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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
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 * 2 along with this work; if not, write to the Free Software Foundation,
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package java.lang.management;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.HashSet;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import javax.management.MBeanServerConnection;
import javax.management.ObjectName;

import com.sun.management.HotSpotDiagnosticMXBean;
import com.sun.management.UnixOperatingSystemMXBean;

import sun.management.ManagementFactoryHelper;
import sun.management.Util;

This enum class defines the list of platform components
that provides monitoring and management support.
Each enum represents one MXBean interface. A MXBean
instance could implement one or more MXBean interfaces.
For example, com.sun.management.GarbageCollectorMXBean
extends java.lang.management.GarbageCollectorMXBean
and there is one set of garbage collection MXBean instances,
each of which implements both c.s.m. and j.l.m. interfaces.
There are two separate enums GARBAGE_COLLECTOR
and SUN_GARBAGE_COLLECTOR so that ManagementFactory.getPlatformMXBeans(Class)
will return the list of MXBeans of the specified type.
To add a new MXBean interface for the Java platform,
add a new enum constant and implement the MXBeanFetcher.
/**
 * This enum class defines the list of platform components
 * that provides monitoring and management support.
 * Each enum represents one MXBean interface. A MXBean
 * instance could implement one or more MXBean interfaces.
 *
 * For example, com.sun.management.GarbageCollectorMXBean
 * extends java.lang.management.GarbageCollectorMXBean
 * and there is one set of garbage collection MXBean instances,
 * each of which implements both c.s.m. and j.l.m. interfaces.
 * There are two separate enums GARBAGE_COLLECTOR
 * and SUN_GARBAGE_COLLECTOR so that ManagementFactory.getPlatformMXBeans(Class)
 * will return the list of MXBeans of the specified type.
 *
 * To add a new MXBean interface for the Java platform,
 * add a new enum constant and implement the MXBeanFetcher.
 */
enum PlatformComponent {

    
Class loading system of the Java virtual machine.
/**
     * Class loading system of the Java virtual machine.
     */
    CLASS_LOADING(
        "java.lang.management.ClassLoadingMXBean",
        "java.lang", "ClassLoading", defaultKeyProperties(),
        true, // singleton
        new MXBeanFetcher<ClassLoadingMXBean>() {
            public List<ClassLoadingMXBean> getMXBeans() {
                return Collections.singletonList(ManagementFactoryHelper.getClassLoadingMXBean());
            }
        }),

    
Compilation system of the Java virtual machine.
/**
     * Compilation system of the Java virtual machine.
     */
    COMPILATION(
        "java.lang.management.CompilationMXBean",
        "java.lang", "Compilation", defaultKeyProperties(),
        true, // singleton
        new MXBeanFetcher<CompilationMXBean>() {
            public List<CompilationMXBean> getMXBeans() {
                CompilationMXBean m = ManagementFactoryHelper.getCompilationMXBean();
                if (m == null) {
                   return Collections.emptyList();
                } else {
                   return Collections.singletonList(m);
                }
            }
        }),

    
Memory system of the Java virtual machine.
/**
     * Memory system of the Java virtual machine.
     */
    MEMORY(
        "java.lang.management.MemoryMXBean",
        "java.lang", "Memory", defaultKeyProperties(),
        true, // singleton
        new MXBeanFetcher<MemoryMXBean>() {
            public List<MemoryMXBean> getMXBeans() {
                return Collections.singletonList(ManagementFactoryHelper.getMemoryMXBean());
            }
        }),

    
Garbage Collector in the Java virtual machine.
/**
     * Garbage Collector in the Java virtual machine.
     */
    GARBAGE_COLLECTOR(
        "java.lang.management.GarbageCollectorMXBean",
        "java.lang", "GarbageCollector", keyProperties("name"),
        false, // zero or more instances
        new MXBeanFetcher<GarbageCollectorMXBean>() {
            public List<GarbageCollectorMXBean> getMXBeans() {
                return ManagementFactoryHelper.
                           getGarbageCollectorMXBeans();
            }
        }),

