Update.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 androidx.room;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
/**
* Marks a method in a {@link Dao} annotated class as an update method.
* <p>
* The implementation of the method will update its parameters in the database if they already
* exists (checked by primary keys). If they don't already exists, this option will not change the
* database.
* <p>
* All of the parameters of the Update method must either be classes annotated with {@link Entity}
* or collections/array of it.
* <p>
* Example:
* <pre>
* {@literal @}Dao
* public interface MusicDao {
* {@literal @}Update
* public void updateSong(Song);
*
* {@literal @}Update
* public int updateSongs(List<Song> songs);
* }
* </pre>
* If the target entity is specified via {@link #entity()} then the parameters can be of arbitrary
* POJO types that will be interpreted as partial entities. For example:
* <pre>
* {@literal @}Entity
* public class Playlist {
* {@literal @}PrimaryKey(autoGenerate = true)
* long playlistId;
* String name;
* {@literal @}ColumnInfo(defaultValue = "")
* String description
* {@literal @}ColumnInfo(defaultValue = "normal")
* String category;
* {@literal @}ColumnInfo(defaultValue = "CURRENT_TIMESTAMP")
* String createdTime;
* {@literal @}ColumnInfo(defaultValue = "CURRENT_TIMESTAMP")
* String lastModifiedTime;
* }
*
* public class PlaylistCategory {
* long playlistId;
* String category;
* String lastModifiedTime
* }
*
* {@literal @}Dao
* public interface PlaylistDao {
* {@literal @}Update(entity = Playlist.class)
* public void updateCategory(PlaylistCategory... category);
* }
* </pre>
*
* @see Insert
* @see Delete
*/
@Retention(RetentionPolicy.CLASS)
public @interface Update {
/**
* The target entity of the update method.
* <p>
* When this is declared, the update method parameters are interpreted as partial entities when
* the type of the parameter differs from the target. The POJO class that represents the entity
* must contain a subset of the fields of the target entity along with its primary keys.
* <p>
* Only the columns represented by the partial entity fields will be updated if an entity with
* equal primary key is found.
* <p>
* By default the target entity is interpreted by the method parameters.
*
* @return the target entity of the update method or none if the method should use the
* parameter type entities.
*/
Class<?> entity() default Object.class;
/**
* What to do if a conflict happens.
* <p>
* Use {@link OnConflictStrategy#ABORT} (default) to roll back the transaction on conflict.
* Use {@link OnConflictStrategy#REPLACE} to replace the existing rows with the new rows.
* Use {@link OnConflictStrategy#IGNORE} to keep the existing rows.
*
* @return How to handle conflicts. Defaults to {@link OnConflictStrategy#ABORT}.
*/
@OnConflictStrategy
int onConflict() default OnConflictStrategy.ABORT;
}