Package 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

Note: The runtime installation of a Java agent is not possible on all JVMs. See the documentation for install() for details on JVMs that are supported out of the box.

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

Note: Byte Buddy does not execute code using an java.security.AccessController. If a security manager is present, the user of this class is responsible for assuring any required privileges. To read an Instrumentation, the net.bytebuddy.agent.getInstrumentation runtime permission is required.

  • Field Details

    • LATENT_RESOLVE

      public static final String LATENT_RESOLVE
      Indicates that the agent should not resolve its own code location for a self-attachment.
      See Also:

    • AGENT_CLASS_PROPERTY

      private static final String AGENT_CLASS_PROPERTY
      The manifest property specifying the agent class.
      See Also:

    • CAN_REDEFINE_CLASSES_PROPERTY

      private static final String CAN_REDEFINE_CLASSES_PROPERTY
      The manifest property specifying the can redefine property.
      See Also:

    • CAN_RETRANSFORM_CLASSES_PROPERTY

      private static final String CAN_RETRANSFORM_CLASSES_PROPERTY
      The manifest property specifying the can retransform property.
      See Also:

    • CAN_SET_NATIVE_METHOD_PREFIX

      private static final String CAN_SET_NATIVE_METHOD_PREFIX
      The manifest property specifying the can set native method prefix property.
      See Also:

    • MANIFEST_VERSION_VALUE

      private static final String MANIFEST_VERSION_VALUE
      The manifest property value for the manifest version.
      See Also:

    • BUFFER_SIZE

      private static final int BUFFER_SIZE
      The size of the buffer for copying the agent installer file into another jar.
      See Also:

    • START_INDEX

      private static final int START_INDEX
      Convenience indices for reading and writing to the buffer to make the code more readable.
      See Also:

    • END_OF_FILE

      private static final int END_OF_FILE
      Convenience indices for reading and writing to the buffer to make the code more readable.
      See Also:

    • SUCCESSFUL_ATTACH

      private static final int SUCCESSFUL_ATTACH
      The status code expected as a result of a successful attachment.
      See Also:

    • BOOTSTRAP_CLASS_LOADER

      @AlwaysNull private static final ClassLoader BOOTSTRAP_CLASS_LOADER
      Representation of the bootstrap ClassLoader.

    • WITHOUT_ARGUMENT

      @AlwaysNull private static final String WITHOUT_ARGUMENT
      Represents a no-op argument for a dynamic agent attachment.

    • ATTACHER_FILE_NAME

      private static final String ATTACHER_FILE_NAME
      The naming prefix of all artifacts for an attacher jar.
      See Also:

    • CLASS_FILE_EXTENSION

      private static final String CLASS_FILE_EXTENSION
      The file extension for a class file.
      See Also:

    • JAR_FILE_EXTENSION

      private static final String JAR_FILE_EXTENSION
      The file extension for a jar file.
      See Also:

    • CLASS_PATH_ARGUMENT

      private static final String CLASS_PATH_ARGUMENT
      The class path argument to specify the class path elements.
      See Also:

    • JAVA_HOME

      private static final String JAVA_HOME
      The Java property denoting the Java home directory.
      See Also:

    • OS_NAME

      private static final String OS_NAME
      The Java property denoting the operating system name.
      See Also:

    • INSTRUMENTATION_METHOD

      private static final String INSTRUMENTATION_METHOD
      The name of the method for reading the installer's instrumentation.
      See Also:

    • FILE_PROTOCOL

      private static final String FILE_PROTOCOL
      Represents the file URL protocol.
      See Also:

    • UNAVAILABLE

      @AlwaysNull private static final Instrumentation UNAVAILABLE
      An indicator variable to express that no instrumentation is available.

    • CANNOT_SELF_RESOLVE

      @AlwaysNull private static final File CANNOT_SELF_RESOLVE
      Represents a failed attempt to self-resolve a jar file location.

    • ATTACHMENT_TYPE_EVALUATOR

      private static final ByteBuddyAgent.AttachmentTypeEvaluator ATTACHMENT_TYPE_EVALUATOR
      The attachment type evaluator to be used for determining if an attachment requires an external process.

  • Constructor Details

    • ByteBuddyAgent

      private ByteBuddyAgent()
      The agent provides only static utility methods and should not be instantiated.

  • Method Details

    • doPrivileged

      private static <T> T doPrivileged(PrivilegedAction<T> action)
      A proxy for java.security.AccessController#doPrivileged that is activated if available.
      Type Parameters:
      T - The type of the action's resolved value.
      Parameters:
      action - The action to execute from a privileged context.
      Returns:
      The action's resolved value.

