Spring Data - Spring Data JPA

Spring Data Jpa

最近博主越来越懒了，深知这样不行。还是决定努力奋斗，如此一来，就有了一下一波复习

演示代码都基于Spring Boot + Spring Data JPA

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什么是Spring Data JPA?

Spring Data 是Spring提供的操作数据的框架在Spring data JPA是Spring data的一个模块,通过Spring data 基于jpa标准操作数据的模块。

Spring Data的核心能力，就是基于JPA操作数据，并且可以简化操作持久层的代码。

Spring Data JPA提供的核心接口

Repository:

@org.springframework.stereotype.Repository
public interface UserRepository  extends Repository<User, Integer> {
}

• 提供了方法名成查询方式: 

　　　　方法的名称要遵循 findBy + 属性名（首字母大写） + 查询条件(首字母大写 Is Equals)

 　　　　findByNameLike(String name)

　　　　findByName(String name)

　　　　findByNameAndAge(String name, