sun.misc.Unsafe.allocateInstance()方法的使用及代码示例

x33g5p2x  于2022-01-31 转载在 其他  
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本文整理了Java中sun.misc.Unsafe.allocateInstance()方法的一些代码示例，展示了Unsafe.allocateInstance()的具体用法。这些代码示例主要来源于Github/Stackoverflow/Maven等平台，是从一些精选项目中提取出来的代码，具有较强的参考意义，能在一定程度帮忙到你。Unsafe.allocateInstance()方法的具体详情如下：
包路径：sun.misc.Unsafe
类名称：Unsafe
方法名：allocateInstance

Unsafe.allocateInstance介绍

[英]Allocates an instance of the given class without running the constructor. The class' will be run, if necessary.
[中]在不运行构造函数的情况下分配给定类的实例。如有必要，该课程将运行。

代码示例

代码示例来源：origin: apache/ignite

/**
 * Allocates instance of given class.
 *
 * @param cls Class.
 * @return Allocated instance.
 */
public static Object allocateInstance(Class cls) throws InstantiationException {
  return UNSAFE.allocateInstance(cls);
}

代码示例来源：origin: apache/geode

public Object allocateInstance(Class<?> c) throws InstantiationException {
 return this.unsafe.allocateInstance(c);
}

代码示例来源：origin: robolectric/robolectric

@Override public <E> E createProxy(Class<E> targetClass, E target) {
  try {
   Object proxy = UNSAFE.allocateInstance(proxyClass);
   field.set(proxy, target);
   return targetClass.cast(proxy);
  } catch (Throwable t) {
   throw new AssertionError(t);
  }
 }
};

代码示例来源：origin: redisson/redisson

public T newInstance() {
   try {
     return type.cast(unsafe.allocateInstance(type));
   } catch (InstantiationException e) {
     throw new ObjenesisException(e);
   }
  }
}

代码示例来源：origin: redisson/redisson

@Override
public Object newInstance(Class clazz, Constructor cons, boolean doesRequireInit, boolean unsafeAsLastResort) {
  try {
    if (!doesRequireInit && FSTUtil.unFlaggedUnsafe != null) { // no performance improvement here, keep for nasty constructables ..
      return FSTUtil.unFlaggedUnsafe.allocateInstance(clazz);
    }
    if ( cons == null ) // no suitable constructor found
    {
      if ( unsafeAsLastResort ) {
        // best effort. use Unsafe to instantiate.
        // Warning: if class contains transient fields which have default values assigned ('transient int x = 3'),
        // those will not be assigned after deserialization as unsafe instantiation does not execute any default
        // construction code.
        // Define a public no-arg constructor to avoid this behaviour (rarely an issue, but there are cases).
        if ( FSTUtil.unFlaggedUnsafe != null ) {
          return FSTUtil.unFlaggedUnsafe.allocateInstance(clazz);
        }
        throw new RuntimeException("no suitable constructor found and no Unsafe instance avaiable. Can't instantiate "+ clazz.getName());
      }
    }
    return cons.newInstance();
  } catch (Throwable ignored) {
    ignored.printStackTrace();
    return null;
  }
}

代码示例来源：origin: neo4j/neo4j

/**
 * Create a new DirectByteBuffer that wraps the given address and has the given capacity.
 * <p>
 * The ByteBuffer does NOT create a Cleaner, or otherwise register the pointer for freeing.
 */
public static ByteBuffer newDirectByteBuffer( long addr, int cap ) throws Exception
{
  if ( directByteBufferCtor == null )
  {
    // Simulate the JNI NewDirectByteBuffer(void*, long) invocation.
    Object dbb = unsafe.allocateInstance( directByteBufferClass );
    initDirectByteBuffer( dbb, addr, cap );
    return (ByteBuffer) dbb;
  }
  // Reflection based fallback code.
  return (ByteBuffer) directByteBufferCtor.newInstance( addr, cap );
}

代码示例来源：origin: org.objenesis/objenesis

public T newInstance() {
   try {
     return type.cast(unsafe.allocateInstance(type));
   } catch (InstantiationException e) {
     throw new ObjenesisException(e);
   }
  }
}

代码示例来源：origin: peter-lawrey/Java-Chronicle

@Override
public E read(Excerpt bytes) {
  E e;
  try {
    e = (E) UnsafeExcerpt.UNSAFE.allocateInstance(classMarshaled);
    e.readExternal(bytes);
  } catch (Exception e2) {
    throw new IllegalStateException(e2);
  }
  return e;
}

代码示例来源：origin: fengjiachun/Jupiter

/**
 * Returns a new {@link String} backed by the given {@code chars}. The char array should not
 * be mutated any more after calling this function.
 */
public static String moveToString(char[] chars) {
  if (STRING_VALUE_OFFSET == -1) {
    // In the off-chance that this JDK does not implement String as we'd expect, just do a copy.
    return new String(chars);
  }
  final String str;
  try {
    str = (String) unsafe.allocateInstance(String.class);
  } catch (InstantiationException e) {
    // This should never happen, but return a copy as a fallback just in case.
    return new String(chars);
  }
  unsafe.putObject(str, STRING_VALUE_OFFSET, chars);
  return str;
}

