Cache JNI jClass jfieldID lookups

.gitignore

@@ -21,4 +21,7 @@ dependency-reduced-pom.xml
 .gradle
 .settings
 .classpath
-.project
+.project
+
+# OSX
+.DS_Store

aws-lambda-java-runtime-interface-client/src/main/jni/Dockerfile.glibc

@@ -69,4 +69,5 @@ RUN /usr/bin/c++ -c \
         -laws-lambda-runtime \
         -lcurl \
         -static-libstdc++ \
-        -lrt
+        -lrt \
+        -O2

aws-lambda-java-runtime-interface-client/src/main/jni/Dockerfile.musl

@@ -58,4 +58,5 @@ RUN /usr/bin/c++ -c \
         -laws-lambda-runtime \
         -lcurl \
         -static-libstdc++ \
-        -static-libgcc
+        -static-libgcc \
+        -O2

aws-lambda-java-runtime-interface-client/src/main/jni/com_amazonaws_services_lambda_runtime_api_client_runtimeapi_NativeClient.cpp

@@ -24,6 +24,48 @@
 
 static aws::lambda_runtime::runtime * CLIENT = nullptr;
 
+static jint JNI_VERSION = JNI_VERSION_1_8;
+
+static jclass invocationRequestClass;
+static jfieldID invokedFunctionArnField;
+static jfieldID deadlineTimeInMsField;
+static jfieldID idField;
+static jfieldID contentField;
+static jfieldID clientContextField;
+static jfieldID cognitoIdentityField;
+static jfieldID xrayTraceIdField;
+
+
+jint JNI_OnLoad(JavaVM* vm, void* reserved) {
+
+    JNIEnv* env;
+    if (vm->GetEnv(reinterpret_cast<void**>(&env), JNI_VERSION) != JNI_OK) {
+        return JNI_ERR;
+    }
+
+    jclass tempInvocationRequestClassRef;
+    tempInvocationRequestClassRef = env->FindClass("com/amazonaws/services/lambda/runtime/api/client/runtimeapi/InvocationRequest");
+    invocationRequestClass = (jclass) env->NewGlobalRef(tempInvocationRequestClassRef);
+    env->DeleteLocalRef(tempInvocationRequestClassRef);
+
+    idField = env->GetFieldID(invocationRequestClass , "id", "Ljava/lang/String;");
+    invokedFunctionArnField = env->GetFieldID(invocationRequestClass , "invokedFunctionArn", "Ljava/lang/String;");
+    deadlineTimeInMsField = env->GetFieldID(invocationRequestClass , "deadlineTimeInMs", "J");
+    contentField = env->GetFieldID(invocationRequestClass , "content", "[B");
+    xrayTraceIdField = env->GetFieldID(invocationRequestClass , "xrayTraceId", "Ljava/lang/String;");
+    clientContextField = env->GetFieldID(invocationRequestClass , "clientContext", "Ljava/lang/String;");
+    cognitoIdentityField = env->GetFieldID(invocationRequestClass , "cognitoIdentity", "Ljava/lang/String;");
+
+    return JNI_VERSION;
+}
+
+void JNI_OnUnload(JavaVM *vm, void *reserved) {
+    JNIEnv* env;
+    vm->GetEnv(reinterpret_cast<void**>(&env), JNI_VERSION);
+
+    env->DeleteGlobalRef(invocationRequestClass);
+}
+
 static void throwLambdaRuntimeClientException(JNIEnv *env, std::string message, aws::http::response_code responseCode){
   jclass lambdaRuntimeExceptionClass = env->FindClass("com/amazonaws/services/lambda/runtime/api/client/runtimeapi/LambdaRuntimeClientException");
   jstring jMessage = env->NewStringUTF(message.c_str());
@@ -56,50 +98,31 @@ JNIEXPORT jobject JNICALL Java_com_amazonaws_services_lambda_runtime_api_client_
     return NULL;
   }
 
-  jclass invocationRequestClass;
-  jfieldID invokedFunctionArnField;
-  jfieldID deadlineTimeInMsField;
-  jfieldID xrayTraceIdField;
-  jfieldID idField; 
   jobject invocationRequest;
-  jfieldID clientContextField;
-  jfieldID cognitoIdentityField;
   jbyteArray jArray;
   const jbyte* bytes;
-  jfieldID contentField;
   auto response = outcome.get_result();
 
-  CHECK_EXCEPTION(env, invocationRequestClass = env->FindClass("com/amazonaws/services/lambda/runtime/api/client/runtimeapi/InvocationRequest"));
   CHECK_EXCEPTION(env, invocationRequest = env->AllocObject(invocationRequestClass));
-
-  CHECK_EXCEPTION(env, idField = env->GetFieldID(invocationRequestClass , "id", "Ljava/lang/String;"));
   CHECK_EXCEPTION(env, env->SetObjectField(invocationRequest, idField, env->NewStringUTF(response.request_id.c_str())));
-
-  CHECK_EXCEPTION(env, invokedFunctionArnField = env->GetFieldID(invocationRequestClass , "invokedFunctionArn", "Ljava/lang/String;"));
   CHECK_EXCEPTION(env, env->SetObjectField(invocationRequest, invokedFunctionArnField, env->NewStringUTF(response.function_arn.c_str())));
-
-  CHECK_EXCEPTION(env, deadlineTimeInMsField = env->GetFieldID(invocationRequestClass , "deadlineTimeInMs", "J"));
   CHECK_EXCEPTION(env, env->SetLongField(invocationRequest, deadlineTimeInMsField, std::chrono::duration_cast<std::chrono::milliseconds>(response.deadline.time_since_epoch()).count()));
 
   if(response.xray_trace_id != ""){
-    CHECK_EXCEPTION(env, xrayTraceIdField = env->GetFieldID(invocationRequestClass , "xrayTraceId", "Ljava/lang/String;"));
     CHECK_EXCEPTION(env, env->SetObjectField(invocationRequest, xrayTraceIdField, env->NewStringUTF(response.xray_trace_id.c_str())));
   }
 
   if(response.client_context != ""){
-    CHECK_EXCEPTION(env, clientContextField = env->GetFieldID(invocationRequestClass , "clientContext", "Ljava/lang/String;"));
     CHECK_EXCEPTION(env, env->SetObjectField(invocationRequest, clientContextField, env->NewStringUTF(response.client_context.c_str())));
   }
 
   if(response.cognito_identity != ""){
-    CHECK_EXCEPTION(env, cognitoIdentityField = env->GetFieldID(invocationRequestClass , "cognitoIdentity", "Ljava/lang/String;"));
     CHECK_EXCEPTION(env, env->SetObjectField(invocationRequest, cognitoIdentityField, env->NewStringUTF(response.cognito_identity.c_str())));
   }
 
   bytes = reinterpret_cast<const jbyte*>(response.payload.c_str());
   CHECK_EXCEPTION(env, jArray = env->NewByteArray(response.payload.length()));
   CHECK_EXCEPTION(env, env->SetByteArrayRegion(jArray, 0, response.payload.length(), bytes));
-  CHECK_EXCEPTION(env, contentField = env->GetFieldID(invocationRequestClass , "content", "[B"));
   CHECK_EXCEPTION(env, env->SetObjectField(invocationRequest, contentField, jArray));
 
   return invocationRequest;