Java学习笔记-JDBC 1

Registering the Driver Class

 

There are 3 ways to register a driver to your java program.

 

1 A JAR file can be automatically register if it contains a file name META-INF/services/java.sql.Driver

 

2 Load the driver class in your java program. For example:

Class.forName("oracle.jdbc.OracleDriver");

 

3 Set jdbc.driver property. You can specify the property with a command-line argument, such as

java -Djdbc.drivers=org.postgresql.Driver ProgramName

 

  Or your application can set the system property with a call such as

System.setProperty("jdbc.drivers", "org.postgresql.Driver");

 

Connecting to the Database

In your Java program, you open a database connection with code that is similar to the following example:

 

String url = "jdbc:postgresql:COREJAVA";
String username = "dbuser";
String password = "secret";
Connection conn = DriverManager.getConnection(url, username, password);

 

Following code is a whole example.

 

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

public class DBTest {

    public static void main(String[] args) {
        
        try {
            runTest();
        } catch (SQLException ex) {
            for (Throwable t : ex) {
                t.printStackTrace();
            }
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
    
    public static void runTest() throws IOException, SQLException {
        
        Connection conn = getConnection();
        
        try {
            Statement stat = conn.createStatement();
            
            stat.executeUpdate("CREATE TABLE Greetings (Message CHAR(20))");
            stat.execute("INSERT INTO Greetings VALUES ('Hello, World!')");
            
            ResultSet result = stat.executeQuery("SELECT * FROM Greetings");
            
            if (result.next()) {
                System.out.println(result.getString(1));
            }
            
            result.close();
            stat.executeUpdate("DROP TABLE Greetings");
            
        } finally {
            conn.close();
        }

    }
    
    public static Connection getConnection() throws IOException, SQLException {
        
        Properties props = new Properties();
        InputStream in = DBTest.class.getResourceAsStream("database.properties");
        props.load(in);
        
        String drivers = props.getProperty("jdbc.drivers");
        if (drivers != null) {
            System.setProperty("jdbc.drivers", drivers);
        } else {
            return null;
        }
        
        String url = props.getProperty("jdbc.url");
        String username = props.getProperty("jdbc.username");
        String password = props.getProperty("jdbc.password");
            
        return DriverManager.getConnection(url, username, password);
    }
}

 

database.properties file

 

jdbc.drivers=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql:///javacore
jdbc.username=root
jdbc.password=mysql