org.springsource.loaded.agent

Class JVMPlugin

java.lang.Object

org.springsource.loaded.agent.JVMPlugin

All Implemented Interfaces:

LoadtimeInstrumentationPlugin, Plugin, ReloadEventProcessorPlugin

public class JVMPlugin
extends java.lang.Object
implements ReloadEventProcessorPlugin, LoadtimeInstrumentationPlugin

Reloading plugin for 'poking' JVM classes that are known to cache reflective state. Some of the behaviour is switched ON based on which classes are loaded. For example the Introspector clearing logic is only activated if the Introspector gets loaded.

Since:

0.7.3

Constructor Summary

Constructors

Constructor and Description
JVMPlugin()

Method Summary

Modifier and Type	Method and Description
boolean	accept(java.lang.String slashedTypeName, java.lang.ClassLoader classLoader, java.security.ProtectionDomain protectionDomain, byte[] bytes) Called by the agent to determine if this plugin is interested in changing the specified type at load time.
byte[]	modify(java.lang.String slashedClassName, java.lang.ClassLoader classLoader, byte[] bytes) Once accept has returned true for a type, the modify method will be called to make the actual change to the classfile bytes.
void	reloadEvent(java.lang.String typename, java.lang.Class<?> clazz, java.lang.String encodedTimestamp) Called when a type has been reloaded.
boolean	shouldRerunStaticInitializer(java.lang.String typename, java.lang.Class<?> clazz, java.lang.String encodedTimestamp) Called when a type has been reloaded, allows the plugin to decide if the static initializer should be re-run for the reloaded type.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

JVMPlugin

public JVMPlugin()

Method Detail

reloadEvent

public void reloadEvent(java.lang.String typename,
                        java.lang.Class<?> clazz,
                        java.lang.String encodedTimestamp)

Description copied from interface: ReloadEventProcessorPlugin

Called when a type has been reloaded. Note, the class is only truly defined to the VM once, and so the Class object (clazz parameter) is always the same for the same type (ignoring multiple classloader situations). It is passed here so that plugins processing events can clear any cached state related to it. The encodedTimestamp is an encoding of the ID that the agent has assigned to this reloaded version of this type.

Specified by:

reloadEvent in interface ReloadEventProcessorPlugin

Parameters:

typename - the (dotted) type name, for example java.lang.String

clazz - the Class object that has been reloaded

encodedTimestamp - an encoded time stamp for this version, containing chars (A-Za-z0-9)

accept

public boolean accept(java.lang.String slashedTypeName,
                      java.lang.ClassLoader classLoader,
                      java.security.ProtectionDomain protectionDomain,
                      byte[] bytes)

Description copied from interface: LoadtimeInstrumentationPlugin

Called by the agent to determine if this plugin is interested in changing the specified type at load time. This is used when the plugin wishes to do some kind of transformation itself before the type is loaded - for example modify it to record something that will later be used on a reload event.

Specified by:

accept in interface LoadtimeInstrumentationPlugin

Parameters:

slashedTypeName - the type name, slashed form (e.g. java/lang/String)

classLoader - the classloader loading the type

protectionDomain - the ProtectionDomain for the class represented by the bytes

bytes - the classfile contents for the type

Returns:

true if this plugin wants to change the bytes for the named type

modify

public byte[] modify(java.lang.String slashedClassName,
                     java.lang.ClassLoader classLoader,
                     byte[] bytes)

Description copied from interface: LoadtimeInstrumentationPlugin

Once accept has returned true for a type, the modify method will be called to make the actual change to the classfile bytes.

Specified by:

modify in interface LoadtimeInstrumentationPlugin

Parameters:

slashedClassName - the class name, slashed form (e.g. java/lang/String)

classLoader - the classloader loading the type

bytes - the classfile contents for the type

Returns:

the new (modified) bytes for the class

shouldRerunStaticInitializer

public boolean shouldRerunStaticInitializer(java.lang.String typename,
                                            java.lang.Class<?> clazz,
                                            java.lang.String encodedTimestamp)

Description copied from interface: ReloadEventProcessorPlugin

Called when a type has been reloaded, allows the plugin to decide if the static initializer should be re-run for the reloaded type. If the reloaded type has a different static initializer, the new one is the one that will run.

Specified by:

shouldRerunStaticInitializer in interface ReloadEventProcessorPlugin

Parameters:

typename - the (dotted) type name, for example java.lang.String

clazz - the Class object that has been reloaded

encodedTimestamp - an encoded time stamp for this version, containing chars (A-Za-z0-9)

Returns:

true if the static initializer should be re-run