    
Memory manager in the Java virtual machine.
/**
     * Memory manager in the Java virtual machine.
     */
    MEMORY_MANAGER(
        "java.lang.management.MemoryManagerMXBean",
        "java.lang", "MemoryManager", keyProperties("name"),
        false, // zero or more instances
        new MXBeanFetcher<MemoryManagerMXBean>() {
            public List<MemoryManagerMXBean> getMXBeans() {
                return ManagementFactoryHelper.getMemoryManagerMXBeans();
            }
        },
        GARBAGE_COLLECTOR),

    
Memory pool in the Java virtual machine.
/**
     * Memory pool in the Java virtual machine.
     */
    MEMORY_POOL(
        "java.lang.management.MemoryPoolMXBean",
        "java.lang", "MemoryPool", keyProperties("name"),
        false, // zero or more instances
        new MXBeanFetcher<MemoryPoolMXBean>() {
            public List<MemoryPoolMXBean> getMXBeans() {
                return ManagementFactoryHelper.getMemoryPoolMXBeans();
            }
        }),

    
Operating system on which the Java virtual machine is running
/**
     * Operating system on which the Java virtual machine is running
     */
    OPERATING_SYSTEM(
        "java.lang.management.OperatingSystemMXBean",
        "java.lang", "OperatingSystem", defaultKeyProperties(),
        true, // singleton
        new MXBeanFetcher<OperatingSystemMXBean>() {
            public List<OperatingSystemMXBean> getMXBeans() {
                return Collections.singletonList(ManagementFactoryHelper.getOperatingSystemMXBean());
            }
        }),

    
Runtime system of the Java virtual machine.
/**
     * Runtime system of the Java virtual machine.
     */
    RUNTIME(
        "java.lang.management.RuntimeMXBean",
        "java.lang", "Runtime", defaultKeyProperties(),
        true, // singleton
        new MXBeanFetcher<RuntimeMXBean>() {
            public List<RuntimeMXBean> getMXBeans() {
                return Collections.singletonList(ManagementFactoryHelper.getRuntimeMXBean());
            }
        }),

    
Threading system of the Java virtual machine.
/**
     * Threading system of the Java virtual machine.
     */
    THREADING(
        "java.lang.management.ThreadMXBean",
        "java.lang", "Threading", defaultKeyProperties(),
        true, // singleton
        new MXBeanFetcher<ThreadMXBean>() {
            public List<ThreadMXBean> getMXBeans() {
                return Collections.singletonList(ManagementFactoryHelper.getThreadMXBean());
            }
        }),


    
Logging facility.
/**
     * Logging facility.
     */
    LOGGING(
        "java.lang.management.PlatformLoggingMXBean",
        "java.util.logging", "Logging", defaultKeyProperties(),
        true, // singleton
        new MXBeanFetcher<PlatformLoggingMXBean>() {
            public List<PlatformLoggingMXBean> getMXBeans() {
                PlatformLoggingMXBean m = ManagementFactoryHelper.getPlatformLoggingMXBean();
                if (m == null) {
                   return Collections.emptyList();
                } else {
                   return Collections.singletonList(m);
                }
            }
        }),

    
Buffer pools.
/**
     * Buffer pools.
     */
    BUFFER_POOL(
        "java.lang.management.BufferPoolMXBean",
        "java.nio", "BufferPool", keyProperties("name"),
        false, // zero or more instances
        new MXBeanFetcher<BufferPoolMXBean>() {
            public List<BufferPoolMXBean> getMXBeans() {
                return ManagementFactoryHelper.getBufferPoolMXBeans();
            }
        }),


    // Sun Platform Extension

    
Sun extension garbage collector that performs collections in cycles.
/**
     * Sun extension garbage collector that performs collections in cycles.
     */
    SUN_GARBAGE_COLLECTOR(
        "com.sun.management.GarbageCollectorMXBean",
        "java.lang", "GarbageCollector", keyProperties("name"),
        false, // zero or more instances
        new MXBeanFetcher<com.sun.management.GarbageCollectorMXBean>() {
            public List<com.sun.management.GarbageCollectorMXBean> getMXBeans() {
                return getGcMXBeanList(com.sun.management.GarbageCollectorMXBean.class);
            }
        }),

