net.bytebuddy.agent

Class ByteBuddyAgent

java.lang.Object

net.bytebuddy.agent.ByteBuddyAgent

public class ByteBuddyAgent
extends Object

The Byte Buddy agent provides a JVM Instrumentation in order to allow Byte Buddy the redefinition of already loaded classes. An agent must normally be specified via the command line via the javaagent parameter. As an argument to this parameter, one must specify the location of this agent's jar file such as for example in

java -javaagent:byte-buddy-agent.jar -jar app.jar

For JDK installations of the Java virtual machine, an agent can however also be installed after startup using the Attach API which is contained in the JDK's tools.jar. As instrumentation is commonly used in unit tests which are normally run on a JDK, the Byte Buddy agent provides a convenience installation method installOnOpenJDK() which is only guaranteed to work on the OpenJDK and compatible JDKs.

Note: This class's name is known to the Byte Buddy main application and must not be altered.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ByteBuddyAgent.Installer An installer class which defined the hook-in methods that are required by the Java agent specification.

Method Summary

Modifier and Type	Method and Description
static Instrumentation	getInstrumentation() Looks up the Instrumentation instance of an installed Byte Buddy agent.
static Instrumentation	installOnOpenJDK() Installs the Byte Buddy agent using the tools.jar's Attach API.

Methods inherited from class java.lang.Object

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

Method Detail

installOnOpenJDK

public static Instrumentation installOnOpenJDK()

Installs the Byte Buddy agent using the tools.jar's Attach API. This installation is only possible on the OpenJDK and compatible JDKs as the tools.jar is not available on non-JDK JVMs or other JDKs. Note that the installation is only performed if the Byte Buddy agent is not yet installed. However, this method implies reflective lookup and reflective invocation such that the returned value should be cached rather than calling this method several times.

Note: If the currently running JVM does not support the runtime installation of an agent, this method throws an IllegalStateException

Returns:

The Instrumentation instance that is provided by the Byte Buddy agent.

getInstrumentation

public static Instrumentation getInstrumentation()

Looks up the Instrumentation instance of an installed Byte Buddy agent. Note that this method implies reflective lookup and reflective invocation such that the returned value should be cached rather than calling this method several times.

Note: This method throws an IllegalStateException If the Byte Buddy agent is not properly installed.

Returns:

The Instrumentation instance which is provided by an installed Byte Buddy agent.