com.sun.squawk
Class Isolate

java.lang.Object
  com.sun.squawk.Isolate

All Implemented Interfaces:

Runnable

public final class Isolate
extends Object
implements Runnable

The Isolate class represents a "process-like" unit of computation that is isolated from other instances of Isolate. The mutable objects of one isolate are logically separate from the mutable objects of another isolate. Similarly, the static variables of one isolate are seperate from the static variables of another isolate.

A Simple Example

  // The creating isolate
  String[] args = {"test"};
  Isolate i = new Isolate("org.example.App", args, null, Isolate.currentIsolate().getParentSuiteSourceURI());
  i.start();
  i.join(); // wait for child isolate to finish
  System.out.println("Child isolate returned with exit code: " + i.getExitCode());

  // The newly created isolate
  package org.example;

  public class App {
      public static void main(String[] args) {
          for(int i = 0; i < args.length; i++ )
              System.out.println(args[i]);
      }
  }

Hibernation

Isolate Lifecycle

Isolate LifecycleNotification

Inter-Isolate Communication

The properties parameter to the Isolate constructor provides another way to set the system properties of the new isolate. If this parameter is not specified, the child isolate starts with the same set of system properties that it would have if initiated as a standalone application. If this parameter is specified, this default set of properties is augmented with those specified in the parameter, in the same way as if they had been specified with -D on a command line invocation. In addition, all isolate's inherit the properties defined on the Squawk command line using the -D option.

OtherDetails

Squawk Isolates are loosely based on the Isolates of JSR 121 - Application Isolation API, but are not compliant with that specification. In particular, Squawk Isolates support hibernation, and use a different inter-isolate communication mechanism than JSR 121.

See Also:

Channel, ServerChannel

SHUTDOWN_EVENT_MASK

public static final int SHUTDOWN_EVENT_MASK

Event kind indicating that an isolate is exiting. Used for Isolate.LifecycleListeners that will be called when the Isolate terminates via exit(int), VM.stopVM(int), or when the last non-daemon thread in this isolate ends. All other ways to terminate an isolate, including VM.haltVM(int) do not cause the shutdown hooks to be run.

See Also:

Constant Field Values

HIBERNATE_EVENT_MASK

public static final int HIBERNATE_EVENT_MASK

Event kind indicating that an isolate is hibernating. Used for Isolate.LifecycleListeners that will be called when the Isolate suspends via hibernate().

See Also:

Constant Field Values

UNHIBERNATE_EVENT_MASK

public static final int UNHIBERNATE_EVENT_MASK

Event kind indicating that an isolate is unhibernating. Used for Isolate.LifecycleListeners that will be called when the Isolate resumes via unhibernate().

See Also:

Constant Field Values

stdout

public final MulticastOutputStream stdout

stderr

public final MulticastOutputStream stderr

Isolate

public Isolate(Hashtable properties,
               String mainClassName,
               String[] args,
               String classPath,
               String parentSuiteSourceURI)

Creates an new isolate. start() will create a new execution context, and start executing the main method of the class specified by mainClassName. System properties can be set for the isolate by passing in a hashtable where the keys are strings of property names and the values are strings containing property values. The passed in property values will override any property values that the isolate inherits from the command line properties.

Note that system properties are disjoint from manifest properties.

Parameters:

properties - a hashtable of properties to be set in the isolate (may be null)

mainClassName - the name of the class with main()

args - the command line arguments

classPath - the path where classes and suites can be found (may be null)

parentSuiteSourceURI - the URI of the suite containing mainClassName. (may be null)

Throws:

NullPointerException - if mainClassName or args is null

ClassCastException - if properties contains keys or values that are not Strings.

Isolate

public Isolate(String mainClassName,
               String[] args,
               String classPath,
               String parentSuiteSourceURI)

Creates an new isolate. start() will create a new execution context, and start executing the main method of the class specified by mainClassName.

