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javaweb link database tutorial

angryTom

Release： 2019-08-02 16:36:37

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javaweb link database tutorial

Statement: I have always thought that connecting a javaweb program to a database is a very difficult problem. As a result, I studied it today and solved it in less than two hours. So to summarize blog.

　The JavaWeb program connects to the SQLserver database in the following steps:

1: at http://www.microsoft.com/en-us /download/details.aspx?id=21599Download the compressed package of sqljdbc.jar

#2: After decompression, copy and paste sqljdbc4.jar into your project In the lib directory of WEB-INF

javaweb link database tutorial

##3: You need to know some technical knowledge about databases:

First, give an example: The following are the steps required for the driver to establish a connection:

try{
     Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
String URL = "jdbc:sqlserver://localhost:1433;DatabaseName=user";
Connection conn = DriverManager.getConnection(URL, userName, userPwd);//userName是你数据库的用户名如sa,
conn.println("连接数据库成功");
conn.close();
}catch (Exception e){
   out.println("数据库连接失败");
}

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1>: Driver interface: java.sql.Driver is required by all JDBC drivers Implemented interface, this interface is provided to different database vendors, and they use different interface names.

　 -:Class name of SQLserver's JDBC driver: "com.microsoft.sqlserver.jdbc.SQLServerDriver"

　 -:Class name of Oracle's JDBC driver: "oracle.jdbc .driver.OracleDriver"

　 -:MySQL JDBC driver class name: "com.mysql.jdbc.Driver"

2>Loading and registering the JDBC driver

　　Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");This statement is used to load

　3>The URL representation of JDBC connection database is usually divided into three forms Part (usually: separated):

1: Protocol: The only allowed protocol in JDBC can only be jdbc.

2: Sub-protocol: Sub-protocol is used to identify a Database driver

　3: Subname: See below for details

　-:Connect to SQLserver: "jdbc:sqlserver://localhost:1433;DatabaseName=user"

　- :Connect to Oracle: "jdbc:thin:@localhost:1521:ORCL"

　 -:Connect to MySQL: "jdbc:mysql://localhost:3306/databasename"

　4> ; Execute SQL statement interface Statement object, common methods of this object:

　 -:void close() Close and release resources

　 -:ResultSet executeQuery(String sql): Execute a certain item Query statements and return results

　　 -:int execulteUpdate(String sql): You can execute insert, undate or delete statements

4: Take a look at what I wrote for the first time Program to operate the database:

## 1> First create a Student class

package com.ll;
public class Student {
    private String name;
    private String time;
    private String banji;
    public String getBanji() {
        return banji;
    }
    public void setBanji(String banji) {
        this.banji = banji;
    }
    private String sex;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getTime() {
        return time;
    }
    public void setTime(String time) {
        this.time = time;
    }
    
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
}

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2> Write the part that connects the dao layer to the database ,

package dao;
import com.ll.Student;//本行及以下是导入SQL以及所需的包  
import java.sql.Connection;  
import java.sql.DriverManager;  
import java.sql.PreparedStatement;  
import java.sql.ResultSet;  
import java.sql.Statement;  
import java.util.ArrayList;  
public class Studentdao   
{  
    public ArrayList queryAllStudents() throws Exception  
    {//实现对数据库的访问  
        Connection conn = null;  
        ArrayList students = new ArrayList();//定义与初始化ArrayList数组，相当于定义数组，但是容量比数组大  
        StringBuffer str= new StringBuffer();  
        try {  
            //获取连接  
                String driverName = "com.microsoft.sqlserver.jdbc.SQLServerDriver";  //加载JDBC驱动   
                String dbURL = "jdbc:sqlserver://localhost:1433;DatabaseName=StudentManagement";  //连接服务器和数据库sample
                //运行SQL语句  
                String userName = "sa";  //默认用户名 
                String userPwd = "zongjin123";  
                Class.forName(driverName);
                conn = DriverManager.getConnection(dbURL, userName, userPwd);
                if(conn!=null)
                {
                System.out.println("Connection Successful!");  //如果连接成功 控制台输出
                }
                else{
                
                       System.out.println("Connection fail!");  
                    return students;
                }
                
            //密码 
                String sql = "select * from student";//SQL语句，选择数据表student中的所有数据  
        Statement stat = conn.createStatement();  
        ResultSet rs = stat.executeQuery(sql);//定义ResultSet类，用于接收获取的数据  
        while (rs.next())  
                {  
                     //实例化VO  
          Student student=new Student();  
                  student.setName(rs.getString("姓名"));
                  student.setBanji(rs.getString("班级"));
                  student.setSex(rs.getString("性别"));
                  student.setTime(rs.getString("年龄"));
                  students.add(student);  
        }  
                rs.close();  
        stat.close();  
                }  
              catch (Exception e1)   
            {  
            e1.printStackTrace();  
            }  
        finally  
        {  
            try  
            {//关闭连接  
                if(conn!=null)  
                {  
                    conn.close();  
                    conn=null;  
                }  
            }  
            catch(Exception ex)  
            {  
            }  
      return students;    
    }  
  }  
}

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　3>Create index.jsp file

<%@ page language="java" contentType="text/html; charset=GB18030"
    pageEncoding="GB18030"%>
<%@page import = "java.util.*" %>
<%@page import = "java.sql.*" %>
<%@page import="com.ll.Student" %>  
<%@page import="dao.Studentdao" %> 
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>  
    <head>  
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">  
               <style type="text/css">  
#body {  
    background-color: #FFD2BD;       
      }     
  </style>  
        <title>JSP Page</title>  
 </head>  
    <body id="body">  
        <h1>学生信息如下所示：</h1><br>  
        <%  
        Studentdao studentDao=new Studentdao();  
        ArrayList students=studentDao.queryAllStudents();  
        %>      
        <table  border="1" >  
            <tr >  
                <td >年龄</td>  
                <td>姓名</td>  
                 <td>性别</td>  
                <td>班级</td>  
            </tr>  
            <%  
            for(int i=0;i<students.size();i++)  
            {  
                Student student=(Student)students.get(i);  
              
           %>  
            <tr>  
                <td><%=student.getSex() %></td>  
                <td><%=student.getName() %></td>    
                 <td><%=student.getSex() %></td>  
                <td><%=student.getBanji() %></td>    
            </tr>  
            <%  
            }  
            %>  
        </table>  
    </body>  
</html>

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　4>The premise is that you have created a table on your SQLserver database, And there is data.

5. The result is:

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