摘錄了一些代碼片段，java.sql.DriverManager類包含了一個static屬性和一個static方法，這個static屬性是一個集合，而static方法的作用是將java.sql.Driver接口的子類對象添加進這個集合，驅動程序就是java.sql.Driver接口的子類，由各數據庫廠商提供，每個子類中都包含一個static代碼塊，代碼塊中通過DriverManager類直接調用其static方法傳入一個本類的實例化對象，只要一個驅動程序被加載就會執行其static代碼塊，DriverManager類中也就包含了該驅動程序的實例化對象了，然後"Attempts to establish a connection to the given database URL. The DriverManager attempts to select an appropriate driver from the set of registered JDBC drivers."（試圖建立到給定數據庫URL的連接。DriverManager試圖從已註冊的JDBC驅動程序集中選擇一個適當的驅動程序。）
package org.gjt.mm.mysql;
import java.sql.SQLException;
public class Driver extends com.mysql.jdbc.Driver{
public Driver() throws SQLException{
super();
}
}
///////////////////////////////////////////////////////////////////////////////////////////////////////////////
package com.mysql.jdbc;
import java.sql.SQLException;
public class Driver extends NonRegisteringDriver implements java.sql.Driver{
static{
try{
java.sql.DriverManager.registerDriver(new Driver());
}catch(SQLException E){
throw new RuntimeException("Can't register driver!");
}
}
public Driver() throws SQLException{}
}
///////////////////////////////////////////////////////////////////////////////////////////////////////////////
package java.sql;
import java.util.concurrent.CopyOnWriteArrayList;
public class DriverManager{
// List of registered JDBC drivers
private final static CopyOnWriteArrayList<DriverInfo> registeredDrivers = new CopyOnWriteArrayList<>();
public static synchronized void registerDriver(java.sql.Driver driver) throws SQLException{
registerDriver(driver, null);
}
public static synchronized void registerDriver(java.sql.Driver driver,DriverAction da) throws SQLException{
if(driver!=null){
registeredDrivers.addIfAbsent(new DriverInfo(driver,da));
}else{
throw new NullPointerException();
}
}
}