    
Sun extension operating system on which the Java virtual machine
is running.
/**
     * Sun extension operating system on which the Java virtual machine
     * is running.
     */
    SUN_OPERATING_SYSTEM(
        "com.sun.management.OperatingSystemMXBean",
        "java.lang", "OperatingSystem", defaultKeyProperties(),
        true, // singleton
        new MXBeanFetcher<com.sun.management.OperatingSystemMXBean>() {
            public List<com.sun.management.OperatingSystemMXBean> getMXBeans() {
                return getOSMXBeanList(com.sun.management.OperatingSystemMXBean.class);
            }
        }),

    
Unix operating system.
/**
     * Unix operating system.
     */
    SUN_UNIX_OPERATING_SYSTEM(
        "com.sun.management.UnixOperatingSystemMXBean",
        "java.lang", "OperatingSystem", defaultKeyProperties(),
        true, // singleton
        new MXBeanFetcher<UnixOperatingSystemMXBean>() {
            public List<UnixOperatingSystemMXBean> getMXBeans() {
                return getOSMXBeanList(com.sun.management.UnixOperatingSystemMXBean.class);
            }
        }),

    
Diagnostic support for the HotSpot Virtual Machine.
/**
     * Diagnostic support for the HotSpot Virtual Machine.
     */
    HOTSPOT_DIAGNOSTIC(
        "com.sun.management.HotSpotDiagnosticMXBean",
        "com.sun.management", "HotSpotDiagnostic", defaultKeyProperties(),
        true, // singleton
        new MXBeanFetcher<HotSpotDiagnosticMXBean>() {
            public List<HotSpotDiagnosticMXBean> getMXBeans() {
                return Collections.singletonList(ManagementFactoryHelper.getDiagnosticMXBean());
            }
        });


    
A task that returns the MXBeans for a component.
/**
     * A task that returns the MXBeans for a component.
     */
    interface MXBeanFetcher<T extends PlatformManagedObject> {
        public List<T> getMXBeans();
    }

    /*
     * Returns a list of the GC MXBeans of the given type.
     */
    private static <T extends GarbageCollectorMXBean>
            List<T> getGcMXBeanList(Class<T> gcMXBeanIntf) {
        List<GarbageCollectorMXBean> list =
            ManagementFactoryHelper.getGarbageCollectorMXBeans();
        List<T> result = new ArrayList<>(list.size());
        for (GarbageCollectorMXBean m : list) {
            if (gcMXBeanIntf.isInstance(m)) {
                result.add(gcMXBeanIntf.cast(m));
            }
        }
        return result;
    }

    /*
     * Returns the OS mxbean instance of the given type.
     */
    private static <T extends OperatingSystemMXBean>
            List<T> getOSMXBeanList(Class<T> osMXBeanIntf) {
        OperatingSystemMXBean m =
            ManagementFactoryHelper.getOperatingSystemMXBean();
        if (osMXBeanIntf.isInstance(m)) {
            return Collections.singletonList(osMXBeanIntf.cast(m));
        } else {
            return Collections.emptyList();
        }
    }

    private final String mxbeanInterfaceName;
    private final String domain;
    private final String type;
    private final Set<String> keyProperties;
    private final MXBeanFetcher<?> fetcher;
    private final PlatformComponent[] subComponents;
    private final boolean singleton;

    private PlatformComponent(String intfName,
                              String domain, String type,
                              Set<String> keyProperties,
                              boolean singleton,
                              MXBeanFetcher<?> fetcher,
                              PlatformComponent... subComponents) {
        this.mxbeanInterfaceName = intfName;
        this.domain = domain;
        this.type = type;
        this.keyProperties = keyProperties;
        this.singleton = singleton;
        this.fetcher = fetcher;
        this.subComponents = subComponents;
    }

    private static Set<String> defaultKeyProps;
    private static Set<String> defaultKeyProperties() {
        if (defaultKeyProps == null) {
            defaultKeyProps = Collections.singleton("type");
        }
        return defaultKeyProps;
    }

