SpringBoot05 数据操作02 -> JPA接口详解
概览
JpaRepository 继承 PagingAndSortingRepository 继承 CrudRepository 继承 Repository
1 Repository
这是一个空接口,主要是用来指定它的子接口是一个持久层接口
实现了Repository的接口默认就是一个持久层接口,会被容器管理起来;这就是为什么我们自己写的接口继承了JpaRepository后不用添加@Repository的原因
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public interface Repository<T, ID extends Serializable> { }
2 CrudRepository
CrudRepository继承自Repository接口,该接口定义了一些简单的增删改查方法
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/* * Copyright 2008-2011 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 * * 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 org.springframework.data.repository; import java.io.Serializable; /** * Interface for generic CRUD operations on a repository for a specific type. * * @author Oliver Gierke * @author Eberhard Wolff */ @NoRepositoryBean public interface CrudRepository<T, ID extends Serializable> extends Repository<T, ID> { /** * Saves a given entity. Use the returned instance for further operations as the save operation might have changed the * entity instance completely. * * @param entity * @return the saved entity */ <S extends T> S save(S entity); /** * Saves all given entities. * * @param entities * @return the saved entities * @throws IllegalArgumentException in case the given entity is {@literal null}. */ <S extends T> Iterable<S> save(Iterable<S> entities); /** * Retrieves an entity by its id. * * @param id must not be {@literal null}. * @return the entity with the given id or {@literal null} if none found * @throws IllegalArgumentException if {@code id} is {@literal null} */ T findOne(ID id); /** * Returns whether an entity with the given id exists. * * @param id must not be {@literal null}. * @return true if an entity with the given id exists, {@literal false} otherwise * @throws IllegalArgumentException if {@code id} is {@literal null} */ boolean exists(ID id); /** * Returns all instances of the type. * * @return all entities */ Iterable<T> findAll(); /** * Returns all instances of the type with the given IDs. * * @param ids * @return */ Iterable<T> findAll(Iterable<ID> ids); /** * Returns the number of entities available. * * @return the number of entities */ long count(); /** * Deletes the entity with the given id. * * @param id must not be {@literal null}. * @throws IllegalArgumentException in case the given {@code id} is {@literal null} */ void delete(ID id); /** * Deletes a given entity. * * @param entity * @throws IllegalArgumentException in case the given entity is {@literal null}. */ void delete(T entity); /** * Deletes the given entities. * * @param entities * @throws IllegalArgumentException in case the given {@link Iterable} is {@literal null}. */ void delete(Iterable<? extends T> entities); /** * Deletes all entities managed by the repository. */ void deleteAll(); }
3 PagingAndSortingRepository
PagingAndSortingRepository继承自CrudRepository接口,该接口不仅有CrudRepository接口中的增删改查方法,还定义了分页查询方法和排序方法
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/* * Copyright 2008-2010 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 * * 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 org.springframework.data.repository; import java.io.Serializable; import org.springframework.data.domain.Page; import org.springframework.data.domain.Pageable; import org.springframework.data.domain.Sort; /** * Extension of {@link CrudRepository} to provide additional methods to retrieve entities using the pagination and * sorting abstraction. * * @author Oliver Gierke * @see Sort * @see Pageable * @see Page */ @NoRepositoryBean public interface PagingAndSortingRepository<T, ID extends Serializable> extends CrudRepository<T, ID> { /** * Returns all entities sorted by the given options. * * @param sort * @return all entities sorted by the given options */ Iterable<T> findAll(Sort sort); /** * Returns a {@link Page} of entities meeting the paging restriction provided in the {@code Pageable} object. * * @param pageable * @return a page of entities */ Page<T> findAll(Pageable pageable); }
4 JpaRepository
JpaRepository继承自PagingAndSortingRepository接口和QueryByExampleExecutor接口,该接口不仅有PagingAndSortingRepository中的方法还有QueryByExampleExecutor中定义的方法
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// // Source code recreated from a .class file by IntelliJ IDEA // (powered by Fernflower decompiler) // package org.springframework.data.jpa.repository; import java.io.Serializable; import java.util.List; import org.springframework.data.domain.Example; import org.springframework.data.domain.Sort; import org.springframework.data.repository.NoRepositoryBean; import org.springframework.data.repository.PagingAndSortingRepository; import org.springframework.data.repository.query.QueryByExampleExecutor; @NoRepositoryBean public interface JpaRepository<T, ID extends Serializable> extends PagingAndSortingRepository<T, ID>, QueryByExampleExecutor<T> { List<T> findAll(); List<T> findAll(Sort var1); List<T> findAll(Iterable<ID> var1); <S extends T> List<S> save(Iterable<S> var1); void flush(); <S extends T> S saveAndFlush(S var1); void deleteInBatch(Iterable<T> var1); void deleteAllInBatch(); T getOne(ID var1); <S extends T> List<S> findAll(Example<S> var1); <S extends T> List<S> findAll(Example<S> var1, Sort var2); }
1. 定义
JpaRepository接口中实现了一些简单的增删改查功能
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@NoRepositoryBean public interface JpaRepository<T, ID extends Serializable> extends PagingAndSortingRepository<T, ID>, QueryByExampleExecutor<T> { List<T> findAll(); List<T> findAll(Sort var1); List<T> findAll(Iterable<ID> var1); <S extends T> List<S> save(Iterable<S> var1); void flush(); <S extends T> S saveAndFlush(S var1); void deleteInBatch(Iterable<T> var1); void deleteAllInBatch(); T getOne(ID var1); <S extends T> List<S> findAll(Example<S> var1); <S extends T> List<S> findAll(Example<S> var1, Sort var2); }
2 技巧
实现了JpaRepository后的接口会被容器自动进行管理