    • 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.

    • attach

      public static void attach(File agentJar, String processId)

      Attaches the given agent Jar on the target process which must be a virtual machine process. The default attachment provider is used for applying the attachment. This operation blocks until the attachment is complete. If the current VM does not supply any known form of attachment to a remote VM, an IllegalStateException is thrown. The agent is not provided an argument.

      Important: It is only possible to attach to processes that are executed by the same operating system user.

      Parameters:
      agentJar - The agent jar file.
      processId - The target process id.

    • attach

      public static void attach(File agentJar, String processId, @MaybeNull String argument)

      Attaches the given agent Jar on the target process which must be a virtual machine process. The default attachment provider is used for applying the attachment. This operation blocks until the attachment is complete. If the current VM does not supply any known form of attachment to a remote VM, an IllegalStateException is thrown.

      Important: It is only possible to attach to processes that are executed by the same operating system user.

      Parameters:
      agentJar - The agent jar file.
      processId - The target process id.
      argument - The argument to provide to the agent.

    • attach

      public static void attach(File agentJar, String processId, ByteBuddyAgent.AttachmentProvider attachmentProvider)

      Attaches the given agent Jar on the target process which must be a virtual machine process. This operation blocks until the attachment is complete. The agent is not provided an argument.

      Important: It is only possible to attach to processes that are executed by the same operating system user.

      Parameters:
      agentJar - The agent jar file.
      processId - The target process id.
      attachmentProvider - The attachment provider to use.

    • attach

      public static void attach(File agentJar, String processId, @MaybeNull String argument, ByteBuddyAgent.AttachmentProvider attachmentProvider)

      Attaches the given agent Jar on the target process which must be a virtual machine process. This operation blocks until the attachment is complete.

      Important: It is only possible to attach to processes that are executed by the same operating system user.

      Parameters:
      agentJar - The agent jar file.
      processId - The target process id.
      argument - The argument to provide to the agent.
      attachmentProvider - The attachment provider to use.

    • attach

      public static void attach(File agentJar, ByteBuddyAgent.ProcessProvider processProvider)

      Attaches the given agent Jar on the target process which must be a virtual machine process. The default attachment provider is used for applying the attachment. This operation blocks until the attachment is complete. If the current VM does not supply any known form of attachment to a remote VM, an IllegalStateException is thrown. The agent is not provided an argument.

      Important: It is only possible to attach to processes that are executed by the same operating system user.

      Parameters:
      agentJar - The agent jar file.
      processProvider - A provider of the target process id.

    • attach

      public static void attach(File agentJar, ByteBuddyAgent.ProcessProvider processProvider, @MaybeNull String argument)

      Attaches the given agent Jar on the target process which must be a virtual machine process. The default attachment provider is used for applying the attachment. This operation blocks until the attachment is complete. If the current VM does not supply any known form of attachment to a remote VM, an IllegalStateException is thrown.

      Important: It is only possible to attach to processes that are executed by the same operating system user.

      Parameters:
      agentJar - The agent jar file.
      processProvider - A provider of the target process id.
      argument - The argument to provide to the agent.

    • attach

      public static void attach(File agentJar, ByteBuddyAgent.ProcessProvider processProvider, ByteBuddyAgent.AttachmentProvider attachmentProvider)

      Attaches the given agent Jar on the target process which must be a virtual machine process. This operation blocks until the attachment is complete. The agent is not provided an argument.

      Important: It is only possible to attach to processes that are executed by the same operating system user.

      Parameters:
      agentJar - The agent jar file.
      processProvider - A provider of the target process id.
      attachmentProvider - The attachment provider to use.

    • attach

      public static void attach(File agentJar, ByteBuddyAgent.ProcessProvider processProvider, @MaybeNull String argument, ByteBuddyAgent.AttachmentProvider attachmentProvider)

      Attaches the given agent Jar on the target process which must be a virtual machine process. This operation blocks until the attachment is complete.

      Important: It is only possible to attach to processes that are executed by the same operating system user.

      Parameters:
      agentJar - The agent jar file.
      processProvider - A provider of the target process id.
      argument - The argument to provide to the agent.
      attachmentProvider - The attachment provider to use.

    • attachNative

      public static void attachNative(File agentLibrary, String processId)

      Attaches the given agent library on the target process which must be a virtual machine process. The default attachment provider is used for applying the attachment. This operation blocks until the attachment is complete. If the current VM does not supply any known form of attachment to a remote VM, an IllegalStateException is thrown. The agent is not provided an argument.

