com.oracle.svm.jvmtiagentbase

Class JNIHandleSet

java.lang.Object

com.oracle.svm.jvmtiagentbase.JNIHandleSet

public abstract class JNIHandleSet
extends Object

Helps with creation and management of JNI handles for JVMTI agents. A JVMTI agent must provide either this class or a subclass of this class. It should contain handles to classes and methods that are needed across different JVMTI calls (for example, a JNIObjectHandle to java/lang/Class). For JNI handles that are created in a JVMTI callback and that should survive a return from native code, a helper method JNIHandleSet.newTrackedGlobalRef(com.oracle.svm.jni.nativeapi.JNIEnvironment, com.oracle.svm.jni.nativeapi.JNIObjectHandle) is provided.

See Also:

JvmtiAgentBase

Constructor Summary

Constructors

Constructor and Description
JNIHandleSet(com.oracle.svm.jni.nativeapi.JNIEnvironment env)

Method Summary

Modifier and Type	Method and Description
com.oracle.svm.jni.nativeapi.JNIObjectHandle	findClass(com.oracle.svm.jni.nativeapi.JNIEnvironment env, String className) Returns a local handle to a Java class object.
com.oracle.svm.jni.nativeapi.JNIMethodId	getMethodId(com.oracle.svm.jni.nativeapi.JNIEnvironment env, com.oracle.svm.jni.nativeapi.JNIObjectHandle clazz, String name, String signature, boolean isStatic) Returns a JNI method ID of a Java method.
com.oracle.svm.jni.nativeapi.JNIMethodId	getMethodIdOptional(com.oracle.svm.jni.nativeapi.JNIEnvironment env, com.oracle.svm.jni.nativeapi.JNIObjectHandle clazz, String name, String signature, boolean isStatic) Returns a JNI method ID of a Java method.
com.oracle.svm.jni.nativeapi.JNIObjectHandle	newClassGlobalRef(com.oracle.svm.jni.nativeapi.JNIEnvironment env, String className) A convenience method to return a global handle to a Java class object.
com.oracle.svm.jni.nativeapi.JNIObjectHandle	newTrackedGlobalRef(com.oracle.svm.jni.nativeapi.JNIEnvironment env, com.oracle.svm.jni.nativeapi.JNIObjectHandle ref) Creates a global JNI handle of the specified local JNI handle.

Methods inherited from class java.lang.Object

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

Constructor Detail

JNIHandleSet

public JNIHandleSet(com.oracle.svm.jni.nativeapi.JNIEnvironment env)

Method Detail

findClass

public com.oracle.svm.jni.nativeapi.JNIObjectHandle findClass(com.oracle.svm.jni.nativeapi.JNIEnvironment env,
                                                              String className)

Returns a local handle to a Java class object. The class must exist. If not found, the VM terminates.

Parameters:

env - JNI environment of the thread running the JVMTI callback.

className - The VM type signature of the class.

Returns:

Local JNI handle representing the class object.

newClassGlobalRef

public com.oracle.svm.jni.nativeapi.JNIObjectHandle newClassGlobalRef(com.oracle.svm.jni.nativeapi.JNIEnvironment env,
                                                                      String className)

A convenience method to return a global handle to a Java class object. The handle will be tracked and freed with a call to JNIHandleSet.destroy(com.oracle.svm.jni.nativeapi.JNIEnvironment). The reference must not be freed manually. The class must exist. If not found, the VM terminates.

Parameters:

env - JNI environment of the thread running the JVMTI callback.

className - Java VM type signature of the class.

Returns:

Global JNI handle representing the class object.

See Also:

JNIHandleSet.newTrackedGlobalRef(com.oracle.svm.jni.nativeapi.JNIEnvironment, com.oracle.svm.jni.nativeapi.JNIObjectHandle)

getMethodId

public com.oracle.svm.jni.nativeapi.JNIMethodId getMethodId(com.oracle.svm.jni.nativeapi.JNIEnvironment env,
                                                            com.oracle.svm.jni.nativeapi.JNIObjectHandle clazz,
                                                            String name,
                                                            String signature,
                                                            boolean isStatic)

Returns a JNI method ID of a Java method. The method must exist. If not found, the VM terminates.

Parameters:

env - JNI environment of the thread running the JVMTI callback.

clazz - Handle to the class containing the method.

name - Name of the method.

signature - Signature of the method. See the JNI specification for more details.

isStatic - Specifies whether the method is static or not.

Returns:

JNI method ID of the Java method.

getMethodIdOptional

public com.oracle.svm.jni.nativeapi.JNIMethodId getMethodIdOptional(com.oracle.svm.jni.nativeapi.JNIEnvironment env,
                                                                    com.oracle.svm.jni.nativeapi.JNIObjectHandle clazz,
                                                                    String name,
                                                                    String signature,
                                                                    boolean isStatic)

Returns a JNI method ID of a Java method. If the method is not found, returns a JNIObjectHandles.nullHandle().

Parameters:

env - JNI environment of the thread running the JVMTI callback.

clazz - Handle to the class containing the method.

name - Name of the method.

signature - Signature of the method. See the JNI specification for more details.

isStatic - Specifies whether the method is static or not.

Returns:

JNI method ID of the Java method if found, JNIObjectHandles.nullHandle() otherwise.

newTrackedGlobalRef

public com.oracle.svm.jni.nativeapi.JNIObjectHandle newTrackedGlobalRef(com.oracle.svm.jni.nativeapi.JNIEnvironment env,
                                                                        com.oracle.svm.jni.nativeapi.JNIObjectHandle ref)

Creates a global JNI handle of the specified local JNI handle. The handle will be tracked and freed with a call to JNIHandleSet.destroy(com.oracle.svm.jni.nativeapi.JNIEnvironment). The handle must not be freed manually. If the specified handle is a JNIObjectHandles.nullHandle() the VM terminates.

Parameters:

env - JNI environment of the thread running the JVMTI callback.

ref - A local JNI object handle.

Returns:

A global JNI object handle.