the DriverManager in the JDBC program is used to load the driver and create a link to the database.
Common methods of this API:
Drivermanager.registerdriver (New Driver ());
drivermanager.getconnection (Url,user,password);
Note: It is not recommended to use the Registerdriver method to register drivers in actual development for two reasons:
1. Looking at the source code of driver, you can see that if this is the case, it will cause the driver to register two times, that is, there will be two driver objects in memory.
2. The program relies on the MySQL API, out of the MySQL jar package, the program will not compile, the future program to switch the underlying database will be very cumbersome.
Recommended way: Class.forName ("Com.mysql.jdbc.Driver");
using this method does not cause the drive object to recur in memory, and in this way, the program simply needs a string to be dependent on the specific driver, making the program more flexible.
URL is used to identify the location of the database, the programmer through the URL address to tell the JDBC program to connect to which database, the URL is written as: jdbc:mysql://localhost:3306/test? key=value
Common Database URL address notation: Oracle notation:
MySQL url:jdbc:mysql://localhost:3306/database name
Oracle Url:jdbc:oracle:thin: @localhost: 1521:sid
Jdbc:oracle:thin: @localhost: 1521:sid
Mysql-jdbc:mysql://localhost:3306/sid
The short form of the MySQL URL address:
Jdbc:mysql:///sid
Common Properties: Useunicode=true&characterencoding=utf-8
//Registration driver
The first type: Drivermanager.registerdriver (new Driver ());
the second type: Class.forName ("Com.mysql.jdbc.Driver");
in the first case, there is a static block of code in the Com.mysql.jdbc.Driver class:
sttic {
try {
Java.sql.DriverManager.registerDriver (New Driver ());
}
catch (SQLException ex) {
throw new RuntimeException ("Can ' t Register driver");
}
}
the problem with the above code:
1, two MySQL drivers will be loaded in the drive manager. Solution: Use reflection
class.forname ("Com.mysql.jdbc.Driver");
Analysis: What are the benefits of using reflection to load drivers?
A. Load only once, loading a driver object,
B. Reduce the coupling and not rely on the driver.
Importjava.sql.Connection;
Import Java.sql.DriverManager;
Import java.sql.SQLException;
Import java.sql.Statement;
Import Org.gjt.mm.mysql.Driver;Registered driver Drivermanager.registerdriver (new Driver ()); Connection TEST Connection conn = Drivermanager.getconnection ("Jdbc:mysql://localhost:3306/mydb1", "root", "root");//Through the Connection object Create an Action SQL statement object Statementstatement st = Conn.createstatement ();//Operation SQL statement String t_sql = "SELECT * from Employee";//Execute SQL return Query result set Resultset;java.sql.resultset rs = St.executequery (T_sql); Traverse the result set while (Rs.next ()) {int id = rs.getint ("id"); String name = rs.getstring ("name"); String gender = rs.getstring ("gender"); SYSTEM.OUT.PRINTLN ("Serial number:" + ID + ", Name:" + name + ", Position:" + gender+ ";");}//Release Resourcesrs.close ();st.close ();conn.close ();
JDBC Operations Database