    private static Set<String> keyProperties(String... keyNames) {
        Set<String> set = new HashSet<>();
        set.add("type");
        for (String s : keyNames) {
            set.add(s);
        }
        return set;
    }

    boolean isSingleton() {
        return singleton;
    }

    String getMXBeanInterfaceName() {
        return mxbeanInterfaceName;
    }

    @SuppressWarnings("unchecked")
    Class<? extends PlatformManagedObject> getMXBeanInterface() {
        try {
            // Lazy loading the MXBean interface only when it is needed
            return (Class<? extends PlatformManagedObject>)
                       Class.forName(mxbeanInterfaceName, false,
                                     PlatformManagedObject.class.getClassLoader());
        } catch (ClassNotFoundException x) {
            throw new AssertionError(x);
        }
    }

    @SuppressWarnings("unchecked")
    <T extends PlatformManagedObject>
        List<T> getMXBeans(Class<T> mxbeanInterface)
    {
        return (List<T>) fetcher.getMXBeans();
    }

    <T extends PlatformManagedObject> T getSingletonMXBean(Class<T> mxbeanInterface)
    {
        if (!singleton)
            throw new IllegalArgumentException(mxbeanInterfaceName +
                " can have zero or more than one instances");

        List<T> list = getMXBeans(mxbeanInterface);
        assert list.size() == 1;
        return list.isEmpty() ? null : list.get(0);
    }

    <T extends PlatformManagedObject>
            T getSingletonMXBean(MBeanServerConnection mbs, Class<T> mxbeanInterface)
        throws java.io.IOException
    {
        if (!singleton)
            throw new IllegalArgumentException(mxbeanInterfaceName +
                " can have zero or more than one instances");

        // ObjectName of a singleton MXBean contains only domain and type
        assert keyProperties.size() == 1;
        String on = domain + ":type=" + type;
        return ManagementFactory.newPlatformMXBeanProxy(mbs,
                                                        on,
                                                        mxbeanInterface);
    }

    <T extends PlatformManagedObject>
            List<T> getMXBeans(MBeanServerConnection mbs, Class<T> mxbeanInterface)
        throws java.io.IOException
    {
        List<T> result = new ArrayList<>();
        for (ObjectName on : getObjectNames(mbs)) {
            result.add(ManagementFactory.
                newPlatformMXBeanProxy(mbs,
                                       on.getCanonicalName(),
                                       mxbeanInterface)
            );
        }
        return result;
    }

    private Set<ObjectName> getObjectNames(MBeanServerConnection mbs)
        throws java.io.IOException
    {
        String domainAndType = domain + ":type=" + type;
        if (keyProperties.size() > 1) {
            // if there are more than 1 key properties (i.e. other than "type")
            domainAndType += ",*";
        }
        ObjectName on = Util.newObjectName(domainAndType);
        Set<ObjectName> set =  mbs.queryNames(on, null);
        for (PlatformComponent pc : subComponents) {
            set.addAll(pc.getObjectNames(mbs));
        }
        return set;
    }

    // a map from MXBean interface name to PlatformComponent
    private static Map<String, PlatformComponent> enumMap;
    private static synchronized void ensureInitialized() {
        if (enumMap == null) {
            enumMap = new HashMap<>();
            for (PlatformComponent pc: PlatformComponent.values()) {
                // Use String as the key rather than Class<?> to avoid
                // causing unnecessary class loading of management interface
                enumMap.put(pc.getMXBeanInterfaceName(), pc);
            }
        }
    }

    static boolean isPlatformMXBean(String cn) {
        ensureInitialized();
        return enumMap.containsKey(cn);
    }

    static <T extends PlatformManagedObject>
        PlatformComponent getPlatformComponent(Class<T> mxbeanInterface)
    {
        ensureInitialized();
        String cn = mxbeanInterface.getName();
        PlatformComponent pc = enumMap.get(cn);
        if (pc != null && pc.getMXBeanInterface() == mxbeanInterface)
            return pc;
        return null;
    }

    private static final long serialVersionUID = 6992337162326171013L;
}