction</servlet-name>
    <servlet-class>com.product.dbutil.register.action.RegisterAction</servlet-class>
  </servlet>
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>LoginAction</servlet-name>
    <servlet-class>com.product.dbutil.login.action.LoginAction</servlet-class>
  </servlet>
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>ProductAction</servlet-name>
    <servlet-class>com.product.dbutil.product.action.ProductAction</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>RegisterAction</servlet-name>
    <url-pattern>/servlet/RegisterAction</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>LoginAction</servlet-name>
    <url-pattern>/servlet/LoginAction</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>ProductAction</servlet-name>
    <url-pattern>/servlet/ProductAction</url-pattern>
  </servlet-mapping>

  <filter>
  <filter-name>MyFilter</filter-name>
  <filter-class>com.product.dbutil.filter.MyFilter</filter-class>
  </filter>

  <filter-mapping>
  <filter-name>MyFilter</filter-name>
  <url-pattern>/main.jsp</url-pattern>
  </filter-mapping>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>