LoadTimeWeaver relying on VM Instrumentation.

Start the JVM specifying the Java agent to be used — for example, as follows where spring-instrument-{version}.jar is a JAR file containing the InstrumentationSavingAgent class shipped with Spring and where {version} is the release version of the Spring Framework (e.g., 5.1.5.RELEASE).

-javaagent:path/to/spring-instrument-{version}.jar

In Eclipse, for example, add something similar to the following to the JVM arguments for the Eclipse "Run configuration":

-javaagent:${project_loc}/lib/spring-instrument-{version}.jar

Nested and Inner Type Summary

Modifier and Type	Class and Description
private static class	InstrumentationLoadTimeWeaver.FilteringClassFileTransformer Decorator that only applies the given target transformer to a specific ClassLoader.
private static class	InstrumentationLoadTimeWeaver.InstrumentationAccessor Inner class to avoid InstrumentationSavingAgent dependency.

Field Summary

Modifier and Type	Field and Description
private static final boolean	AGENT_CLASS_PRESENT
private final ClassLoader	classLoader
private final Instrumentation	instrumentation
private final List<ClassFileTransformer>	transformers

Access	Constructor and Description
public	InstrumentationLoadTimeWeaver() Create a new InstrumentationLoadTimeWeaver for the default ClassLoader.
public	InstrumentationLoadTimeWeaver(ClassLoader the ClassLoader that registered transformers are supposed to apply to classLoader) Create a new InstrumentationLoadTimeWeaver for the given ClassLoader.

Method Summary

Modifier and Type	Method and Description
public void	addTransformer(ClassFileTransformer the `ClassFileTransformer` to add transformer) Implements org.springframework.instrument.classloading.LoadTimeWeaver.addTransformer. Add a `ClassFileTransformer` to be applied by this `LoadTimeWeaver`.
public ClassLoader	getInstrumentableClassLoader() Implements org.springframework.instrument.classloading.LoadTimeWeaver.getInstrumentableClassLoader. We have the ability to weave the current class loader when starting the JVM in this way, so the instrumentable class loader will always be the current loader.
private static Instrumentation	Returns: the Instrumentation instance, or `null` if none found getInstrumentation() Obtain the Instrumentation instance for the current VM, if available.
public ClassLoader	getThrowawayClassLoader() Implements org.springframework.instrument.classloading.LoadTimeWeaver.getThrowawayClassLoader. This implementation always returns a `SimpleThrowawayClassLoader`.
public static boolean	isInstrumentationAvailable() Check whether an Instrumentation instance is available for the current VM.
public void	removeTransformers() Remove all registered transformers, in inverse order of registration.

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

Field Detail

AGENT_CLASS_PRESENT	back to summary
private static final boolean AGENT_CLASS_PRESENT

classLoader	back to summary
private final ClassLoader classLoader Annotations @Nullable

instrumentation	back to summary
private final Instrumentation instrumentation Annotations @Nullable

transformers	back to summary
private final List<ClassFileTransformer> transformers

InstrumentationLoadTimeWeaver	back to summary
public InstrumentationLoadTimeWeaver() Create a new InstrumentationLoadTimeWeaver for the default ClassLoader.

InstrumentationLoadTimeWeaver	back to summary
public InstrumentationLoadTimeWeaver(ClassLoader classLoader) Create a new InstrumentationLoadTimeWeaver for the given ClassLoader. Parameters classLoader:ClassLoader the ClassLoader that registered transformers are supposed to apply to

Method Detail

addTransformer back to summary

addTransformer	back to summary
public void addTransformer(ClassFileTransformer transformer) Implements org.springframework.instrument.classloading.LoadTimeWeaver.addTransformer. Doc from org.springframework.instrument.classloading.LoadTimeWeaver.addTransformer. Add a `ClassFileTransformer` to be applied by this `LoadTimeWeaver`. Parameters transformer:ClassFileTransformer the `ClassFileTransformer` to add Annotations @Override

public void addTransformer(ClassFileTransformer transformer)

Implements org.springframework.instrument.classloading.LoadTimeWeaver.addTransformer.

Doc from org.springframework.instrument.classloading.LoadTimeWeaver.addTransformer.

Add a ClassFileTransformer to be applied by this LoadTimeWeaver.