Parameters:

mainClassName - the name of the class with main()

args - the command line arguments

classPath - the path where classes and suites can be found (may be null)

parentSuiteSourceURI - the URI of the suite containing mainClassName. (may be null)

Throws:

NullPointerException - if mainClassName or args is null

Isolate

public Isolate(Hashtable properties,
               int midletNum,
               String classPath,
               String parentSuiteSourceURI)

Creates an new isolate. start() will create a new execution context, and start executing the startApp method of the MIDlet specified by the manifest property named MIDlet-midletNum. System properties can be set for the isolate by passing in a hashtable where the keys are strings of property names and the values are strings containing property values. The passed in property values will override any property values that the isolate inherits from the command line properties.

Note that system properties are disjoint from manifest properties.

Parameters:

properties - a hashtable of properties to be set in the isolate (may be null)

midletNum - the midlet property that contains the name of the MIDlet to instantiate

classPath - the path where classes and suites can be found (may be null)

parentSuiteSourceURI - the URI of the suite containing the midlet and the MIDlet properties. (may be null)

Throws:

NullPointerException - if mainClassName or args is null

ClassCastException - if properties contains keys or values that are not Strings.

getName

public String getName()

Gets name of the isolate. By default, this is the mainClassName passed to the constructor, or the MIDlet's class name

Returns:

the isolate name

setName

public void setName(String newName)

Sets name of the isolate.

Parameters:

newName - (must not be null)

getClassPath

public String getClassPath()

Gets the class path for the isolate.

Returns:

the class path

getIsolates

public static Isolate[] getIsolates()

Returns an array of Isolate objects. The array contains one entry for each isolate object that is currently reachable in the system. These isolates may be in the NEW, ALIVE, HIBERNATED, or EXITED states. The system only keeps ALIVE isolates reachable, so isolates in other states may become unreachable unless referenced by an ALIVE isolate. New isolates may have been constructed or existing ones terminated by the time method returns.

Returns:

the Isolate objects present at the time of the call

getParentSuiteSourceURI

public String getParentSuiteSourceURI()

Returns:

the URI of suite from which this isolate was started. This value will be "memory:bootstrap" if the isolate was not given an explicit suite at creation time.

getMainClassName

public String getMainClassName()

Get the name of the main class.

Returns:

the name

currentIsolate

public static Isolate currentIsolate()

Gets the current isolate context.

Returns:

the current Isolate context.

isTrusted

public boolean isTrusted()

Determines if this isolate can access trusted classes. A trusted class will call this method in its static constructor.

Returns:

boolean

getMainClassArguments

public String[] getMainClassArguments()

Get the arguments.

Returns:

the arguments

getLeafSuite

public Suite getLeafSuite()

Gets the suite that is the starting point for class lookup in this isolate. If it is not closed, then it's also the suite into which any dynamically loaded classes (i.e. those loaded via Class.forName(String)) are installed.

Returns:

the leaf suite

getDefaultTranslator

public static TranslatorInterface getDefaultTranslator()
                                                throws AllowInlinedPragma

Gets a translator that is to be used to locate, load and convert classes that are not currently installed in this isolate's runtime environment.

Returns:

a translator for installing new classes or null if the system does not support dynamic class loading

Throws:

AllowInlinedPragma

getTranslator

public TranslatorInterface getTranslator()
                                  throws AllowInlinedPragma

Gets a translator that is to be used to locate, load and convert classes that are not currently installed in this isolate's runtime environment.

Returns:

a translator for installing new classes or null if the system does not support dynamic class loading

Throws:

AllowInlinedPragma

setProperty

public void setProperty(String key,
                        String value)

Adds a named property to this isolate. These properties are included in the look up performed by System.getProperty(java.lang.String).

Parameters:

key - the name of the property

value - the value of the property or null to remove the property

getProperty

public String getProperty(String key)

Gets a named property of this isolate.

Isolate properties include those passed into the isolate's constructor, properties inhertited from the squawk command line, and properties set by setProperty(java.lang.String, java.lang.String).

Parameters:

key - the name of the property to get

Returns:

the value of the property named by 'key' or null if there is no such property

getProperties

public Enumeration getProperties()

Get an enumeration of isolate property keys. These keys can be used with getProperty(String) to get the property values.

