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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>.

     *

     */

    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) ;

}