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/*
* This file is available under and governed by the GNU General Public
* License version 2 only, as published by the Free Software Foundation.
* However, the following notice accompanied the original version of this
* file, and Oracle licenses the original version of this file under the BSD
* license:
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/*
Copyright 2009-2013 Attila Szegedi
Licensed under both the Apache License, Version 2.0 (the "Apache License")
and the BSD License (the "BSD License"), with licensee being free to
choose either of the two at their discretion.
You may not use this file except in compliance with either the Apache
License or the BSD License.
If you choose to use this file in compliance with the Apache License, the
following notice applies to you:
You may obtain a copy of the Apache License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
implied. See the License for the specific language governing
permissions and limitations under the License.
If you choose to use this file in compliance with the BSD License, the
following notice applies to you:
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
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notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
* Neither the name of the copyright holder nor the names of
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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package jdk.dynalink.beans;
import java.io.Serializable;
import java.util.Objects;
import jdk.dynalink.StandardOperation;
Object that allows access to the static members of a class (its static methods, properties, and fields), as well as construction of instances using StandardOperation.NEW operation. In Dynalink, Class objects are not treated specially and act as ordinary Java objects; you can use e.g. GET:PROPERTY:superclass as a property getter to invoke clazz.getSuperclass(). On the other hand, you can not use Class objects to access static members of a class, nor to create new instances of the class using NEW. This is consistent with how Class objects behave in Java: in Java, you write e.g. new BitSet() instead of new BitSet.class(). Similarly, you write System.out and not System.class.out. It is this aspect of using a class name as the constructor and a namespace for static members that StaticClass embodies. Objects of this class are recognized by the BeansLinker as being special, and operations on them will be linked against the represented class' static members. The "class" synthetic property is additionally recognized and returns the Java Class object, just as in Java System.class evaluates to the Class object for the Class objects exposed through BeansLinker expose the "static" synthetic property which returns their StaticClass object (there is no equivalent to this in Java).
In summary, instances of this class act as namespaces for static members and
as constructors for classes, much the same way as specifying a class name in
Java language does, except that in Java this is just a syntactic element,
while in Dynalink they are expressed as actual objects.
StaticClass objects representing Java array types will act as constructors taking a single int argument and create an array of the specified size.
If the class has several constructors, StandardOperation.NEW on StaticClass will try to select the most specific applicable constructor. You might want to expose a mechanism in your language for selecting a constructor with an explicit signature through BeansLinker.getConstructorMethod(Class<?>, String).
/**
* Object that allows access to the static members of a class (its static
* methods, properties, and fields), as well as construction of instances using
* {@link StandardOperation#NEW} operation. In Dynalink, {@link Class} objects
* are not treated specially and act as ordinary Java objects; you can use e.g.
* {@code GET:PROPERTY:superclass} as a property getter to
* invoke {@code clazz.getSuperclass()}. On the other hand, you can not use
* {@code Class} objects to access static members of a class, nor to create new
* instances of the class using {@code NEW}. This is consistent with how
* {@code Class} objects behave in Java: in Java, you write e.g.
* {@code new BitSet()} instead of {@code new BitSet.class()}. Similarly, you
* write {@code System.out} and not {@code System.class.out}. It is this aspect
* of using a class name as the constructor and a namespace for static members
* that {@code StaticClass} embodies.
* <p>
* Objects of this class are recognized by the {@link BeansLinker} as being
* special, and operations on them will be linked against the represented class'
* static members. The {@code "class"} synthetic property is additionally
* recognized and returns the Java {@link Class} object, just as in Java
* {@code System.class} evaluates to the {@code Class} object for the
* {@code} System class. Conversely, {@link Class} objects exposed through
* {@link BeansLinker} expose the {@code "static"} synthetic property which
* returns their {@code StaticClass} object (there is no equivalent to this in
* Java).
* <p>
* In summary, instances of this class act as namespaces for static members and
* as constructors for classes, much the same way as specifying a class name in
* Java language does, except that in Java this is just a syntactic element,
* while in Dynalink they are expressed as actual objects.
* <p>{@code StaticClass} objects representing Java array types will act as
* constructors taking a single int argument and create an array of the
* specified size.
* <p>
* If the class has several constructors, {@link StandardOperation#NEW} on
* {@code StaticClass} will try to select the most specific applicable
* constructor. You might want to expose a mechanism in your language for
* selecting a constructor with an explicit signature through
* {@link BeansLinker#getConstructorMethod(Class, String)}.
*/
public final class StaticClass implements Serializable {
private static final ClassValue<StaticClass> staticClasses = new ClassValue<StaticClass>() {
@Override
protected StaticClass computeValue(final Class<?> type) {
return new StaticClass(type);
}
};
private static final long serialVersionUID = 1L;
The runtime Class object whose static members this StaticClass represents. /**
* The runtime {@code Class} object whose static members this
* {@code StaticClass} represents.
*/
private final Class<?> clazz;
/*private*/ StaticClass(final Class<?> clazz) {
this.clazz = Objects.requireNonNull(clazz);
}
Retrieves the StaticClass instance for the specified class. Params: - clazz – the class for which the static facet is requested.
Returns: the StaticClass instance representing the specified class.
/**
* Retrieves the {@link StaticClass} instance for the specified class.
* @param clazz the class for which the static facet is requested.
* @return the {@link StaticClass} instance representing the specified class.
*/
public static StaticClass forClass(final Class<?> clazz) {
return staticClasses.get(clazz);
}
Returns the represented Java class.
Returns: the represented Java class.
/**
* Returns the represented Java class.
* @return the represented Java class.
*/
public Class<?> getRepresentedClass() {
return clazz;
}
@Override
public String toString() {
return "StaticClass[" + clazz.getName() + "]";
}
Returns forClass(Class<?>) for the underlying clazz field ensuring that deserialization doesn't create non-canonical instances. Returns: forClass(Class<?>) for the underlying clazz field.
/**
* Returns {@link #forClass(Class)} for the underlying {@code clazz} field
* ensuring that deserialization doesn't create non-canonical instances.
* @return {@link #forClass(Class)} for the underlying {@code clazz} field.
*/
private Object readResolve() {
return forClass(clazz);
}
}