Java Language Tutorial => Example of initialization inside of...

Example

/* Callback for JVMTI_EVENT_VM_INIT */
static void JNICALL vm_init(jvmtiEnv* jvmti, JNIEnv* env, jthread thread)
{
    jint runtime_version;
    jvmti->GetVersionNumber(&runtime_version);
    stdout_message("JVMTI Version: %d\n", runtime_verision);
}

/* Agent_OnLoad() is called first, we prepare for a VM_INIT event here. */
JNIEXPORT jint JNICALL
Agent_OnLoad(JavaVM* vm, char* options, void* reserved)
{
    jint rc;
    jvmtiEventCallbacks callbacks;
    jvmtiCapabilities capabilities;
    jvmtiEnv* jvmti;

    /* Get JVMTI environment */
    rc = vm->GetEnv(reinterpret_cast<void **>(&jvmti), JVMTI_VERSION);
    if (rc != JNI_OK)
    {
        return -1;
    }

    /* Immediately after getting the jvmtiEnv* we need to ask for the
    *  capabilities this agent will need.
    */
    jvmti->GetCapabilities(&capabilities);
    capabilities.can_tag_objects = 1;
    jvmti->AddCapabilities(&capabilities);
    
    /* Set callbacks and enable event notifications */
    memset(&callbacks, 0, sizeof(callbacks));
    callbacks.VMInit = &vm_init;

    jvmti->SetEventCallbacks(&callbacks, sizeof(callbacks));
    jvmti->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_VM_INIT, nullptr);

    return JNI_OK;
}

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Java Language JVM Tool Interface Example of initialization inside of Agent_OnLoad method

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