Isolate properties include those passed into the isolate's constructor, properties inhertited from the squawk command line, and properties set by setProperty(java.lang.String, java.lang.String).

Returns:

enumeration of property keys

addLifecycleListener

public void addLifecycleListener(Isolate.LifecycleListener listener,
                                 int eventSet)

Add a listener to be run when this isolate terminates, hibernates, or unhibernates, depending on evenSet.

The listener may listen to multiple events by using bitwise OR to construct a set of events from the various event masks.

This isolate may be the current isolate (the local case) or another isolate (the remote case). If this isolate is remote, then this method will also add a listener to the local isolate that will remove this listener on the remote isolate. This cleans up the listeners if the local isolate exits before the remote isolate does.

Execution:

The listener will run in the current Isolate's context. All listener from the same Isolate may run in the same thread. Any RuntimeExceptions thrown by the listener will be printed to System.err, but are otherwise ignored.

Parameters:

listener - a LifecycleListener that will be called when event occurs.

eventSet - a set of lifecycle events to be monitored. One or more of SHUTDOWN_EVENT_MASK, HIBERNATE_EVENT_MASK, or UNHIBERNATE_EVENT_MASK.

Throws:

IllegalArgumentException - when eventSet does not contain SHUTDOWN_EVENT_MASK, HIBERNATE_EVENT_MASK, or UNHIBERNATE_EVENT_MASK

See Also:

removeLifecycleListener(com.sun.squawk.Isolate.LifecycleListener, int), exit(int), hibernate(), unhibernate()

removeLifecycleListener

public boolean removeLifecycleListener(Isolate.LifecycleListener listener,
                                       int eventSet)

Remove an Isolate.LifecycleListener from this isolate. Must be called from the same isolate that added the listener.

Parameters:

listener - a Isolate.LifecycleListener to be removed.

eventSet - a set of lifecycle events that the listener should stop listening to. One or more of SHUTDOWN_EVENT_MASK, HIBERNATE_EVENT_MASK, or UNHIBERNATE_EVENT_MASK.

Returns:

true if the listener was registered with the all of the events in the eventSet on this isolate; false otherwise.

Throws:

IllegalArgumentException - when eventSet does not contain SHUTDOWN_EVENT_MASK, HIBERNATE_EVENT_MASK, or UNHIBERNATE_EVENT_MASK

See Also:

addLifecycleListener(com.sun.squawk.Isolate.LifecycleListener, int)

intern

public static String intern(String value)

Returns a canonical representation for the string object from the current isolate.

A pool of strings, initially empty, is maintained privately by the class Isolate.

When the intern method is invoked, if the pool already contains a string equal to this String object as determined by the Object.equals(Object) method, then the string from the pool is returned. Otherwise, this String object is added to the pool and a reference to this String object is returned.

It follows that for any two strings s and t, s.intern() == t.intern() is true if and only if s.equals(t) is true.

All literal strings and string-valued constant expressions are interned. String literals are defined in §3.10.5 of the Java Language Specification

Parameters:

value -

Returns:

a string that has the same contents as this string, but is guaranteed to be from a pool of unique strings.

start

public void start()

Start the isolate running.

Throws:

IllegalStateException - if the isolate has already been started

run

public final void run()
               throws IllegalStateException

Deprecated. This is called by the system (in start()}, and shouldn't be called directly

Starts running this isolate.

Specified by:

run in interface Runnable

Throws:

IllegalStateException - if this isolate has already been started

See Also:

Thread.run()

join

public void join()

Waits for all the other threads and child isolates belonging to this isolate to stop. WARNING: Only one thread can join an isolate, becuase this method clears the childIsolates list

isClassKlassInitialized

public boolean isClassKlassInitialized()

Test to see if class Klass is initialized.

Returns:

true if it is

exit

public void exit(int code)

Stop the isolate. The handleLifecycleListenerEvent() method will be called on any LifecycleListeners registered to handle EXIT events on this isolate.

