/*
* @(#)ValueExp.java 4.23 05/11/17
*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package javax.management;
/**
* Represents values that can be passed as arguments to
* relational expressions. Strings, numbers, attributes are valid values
* and should be represented by implementations of <CODE>ValueExp</CODE>.
*
* @since 1.5
*/
/*
We considered generifying this interface as ValueExp<T>, where T is
the Java type that this expression generates. This allows some additional
checking in the various methods of the Query class, but in practice
not much. Typically you have something like
Query.lt(Query.attr("A"), Query.value(5)). We can arrange for Query.value
to have type ValueExp<Integer> (or maybe ValueExp<Long> or ValueExp<Number>)
but for Query.attr we can't do better than ValueExp<?> or plain ValueExp.
So even though we could define Query.lt as:
QueryExp <T> lt(ValueExp<T> v1, ValueExp<T> v2)
and thus prevent comparing a
number against a string, in practice the first ValueExp will almost always
be a Query.attr so this check serves no purpose. You would have to
write Query.<Number>attr("A"), for example, which would be awful. And,
if you wrote Query.<Integer>attr("A") you would then discover that you
couldn't compare it against Query.value(5) if the latter is defined as
ValueExp<Number>, or against Query.value(5L) if it is defined as
ValueExp<Integer>.
Worse, for Query.in we would like to define:
QueryExp <T> in(ValueExp<T> val, ValueExp<T>[] valueList)
but this is unusable because you cannot write
"new ValueExp<Integer>[] {...}" (the compiler forbids it).
The few mistakes you might catch with this generification certainly
wouldn't justify the hassle of modifying user code to get the checks
to be made and the "unchecked" warnings that would arise if it
wasn't so modified.
We could reconsider this if the Query methods were augmented, for example
with:
AttributeValueExp<Number> numberAttr(String name);
AttributeValueExp<String> stringAttr(String name);
AttributeValueExp<Boolean> booleanAttr(String name);
QueryExp <T> in(ValueExp<T> val, Set<ValueExp<T>> valueSet).
But it's not really clear what numberAttr should do if it finds that the
attribute is not in fact a Number.
*/
public interface ValueExp extends java.io.Serializable {
/**
* Applies the ValueExp on a MBean.
*
* @param name The name of the MBean on which the ValueExp will be applied.
*
* @return The <CODE>ValueExp</CODE>.
*
* @exception BadStringOperationException
* @exception BadBinaryOpValueExpException
* @exception BadAttributeValueExpException
* @exception InvalidApplicationException
*/
public ValueExp apply(ObjectName name)
throws BadStringOperationException, BadBinaryOpValueExpException,
BadAttributeValueExpException, InvalidApplicationException;
/**
* Sets the MBean server on which the query is to be performed.
*
* @param s The MBean server on which the query is to be performed.
*
* @deprecated This method is not needed because a
* <code>ValueExp</code> can access the MBean server in which it
* is being evaluated by using {@link QueryEval#getMBeanServer()}.
*/
@Deprecated
public void setMBeanServer(MBeanServer s) ;
}