Class.forName(“com.mysql.jdbc.Driver”);

DriverManager.registerDriver(com.mysql.jdbc.Driver);

jdbc:子協(xié)議:子名稱
協(xié)議：JDBC URL中的協(xié)議總是jdbc 
子協(xié)議：子協(xié)議用于標識一個數(shù)據(jù)庫驅(qū)動程序
子名稱：一種標識數(shù)據(jù)庫的方法。子名稱可以依不同的子協(xié)議而變化，用子名稱的目的是為了定位數(shù)據(jù)庫提供足夠的信息。包含主機名(對應(yīng)服務(wù)端的ip地址)，端口號，數(shù)據(jù)庫名

// 對于 Oracle 數(shù)據(jù)庫連接，采用如下形式： 
jdbc:oracle:thin:@localhost:1521:DatabaseName
// 對于 SQLServer 數(shù)據(jù)庫連接，采用如下形式：
jdbc:microsoft:sqlserver//localhost:1433; DatabaseName=sid
// 對于 MYSQL 數(shù)據(jù)庫連接，采用如下形式：   
jdbc:mysql://localhost:3306/DatabaseName
// 插入中文的時候，這個url要寫成這個
jdbc:mysql://localhost:3306/數(shù)據(jù)庫名稱?useUnicode=true&characterEncoding=UTF-8

package com.company;
// 導(dǎo)入依賴包
import org.junit.Test;
import java.io.FileInputStream;
import java.sql.Connection;
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;

public class Demo1 {
/*
*獲取connect的三種方式
*  */
    public static void main(String[] args) {
        System.out.println("JDBC Test...");
    }
	
	// 使用Driver來實現(xiàn)數(shù)據(jù)庫連接
    @Test
    public void test1() throws SQLException {
		// 
        Driver driver=new com.mysql.jdbc.Driver();
        Properties p1 = new Properties();
        p1.setProperty("user", "root");
        p1.setProperty("password", "mysql123");
        Connection connect = driver.connect("jdbc:mysql://localhost:3306/myemployees", p1);
        System.out.println("connect = " + connect);

    }
	
	// 使用DriverManager來實現(xiàn)數(shù)據(jù)庫連接
    @Test
    public void test2() throws SQLException {
        com.mysql.jdbc.Driver driver = new com.mysql.jdbc.Driver();
        Properties p1 = new Properties();
        p1.setProperty("user", "root");
        p1.setProperty("password", "mysql123");
        DriverManager.registerDriver(driver);
        Connection connection = DriverManager.getConnection
                ("jdbc:mysql://localhost:3306/myemployees", p1);

        System.out.println("connection = " + connection);

    }
	// 將賬號密碼抽出到配置文件中，并使用IO流讀取配置文件的方式連接數(shù)據(jù)庫
    @Test
    public void test3() throws Exception {
        Properties p = new Properties();

        FileInputStream fis = new FileInputStream("p.properties");
        p.load(fis);
        fis.close();
        Class.forName(p.getProperty("driverClass"));
        Connection connection = DriverManager.getConnection(p.getProperty("url"),
                p.getProperty("user"), p.getProperty("password"));
        System.out.println("connection = " + connection);

    }
}

url=jdbc:mysql://localhost:3306/myemployees
user=root
password=mysql123
driverClass=com.mysql.jdbc.Driver

// 使用PreparedStatement來完成數(shù)據(jù)的增刪改查操作
package com.company.jdbc;

import org.junit.Test;

import java.io.FileInputStream;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;

/*
 對數(shù)據(jù)庫進行增，刪，改，查的操作
 */
public class CRUDDemo {

    /*
        添加一條數(shù)據(jù)

        CREATE TABLE student(
        sid INT,
        sname VARCHAR(20),
        sage INT
        )
     */
    @Test
    public void test() throws SQLException {
        //1.獲取數(shù)據(jù)庫連接對象
        Connection connection = JDBCUtils.getConnection();
        //2.預(yù)編譯
        // ? : 占位符（只能是設(shè)置數(shù)據(jù)的地方可以寫成占位符）
        String sql = "insert into student(sid,sname,sage) values(?,?,?)";
        PreparedStatement ps = connection.prepareStatement(sql);
        //3.給占位符賦值
        /*
        setInt(int parameterIndex, int x)
        parameterIndex : 參數(shù)索引（第幾個占位符）
        x : 數(shù)據(jù)
         */
        ps.setInt(1,100);
        //數(shù)據(jù)設(shè)置成中文可不可以取決于表的編碼集
        ps.setString(2,"longge");
        ps.setInt(3,20);
        //4.執(zhí)行sql
        //返回值 ： 有幾條數(shù)據(jù)受到影響
        int result = ps.executeUpdate();//增，刪，改的語句使用該方法
        System.out.println("有"+result+"條數(shù)據(jù)受到影響");
        //5.關(guān)資源
        JDBCUtils.close(ps,connection);
    }

