org.apache.juneau.Value Maven / Gradle / Ivy
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// * to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance *
// * with the License. You may obtain a copy of the 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. *
// ***************************************************************************************************************************
package org.apache.juneau;
import static org.apache.juneau.internal.ClassUtils.*;
import java.lang.reflect.*;
/**
* Represents a simple settable value.
*
*
* This object is not thread safe.
*
* @param The value type.
*/
public class Value {
/**
* Returns the generic parameter type of the Value parameter at the specified position.
*
* Example:
*
* public class A {
* public void doX(Value<Foo> foo) {...}
* }
*
*
* Class t = Value.getValueType (A.class .getMethod("doX" , Value.class ));
* assertTrue (t == Foo.class );
*
*
* @param m The method containing the parameter.
* @param i The index of the parameter.
* @return The parameter type of the value, or null if the method parameter is not of type Value.
*/
public static Type getParameterType(Method m, int i) {
return getParameterType(m.getGenericParameterTypes()[i]);
}
/**
* Returns the generic parameter type of the Value type.
*
* @param t The type to find the parameter type of.
* @return The parameter type of the value, or null if the type is not a subclass of Value.
*/
public static Type getParameterType(Type t) {
if (t instanceof ParameterizedType) {
ParameterizedType pt = (ParameterizedType)t;
if (pt.getRawType() == Value.class) {
Type[] ta = pt.getActualTypeArguments();
if (ta.length > 0)
return ta[0];
}
} else if (t instanceof Class) {
Class c = (Class)t;
if (Value.class.isAssignableFrom(c)) {
return resolveParameterType(Value.class, 0, c);
}
}
return null;
}
/**
* Convenience method for checking if the specified type is this class.
*
* @param t The type to check.
* @return true if the specified type is this class.
*/
public static boolean isType(Type t) {
return
(t instanceof ParameterizedType && ((ParameterizedType)t).getRawType() == Value.class)
|| (t instanceof Class && Value.class.isAssignableFrom((Class)t));
}
private T t;
private ValueListener listener;
/**
* Constructor.
*/
public Value() {
}
/**
* Constructor.
*
* @param t Initial value.
*/
public Value(T t) {
set(t);
}
/**
* Adds a listener for this value.
*
* @param listener The new listener for this value.
* @return This object (for method chaining).
*/
public Value listener(ValueListener listener) {
this.listener = listener;
return this;
}
/**
* Sets the value.
*
* @param t The new value.
* @return This object (for method chaining).
*/
public Value set(T t) {
this.t = t;
if (listener != null)
listener.onSet(t);
return this;
}
/**
* Returns the value.
*
* @return The value, or null if it is not set.
*/
public T get() {
return t;
}
/**
* Returns true if the value is set.
*
* @return true if the value is set.
*/
public boolean isSet() {
return get() != null;
}
}