Class Nexus
- java.lang.Object
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- java.lang.ref.Reference<T>
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- java.lang.ref.WeakReference<java.lang.ClassLoader>
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- net.bytebuddy.dynamic.Nexus
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public class Nexus extends java.lang.ref.WeakReference<java.lang.ClassLoader>
This nexus is a global dispatcher for initializing classes with
LoadedTypeInitializer
s. To do so, this class is to be loaded by the system class loader in an explicit manner. Any instrumented class is then injected a code block into its static type initializer that makes a call to this very same nexus which had the loaded type initializer registered before hand.Note: Availability of the
Nexus
class and its injection into the system class loader can be disabled entirely by setting thePROPERTY
system property tofalse
.Important: The nexus must never be accessed directly but only by the
NexusAccessor
which makes sure that the nexus is loaded by the system class loader. Otherwise, a class might not be able to initialize itself if it is loaded by different class loader that does not have the system class loader in its hierarchy.
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Field Summary
Fields Modifier and Type Field Description private int
classLoaderHashCode
The class loader's hash code upon registration.private int
identification
A random value that uniquely identifies a Nexus entry in order to avoid conflicts when applying the self-initialization strategy in multiple transformations.private java.lang.String
name
The name of a type for which a loaded type initializer is registered.private static java.lang.ref.ReferenceQueue<java.lang.ClassLoader>
NO_QUEUE
An type-safe constant for a non-operational reference queue.static java.lang.String
PROPERTY
A system property that allows to disable the use of theNexus
class which is normally injected into the system class loader.private static java.util.concurrent.ConcurrentMap<Nexus,java.lang.Object>
TYPE_INITIALIZERS
A map of keys identifying a loaded type by its name and class loader mapping their potentialLoadedTypeInitializer
where the class loader of these initializers is however irrelevant.
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Constructor Summary
Constructors Modifier Constructor Description private
Nexus(java.lang.Class<?> type, int identification)
Creates a key for identifying a loaded type initializer.private
Nexus(java.lang.String name, java.lang.ClassLoader classLoader, java.lang.ref.ReferenceQueue<? super java.lang.ClassLoader> referenceQueue, int identification)
Creates a key for identifying a loaded type initializer.
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description static void
clean(java.lang.ref.Reference<? super java.lang.ClassLoader> reference)
Cleans any stale entries from this nexus.boolean
equals(java.lang.Object other)
int
hashCode()
static void
initialize(java.lang.Class<?> type, int identification)
Initializes a loaded type.private static java.lang.String
nonAnonymous(java.lang.String typeName)
Normalizes a type name if it is loaded by an anonymous class loader.static void
register(java.lang.String name, java.lang.ClassLoader classLoader, java.lang.ref.ReferenceQueue<? super java.lang.ClassLoader> referenceQueue, int identification, java.lang.Object typeInitializer)
Registers a new loaded type initializer.java.lang.String
toString()
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Field Detail
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PROPERTY
public static final java.lang.String PROPERTY
A system property that allows to disable the use of theNexus
class which is normally injected into the system class loader.- See Also:
- Constant Field Values
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NO_QUEUE
private static final java.lang.ref.ReferenceQueue<java.lang.ClassLoader> NO_QUEUE
An type-safe constant for a non-operational reference queue.
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TYPE_INITIALIZERS
private static final java.util.concurrent.ConcurrentMap<Nexus,java.lang.Object> TYPE_INITIALIZERS
A map of keys identifying a loaded type by its name and class loader mapping their potentialLoadedTypeInitializer
where the class loader of these initializers is however irrelevant.
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name
private final java.lang.String name
The name of a type for which a loaded type initializer is registered.
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classLoaderHashCode
private final int classLoaderHashCode
The class loader's hash code upon registration.
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identification
private final int identification
A random value that uniquely identifies a Nexus entry in order to avoid conflicts when applying the self-initialization strategy in multiple transformations.
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Constructor Detail
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Nexus
private Nexus(java.lang.Class<?> type, int identification)
Creates a key for identifying a loaded type initializer.- Parameters:
type
- The loaded type for which a key is to be created.identification
- An identification for the initializer to run.
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Nexus
private Nexus(java.lang.String name, java.lang.ClassLoader classLoader, java.lang.ref.ReferenceQueue<? super java.lang.ClassLoader> referenceQueue, int identification)
Creates a key for identifying a loaded type initializer.- Parameters:
name
- The name of a type for which a loaded type initializer is registered.classLoader
- The class loader for which a loaded type initializer is registered.referenceQueue
- The reference queue to notify upon the class loader's collection ornull
if no queue should be notified.identification
- An identification for the initializer to run.
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Method Detail
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nonAnonymous
private static java.lang.String nonAnonymous(java.lang.String typeName)
Normalizes a type name if it is loaded by an anonymous class loader.- Parameters:
typeName
- The name as returned byClass.getName()
.- Returns:
- The non-anonymous name of the given class.
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initialize
public static void initialize(java.lang.Class<?> type, int identification) throws java.lang.Exception
Initializes a loaded type. This method must only be invoked via the system class loader.
Important: This method must never be called directly but only by using a
NexusAccessor.InitializationAppender
which enforces to access this class for the system class loader to assure a VM global singleton. This avoids a duplication of the class if this nexus is loaded by different class loaders. For this reason, the last parameter must not use a Byte Buddy specific type as those types can be loaded by different class loaders, too. Any access of the instance is done using Java reflection instead.- Parameters:
type
- The loaded type to initialize.identification
- An identification for the initializer to run.- Throws:
java.lang.Exception
- If an exception occurs.
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register
public static void register(java.lang.String name, java.lang.ClassLoader classLoader, java.lang.ref.ReferenceQueue<? super java.lang.ClassLoader> referenceQueue, int identification, java.lang.Object typeInitializer)
Registers a new loaded type initializer.
Important: This method must never be called directly but only by using a
NexusAccessor
which enforces to access this class for the system class loader to assure a VM global singleton. This avoids a duplication of the class if this nexus is loaded by different class loaders. For this reason, the last parameter must not use a Byte Buddy specific type as those types can be loaded by different class loaders, too. Any access of the instance is done using Java reflection instead.- Parameters:
name
- The name of the type for the loaded type initializer.classLoader
- The class loader of the type for the loaded type initializer.referenceQueue
- The reference queue to notify upon the class loader's collection which will be enqueued a reference which can be handed toclean(Reference)
ornull
if no reference queue should be notified.identification
- An identification for the initializer to run.typeInitializer
- The type initializer to register. The initializer must be an instance ofLoadedTypeInitializer
where it does however not matter which class loader loaded this latter type.
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clean
public static void clean(java.lang.ref.Reference<? super java.lang.ClassLoader> reference)
Cleans any stale entries from this nexus. Entries are considered stale if their class loader was collected before a class was initialized.
Important: This method must never be called directly but only by using a
NexusAccessor
which enforces to access this class for the system class loader to assure a VM global singleton. This avoids a duplication of the class if this nexus is loaded by different class loaders. For this reason, the last parameter must not use a Byte Buddy specific type as those types can be loaded by different class loaders, too. Any access of the instance is done using Java reflection instead.- Parameters:
reference
- The stale reference to clean.
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hashCode
public int hashCode()
- Overrides:
hashCode
in classjava.lang.Object
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equals
public boolean equals(java.lang.Object other)
- Overrides:
equals
in classjava.lang.Object
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toString
public java.lang.String toString()
- Overrides:
toString
in classjava.lang.Object
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