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25 
26 package javax.management;
27 
28 // java import
29 import java.io.Serializable;
30 
31 /**
32  * Allows a query to be performed in the context of a specific MBean server.
33  *
34  * @since 1.5
35  */
36 public abstract class QueryEval implements Serializable {
37 
38     /* Serial version */
39     private static final long serialVersionUID = 2675899265640874796L;
40 
41     private static ThreadLocal<MBeanServer> server =
42         new InheritableThreadLocal<MBeanServer>();
43 
44     /**
45      * <p>Sets the MBean server on which the query is to be performed.
46      * The setting is valid for the thread performing the set.
47      * It is copied to any threads created by that thread at the moment
48      * of their creation.</p>
49      *
50      * <p>For historical reasons, this method is not static, but its
51      * behavior does not depend on the instance on which it is
52      * called.</p>
53      *
54      * @param s The MBean server on which the query is to be performed.
55      *
56      * @see #getMBeanServer
57      */
setMBeanServer(MBeanServer s)58     public void setMBeanServer(MBeanServer s) {
59         server.set(s);
60     }
61 
62     /**
63      * <p>Return the MBean server that was most recently given to the
64      * {@link #setMBeanServer setMBeanServer} method by this thread.
65      * If this thread never called that method, the result is the
66      * value its parent thread would have obtained from
67      * <code>getMBeanServer</code> at the moment of the creation of
68      * this thread, or null if there is no parent thread.</p>
69      *
70      * @return the MBean server.
71      *
72      * @see #setMBeanServer
73      *
74      */
getMBeanServer()75     public static MBeanServer getMBeanServer() {
76         return server.get();
77     }
78 }
79