com.mongodb.lang.Nullable Maven / Gradle / Ivy

/*
 * Copyright 2008-present MongoDB, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.mongodb.lang;

import javax.annotation.Nonnull;
import javax.annotation.meta.TypeQualifierNickname;
import javax.annotation.meta.When;
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;

/**
 * A common annotation to declare that annotated elements can be {@code null} under some circumstance. Leverages JSR 305 meta-annotations to
 * indicate nullability in Java to common tools with JSR 305 support and used by Kotlin to infer nullability of Spring API.
 *
 * Should be used at parameter, return value, and field level. Methods override should repeat parent {@code @Nullable} annotations
 * unless they behave differently.
 *
 * Can be used in association with {@code NonNullApi} to override the default non-nullable semantic to nullable.
 *
 * @see NonNullApi
 * @see NonNull
 * @since 3.7
 */
@Target({ElementType.METHOD, ElementType.PARAMETER, ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Nonnull(when = When.MAYBE)
@TypeQualifierNickname
public @interface Nullable {
}