J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 2005-2006 Sun Microsystems, Inc. All Rights Reserved. |
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| 4 | * |
| 5 | * This code is free software; you can redistribute it and/or modify it |
| 6 | * under the terms of the GNU General Public License version 2 only, as |
| 7 | * published by the Free Software Foundation. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun in the LICENSE file that accompanied this code. |
| 10 | * |
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT |
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| 14 | * version 2 for more details (a copy is included in the LICENSE file that |
| 15 | * accompanied this code). |
| 16 | * |
| 17 | * You should have received a copy of the GNU General Public License version |
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, |
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| 20 | * |
| 21 | * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any questions. |
| 24 | */ |
| 25 | |
| 26 | package com.sun.jmx.mbeanserver; |
| 27 | |
| 28 | import static com.sun.jmx.mbeanserver.Util.*; |
| 29 | import java.util.Map; |
| 30 | import java.lang.ref.WeakReference; |
| 31 | import java.lang.reflect.InvocationHandler; |
| 32 | import java.lang.reflect.Proxy; |
| 33 | import javax.management.JMX; |
| 34 | import javax.management.MBeanServerConnection; |
| 35 | import javax.management.MBeanServerInvocationHandler; |
| 36 | import javax.management.ObjectName; |
| 37 | |
| 38 | /** |
| 39 | * @since 1.6 |
| 40 | */ |
| 41 | |
| 42 | /* |
| 43 | * This class handles the mapping between MXBean references and |
| 44 | * ObjectNames. Consider an MXBean interface like this: |
| 45 | * |
| 46 | * public interface ModuleMXBean { |
| 47 | * ProductMXBean getProduct(); |
| 48 | * void setProduct(ProductMXBean product); |
| 49 | * } |
| 50 | * |
| 51 | * This defines an attribute called "Product" whose originalType will |
| 52 | * be ProductMXBean and whose openType will be ObjectName. The |
| 53 | * mapping happens as follows. |
| 54 | * |
| 55 | * When the MXBean's getProduct method is called, it is supposed to |
| 56 | * return a reference to another MXBean, or a proxy for another |
| 57 | * MXBean. The MXBean layer has to convert this into an ObjectName. |
| 58 | * If it's a reference to another MXBean, it needs to be able to look |
| 59 | * up the name under which that MXBean has been registered in this |
| 60 | * MBeanServer; this is the purpose of the mxbeanToObjectName map. If |
| 61 | * it's a proxy, it can check that the MBeanServer matches and if so |
| 62 | * extract the ObjectName from the proxy. |
| 63 | * |
| 64 | * When the setProduct method is called on a proxy for this MXBean, |
| 65 | * the argument can be either an MXBean reference (only really logical |
| 66 | * if the proxy has a local MBeanServer) or another proxy. So the |
| 67 | * mapping logic is the same as for getProduct on the MXBean. |
| 68 | * |
| 69 | * When the MXBean's setProduct method is called, it needs to convert |
| 70 | * the ObjectName into an object implementing the ProductMXBean |
| 71 | * interface. We could have a lookup table that reverses |
| 72 | * mxbeanToObjectName, but this could violate the general JMX property |
| 73 | * that you cannot obtain a reference to an MBean object. So we |
| 74 | * always use a proxy for this. However we do have an |
| 75 | * objectNameToProxy map that allows us to reuse proxy instances. |
| 76 | * |
| 77 | * When the getProduct method is called on a proxy for this MXBean, it |
| 78 | * must convert the returned ObjectName into an instance of |
| 79 | * ProductMXBean. Again it can do this by making a proxy. |
| 80 | * |
| 81 | * From the above, it is clear that the logic for getX on an MXBean is |
| 82 | * the same as for setX on a proxy, and vice versa. |
| 83 | */ |
| 84 | public class MXBeanLookup { |
| 85 | private MXBeanLookup(MBeanServerConnection mbsc) { |
| 86 | this.mbsc = mbsc; |
| 87 | } |
| 88 | |
| 89 | static MXBeanLookup lookupFor(MBeanServerConnection mbsc) { |
| 90 | synchronized (mbscToLookup) { |
| 91 | WeakReference<MXBeanLookup> weakLookup = mbscToLookup.get(mbsc); |
| 92 | MXBeanLookup lookup = (weakLookup == null) ? null : weakLookup.get(); |
| 93 | if (lookup == null) { |
| 94 | lookup = new MXBeanLookup(mbsc); |
| 95 | mbscToLookup.put(mbsc, new WeakReference<MXBeanLookup>(lookup)); |
| 96 | } |
| 97 | return lookup; |
| 98 | } |
| 99 | } |
| 100 | |
| 101 | synchronized <T> T objectNameToMXBean(ObjectName name, Class<T> type) { |
| 102 | WeakReference<Object> wr = objectNameToProxy.get(name); |
| 103 | if (wr != null) { |
| 104 | Object proxy = wr.get(); |
| 105 | if (type.isInstance(proxy)) |
| 106 | return type.cast(proxy); |
| 107 | } |
| 108 | T proxy = JMX.newMXBeanProxy(mbsc, name, type); |
| 109 | objectNameToProxy.put(name, new WeakReference<Object>(proxy)); |
| 110 | return proxy; |
| 111 | } |
| 112 | |
| 113 | synchronized ObjectName mxbeanToObjectName(Object mxbean) { |
| 114 | if (mxbean instanceof Proxy) { |
| 115 | InvocationHandler ih = Proxy.getInvocationHandler(mxbean); |
| 116 | if (ih instanceof MBeanServerInvocationHandler) { |
| 117 | MBeanServerInvocationHandler mbsih = |
| 118 | (MBeanServerInvocationHandler) ih; |
| 119 | if (mbsih.getMBeanServerConnection().equals(mbsc)) |
| 120 | return mbsih.getObjectName(); |
| 121 | } |
| 122 | return null; |
| 123 | } else |
| 124 | return mxbeanToObjectName.get(mxbean); |
| 125 | } |
| 126 | |
| 127 | synchronized void addReference(ObjectName name, Object mxbean) { |
| 128 | mxbeanToObjectName.put(mxbean, name); |
| 129 | } |
| 130 | |
| 131 | synchronized boolean removeReference(ObjectName name, Object mxbean) { |
| 132 | if (name.equals(mxbeanToObjectName.get(mxbean))) { |
| 133 | mxbeanToObjectName.remove(mxbean); |
| 134 | return true; |
| 135 | } else |
| 136 | return false; |
| 137 | /* removeReference can be called when the above condition fails, |
| 138 | * notably if you try to register the same MXBean twice. |
| 139 | */ |
| 140 | } |
| 141 | |
| 142 | private final MBeanServerConnection mbsc; |
| 143 | private final WeakIdentityHashMap<Object, ObjectName> |
| 144 | mxbeanToObjectName = WeakIdentityHashMap.make(); |
| 145 | private final Map<ObjectName, WeakReference<Object>> |
| 146 | objectNameToProxy = newMap(); |
| 147 | private static WeakIdentityHashMap<MBeanServerConnection, |
| 148 | WeakReference<MXBeanLookup>> |
| 149 | mbscToLookup = WeakIdentityHashMap.make(); |
| 150 | } |