JDBC Series: (1) Connect to database through JDBC

• 1. What is JDBC

• 2. Three ways of JDBC Connection database

• 2.1. The first way of realization

• 2.2. The second way of realization

• 2.3. The third way of realization

• 3, the internal realization of Com.mysql.jdbc.Driver

1. What is JDBC

Techniques for sending SQL statements using Java Code (Programs)

Using JDBC to send SQL prerequisites needs to know: The database's IP address, port, data name, user name, and password.

JDBC Url= protocol name + sub-protocol name + data source name. The a  protocol name is always "JDBC". The b  sub-protocol name is determined by the creator of the JDBC driver. The c  data source name may also contain information such as the user and password, which can also be provided separately. Several common database connections-------------------------------Oracle------------------driver: Oracle.jdbc.driver.oracledriverurl:jdbc:o Racle:thin: @machine_name:p ort:dbname Note: machine_name: The name of the machine where the database resides;       port: port number, The default is 1521-------------------------------MySQL-------------------driver: com.mysql.jdbc.driverurl:jdbc:mysql://machine _name:port/dbname Note: machine_name: The name of the machine where the database resides;       port: port number, default 3306     ---------------------------sql  Server------------------Driver:com.microsoft.jdbc.sqlserver.sqlserverdriverurl:jdbc:microsoft:sqlserver://< machine_name><:p ort>;D atabasename=<dbname> Note: machine_name: The name of the machine where the database resides;       port: Port number, The default is 1433--------------------------DB2--------------------------driver: com.ibm.db2.jdbc.app.db2driverurl:jdbc:db2:// <machine_name><:p ort>/dbname Note: machine_name: The name of the machine where the database resides;Nbsp;     port: Port number, default is------------------------------------------------------- 

2. Three ways of JDBC Connection database

2.1. The first way of realization

Package Com.rk.db.a_jdbc;import Java.sql.driver;import Java.sql.connection;import java.sql.sqlexception;import java.util.properties;/** * JDBC Connection Database * The first method: establish a database connection by creating a driver class object for the JDBC implementation class * @author RK * */public class Demo01{public static void Main (string[] args) throws sqlexception{//JDBC Protocol: Database sub-protocol: Host: Port/connected database//string URL = "jdbc:mysql://localhost:3306/ TestDB "; String username = "root"; String password = "root";//1. Create driver class object Driver Driver = new Com.mysql.jdbc.Driver ();//set user name and Password properties props = new Proper Ties ();p rops.setproperty ("User", username);p rops.setproperty ("password", password);//2. Connect to the database and return to the Connection object connection conn = driver.connect (URL, props); SYSTEM.OUT.PRINTLN (conn);}}

2.2. The second way of realization

Package Com.rk.db.a_jdbc;import Java.sql.driver;import Java.sql.drivermanager;import java.sql.connection;import java.sql.sqlexception;/** * JDBC Connection Database * The second method: connect to the database using the Drive Manager class (registered two times, not necessary) * @author RK * */public class Demo02{public static void Main (string[] args) throws sqlexception{string url = "Jdbc:mysql://localhost:3306/testdb"; String username = "root"; String password = "root";D river Driver = new Com.mysql.jdbc.Driver ();//1. Registering drivers (multiple drivers can be registered) Drivermanager.registerdriver (driver);//2. Connect to a specific database connection conn = drivermanager.getconnection (URL, username, password); SYSTEM.OUT.PRINTLN (conn);}}

2.3. The third way of realization

Package Com.rk.db.a_jdbc;import Java.sql.drivermanager;import Java.sql.connection;import java.sql.SQLException;/** * JDBC Connection Database * Third method: Use the Load driver class to register the driver (this is the recommended way to connect to the database) * @author RK * */public class demo03{public static void Main (String [] args) throws classnotfoundexception, sqlexception{string url = "Jdbc:mysql://localhost:3306/testdb"; String user = "root"; String password = "root";//Load a static block of code by getting a bytecode object to register the driver Class.forName ("Com.mysql.jdbc.Driver");// Connect to a specific database connection conn = Drivermanager.getconnection (Url,user,password); SYSTEM.OUT.PRINTLN (conn);}}

3, the internal realization of Com.mysql.jdbc.Driver

Here is the main explanation of a problem, that is, in 2.3, and did not write code with DriverManager to Com.mysql.jdbc.Driver instance registration, the reason is Com.mysql.jdbc.Driver source.

A static (static) code snippet is provided in the Com.mysql.jdbc.Driver class as follows:

Java.sql.DriverManager.registerDriver (New Driver ());

The complete code is as follows:

The static code snippet is provided in the------Com.mysql.jdbc.Driver class and is actively registered with DriverManager Java.sql.DriverManager.registerDriver (new  Driver ());p ackage com.mysql.jdbc;import java.sql.sqlexception;public class driver  extends nonregisteringdriver implements java.sql.driver {    //     // Register ourselves with the DriverManager     //    static {        try {             java.sql.drivermanager.registerdriver (New  driver ());        } catch  (SQLException E)  {             throw new runtimeexception (" Can ' t register driver! ');         }    }    /**     * construct a new driver and register it  with drivermanager     */    public driver ()  throws sqlexception {        // required for  class.forname (). newinstance ()     }}

JDBC Series: (1) Connect to database through JDBC