java JDBC 在应用如何SPI破坏双亲委派

在DriverManager中的有使用ServiceLoader#load()加载JDBC第三方厂商实现类

代码如下：

AccessController.doPrivileged(new PrivilegedAction() {
            public Void run() {

                ServiceLoader loadedDrivers = ServiceLoader.load(Driver.class);
                Iterator driversIterator = loadedDrivers.iterator();

                /* Load these drivers, so that they can be instantiated.
                 * It may be the case that the driver class may not be there
                 * i.e. there may be a packaged driver with the service class
                 * as implementation of java.sql.Driver but the actual class
                 * may be missing. In that case a java.util.ServiceConfigurationError
                 * will be thrown at runtime by the VM trying to locate
                 * and load the service.
                 *
                 * Adding a try catch block to catch those runtime errors
                 * if driver not available in classpath but it's
                 * packaged as service and that service is there in classpath.
                 */
                try{
                    while(driversIterator.hasNext()) {
                        driversIterator.next();
                    }
                } catch(Throwable t) {
                // Do nothing
                }
                return null;
            }
        });

 其中ServiceLoader.load(Driver.class)的方法如下：

public static  ServiceLoader load(Class service) {
        ClassLoader cl = Thread.currentThread().getContextClassLoader();
        return ServiceLoader.load(service, cl);
    }

 Thread.currentThread().getContextClassLoader()来获取java的根加载器。