java未开源的Unsafe类

如何使用Unsafe类呢？

方式一：通过Unsafe提供的工厂方法。

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Unsafe unsafe = Unsafe.getUnsafe(); 通过这样的方式获得Unsafe的实力会抛出异常信息，因为在unsafe的源码中会有对安全性的检查

 

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：通过反射的方式。

因为在开源版本的Unsafe.java中声明了一个实例域，所以我们可以通过反射的方式来获得这个域。

 

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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);

    }