servlet中Java连接数据库后的基本操作

时间：2023-03-08 18:33:35

servlet中Java连接数据库后的基本操作

  1. 在eclipse中新建一个工程:login
  2. 在Server中新建一个服务器,基本的操作不用说了,在前两天的笔记中可以找到;
  3. 需要知道数据库的用户名和密码:用户名:user.密码:yufei
  4. 需要改变的地方:

地方一: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_2_5.xsd" id="WebApp_ID" version="2.5">

<display-name>login</display-name>

<welcome-file-list>

<welcome-file>login.html</welcome-file>

</welcome-file-list>

<!-- 注册servlet -->

<servlet>

<!-- servlet的名字 (名字可以随便取)但是约定俗成的名字是开发的servlet的名字 -->

<servlet-name>LoginServlet</servlet-name>

<!-- 配置servlet的包名 (不要带上后缀) -->

<servlet-class>login.com.LoginServlet</servlet-class>

</servlet>

<!-- 映射servlet -->

<servlet-mapping>

<!-- 映射servlet的名字     必须和你注册的servlet的名字一样 -->

<servlet-name>LoginServlet</servlet-name>

<!-- 配置servlet处理的路径(路径可以随便取)但是约定俗成的名字是开发的servlet的名字 -->

<url-pattern>/LoginServlet</url-pattern>

</servlet-mapping>

</web-app>

地方二:在Java Resources 里面新建包和html文件比如:login.com(包),LoginServlet.java文件

下面是:LoginServlet.java里面的内容:

package     login.com;
import     java.io.IOException;

import     java.io.PrintWriter;

import java.sql.Connection;

import     java.sql.DriverManager;

import     java.sql.PreparedStatement;

import     java.sql.ResultSet;

import     java.sql.SQLException;

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;

public class     LoginServlet extends HttpServlet{

@Override

protected void     doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException,     IOException {

// TODO     Auto-generated method stub

//处理中文的乱码

resp.setContentType("text/html;charset=utf-8");//响应

req.setCharacterEncoding("utf-8");     //请求

String name =     req.getParameter("username"); //username是输入框对应的name                          String pwd =     req.getParameter("pwd");                          try {

try {

//表单填写的都是字符串

Class.forName("com.mysql.jdbc.Driver");

Connection     connection =     DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/login",     "root", "yufei");

//                                             System.out.println(connection);

String     sql = "select * from conn where name=? and pwd=? ;";

PreparedStatement     preparedStatement = connection.prepareStatement(sql);

System.out.println("name:"+name+"============"     +"pwd" + pwd);

preparedStatement.setString(1,     name);

preparedStatement.setString(2,     pwd);

ResultSet     re = preparedStatement.executeQuery();

PrintWriter     out = resp.getWriter();

out.print("<h1>==========</h1>");

String     sql1 = "select * from student";

PreparedStatement     sprint = connection.prepareStatement(sql1);

ResultSet     studinf = sprint.executeQuery();

while(re.next()){

out.print("<h1>登录成功</h1>");

out.print("<h5>学生的信息是:</h5>");

while(studinf.next()){

out.print("<p>学生的姓名是:"+     studinf.getString("name")+"===id号:"+studinf.getString("id")+"===性别是:"+studinf.getString("gender")+"===年龄是:"+studinf.getString("age")+"</p>");

}

return;//终止程序

}

out.print("<h1>登录失败</h1>");

} catch     (SQLException e) {

//     TODO Auto-generated catch block

e.printStackTrace();

}

} catch     (ClassNotFoundException e) {

// TODO     Auto-generated catch block

e.printStackTrace();

}

}

//form默认的提交方式是get

@Override

protected void doGet(HttpServletRequest     req, HttpServletResponse resp) throws ServletException, IOException {

// TODO     Auto-generated method stub

doPost(req,resp);

}

}

地方三:在文件WebContent里面新建一个html文件,比如:login.html

下面是:login.html内容:

<!DOCTYPE html>

<html>

<head>

<meta charset="UTF-8">

<title>login</title>

</head>

<body>

<h1>&nbsp;welcome to login</h1>

<div style='outline:1px black solid;width:340px;  text-align: center;'>

<h1>登录页面</h1>

<!--   <a href='HelloServer'>获得连接</a>     -->

<!-- <%=request.getContextPath()%>/ -->

<form action='LoginServlet' method='post'>

<p>用户名:<input type='text'     name='username'/></p>

<p>密码: <input type='password'     name='pwd'/></p>

<button>login</button>

</form>

</div>

</body>

</html>

地方四:添加夹包-在文件夹WEB-INF的lib里面加上夹包Server和mysql

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