com.ea.agentloader

Class AgentLoader

java.lang.Object

com.ea.agentloader.AgentLoader

public class AgentLoader
extends Object

Utilities to load java agents dynamically.

Deals with the problem of finding the proper jvm classes.

Author:

Daniel Sperry

See Also:

Instrumentation

Constructor Summary

Constructors

Constructor and Description
AgentLoader()

Method Summary

Modifier and Type	Method and Description
static void	createAgentJar(OutputStream out, String agentClass, String bootClassPath, boolean canRedefineClasses, boolean canRetransformClasses, boolean canSetNativeMethodPrefix) Creates an agent jar with the proper manifest file to start a javaagent.
static File	createTemporaryAgentJar(String agentClass, String bootClassPath, boolean canRedefineClasses, boolean canRetransformClasses, boolean canSetNativeMethodPrefix) Creates a jar in runtime with the proper manifest file to start the javaagent.
static String	getPid() Gets the current jvm's pid.
static void	loadAgent(String agentJar, String options) Dynamically loads a java agent.
static void	loadAgentClass(String agentClassName, String options) Creates loads the agent class directly.
static void	loadAgentClass(String agentClass, String options, String bootClassPath, boolean canRedefineClasses, boolean canRetransformClasses, boolean canSetNativeMethodPrefix) Creates loads the agent class directly.

Methods inherited from class java.lang.Object

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

Constructor Detail

AgentLoader

public AgentLoader()

Method Detail

loadAgent

public static void loadAgent(String agentJar,
                             String options)

Dynamically loads a java agent. Deals with the problem of finding the proper jvm classes.

Parameters:

agentJar - the agent jar

options - options that will be passed back to the agent, can be null

See Also:

Instrumentation

loadAgentClass

public static void loadAgentClass(String agentClassName,
                                  String options)

Creates loads the agent class directly. The agent class must be visible from the system class loader.

This method creates a temporary jar with the proper manifest and loads the agent using the jvm attach facilities.

This will not work if the agent class can't be loaded by the system class loader.
This can be worked around like by adding the specific class and any other dependencies to the system class loader:

     if(MyAgent.class.getClassLoader() != ClassLoader.getSystemClassLoader()) {
         ClassPathUtils.appendToSystemPath(ClassPathUtils.getClassPathFor(MyAgent.class));
         ClassPathUtils.appendToSystemPath(ClassPathUtils.getClassPathFor(OtherDepenencies.class));
     }
     loadAgent(MyAgent.class.getName(), null, null, true, true, false);
 

Parameters:

agentClassName - the agent class name

options - options that will be passed back to the agent, can be null

loadAgentClass

public static void loadAgentClass(String agentClass,
                                  String options,
                                  String bootClassPath,
                                  boolean canRedefineClasses,
                                  boolean canRetransformClasses,
                                  boolean canSetNativeMethodPrefix)

Creates loads the agent class directly.

This method creates a temporary jar with the proper manifest and loads the agent using the jvm attach facilities.

This will not work if the agent class can't be loaded by the system class loader.
This can be worked around like by adding the specific class and any other dependencies to the system class loader:

     if(MyAgent.class.getClassLoader() != ClassLoader.getSystemClassLoader()) {
         ClassPathUtils.appendToSystemPath(ClassPathUtils.getClassPathFor(MyAgent.class));
         ClassPathUtils.appendToSystemPath(ClassPathUtils.getClassPathFor(OtherDepenencies.class));
     }
     loadAgent(MyAgent.class.getName(), null, null, true, true, false);
 

Parameters:

agentClass - the agent class

options - options that will be passed back to the agent, can be null

bootClassPath - list of jars to be loaded with the agent, can be null

canRedefineClasses - if the ability to redefine classes is need by the agent, suggested default: false

canRetransformClasses - if the ability to retransform classes is need by the agent, suggested default: false

canSetNativeMethodPrefix - if the ability to set native method prefix is need by the agent, suggested default: false

See Also:

ClassPathUtils, Instrumentation

getPid

public static String getPid()

Gets the current jvm's pid.

Returns:

the pid as String

createTemporaryAgentJar

public static File createTemporaryAgentJar(String agentClass,
                                           String bootClassPath,
                                           boolean canRedefineClasses,
                                           boolean canRetransformClasses,
                                           boolean canSetNativeMethodPrefix)
                                    throws IOException

Creates a jar in runtime with the proper manifest file to start the javaagent.

This method is convenient to java agent developers since they can test their agents without creating a jar first.

Parameters:

agentClass - the agent class

bootClassPath - list of jars to be loaded with the agent, can be null

canRedefineClasses - if the ability to redefine classes is need by the agent, suggested default: false

canRetransformClasses - if the ability to retransform classes is need by the agent, suggested default: false

canSetNativeMethodPrefix - if the ability to set native method prefix is need by the agent, suggested default: false

Throws:

IOException

createAgentJar

public static void createAgentJar(OutputStream out,
                                  String agentClass,
                                  String bootClassPath,
                                  boolean canRedefineClasses,
                                  boolean canRetransformClasses,
                                  boolean canSetNativeMethodPrefix)
                           throws IOException

Creates an agent jar with the proper manifest file to start a javaagent.

Parameters:

agentClass - the agent class

bootClassPath - list of jars to be loaded with the agent, can be null

canRedefineClasses - if the ability to redefine classes is need by the agent, suggested default: false

canRetransformClasses - if the ability to retransform classes is need by the agent, suggested default: false

canSetNativeMethodPrefix - if the ability to set native method prefix is need by the agent, suggested default: false

Throws:

IOException