代码示例来源：origin: fengjiachun/Jupiter

/**
 * Returns a new {@link String} backed by the given {@code chars}. The char array should not
 * be mutated any more after calling this function.
 */
public static String moveToString(char[] chars) {
  if (STRING_VALUE_OFFSET == -1) {
    // In the off-chance that this JDK does not implement String as we'd expect, just do a copy.
    return new String(chars);
  }
  final String str;
  try {
    str = (String) unsafe.allocateInstance(String.class);
  } catch (InstantiationException e) {
    // This should never happen, but return a copy as a fallback just in case.
    return new String(chars);
  }
  unsafe.putObject(str, STRING_VALUE_OFFSET, chars);
  return str;
}

代码示例来源：origin: com.google.protobuf/protobuf-java

/**
 * Returns a new {@link String} backed by the given {@code chars}. The char array should not
 * be mutated any more after calling this function.
 */
static String moveToString(char[] chars) {
 if (STRING_VALUE_OFFSET == -1) {
  // In the off-chance that this JDK does not implement String as we'd expect, just do a copy.
  return new String(chars);
 }
 final String str;
 try {
  str = (String) UNSAFE.allocateInstance(String.class);
 } catch (InstantiationException e) {
  // This should never happen, but return a copy as a fallback just in case.
  return new String(chars);
 }
 putObject(str, STRING_VALUE_OFFSET, chars);
 return str;
}

代码示例来源：origin: RuedigerMoeller/fast-serialization

@Override
public Object newInstance(Class clazz, Constructor cons, boolean doesRequireInit, boolean unsafeAsLastResort) {
  try {
    if (!doesRequireInit && FSTUtil.unFlaggedUnsafe != null) { // no performance improvement here, keep for nasty constructables ..
      return FSTUtil.unFlaggedUnsafe.allocateInstance(clazz);
    }
    if ( cons == null ) // no suitable constructor found
    {
      if ( unsafeAsLastResort ) {
        // best effort. use Unsafe to instantiate.
        // Warning: if class contains transient fields which have default values assigned ('transient int x = 3'),
        // those will not be assigned after deserialization as unsafe instantiation does not execute any default
        // construction code.
        // Define a public no-arg constructor to avoid this behaviour (rarely an issue, but there are cases).
        if ( FSTUtil.unFlaggedUnsafe != null ) {
          return FSTUtil.unFlaggedUnsafe.allocateInstance(clazz);
        }
        throw new RuntimeException("no suitable constructor found and no Unsafe instance avaiable. Can't instantiate "+ clazz.getName());
      }
    }
    return cons.newInstance();
  } catch (Throwable ignored) {
    logger.log(FSTLogger.Level.INFO, "Failed to construct new instance", ignored);
    return null;
  }
}

代码示例来源：origin: redisson/redisson

public <T extends FSTStruct> T createWrapper(Class<T> onHeap, Bytez bytes, long index) throws Exception {
  Class proxy = getProxyClass(onHeap);
  T res = (T) FSTUtil.getUnsafe().allocateInstance(proxy);
  res.baseOn(bytes, index, this);
  return res;
}

代码示例来源：origin: redisson/redisson

protected static <C extends FSTStruct> Object allocInstance(Class<C> clazz) throws Exception {
    return FSTUtil.getUnsafe().allocateInstance(FSTStructFactory.getInstance().getProxyClass(clazz));
//        return FSTStructFactory.getInstance().getProxyClass(clazz).newInstance();
  }

代码示例来源：origin: RuedigerMoeller/fast-serialization

public <T extends FSTStruct> T createWrapper(Class<T> onHeap, Bytez bytes, long index) throws Exception {
  Class proxy = getProxyClass(onHeap);
  T res = (T) FSTUtil.getUnsafe().allocateInstance(proxy);
  res.baseOn(bytes, index, this);
  return res;
}

代码示例来源：origin: RuedigerMoeller/fast-serialization

protected static <C extends FSTStruct> Object allocInstance(Class<C> clazz) throws Exception {
    return FSTUtil.getUnsafe().allocateInstance(FSTStructFactory.getInstance().getProxyClass(clazz));
//        return FSTStructFactory.getInstance().getProxyClass(clazz).newInstance();
  }

代码示例来源：origin: com.thoughtworks.xstream/xstream

public Object newInstance(Class type) {
  if (exception != null) {
    ObjectAccessException ex = new ObjectAccessException("Cannot construct type", exception);
    ex.add("construction-type", type.getName());
    throw ex;
  }
  ErrorWritingException ex = null;
  if (type == void.class || type == Void.class) {
    ex = new ConversionException("Type void cannot have an instance");
  } else {
    try {
      return unsafe.allocateInstance(type);
    } catch (final SecurityException e) {
      ex = new ObjectAccessException("Cannot construct type", e);
    } catch (final InstantiationException e) {
      ex = new ConversionException("Cannot construct type", e);
    } catch (final IllegalArgumentException e) {
      ex = new ObjectAccessException("Cannot construct type", e);
    }
  }
  ex.add("construction-type", type.getName());
  throw ex;
}

代码示例来源：origin: webx/citrus

@SuppressWarnings("restriction")
protected Object instantiate()
    throws Exception {
  return _unsafe.allocateInstance(_type);
}

代码示例来源：origin: aaberg/sql2o

public Object newInstance() {
    try {
      return theUnsafe.allocateInstance(clazz);
    } catch (InstantiationException e) {
      throw new Sql2oException("Could not create a new instance of class " + clazz, e);
    }
  }
};

代码示例来源：origin: aaberg/sql2o

public Object newInstance() {
    try {
      return theUnsafe.allocateInstance(clazz);
    } catch (InstantiationException e) {
      throw new Sql2oException("Could not create a new instance of class " + clazz, e);
    }
  }
};

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