/*******************************************************************************
* Copyright (c) 2000, 2011 IBM Corporation and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.jdi.hcr;
/**
* Hot code replacement extension to <code>com.sun.jdi.VirtualMachine</code>.
*/
public interface VirtualMachine {
/** All the given type were reloaded */
public static final int RELOAD_SUCCESS = 0;
/** The VM is inconsistent after the reload operation */
public static final int RELOAD_FAILURE = 1;
/** The reload operation was ignored */
public static final int RELOAD_IGNORED = 2;
/**
* Determines if this implementation supports the early return of the top
* stack frame of a thread.
*
* @return <code>true</code> if the feature is supported, <code>false</code>
* otherwise.
*/
public boolean canDoReturn();
/**
* Determines if this implementation supports the retrieval of a class file
* version.
*
* @return <code>true</code> if the feature is supported, <code>false</code>
* otherwise.
*/
public boolean canGetClassFileVersion();
/**
* Determines if this implementation supports the reenter stepping.
*
* @return <code>true</code> if the feature is supported, <code>false</code>
* otherwise.
*/
public boolean canReenterOnExit();
/**
* Determines if this implementation supports the replacement of classes on
* the fly.
*
* @return <code>true</code> if the feature is supported, <code>false</code>
* otherwise.
*/
public boolean canReloadClasses();
/**
* Notifies the VM that the class file base that it is running from has
* changed. Classes are given by their names.
* <p>
* The class file base is the collection of class files available on the
* various VM's class paths consulted by the class loaders that are integral
* to the system. In JDK 1.2, these would include all files on the boot
* class path (used by the bootstrap class loader), the extension directory
* (used by the extension class loader), and the regular class path (used by
* the application class loader). The notion is important because only those
* classes that the VM knows to be in the class file base will be eligible
* for hot code replacement. Classes that are actually loaded by
* non-standard class loaders cannot be replaced on the fly (because the VM
* has no way of asking non-standard class loaders to reload them). Classes
* loaded from the class file base by cooperating class loaders are said to
* be HCR-eligible.
* <p>
* The VM is expected to:
* <ol>
* <li>Suspend all running threads.
* <li>For a given JNI signature, try to find the definition of the
* corresponding class.
* <ul>
* <li>If the class definition can be found then it replaces the previous
* definition for that class.
* <li>If a definition for the class is not found, then it is unloaded.
* <ul>
* <li>This operation returns only when the classes have been reloaded
* and/or deleted.
* <li>If the suspend policy of the class unload event is not to suspend the
* VM, then the VM resumes all the threads that it has suspended.
* <li>Finally for each class that has been reloaded, the VM is expected to
* <ul>
* <li>send a class unload event,
* <li>note the VM is already suspended if the suspend policy of class
* unload event said so,
* <li>when the frontend resumes the VM, send a class prepare event,
* <li>suspend the VM according to the suspend policy of the class prepare
* event request.
* </ul>
* <li>For each class that has been unloaded, the VM is expected to
* <ul>
* <li>send a class unload event,
* <li>suspend the VM if it was requested by the class unload event request.
* </ul>
* </ol>
* <p>
* Subsequent references to classes will work with the new class definition.
* Note the existing <code>com.sun.jdi.ReferenceType</code>,
* <code>com.sun.jdi.Method</code> and <code>com.sun.jdi.Field</code> still
* refer to the old class definition. So they should be discarded when the
* class unload event come in.
* <p>
* The VM does not discard stack frames automatically:
* <ul>
* <li>methods on the stack are not affected, and could therefore be
* referencing obsolete code
* <li>replacing a class does not affect anything on the stack
* <li>subsequent class and method lookups find the replacements
* </ul>
* <p>
* Installed breakpoints are not automatically carried over to the reloaded
* class:
* <ul>
* <li>breakpoints are resolved to particular locations in particular
* classes and methods
* <li>the VM must clear breakpoints to methods in classes that have been
* reloaded or unloaded (the debugger will reinstall them when it gets the
* class prepare event.)
* </ul>
* <p>
* A change notice encompasses changes to the content of a class file in the
* base, the addition of a class files to the base, and the removal of a
* class file from the base.
* <p>
* Change notices apply to all classes that are HCR-eligible (i.e., loaded
* by one of the cooperative system class loaders); other classes are never
* affected.
* <p>
* Returns whether the operation could be completed as specified above,
* whether it was ignored (for example if the VM doesn't support this kind
* of replacement), or whether the operation failed and the VM should be
* restarted.
* @param arg1 the names of the classes that have changed
* @return whether the operation could be completed as specified above,
* whether it was ignored (for example if the VM doesn't support this kind
* of replacement), or whether the operation failed and the VM should be
* restarted
*
*/
public int classesHaveChanged(String[] arg1);
}