Javassist 3.30.2-GA · javassist.util.HotSwapper · APIdia, the JavaDoc alternative

A utility class for dynamically reloading a class by the Java Platform Debugger Architecture (JPDA), or HotSwap. It works only with JDK 1.4 and later.

Note

The new definition of the reloaded class must declare the same set of methods and fields as the original definition. The schema change between the original and new definitions is not allowed by the JPDA.

To use this class, the JVM must be launched with the following command line options:

For Java 1.4,

java -Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=8000

For Java 5,

java -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=8000

Note that 8000 is the port number used by HotSwapper. Any port number can be specified. Since HotSwapper does not launch another JVM for running a target application, this port number is used only for inter-thread communication.

Furthermore, JAVA_HOME/lib/tools.jar must be included in the class path.

Using HotSwapper is easy. See the following example:

CtClass clazz = ...
byte[] classFile = clazz.toBytecode();
HotSwapper hs = new HostSwapper(8000);  // 8000 is a port number.
hs.reload("Test", classFile);

reload() first unload the Test class and load a new version of the Test class. classFile is a byte array containing the new contents of the class file for the Test class. The developers can repatedly call reload() on the same HotSwapper object so that they can reload a number of classes.

HotSwap depends on the debug agent to perform hot-swapping but it is reported that the debug agent is buggy under massively multithreaded environments. If you encounter a problem, try HotSwapAgent.

Modifier and Type	Field and Description
private static final String	HOST_NAME
private VirtualMachine	jvm
private Map<ReferenceType, byte[]>	newClassFiles
private MethodEntryRequest	request
private Trigger	trigger
private static final String	TRIGGER_NAME

Access	Constructor and Description
public	HotSwapper(int the port number used for the connection to the JVM. port) Connects to the JVM.
public	HotSwapper(String the port number used for the connection to the JVM. port) Connects to the JVM.

Method Summary

Modifier and Type	Method and Description
private void	deleteEventRequest(EventRequestManager manager, MethodEntryRequest request)
private Connector	findConnector(String connector)
pack-priv void	hotswap()
private static MethodEntryRequest	methodEntryRequests(EventRequestManager manager, String classpattern)
public void	reload(String the fully-qualified class name. className, byte[] the contents of the class file. classFile) Reloads a class.
public void	reload(Map<String, byte[]> a map between fully-qualified class names and class files. The type of the class names is `String` and the type of the class files is `byte[]`. classFiles) Reloads a class.
private void	reload2(Map<ReferenceType, byte[]> map, String msg)
private void	startDaemon()
private ReferenceType	toRefType(String className)
pack-priv EventSet	waitEvent()

Inherited from java.lang.Object:: clone equals finalize getClass hashCode notify notifyAll toString wait wait wait

HOST_NAME	back to summary
private static final String HOST_NAME

jvm	back to summary
private VirtualMachine jvm

newClassFiles	back to summary
private Map<ReferenceType, byte[]> newClassFiles

request	back to summary
private MethodEntryRequest request

trigger	back to summary
private Trigger trigger

TRIGGER_NAME	back to summary
private static final String TRIGGER_NAME

HotSwapper	back to summary
public HotSwapper(int port) throws IOException, IllegalConnectorArgumentsException Connects to the JVM. Parameters port:int the port number used for the connection to the JVM.

HotSwapper	back to summary
public HotSwapper(String port) throws IOException, IllegalConnectorArgumentsException Connects to the JVM. Parameters port:String the port number used for the connection to the JVM.

Method Detail

deleteEventRequest	back to summary
private void deleteEventRequest(EventRequestManager manager, MethodEntryRequest request) Annotations @SuppressWarnings:unused

findConnector	back to summary
private Connector findConnector(String connector) throws IOException

hotswap	back to summary
pack-priv void hotswap()

methodEntryRequests	back to summary
private static MethodEntryRequest methodEntryRequests(EventRequestManager manager, String classpattern)

reload	back to summary
public void reload(String className, byte[] classFile) Reloads a class. Parameters className:String the fully-qualified class name. classFile:byte[] the contents of the class file.

reload

back to summary

public void reload(String className, byte[] classFile)

Reloads a class.

Parameters

className:String: the fully-qualified class name.
classFile:byte[]: the contents of the class file.

reload back to summary

reload	back to summary
public void reload(Map<String, byte[]> classFiles) Reloads a class. Parameters classFiles:Map<String, byte[]> a map between fully-qualified class names and class files. The type of the class names is `String` and the type of the class files is `byte[]`.

public void reload(Map<String, byte[]> classFiles)

Reloads a class.

Parameters

classFiles:Map<String, byte[]>: a map between fully-qualified class names and class files. The type of the class names is String and the type of the class files is byte[].

reload2	back to summary
private void reload2(Map<ReferenceType, byte[]> map, String msg)

startDaemon	back to summary
private void startDaemon()

toRefType	back to summary
private ReferenceType toRefType(String className)

waitEvent	back to summary
pack-priv EventSet waitEvent() throws InterruptedException

public Class HotSwapper

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail