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Cassandra support for Spring Data
/*
* Copyright 2020 the original author or authors.
*
* 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
*
* https://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 org.springframework.data.cassandra.core.mapping;
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.meta.When;
import org.springframework.core.annotation.AliasFor;
/**
* The annotation to configure a value object as embedded in the current table.
*
* Depending on the {@link OnEmpty value} of {@link #onEmpty()} the property is set to {@literal null} or an empty
* instance in the case all embedded values are {@literal null} when reading from the result set.
*
* @author Christoph Strobl
* @since 3.0
*/
@Documented
@Retention(value = RetentionPolicy.RUNTIME)
@Target(value = { ElementType.ANNOTATION_TYPE, ElementType.FIELD, ElementType.METHOD })
public @interface Embedded {
/**
* Set the load strategy for the embedded object if all contained fields yield {@literal null} values.
*
* {@link Nullable @Embedded.Nullable} and {@link Empty @Embedded.Empty} offer shortcuts for this.
*
* @return never {@link} null.
*/
OnEmpty onEmpty();
/**
* @return prefix for columns in the embedded value object. An empty {@link String} by default.
*/
String prefix() default "";
/**
* Load strategy to be used {@link Embedded#onEmpty()}.
*
* @author Christoph Strobl
*/
enum OnEmpty {
USE_NULL, USE_EMPTY
}
/**
* Shortcut for a nullable embedded property.
*
*
* @Embedded.Nullable private Address address;
*
*
* as alternative to the more verbose
*
*
* @Embedded(onEmpty = USE_NULL) @javax.annotation.Nonnull(when = When.MAYBE) private Address address;
*
*
* @author Christoph Strobl
* @see Embedded#onEmpty()
*/
@Embedded(onEmpty = OnEmpty.USE_NULL)
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ ElementType.FIELD, ElementType.METHOD })
@javax.annotation.Nonnull(when = When.MAYBE)
@interface Nullable {
/**
* @return prefix for columns in the embedded value object. An empty {@link String} by default.
*/
@AliasFor(annotation = Embedded.class, attribute = "prefix")
String prefix() default "";
/**
* @return value for columns in the embedded value object. An empty {@link String} by default.
*/
@AliasFor(annotation = Embedded.class, attribute = "prefix")
String value() default "";
}
/**
* Shortcut for an empty embedded property.
*
*
* @Embedded.Empty private Address address;
*
*
* as alternative to the more verbose
*
*
* @Embedded(onEmpty = USE_EMPTY) @javax.annotation.Nonnull(when = When.NEVER) private Address address;
*
*
* @author Christoph Strobl
* @see Embedded#onEmpty()
*/
@Embedded(onEmpty = OnEmpty.USE_EMPTY)
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ ElementType.FIELD, ElementType.METHOD })
@javax.annotation.Nonnull(when = When.NEVER)
@interface Empty {
/**
* @return prefix for columns in the embedded value object. An empty {@link String} by default.
*/
@AliasFor(annotation = Embedded.class, attribute = "prefix")
String prefix() default "";
/**
* @return value for columns in the embedded value object. An empty {@link String} by default.
*/
@AliasFor(annotation = Embedded.class, attribute = "prefix")
String value() default "";
}
}