java-web 登陆功能

目录结构

web.xml

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" metadata-complete="false" version="3.0">

	<servlet>
		<servlet-name>FirstServlet</servlet-name>
		<servlet-class>FirstServlet</servlet-class>
	</servlet>

	<servlet-mapping>
		<servlet-name>FirstServlet</servlet-name>
		<url-pattern>/Second</url-pattern>
	</servlet-mapping>

</web-app>

web.xml中配置servlet

  • <servlet-name>可以随便起名,但是要在<servlet>和<servlet-map>中一致。
  • <servlet-class>是以WEB-INF/classes为根路径。在写完java文件后,将产生的class文件放到WEB-INF/classes。
  • <url-pattern>可以随便起名,最后表现在URL中应用名之后的部分,即http://localhost/应用名/<url-pattern>,不能少去第一个/。
dao/DBdao

package dao;

import java.sql.Connection;
import java.sql.DriverManager;

public class DBdao{
	public static Connection getConnection(){

		String dbUrl = "jdbc:mysql://localhost:3306/web?characterEncoding=UTF-8";
		String dbUser = "root";
		String dbPassword = "jinliang";

		Connection conn = null;
		try{
			Class.forName("com.mysql.jdbc.Driver");
			conn = DriverManager.getConnection(dbUrl, dbUser, dbPassword);
		}catch(Exception e){
			e.printStackTrace();
		}
		return conn;
	}
}
  • Class.forName("com.mysql.jdbc.Driver");Driver是一个java.sql包中的接口,该方法通过当前类加载器加载实现Driver接口的mysql数据库驱动,并返回Class类。
  • DriverManager.getConnection()方法获得对数据库的连接
FirstServlet/java

import java.io.IOException;
import java.io.PrintStream;

import java.sql.Statement;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;

import dao.DBdao;

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

public class FirstServlet extends HttpServlet{
	public void service(HttpServletRequest request,HttpServletResponse response) throws IOException,ServletException
	{
		request.setCharacterEncoding("UTF-8");
		response.setContentType("text/html;charset=UTF-8");

		PrintStream out = new PrintStream(response.getOutputStream());

		String name = request.getParameter("userName");
		String password = request.getParameter("password");

		Connection conn = null;
		Statement statement = null;

		String sql = "select * from user where username="+"'"+name+"'";

		try{
			//获得数据库连接
			conn = DBdao.getConnection();
                        //获得Statement对象用来执行sql语句
			statement = conn.createStatement();
			//执行sql查询,并返回结果集对象
			ResultSet rs = statement.executeQuery(sql);

			if(rs.next()){
				if(rs.getString("password").equals(password)){
					out.print("<h1>success</h1>");
				}
			}
		}
		catch(Exception e){
			e.printStackTrace();
		}
	}
}

登陆界面

callFirstServlet.jsp

<%@ page pageEncoding="UTF-8"%>
<form method="post" action="Second">
	<input type="text" name="userName"/>
	<input type="password" name="password"/>
	<input type="submit"/>
</form>
  • form表单在点击提交后,通过post方式,将表单中的数据以name:value键值对存入request,并发送request至action,即web.xml中配置的FirstServlet。
  • tomcat接收到表单请求后,将其层层包装,最后递交至FirstServlet中service方法的request参数,从参数中获得姓名和密码。将该密码与从数据库通过姓名查询到的密码比对,确定是否通过,并将结果放在response中,由tomcat再次包装后返回至客户端浏览器。
posted @ 2019-04-02 17:34  gengqzh  阅读(214)  评论(0编辑  收藏  举报
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