      Important: It is only possible to attach to processes that are executed by the same operating system user.

      Parameters:
      agentLibrary - The agent jar file.
      processId - The target process id.

    • attachNative

      public static void attachNative(File agentLibrary, String processId, @MaybeNull String argument)

      Attaches the given agent library on the target process which must be a virtual machine process. The default attachment provider is used for applying the attachment. This operation blocks until the attachment is complete. If the current VM does not supply any known form of attachment to a remote VM, an IllegalStateException is thrown.

      Important: It is only possible to attach to processes that are executed by the same operating system user.

      Parameters:
      agentLibrary - The agent library.
      processId - The target process id.
      argument - The argument to provide to the agent.

    • attachNative

      public static void attachNative(File agentLibrary, String processId, ByteBuddyAgent.AttachmentProvider attachmentProvider)

      Attaches the given agent library on the target process which must be a virtual machine process. This operation blocks until the attachment is complete. The agent is not provided an argument.

      Important: It is only possible to attach to processes that are executed by the same operating system user.

      Parameters:
      agentLibrary - The agent library.
      processId - The target process id.
      attachmentProvider - The attachment provider to use.

    • attachNative

      public static void attachNative(File agentLibrary, String processId, @MaybeNull String argument, ByteBuddyAgent.AttachmentProvider attachmentProvider)

      Attaches the given agent library on the target process which must be a virtual machine process. This operation blocks until the attachment is complete.

      Important: It is only possible to attach to processes that are executed by the same operating system user.

      Parameters:
      agentLibrary - The agent library.
      processId - The target process id.
      argument - The argument to provide to the agent.
      attachmentProvider - The attachment provider to use.

    • attachNative

      public static void attachNative(File agentLibrary, ByteBuddyAgent.ProcessProvider processProvider)

      Attaches the given agent library on the target process which must be a virtual machine process. The default attachment provider is used for applying the attachment. This operation blocks until the attachment is complete. If the current VM does not supply any known form of attachment to a remote VM, an IllegalStateException is thrown. The agent is not provided an argument.

      Important: It is only possible to attach to processes that are executed by the same operating system user.

      Parameters:
      agentLibrary - The agent library.
      processProvider - A provider of the target process id.

    • attachNative

      public static void attachNative(File agentLibrary, ByteBuddyAgent.ProcessProvider processProvider, @MaybeNull String argument)

      Attaches the given agent library on the target process which must be a virtual machine process. The default attachment provider is used for applying the attachment. This operation blocks until the attachment is complete. If the current VM does not supply any known form of attachment to a remote VM, an IllegalStateException is thrown.

      Important: It is only possible to attach to processes that are executed by the same operating system user.

      Parameters:
      agentLibrary - The agent library.
      processProvider - A provider of the target process id.
      argument - The argument to provide to the agent.

    • attachNative

      public static void attachNative(File agentLibrary, ByteBuddyAgent.ProcessProvider processProvider, ByteBuddyAgent.AttachmentProvider attachmentProvider)

      Attaches the given agent library on the target process which must be a virtual machine process. This operation blocks until the attachment is complete. The agent is not provided an argument.

      Important: It is only possible to attach to processes that are executed by the same operating system user.

      Parameters:
      agentLibrary - The agent library.
      processProvider - A provider of the target process id.
      attachmentProvider - The attachment provider to use.

    • attachNative

      public static void attachNative(File agentLibrary, ByteBuddyAgent.ProcessProvider processProvider, @MaybeNull String argument, ByteBuddyAgent.AttachmentProvider attachmentProvider)

      Attaches the given agent library on the target process which must be a virtual machine process. This operation blocks until the attachment is complete.

      Important: It is only possible to attach to processes that are executed by the same operating system user.

      Parameters:
      agentLibrary - The agent library.
      processProvider - A provider of the target process id.
      argument - The argument to provide to the agent.
      attachmentProvider - The attachment provider to use.

    • install

      public static Instrumentation install()

      Installs an agent on the currently running Java virtual machine. Unfortunately, this does not always work. The runtime installation of a Java agent is supported for:

      • JVM version 9+: For Java VM of at least version 9, the attachment API was moved into a module and the runtime installation is possible if the jdk.attach module is available to Byte Buddy which is typically only available for VMs shipped with a JDK.
      • OpenJDK / Oracle JDK / IBM J9 versions 8-: The installation for HotSpot is only possible when bundled with a JDK and requires a tools.jar bundled with the VM which is typically only available for JDK-versions of the JVM.
      • When running Linux and including the optional junixsocket-native-common depedency, Byte Buddy emulates a Unix socket connection to attach to the target VM.