    /*
        改
     */
    @Test
    public void test2() throws SQLException {
        //1.獲取數(shù)據(jù)庫連接對象
        Connection connection = JDBCUtils.getConnection();
        //2.預(yù)編譯
        String sql = "update student set sid=? where sid=?";
        PreparedStatement ps = connection.prepareStatement(sql);
        //3.給占位符賦值
        ps.setInt(1,10);
        ps.setInt(2,100);
        //4.執(zhí)行sql語句
        int result = ps.executeUpdate();
        System.out.println("有"+result+"條數(shù)據(jù)受到影響");
        //5.關(guān)閉資源
        JDBCUtils.close(ps,connection);
    }

    /*
        刪除數(shù)據(jù)
     */
    @Test
    public void test3() throws SQLException {
        //1.獲取數(shù)據(jù)庫連接對象
        Connection connection = JDBCUtils.getConnection();
        //2.預(yù)編譯
        String sql = "delete from student where sid=?";
        PreparedStatement ps = connection.prepareStatement(sql);
        //3.給占位符賦值
        ps.setInt(1,10);
        //4.執(zhí)行sql語句
        int i = ps.executeUpdate();
        System.out.println("有"+i+"條數(shù)據(jù)受到影響");
        //5.關(guān)閉資源
        JDBCUtils.close(ps,connection);
    }

    /*
        查詢數(shù)據(jù)
     */
    @Test
    public void test4() throws Exception {
        List<Student> students = getStudent();
        for (Student s : students) {
            System.out.println(s);
        }

    }

    public List<Student> getStudent() throws Exception {
        //1.獲取數(shù)據(jù)庫連接對象
        Connection connection = JDBCUtils.getConnection();
        //2.預(yù)編譯
        PreparedStatement ps = connection.prepareStatement("select sid,sname,sage from student");
        //3.執(zhí)行sql語句
        ResultSet resultSet = ps.executeQuery();//查詢語必須執(zhí)行此方法

        List<Student> list =  new ArrayList<>();
        //4.遍歷ResultSet
        while(resultSet.next()){//是否有數(shù)據(jù)
            /*
                getInt(String columnLabel) :根據(jù)字段名獲取對應(yīng)的數(shù)據(jù)
                getInt(int columnIndex) ： 根據(jù)列的索引獲取對應(yīng)的數(shù)據(jù)
             */
            int sid = resultSet.getInt("sid");
            String sname = resultSet.getString("sname");
            int sage = resultSet.getInt("sage");

            //System.out.println(sid + " " + sname + " " + sage);
            list.add(new Student(sid,sname,sage));
        }
        //5.關(guān)閉資源
        JDBCUtils.close(ps,connection,resultSet);

        return list;
    }

}

//JDBCUtils類，專門實現(xiàn)數(shù)據(jù)庫的連接與資源釋放操作
package com.company.jdbc;

import java.io.FileInputStream;
import java.io.IOException;
import java.sql.*;
import java.util.Properties;

public class JDBCUtils {
    private static String driverClass;
    private static String url;
    private static String username;
    private static String password;

    static{
        FileInputStream fis = null;
        try {
            //1.獲取數(shù)據(jù)庫連接對象
            //通過Properties讀取內(nèi)容
            //1.創(chuàng)建Properties對象
            Properties p = new Properties();
            //2.加載流
            fis = new FileInputStream("jdbc.properties");
            p.load(fis);
            driverClass = p.getProperty("driverClass");
            url = p.getProperty("url");
            username = p.getProperty("username");
            password = p.getProperty("password");
        }catch (Exception e){
            //終止程序的運行
            e.printStackTrace();
            //將編譯時異常轉(zhuǎn)換成運行時異常
            throw new RuntimeException("xxxxxxxx");
        }finally {
            if (fis != null){
                //3.關(guān)資源
                try {
                    fis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    /*
        獲取連接對象
     */
    public static Connection getConnection(){
        try {
            Class.forName(driverClass);
            //獲取數(shù)據(jù)庫連接對象
            Connection connection = DriverManager.getConnection(url, username, password);
            return connection;
        }catch (Exception e){
            e.printStackTrace();
            throw new RuntimeException("獲取連接失敗");
        }
    }

    /*
        關(guān)閉資源
     */
    public static void close(PreparedStatement ps, Connection connection) {
        if (ps != null){
            try {
                ps.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }

        if (connection != null){
            try {
                connection.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
    }

    public static void close(PreparedStatement ps, Connection connection, ResultSet resultSet) {
        close(ps,connection);
        if (resultSet != null){
            try {
                resultSet.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
    }
}