一、JDBC體系結構

JDBC介面（API）包括兩個層次：

• 面向應用的API：Java API，抽象介面，供應用程式開發人員使用（連接資料庫，執行SQL陳述句，獲得結果），
• 面向資料庫的API：Java Driver API，供開發商開發資料庫驅動程式用，

二、Java獲取資料庫連接方法1

import org.junit.Test;

import java.sql.Connection;
import java.sql.Driver;
import java.sql.SQLException;
import java.util.Properties;

public class DriverTest {

    /**
     * 獲取mysql連接
     */
    @Test
    public void test() throws ClassNotFoundException, IllegalAccessException, InstantiationException, SQLException {

        Driver driver = null;

        //1.獲取驅動
        String driverClassName = "com.mysql.cj.jdbc.Driver";

        Class clazz = Class.forName(driverClassName);
        driver =(Driver) clazz.newInstance();

        //2.獲取連接
        String url = "jdbc:mysql://10.10.128.100:3306/dw";
        Properties props = new Properties();
        props.setProperty("user","root");
        props.setProperty("password","nio123456!A");
        Connection conn = driver.connect(url,props);
        System.out.println(conn);
        conn.close();
    }
}

三、Java獲取資料庫連接方法2

public class DriverTest {

    @Test
    public void test2() throws ClassNotFoundException, IllegalAccessException, InstantiationException, SQLException {
        //1.注冊驅動
        String driverClassName = "com.mysql.cj.jdbc.Driver";
        Class clazz = Class.forName(driverClassName);
        Driver driver = (Driver) clazz.newInstance();
        DriverManager.registerDriver(driver);

        //2.獲取連接
        String url = "jdbc:mysql://10.10.128.100:3306/dw";
        String user = "root";
        String password = "nio123456!A";
        Connection conn = DriverManager.getConnection(url,user,password);
        System.out.println(conn);
        conn.close();
    }
}

輸出如下所示：

四、Java最常用獲取資料庫連接的方法

import org.junit.Test;

import java.sql.Connection;
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;

public class DriverTest {

    @Test
    public  void  test3() throws ClassNotFoundException, SQLException {
        String driverClassName = "com.mysql.cj.jdbc.Driver";
        String url = "jdbc:mysql://10.10.128.100:3306/dw";
        String user = "root";
        String password = "nio123456!A";

        //1.加載驅動
        Class.forName(driverClassName);

        //2.獲取連接
        Connection conn = DriverManager.getConnection(url, user, password);

        System.out.println(conn);
    }
}

五、將資料庫資訊放到組態檔中

application.properties

driverClassName: com.mysql.cj.jdbc.Driver
url: jdbc:mysql://10.10.128.100:3306/dw?useUnicode=true&characterEncoding=utf-8
username: root
password: nio123456!A

import org.junit.Test;

import java.io.IOException;
import java.sql.Connection;
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;

public class DriverTest {

    @Test
    public void test4() throws IOException, ClassNotFoundException, SQLException {
        Properties props = new Properties();
        props.load(this.getClass().getClassLoader().getResourceAsStream("application.properties"));


        String driverClassName = props.getProperty("driverClassName");
        String url = props.getProperty("url");
        String user = props.getProperty("username");
        String password = props.getProperty("password");

        Class.forName(driverClassName);

        //2.獲取連接
        Connection conn = DriverManager.getConnection(url, user, password);

        System.out.println(conn);

    }
}

• Class是當前類的Class物件，Class.getClassLoader()是獲取當前類的類加載器，
• getResourceAsStream()是獲取資源的輸入流，類加載器默認是從classPath路徑加載資源，
• 當使用Class.getClassLoader.getResourceAsStream()加載資源時，是從classPath路徑下進行加載，放在resources下的檔案加載時不能加（“/”），

六、獲取連接工具類

import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;

public class jdbcUtils {

    /**
     * 獲取連接
     * @return
     * @throws IOException
     * @throws ClassNotFoundException
     * @throws SQLException
     */
    public static Connection getConnection() throws IOException, ClassNotFoundException, SQLException {
        Properties props = new Properties();
        props.load(JdbcUtils.class.getClassLoader().getResourceAsStream("application" +
                ".properties"));

        String driverClassName = props.getProperty("driverClassName");
        String url = props.getProperty("url");
        String user = props.getProperty("username");
        String password = props.getProperty("password");

        Class.forName(driverClassName);

        //2.獲取連接
        Connection conn = DriverManager.getConnection(url, user, password);

        return conn;
    }
}