Parameters:

code - the exit code

Throws:

IllegalStateException - if this isolate is not ALIVE

save

public void save(DataOutputStream dos,
                 String uri)
          throws IOException

Serializes the object graph rooted by this hibernated isolate and writes it to a given stream. The endianess of the serialized object graph is the endianess of the unerdlying platform.

Parameters:

dos - the DataOutputStream to which the serialized isolate should be written

uri - a URI identifying the serialized isolate

Throws:

IOException

IllegalStateException - if this isolate is not currently hibernated or exited

save

public void save(DataOutputStream dos,
                 String uri,
                 boolean bigEndian)
          throws IOException

Serializes the object graph rooted by this hibernated isolate and writes it to a given stream.

Parameters:

dos - the DataOutputStream to which the serialized isolate should be written

uri - a URI identifying the serialized isolate

bigEndian - the endianess to be used when serializing this isolate

Throws:

IOException

IllegalStateException - if this isolate is not currently hibernated or exited

load

public static Isolate load(DataInputStream dis,
                           String uri)

Loads a serialized isolate from an input stream into RAM. It is up to the caller to unhibernate the isolate.

Parameters:

dis - the data input stream to load from

uri - a URI identifying the serialized isolate

Returns:

isolate that was stored in dis

hibernate

public void hibernate()
               throws IOException,
                      IllegalStateException

Hibernate the isolate. The handleLifecycleListenerEvent() method will be called on any LifecycleListeners registered to handle HIBERNATE events on this isolate. Any Channel I/O will be hibernated, and interisolate communication channels will be broken. If the current thread is in this isolate then this function will only return when the isolate is unhibernated.

Throws:

IOException - if the underlying IO system cannot be serialized

IllegalStateException - if this isolate is not ALIVE or if it has a debugger attached to it

unhibernate

public void unhibernate()

Unhibernate the isolate. The handleLifecycleListenerEvent() method will be called on any LifecycleListeners registered to handle UNHIBERNATE events on this isolate.

Throws:

IllegalStateException - if the isolate is not HIBERNATED

isHibernated

public boolean isHibernated()

Determines if this isolate is hibernated.

Returns:

true if it is

isAlive

public boolean isAlive()

Determines if this isolate has been (re)started and not yet (re)hibernated or exited.

Returns:

true if it is

isExited

public boolean isExited()

Determines if this isolate is exited.

Returns:

true if it is

isNew

public boolean isNew()

Determines if this isolate has not yet been started.

Returns:

true if it is

isBeingDebugged

public boolean isBeingDebugged()

Determines whether this isolate is being debugged

Returns:

true if it is

isMidlet

public boolean isMidlet()

Return true if this isolate was created to run a midlet.

Returns:

true if a midlet

getExitCode

public int getExitCode()

Get the isolate exit code.

Returns:

the exit code

toString

public String toString()

Get the string representation of the isolate.

Overrides:

toString in class Object

Returns:

the string

addOut

public void addOut(String url)

Adds a new connection to which System.out will send its output.

If the current thread is not owned by this isolate, opening of the connection is delayed until the next time System.out is written to by one of this isolate's threads. Otherwise the connection is opened as part of this call.

Output will be multicast to the new stream as well as any preexisting connection streams.

The following code snippet is an example of how to pipe the standard output of the current isolate to a network connection:

     Thread.currentThread().getIsolate().addOut("socket://server.domain.com:9999").
 

Parameters:

url - the URL used to open the connection via Connector.openOutputStream(java.lang.String)

See Also:

listOut(), removeOut(java.lang.String), clearOut()

addErr

public void addErr(String url)

Adds a new connection to which System.err will send its output.

If the current thread is not owned by this isolate, opening of the connection is delayed until the next time System.err is written to by one of this isolate's threads. Otherwise the connection is opened as part of this call.

Output will be multicast to the new stream as well as any preexisting connection streams.

Parameters:

url - the URL used to open the connection via Connector.openOutputStream(java.lang.String)

See Also:

listErr(), removeErr(java.lang.String), clearErr()

removeOut

public void removeOut(String url)

Removes the connection identified by url (if any) to which System.out is currently sending its output. The removed connection is immediately flushed and closed. Any IO exceptions are caught and might be printed.

