StandardMBeanMetaDataImpl


1   /*
2    * @(#)StandardMBeanMetaDataImpl.java   1.2 05/05/27
3    *
4    * Copyright 2005 Sun Microsystems, Inc. All rights reserved.
5    * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6    */
7   
8   package com.sun.jmx.mbeanserver;
9   
10  import javax.management.MBeanInfo  ;
11  import javax.management.StandardMBean  ;
12  
13  /**
14   * Override StandardMetaDataImpl in order to redefine the caching
15   * of MBean Information in StandardMBean.
16   *
17   * @since 1.6
18   */
19  public final class StandardMBeanMetaDataImpl extends StandardMetaDataImpl {
20  
21      private final StandardMBean   mbean;
22  
23      /**
24       * Constructor.
25       */
26      public StandardMBeanMetaDataImpl(StandardMBean   mbean) {
27          super(false);
28          this.mbean = mbean;
29      }
30  
31      /**
32       * We need to override this method because some methods
33       * from BaseMetaDataImpl rely on MetaData#getMBeanInfo().
34       * <p>
35       * The default caching implemented in StandardMetaDataImpl
36       * will not work if two instances of class <var>c</var>
37       * can have different management interfaces, which is
38       * made possible by {@link javax.management.StandardMBean}.
39       *
40       * @return mbean.getMBeanInfo();
41       */
42      MBeanInfo   getCachedMBeanInfo(Class   beanClass) {
43  
44          if (beanClass == null) return null;
45  
46          // Need the synchronized block as long as implementation
47          // and mbeanInterface are not final.
48          //
49          synchronized (mbean) {
50              // Consistency checking: beanClass must be equal
51              // to mbean.getImplementationClass().
52              //
53              final Class   implementationClass =
54                  mbean.getImplementationClass();
55              if (implementationClass == null) return null;
56              if (!beanClass.equals(implementationClass)) return null;
57  
58              // Should always come here (null cases excepted)...
59              //
60              return mbean.getMBeanInfo();
61          }
62      }
63  
64      /**
65       * We need to override this method because some methods
66       * from StandardMetaDataImpl rely on it.
67       * <p>
68       * The default caching implemented in StandardMetaDataImpl
69       * will not work if two instances of class <var>c</var>
70       * can have different management interfaces, which is
71       * made possible by {@link javax.management.StandardMBean}.
72       *
73       * @return mbean.getMBeanInterface();
74       */
75      Class   getCachedMBeanInterface(Class   beanClass) {
76          // Need the synchronized block as long as implementation
77          // and mbeanInterface are not final.
78          //
79          synchronized (mbean) {
80              // Consistency checking: beanClass must be equal
81              // to mbean.getImplementationClass().
82              //
83              final Class   implementationClass =
84                  mbean.getImplementationClass();
85              if (implementationClass == null) return null;
86              if (!beanClass.equals(implementationClass)) return null;
87  
88              // Should always come here (null cases excepted)...
89              //
90              return mbean.getMBeanInterface();
91          }
92      }
93  
94      /**
95       * Need to override this method because default caching implemented
96       * in StandardMetaDataImpl will not work if two instances of class
97       * <var>c</var> can have different <var>mbeanInterface</var>.
98       * <p>
99       * The default caching mechanism in StandardMetaDataImpl uses
100      * class static {@link java.util.WeakHashMap WeakHashMaps} - and
101      * is common to all instance of StandardMetaData - hence to
102      * all MBeanServer.
103      * <p>
104      * As this default mechanism might not always work for
105      * StandardMBean objects (may have several instances of class
106      * <var>c</var> with different MBean interfaces), we disable
107      * this default caching by defining an empty
108      * <code>cacheMBeanInfo()</code> method.
109      * <p>
110      * Caching in our case is no longer performed by the MetaData
111      * object, but by the StandardMBean object.
112      */
113     void cacheMBeanInfo(Class   c, Class   mbeanInterface, MBeanInfo   mbeanInfo) {
114     }
115 }
116
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