Class ClassManager
- All Implemented Interfaces:
CSProcess
A process for retrieving and registering classes that cannot be found locally. A single instance of this process runs, with other components in the dynamic class loading infrastructure invoking the public methods to request the loading of a class.
When a class is requested, the system class loader will be tried first. If this fails, a cache
of classes received dynamically will be tried. If this fails, and a NodeClassLoader
has
already been started for communication with the remote node, it will be used to retrieve the class
file from that node. If a NodeClassLoader
has not been started, one will be created
and used for all subsequent requests to be issued to the remote node.
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Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionprivate static class
Marshals a set of parameters for passing information betweengetClass
and the main process thread.private static class
Used in theclasses
hash table to represent class names. -
Field Summary
FieldsModifier and TypeFieldDescriptionprivate Hashtable
MapsRegisteredClass
objects tobyte[]
binary images.private Hashtable
MapsString
class names tobyte[]
binary images.private Hashtable
MapsNetChannelLocation
objects toNodeClassLoader
objects to use to retrieve classes from that node.private Hashtable
MapsString
class names toJarManifestReply
objects.private Hashtable
MapsString
class names toNodeClassLoader
objects to use to retrieve them.private Any2OneChannel
Used to pass requests to the main process thread from calls to theregisterClass
method.private One2OneChannel
Used to pass replies from the main process thread to callers of theregisterClass
method.private Any2OneChannel
Used to pass requests to the main process thread from calls to thegetClass
method.private ClassLoader
A local reference to the system class loader. -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptioncheckForPendingClass
(String name) Attempts to load the class from a remote node if it has previously been marked as pending.private void
classNoLongerPending
(String name) Marks a class as arrived after it was previously marked as pending.void
classPending
(String name, ClassLoader clToUse, JFTP.JarManifestReply jmr) Marks a class as scheduled for later arrival.void
getClass
(String name, NetChannelLocation classSourceChannelLoc, ChannelOutput replyChan) Requests that the class manager process attempt to load the given class.byte[]
getClassBytes
(String name) Gets the binary image for a given class.boolean
pendingClassManifestAvailable
(String className) Returns true iff a manifest reply has been stored for the specified class.registerClass
(Class cls, byte[] fileBytes) Stores the binary image for the class to optimize any further requests for the same class.void
run()
Process execution method.
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Field Details
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classReqs
Used to pass requests to the main process thread from calls to thegetClass
method. -
classRegChan
Used to pass requests to the main process thread from calls to theregisterClass
method. -
classRegReplyChan
Used to pass replies from the main process thread to callers of theregisterClass
method. -
systemClassLoader
A local reference to the system class loader. This is held as an attribute so that it would be possible to change the class loader that this process tries by default when resolving classes. -
classes
MapsRegisteredClass
objects tobyte[]
binary images. -
classLoaders
MapsNetChannelLocation
objects toNodeClassLoader
objects to use to retrieve classes from that node. -
classFiles
MapsString
class names tobyte[]
binary images. -
classPendings
MapsString
class names toNodeClassLoader
objects to use to retrieve them. -
classManifests
MapsString
class names toJarManifestReply
objects.
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Constructor Details
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ClassManager
ClassManager()
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Method Details
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run
public void run()Process execution method. Requests are issued to the process by calling the other methods. These will synchronize with the process thread and transfer information to it via internal channels. -
classPending
Marks a class as scheduled for later arrival. This is called when a
NodeClassLoader
receives aJarManifestReply
from a remote node to indicate that requests for the class should be directed to that class loader. If a JFTP process receives a request for a class that is not held locally it will check the set of pending classes to determine the class loader that it should invoke to retrieve the class.The original manifest reply is also associated with the class so that this can be forwarded to other class loaders replicating the behaviour of the original JFTP process that loaded the class from disk.
- Parameters:
name
- the name of the class.clToUse
- the class loader that can retrieve the class.jmr
- the manifest reply to associate with the class.
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classNoLongerPending
Marks a class as arrived after it was previously marked as pending. This is called when a
NodeClassLoader
has received a class as a result of an issued request or a JFTP process push.- Parameters:
name
- the name of the class that has arrived.
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pendingClassManifestAvailable
Returns true iff a manifest reply has been stored for the specified class. To retrieve the manifest reply, callcheckForPendingClass
which will also issue a request to load the class from the remote node.- Parameters:
className
- the name of the class to check.
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checkForPendingClass
Attempts to load the class from a remote node if it has previously been marked as pending. The class loader associated with the class by a call to
classPending
will be used. If there is no associated class loader, no action is taken. If there is a manifest reply associated with the class this will be returned for possible forwarding to another node.If this method issues a call to a class loader this may block until the class has arrived. This may take a large amount of time if the class has to be routed through a chain of JFTP processes and class loaders.
- Parameters:
name
- the name of the class to check.
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getClass
public void getClass(String name, NetChannelLocation classSourceChannelLoc, ChannelOutput replyChan) Requests that the class manager process attempt to load the given class. This method will return once synchronization with the main thread has occurred. The caller will be notified of completion of the operation on the reply channel passed.- Parameters:
name
- the name of the class to retrieve.classSourceChannelLoc
- location of the channel to request fromreplyChan
- reply channel to notify the caller of operation completion
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registerClass
Stores the binary image for the class to optimize any further requests for the same class. This method will synchronize with the main class manager thread which will update the hash tables to associate the image with the class and mark the class as having arrived if it was previously marked as pending.- Parameters:
cls
- class that has been loaded.fileBytes
- the binary image defining the class.- Returns:
- the class - typically the
cls
parameter but possibly a different class if one has already been registered by another class loader.
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getClassBytes
Gets the binary image for a given class.- Parameters:
name
- name of the class.- Returns:
- the binary image registered by a call to
registerClass
.
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