Java DriverManager Simple Introduction __java

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DriverManager class of simple learning ... solve the problem

DriverManager the basic services of a set of JDBC drivers in the java.sql package

Package com.evada.de;
Import java.sql.Connection;
Import Java.sql.Driver;
Import Java.sql.DriverManager;

Import java.util.Enumeration;
 /** * Manages a single, reusable connection with a static factory approach * Created by Ay on 2016/5/1.
        * * public class connutils{Private Connutils () {} private static Connection con;//Create a connection to the database in a static code block static{try{
        PostgreSQL driver name Class.forName ("Org.postgresql.Driver");
        Database connection path String URL = "Jdbc:postgresql://127.0.0.1:5432/postgres";
    Username and password con = drivermanager.getconnection (URL, "Postgres", "888888");
    }catch (Exception e) {throw new RuntimeException (E.getmessage (), E);

}//Using a static Method-static factory method, returns the Connection instance public static Connection Getcon () {return con;} Main function test with public static void main (string[] args) {//Get all database-driven enumeration<driver> driverenum = Driverman
    Ager.getdrivers ();
    Print out all drive information while (Driverenum.hasmoreelements ()) {System.out.println (driverenum.nextelement ());
 }
}
}

Run Result:

org.mariadb.jdbc.driver@7cef4e59
com.alibaba.druid.proxy.druiddriver@3ada9e37
com.alibaba.druid.mock.mockdriver@4ec6a292
Org.postgresql.driver@71c7db30

EXPLANATION, because our project package has the following image of the database driver, so will print the following information

the difference between the two:
Drivermanager.registerdriver (New Driver ());
Class.forName ("Com.mysql.jdbc.Driver");

Org.postgresql.Driver class source code as follows, you can see PostgreSQL is through a single case form, new a driver driver, that is, in the connection to the database is only a new one driver

static {
        Sharedtimer = new Sharedtimer (logger);

        try {
            //Register register
            ();
        } catch (SQLException var1) {
            throw new Exceptionininitializererror (VAR1);
        }

        protocols = new string[]{"jdbc", "PostgreSQL"};
    }

    public static void register () throws SQLException {
        if (isregistered ()) {
            throw new IllegalStateException (" Driver is already registered ...);
        } else {
            Driver registereddriver = new Driver ();
            Drivermanager.registerdriver (registereddriver);
            Registereddriver = Registereddriver;
        }
    

Then look at the source code of DriverManager, it will driver packaging into the Driverinfo,

Public
static synchronized void Registerdriver (Java.sql.Driver Driver,
            driveraction da)
        throws SQLException {

        /* Register The driver if it has not already been added to our list */
        if (driver!= null) {
            //Will Drive Wrap to Driverinfo
            registereddrivers.addifabsent (New Driverinfo (Driver, DA));
            Compatibility with the original DriverManager
            throw new NullPointerException ();
        }

        println ("Registerdriver:" + driver);

    }

Class.forName ("Com.mysql.jdbc.Driver");
Conclusion: Drivermanager.registerdriver (New Driver ()); More new one Driver waste; Class.forName ("Com.mysql.jdbc.Driver"); Single case form, more recommended ... Reading Comprehension

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