Parameters

transformer:ClassFileTransformer: the ClassFileTransformer to add

Annotations

@Override

getInstrumentableClassLoader back to summary

getInstrumentableClassLoader	back to summary
public ClassLoader getInstrumentableClassLoader() Implements org.springframework.instrument.classloading.LoadTimeWeaver.getInstrumentableClassLoader. We have the ability to weave the current class loader when starting the JVM in this way, so the instrumentable class loader will always be the current loader. Returns:ClassLoader Doc from org.springframework.instrument.classloading.LoadTimeWeaver.getInstrumentableClassLoader. the `ClassLoader` which will expose instrumented classes according to the registered transformers Annotations @Override

public ClassLoader getInstrumentableClassLoader()

Implements org.springframework.instrument.classloading.LoadTimeWeaver.getInstrumentableClassLoader.

We have the ability to weave the current class loader when starting the JVM in this way, so the instrumentable class loader will always be the current loader.

Returns:ClassLoader

Doc from org.springframework.instrument.classloading.LoadTimeWeaver.getInstrumentableClassLoader.

the ClassLoader which will expose instrumented classes according to the registered transformers

Annotations

@Override

getInstrumentation back to summary

getInstrumentation	back to summary
private static Instrumentation getInstrumentation() Obtain the Instrumentation instance for the current VM, if available. Returns:Instrumentation the Instrumentation instance, or `null` if none found Annotations @Nullable See Also `isInstrumentationAvailable()`

private static Instrumentation getInstrumentation()

Obtain the Instrumentation instance for the current VM, if available.

Returns:Instrumentation

the Instrumentation instance, or null if none found

Annotations

@Nullable

See Also

isInstrumentationAvailable()

getThrowawayClassLoader back to summary

getThrowawayClassLoader	back to summary
public ClassLoader getThrowawayClassLoader() Implements org.springframework.instrument.classloading.LoadTimeWeaver.getThrowawayClassLoader. This implementation always returns a `SimpleThrowawayClassLoader`. Returns:ClassLoader Doc from org.springframework.instrument.classloading.LoadTimeWeaver.getThrowawayClassLoader. a temporary throwaway `ClassLoader`; should return a new instance for each call, with no existing state Annotations @Override

public ClassLoader getThrowawayClassLoader()

Implements org.springframework.instrument.classloading.LoadTimeWeaver.getThrowawayClassLoader.

This implementation always returns a SimpleThrowawayClassLoader.

Returns:ClassLoader

Doc from org.springframework.instrument.classloading.LoadTimeWeaver.getThrowawayClassLoader.

a temporary throwaway ClassLoader; should return a new instance for each call, with no existing state

Annotations

@Override

isInstrumentationAvailable back to summary

isInstrumentationAvailable	back to summary
public static boolean isInstrumentationAvailable() Check whether an Instrumentation instance is available for the current VM. See Also `getInstrumentation()`

public static boolean isInstrumentationAvailable()

Check whether an Instrumentation instance is available for the current VM.

See Also: getInstrumentation()

removeTransformers	back to summary
public void removeTransformers() Remove all registered transformers, in inverse order of registration.

org.springframework.instrument.classloading back to summary

private Class InstrumentationLoadTimeWeaver.FilteringClassFileTransformer

Class Inheritance

extends Object
implements ClassFileTransformer

java.lang.Object
org.springframework.instrument.classloading.InstrumentationLoadTimeWeaver.FilteringClassFileTransformer

All Implemented Interfaces

java.lang.instrument.ClassFileTransformer

Decorator that only applies the given target transformer to a specific ClassLoader.

Field Summary

Modifier and Type	Field and Description
private final ClassLoader	targetClassLoader
private final ClassFileTransformer	targetTransformer

Constructor Summary

Access	Constructor and Description
public	FilteringClassFileTransformer(ClassFileTransformer targetTransformer, ClassLoader targetClassLoader)

Method Summary

Modifier and Type Method and Description

Modifier and Type	Method and Description
public String	toString() Overrides java.lang.Object.toString. Returns a string representation of the object.
public byte[]	transform(ClassLoader the defining loader of the class to be transformed, may be `null` if the bootstrap loader loader, String the name of the class in the internal form of fully qualified class and interface names as defined in The Java Virtual Machine Specification. For example, `"java/util/List"`. className, Class<?> if this is triggered by a redefine or retransform, the class being redefined or retransformed; if this is a class load, `null` classBeingRedefined, ProtectionDomain the protection domain of the class being defined or redefined protectionDomain, byte[] the input byte buffer in class file format - must not be modified classfileBuffer) Overrides default java.lang.instrument.ClassFileTransformer.transform. Transforms the given class file and returns a new replacement class file.

public String

toString()

Overrides java.lang.Object.toString.

