android/arch/persistence/room/Transaction.java

/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * 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 android.arch.persistence.room;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * Marks a method in an abstract {@link Dao} class as a transaction method.
 * <p>
 * The derived implementation of the method will execute the super method in a database transaction.
 * All the parameters and return types are preserved. The transaction will be marked as successful
 * unless an exception is thrown in the method body.
 * <p>
 * Example:
 * <pre>
 * {@literal @}Dao
 * public abstract class ProductDao {
 *    {@literal @}Insert
 *     public abstract void insert(Product product);
 *    {@literal @}Delete
 *     public abstract void delete(Product product);
 *    {@literal @}Transaction
 *     public void insertAndDeleteInTransaction(Product newProduct, Product oldProduct) {
 *         // Anything inside this method runs in a single transaction.
 *         insert(newProduct);
 *         delete(oldProduct);
 *     }
 * }
 * </pre>
 */
@Target({ElementType.METHOD})
@Retention(RetentionPolicy.CLASS)
public @interface Transaction {
}