java未開源的Unsafe類

如何使用Unsafe類呢？

方式一：通過Unsafe提供的工廠方法。

Unsafe unsafe = Unsafe.getUnsafe(); 通過這樣的方式獲得Unsafe的實力會拋出異常信息，因為在unsafe的源碼中會有對安全性的檢查

public static Unsafe getUnsafe() {
        Class cc = sun.reflect.Reflection.getCallerClass(2);
        if (cc.getClassLoader() != null)
            throw new SecurityException("Unsafe");
        return theUnsafe;
    }

Exception in thread "main" java.lang.SecurityException: Unsafe
	at sun.misc.Unsafe.getUnsafe(Unsafe.java:68)
	at org.wk.core.concurrent.InitUnsafe.main(InitUnsafe.java:12)

方式二：通過反射的方式。

因為在開源版本的Unsafe.java中聲明了一個實例域，所以我們可以通過反射的方式來獲得這個域。

 

private static final Unsafe theUnsafe = new Unsafe();

//使用方法
private static Unsafe getUnsafeInstance() throws SecurityException,
			NoSuchFieldException, IllegalArgumentException,
			IllegalAccessException {
		Field theUnsafeInstance = Unsafe.class.getDeclaredField("theUnsafe");
		theUnsafeInstance.setAccessible(true);
		return (Unsafe) theUnsafeInstance.get(Unsafe.class);
	}