Parameters:

url - the URL identifying the connection to be removed

Throws:

IllegalArgumentException - if url does not name a current out stream

See Also:

listOut(), addOut(java.lang.String), clearOut()

removeErr

public void removeErr(String url)

Removes the connection identified by url (if any) to which System.err is currently sending its output. The removed connection is immediately flushed and closed. Any IO exceptions are caught and might be printed.

Parameters:

url - the URL identifying the connection to be removed

Throws:

IllegalArgumentException - if url does not name a current error stream

See Also:

listErr(), addErr(java.lang.String), clearErr()

clearOut

public void clearOut()

Removes all the connections to which System.out is sending its output. The removed connections are immediately flushed and closed.. Any IO exceptions are caught and might be printed.

See Also:

addOut(java.lang.String), removeOut(java.lang.String)

clearErr

public void clearErr()

Removes all the connections to which System.err is sending its output. The removed connections are immediately flushed and closed. Any IO exceptions are caught and are unlikely to be printed.

See Also:

addErr(java.lang.String), removeErr(java.lang.String)

listOut

public String[] listOut()

Gets a list of URLs denoting the streams to which System.out is currently sending its output. Note that due to multi-threading, the returned list may not reflect the complete set of streams. If a stream was added by another thread, then the returned list may not include the URL of the added stream. If a stream was removed by another thread, then the returned list may include the URL of the removed stream.

Returns:

the list of streams to which System.out is currently sending its output

See Also:

addOut(java.lang.String)

listErr

public String[] listErr()

Gets a list of URLs denoting the streams to which System.err is currently sending its output. Note that due to multi-threading, the returned list may not reflect the complete set of streams. If a stream was added by another thread, then the returned list may not include the URL of the added stream. If a stream was removed by another thread, then the returned list may include the URL of the removed stream.

Returns:

the list of streams to which System.err is currently sending its output

See Also:

addErr(java.lang.String)

recordMailbox

public void recordMailbox(Mailbox mailbox)

Record this mailbox with the system. Called by Mailbox().

Parameters:

mailbox - the mailbox to record.

forgetMailbox

public void forgetMailbox(Mailbox mailbox)

Tell the system to forget about this mailbox. Called by Mailbox.close().

Parameters:

mailbox - the mailbox to forget.

recordMailboxAddress

public void recordMailboxAddress(MailboxAddress address)

Record all MailboxAddress objects that this Isolate uses to send messages to.

Parameters:

address - the mailbox to record.

forgetMailboxAddress

public void forgetMailboxAddress(MailboxAddress address)

Tell the system to forget about this mailbox. Called by Mailbox.close().

Parameters:

address - the mailbox to forget.

cleanupMailboxes

public void cleanupMailboxes()

Tell remote isolates that we won't talk to them again, and close our Mailboxes. After this call, remote isolates may have MailboxAddress objects that refer to the closed mailboxes, but when they try to use the address, they will get an exception.

printAllThreadStates

public void printAllThreadStates(PrintStream out)

Print out the thread state and stack trace for each thread belonging this isolate.

Parameters:

out - stream to print on

printAllIsolateStates

public static void printAllIsolateStates(PrintStream out)

Print out the thread state and stack trace for each thread of each isolate in the system.

Parameters:

out - stream to print on

getDebugger

public Debugger getDebugger()

Gets the debugger under which this isolate is executing.

Returns:

the debugger under which this isolate is executing (if any)

getChildThreads

public Enumeration getChildThreads()

Gets the child threads of this isolate.

Returns:

an Enumeration over the child threads of this isolate

getChildThreadCount

public int getChildThreadCount()

Gets the number of child threads of this isolate.

Returns:

the number of child threads of this isolate

getId

public int getId()

Gets the unique id for this isolate. The id is only unique among isolates that have allocated in the current run of this VM.

Returns:

the id of this isolate

updateBreakpoints

public void updateBreakpoints(Isolate.Breakpoint[] breakpoints)