      If an agent cannot be installed, an IllegalStateException is thrown.

      Important: This is a rather computation-heavy operation. Therefore, this operation is not repeated after an agent was successfully installed for the first time. Instead, the previous instrumentation instance is returned. However, invoking this method requires synchronization such that subsequently to an installation, getInstrumentation() should be invoked instead.

      Returns:
      An instrumentation instance representing the currently running JVM.

    • install

      public static Instrumentation install(ByteBuddyAgent.AttachmentProvider attachmentProvider)

      Installs an agent on the currently running Java virtual machine using the supplied attachment provider.

      If an agent cannot be installed, an IllegalStateException is thrown.

      Important: This is a rather computation-heavy operation. Therefore, this operation is not repeated after an agent was successfully installed for the first time. Instead, the previous instrumentation instance is returned. However, invoking this method requires synchronization such that subsequently to an installation, getInstrumentation() should be invoked instead.

      Parameters:
      attachmentProvider - The attachment provider to use for the installation.
      Returns:
      An instrumentation instance representing the currently running JVM.

    • install

      public static Instrumentation install(ByteBuddyAgent.ProcessProvider processProvider)

      Installs an agent on the Java virtual machine resolved by the process provider. Unfortunately, this does not always work. The runtime installation of a Java agent is supported for:

      • JVM version 9+: For Java VM of at least version 9, the attachment API was moved into a module and the runtime installation is possible if the jdk.attach module is available to Byte Buddy which is typically only available for VMs shipped with a JDK.
      • OpenJDK / Oracle JDK / IBM J9 versions 8-: The installation for HotSpot is only possible when bundled with a JDK and requires a tools.jar bundled with the VM which is typically only available for JDK-versions of the JVM.
      • When running Linux and including the optional junixsocket-native-common depedency, Byte Buddy emulates a Unix socket connection to attach to the target VM.

      If an agent cannot be installed, an IllegalStateException is thrown.

      Parameters:
      processProvider - The provider for the current JVM's process id.
      Returns:
      An instrumentation instance representing the currently running JVM.

    • install

      public static Instrumentation install(ByteBuddyAgent.AttachmentProvider attachmentProvider, ByteBuddyAgent.ProcessProvider processProvider)

      Installs an agent on the currently running Java virtual machine using the supplied attachment provider and process provider.

      If an agent cannot be installed, an IllegalStateException is thrown.

      Parameters:
      attachmentProvider - The attachment provider to use for the installation.
      processProvider - The provider for the current JVM's process id.
      Returns:
      An instrumentation instance representing the currently running JVM.

    • install

      private static void install(ByteBuddyAgent.AttachmentProvider attachmentProvider, String processId, @MaybeNull String argument, ByteBuddyAgent.AgentProvider agentProvider, boolean isNative)
      Installs a Java agent on a target VM.
      Parameters:
      attachmentProvider - The attachment provider to use.
      processId - The process id of the target JVM process.
      argument - The argument to provide to the agent.
      agentProvider - The agent provider for the agent jar or library.
      isNative - true if the agent is native.

    • installExternal

      private static void installExternal(ByteBuddyAgent.AttachmentProvider.Accessor.ExternalAttachment externalAttachment, String processId, File agent, boolean isNative, @MaybeNull String argument) throws Exception
      Installs a Java agent to the current VM via an external process. This is typically required starting with OpenJDK 9 when the jdk.attach.allowAttachSelf property is set to false what is the default setting.
      Parameters:
      externalAttachment - A description of the external attachment.
      processId - The process id of the current process.
      agent - The Java agent to install.
      isNative - true if the agent is native.
      argument - The argument to provide to the agent or null if no argument should be supplied.
      Throws:
      Exception - If an exception occurs during the attachment or the external process fails the attachment.

    • trySelfResolve

      @MaybeNull private static File trySelfResolve()
      Attempts to resolve the location of the Attacher class for a self-attachment. Doing so avoids the creation of a temporary jar file.
      Returns:
      The self-resolved jar file or null if the jar file cannot be located.

    • doGetInstrumentation

      @MaybeNull private static Instrumentation doGetInstrumentation()
      Performs the actual lookup of the Instrumentation from an installed Byte Buddy agent and returns the instance, or returns null if not present.
      Returns:
      The Byte Buddy agent's Instrumentation instance.