Dynamic bytecode modification of classes and class hierarchies
Various systems and methods for dynamic bytecode modification of classes and class hierarchies are described herein. In various embodiments, a Java® agent is received at a launch of a Java® Virtual Machine (JVM®), the agent implementing a premain method, the premain method accepting a reference to an instrumentation instance. The instrumentation reference is then stored, a deployment container is initialized, and, within the deployment container, an instance of an application is created. The instrumentation reference is then provided to the application instance. A class transformer is then retrieved from a persistence provider, and the class transformer is wrapped by an O.R. Persistence Container Class Transformer, which is then registered with the instrumentation instance. A class to be transformed is passed to the class transformer, which dynamically modifies the bytecode of the class before the class is loaded by the JVM®.
1. A method comprising:
receiving an agent at a launch of a Java® Virtual Machine (JVM®), the agent including a field for storing a reference to an instrumentation instance and implementing a premain method, the premain method accepting the reference to the instrumentation instance;
storing the instrumentation reference;
initializing a deployment container;
creating an instance of an application within the deployment container;
providing the instrumentation reference to the application instance;
retrieving a class transformer from a persistence provider;
registering the class transformer with the instrumentation instance;
passing bytecode of a class to be transformed to the class transformer;
dynamically modifying, using the class transformer, the bytecode of the class before the class is loaded by the JVM® when the class is to be loaded by a class loader other than a regular class loader of the application, wherein the modified class, after being loaded by the JVM®, is arranged to execute according to its modified bytecode.
2. The method of claim 1 , wherein the deployment container is one of an O.R. (Object-Relational) Persistence Deployment Container, an EJB® (Enterprise JavaBeans®) Deployment Container, and a Web Deployment Container.
3. The method of claim 1 , wherein the persistence provider is a Java® Persistence Application Programming Interface (JPA) Persistence Provider.
4. The method of claim 3 , further comprising:
instantiating an entity manager factory during deployment of the application only when dynamic bytecode modification is enabled and when the JPA Persistence Provider is a not the default provider.
5. The method of claim 1 , further comprising:
checking, prior to the dynamic modification, whether the class to be modified is to be loaded by a heavy class loader of the application.
6. The method of claim 1 , further comprising:
instantiating, using lazy initialization, an entity manager factory upon receiving a client request when the JPA provider is the default provider.
7. A non-transitory computer-readable storage medium, with
instructions stored thereon, which when executed by at least one processor of a computing device, cause the computing device to perform operations comprising:
receiving an agent at a launch of a Java® Virtual Machine (JVM®), the agent including a field for storing a reference to an instrument instance and implementing a premain method, the premain method accepting a reference to an instrumentation instance;
storing the instrumentation reference;
initializing a deployment container;
creating an instance of an application within the deployment container;
providing the instrumentation reference to the application instance;
retrieving a class transformer from a persistence provider;
registering the class transformer with the instrumentation instance;
passing bytecode of a class to be transformed to the class transformer;
dynamically modifying, using the class transformer, the bytecode of the class before the class is loaded by the JVM® when the class is to be loaded by a class loader other than a regular class loader of the application, wherein the modified class, after being loaded by the JVM®, is arranged to execute according to its modified bytecode.
8. The non-transitory computer-readable storage medium of claim 7 , wherein the deployment container is one of an O.R. (Object-Relational) Persistence Deployment Container, an EJB® (Enterprise JavaBeans®) Deployment Container, and a Web Deployment Container.
9. The non-transitory computer-readable storage medium of claim 7 , wherein the persistence provider is a Java® Persistence Application Programming Interface (JPA) Persistence Provider.
10. The non-transitory computer-readable storage medium of claim 7 , with further instructions stored thereon which, when executed by the processor, cause the computing device to:
check, prior to the dynamic modification, whether the class to be modified is to be loaded by a heavy class loader of the application.
11. The non-transitory computer-readable storage medium of claim 7 , with further instructions stored thereon which, when executed by the processor, cause the computing device to:
instantiate an entity manager factory during deployment of the application only when dynamic bytecode modification is enabled and when the JPA Persistence Provider is a not the default provider.
12. The non-transitory computer-readable storage medium of claim 7 , with further instructions stored thereon which, when executed by the processor, cause the computing device to:
instantiate, using lazy initialization, an entity manager factory upon receiving a client request when the JPA provider is the default provider.
13. A system, comprising:
a processor and a memory device operatively coupled via a bus; and instructions stored in the memory device and executable by the processor to:
receive an agent at a launch of a Java® Virtual Machine (JVM®), the agent including a field for storing a reference to an instrument instance and implementing a premain method, the premain method accepting a reference to an instrumentation instance;
store the instrumentation reference;
initialize a deployment container;
create an instance of an application within the deployment container;
provide the instrumentation reference to the application instance;
retrieve a class transformer from a persistence provider;
register the class transformer with the instrumentation instance;
pass bytecode of a class to be transformed to the class transformer;
dynamically modify, using the class transformer, the bytecode of the class before the class is loaded by the JVM® when the class is to be loaded by a class loader other than a regular class loader of the application, wherein the modified class, after being loaded by the JVM®, is arranged to execute according to its modified bytecode.
14. The system of claim 13 , wherein the deployment container is one of an O.R. (Object-Relational) Persistence Deployment Container, an EJB® (Enterprise JavaBeans®) Deployment Container, and a Web Deployment Container.
15. The system of claim 13 , wherein the persistence provider is a Java® Persistence Application Programming Interface (JPA) Persistence Provider.
16. The system of claim 13 , instructions stored in the memory device and executable by the processor to:
check, prior to the dynamic modification, whether the class to be modified is to be loaded by a heavy class loader of the application.
17. The system of claim 13 , instructions stored in the memory device and executable by the processor to:
instantiate an entity manager factory during deployment of the application only when dynamic bytecode modification is enabled and when the JPA Persistence Provider is a not the default provider.
18. The system of claim 13 , instructions stored in the memory device and executable by the processor to:
instantiate, using lazy initialization, an entity manager factory upon receiving a client request when the JPA provider is the default provider.