add annotation

Signed-off-by: Stephen Crawford <steecraw@amazon.com>

libs/common/src/main/java/org/opensearch/common/NotNull.java

@@ -0,0 +1,32 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.common;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+import javax.annotation.Nonnull;
+import javax.annotation.meta.TypeQualifierNickname;
+
+/**
+ * The presence of this annotation on a method indicates that
+ * {@code null} will not be returned from that method.
+ *
+ * @opensearch.api
+ */
+@Documented
+@TypeQualifierNickname
+@Nonnull
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ ElementType.METHOD })
+public @interface NotNull {
+}
+

server/build.gradle

@@ -92,6 +92,8 @@ dependencies {
   api project(':libs:opensearch-secure-sm')
   api project(':libs:opensearch-x-content')
   api project(":libs:opensearch-geo")
+    implementation 'org.jetbrains:annotations:23.0.0'
+  implementation 'org.jetbrains:annotations:23.0.0'
 
   compileOnly project(':libs:opensearch-plugin-classloader')
   testRuntimeOnly project(':libs:opensearch-plugin-classloader')

server/src/main/java/org/opensearch/plugins/IdentityPlugin.java

@@ -8,7 +8,7 @@
 
 package org.opensearch.plugins;
 
-import org.opensearch.common.Nullable;
+import org.opensearch.common.NotNull;
 import org.opensearch.identity.Subject;
 
 /**
@@ -21,6 +21,6 @@ public interface IdentityPlugin {
     /**
      * Get the current subject
      * */
-    @Nullable
+    @NotNull
     public Subject getSubject();
 }