Returns a string representation of the object.

public byte[]

transform(ClassLoader

the defining loader of the class to be transformed, may be null if the bootstrap loader

loader, String

the name of the class in the internal form of fully qualified class and interface names as defined in The Java Virtual Machine Specification. For example, "java/util/List".

className, Class<?>

if this is triggered by a redefine or retransform, the class being redefined or retransformed; if this is a class load, null

classBeingRedefined, ProtectionDomain

the protection domain of the class being defined or redefined

protectionDomain, byte[]

the input byte buffer in class file format - must not be modified

classfileBuffer)

Overrides default java.lang.instrument.ClassFileTransformer.transform.

Transforms the given class file and returns a new replacement class file.

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

Field Detail

targetClassLoader	back to summary
private final ClassLoader targetClassLoader Annotations @Nullable

targetTransformer	back to summary
private final ClassFileTransformer targetTransformer

Constructor Detail

FilteringClassFileTransformer	back to summary
public FilteringClassFileTransformer(ClassFileTransformer targetTransformer, ClassLoader targetClassLoader)

Method Detail

toString back to summary

toString	back to summary
public String toString() Overrides java.lang.Object.toString. Doc from java.lang.Object.toString. Returns a string representation of the object. Satisfying this method's contract implies a non-`null` result must be returned. Returns:String a string representation of the object Annotations @Override

public String toString()

Overrides java.lang.Object.toString.

Doc from java.lang.Object.toString.

Returns a string representation of the object. Satisfying this method's contract implies a non-null result must be returned.

Returns:String

a string representation of the object

Annotations

@Override

transform back to summary

transform	back to summary
public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer) throws IllegalClassFormatException Overrides default java.lang.instrument.ClassFileTransformer.transform. Doc from java.lang.instrument.ClassFileTransformer.transform. Transforms the given class file and returns a new replacement class file. This method is invoked when the `Module` bearing `transform` is not overridden. Parameters loader:ClassLoader the defining loader of the class to be transformed, may be `null` if the bootstrap loader className:String the name of the class in the internal form of fully qualified class and interface names as defined in The Java Virtual Machine Specification. For example, `"java/util/List"`. classBeingRedefined:Class<?> if this is triggered by a redefine or retransform, the class being redefined or retransformed; if this is a class load, `null` protectionDomain:ProtectionDomain the protection domain of the class being defined or redefined classfileBuffer:byte[] the input byte buffer in class file format - must not be modified Returns:byte[] a well-formed class file buffer (the result of the transform), or `null` if no transform is performed Annotations @Override @Nullable Exceptions IllegalClassFormatException: if the input does not represent a well-formed class file

public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer) throws IllegalClassFormatException

Overrides default java.lang.instrument.ClassFileTransformer.transform.

Doc from java.lang.instrument.ClassFileTransformer.transform.

Transforms the given class file and returns a new replacement class file. This method is invoked when the Module bearing transform is not overridden.

Parameters

loader:ClassLoader: the defining loader of the class to be transformed, may be null if the bootstrap loader
className:String: the name of the class in the internal form of fully qualified class and interface names as defined in The Java Virtual Machine Specification. For example, "java/util/List".
classBeingRedefined:Class<?>: if this is triggered by a redefine or retransform, the class being redefined or retransformed; if this is a class load, null
protectionDomain:ProtectionDomain: the protection domain of the class being defined or redefined
classfileBuffer:byte[]: the input byte buffer in class file format - must not be modified

Returns:byte[]

a well-formed class file buffer (the result of the transform), or null if no transform is performed

Annotations

@Override
@Nullable

Exceptions

IllegalClassFormatException:: if the input does not represent a well-formed class file

public Class InstrumentationLoadTimeWeaver

Nested and Inner Type Summary

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail

private Class InstrumentationLoadTimeWeaver.FilteringClassFileTransformer

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail

private Class InstrumentationLoadTimeWeaver.InstrumentationAccessor

Constructor Summary

Method Summary

Constructor Detail

Method Detail