基于Servlet、JSP、JDBC、MySQL登录模块(包括使用的过滤器和配置)

遇见前文的注冊模块，本篇是登录模块。主要包含登录主界面，和登录相关编写的LoginAction、LoginDao和LoginService。以及配置的Filter。以下按逻辑顺序记录具体过程和代码:

一、在前文的index文件夹点击登录button后。通过javascript跳转至LoginAction。

<script type="text/javascript">
 function login(){
   var th = document.form1;
   if(th.username.value==""){
      alert("用户名不能为空！
。");
      th.username.focus();
      return ;
   }
   if(th.pswd.value==""){
      alert("password不能为空！
！
");
      th.pswd.focus();
      return ;
   }
   th.action="<%=path%>/servlet/LoginAction";
		th.submit();
	}
</script>

二、就是关于登录这个事件，须要创建三个文件各自是LogingAction，是个Servlet。LoginService是个接口，LoginDao实现上面的接口，查询数据库。

跟前文的注冊模块一样的哈。

LogingAction.java

package com.product.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.login.dao.LoginDao;
import com.product.login.service.LoginService;

public class LoginAction extends HttpServlet {

	private LoginService service;
	/**
	 * 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 {

		request.setCharacterEncoding("utf-8");
		response.setContentType("text/html; charset=utf-8");
		String path = request.getContextPath();
		PrintWriter out = response.getWriter();
        String username = request.getParameter("username");
        String pswd = request.getParameter("pswd");
        List<Object> params = new ArrayList<Object>();
        params.add(username);
        params.add(pswd);
        boolean flag = service.login(params);
        out.println("username = " + username);
        out.println("pswd = " + pswd);
        
        if(flag){
        request.getSession().setAttribute("username", username);
        response.sendRedirect(path + "/main.jsp");
        }else{
        	out.println("登录失败 ");
        }
		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();
	}

}

要点:创建一个Session，将username存进去传递给main.jsp。

也即在main.jsp的时候我要知道当前是谁在登录。

        if(flag){
        request.getSession().setAttribute("username", username);
        response.sendRedirect(path + "/main.jsp");
        }

LoginService.java

package com.product.login.service;

import java.util.List;

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

LoginDao.java

package com.product.login.dao;

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

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

public class LoginDao implements LoginService {
	private JdbcUtils jdbcUtils;
	public LoginDao(){
		jdbcUtils = new JdbcUtils();
	}
	@Override
	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){
			e.printStackTrace();
		}finally{
			jdbcUtils.releaseConn();
		}
		return flag;
	}

}

三、这样假设登录成功的话就跳转到了main.jsp界面：

main.jsp代码例如以下:

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
	String path = request.getContextPath();
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN" "http://www.w3c.org/TR/1999/REC-html401-19991224/frameset.dtd">
<HTML xmlns="http://www.w3.org/1999/xhtml">
<HEAD>
<TITLE>后台管理系统</TITLE>
<META http-equiv=content-type content="text/html; charset=utf-8">
</HEAD>
<FRAMESET rows=105,* cols="*" bordercolor="04376E">
	<FRAME name=ads marginWidth=0 marginHeight=0 src="<%=path%>/top.jsp"
		frameBorder=0 noResize scrolling=no longDesc="">
	<FRAMESET rows=675 cols=198,* frameborder="yes">
		<FRAME name=list marginWidth=0 marginHeight=0 src="<%=path%>/left.jsp"
			frameBorder=0 noResize scrolling=yes longDesc="">
		<FRAME name=main marginWidth=0 marginHeight=0
			src="<%=path%>/postdata.jsp" frameBorder=0 scrolling=yes longDesc="">
	</FRAMESET>
	<NOFRAMES>
	</NOFRAMES>
</FRAMESET>
<body>
</body>
</HTML>

能够看到main.jsp在书写上利用了<frameset>标签。在里面嵌套<frame>,各自是top.jsp left.jsp postdata.jsp.使用说明參见:链接1 链接2

在index.jsp里添加了底部的jsp，使用的是iframe：

<IFRAME name="top" align="default" src="<%=path %>/bottom.jsp"
frameBorder=0 width=100% scrolling=no height=88>
<h1>&nbsp;</h1>
</IFRAME>

正好能够对照其差别，详见链接1 链接2 链接3  iframe使用时经常要和target配合使用。參见  链接1 链接2

top.jsp left.jsp postdata.jsp这三个的代码就不贴了。在源代码里。

四：filter的使用

起因是浏览器直接输入http://localhost:8080/xianfengYan/main.jsp 这时还没有登录，没有验证。我们不希望游客訪问这个界面，因此须要加个过滤器进行过滤，直接将页面跳转至index.jsp.

新建包package com.product.filter;

MyFilter.java

package com.product.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;

public class MyFilter implements Filter {

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

	@Override
	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		// TODO Auto-generated method stub
		//过滤用户的请求，推断是否登录
		
		HttpServletRequest httpServletRequest = (HttpServletRequest)request;
		HttpServletResponse httpServletResponse = (HttpServletResponse)response;
		httpServletRequest.setCharacterEncoding("utf-8");
		httpServletResponse.setCharacterEncoding("utf-8");
		String path = httpServletRequest.getContextPath();
		String username = (String)httpServletRequest.getSession().getAttribute("username");
		if(username == null){
			httpServletResponse.sendRedirect(path + "/index.jsp");
		}
		chain.doFilter(httpServletRequest, httpServletResponse);
	}

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

}

然后再web.xml里进行配置:

	<filter>
		<filter-name>MyFilter</filter-name>
		<filter-class>com.product.filter.MyFilter</filter-class>
	</filter>
	<filter-mapping>
		<filter-name>MyFilter</filter-name>
		<url-pattern>/main.jsp</url-pattern>
	</filter-mapping>

url-pattern里表示过滤的页面，我们指定过滤/main.jsp这个界面。

代码下载链接:http://download.csdn.net/detail/yanzi1225627/7448175

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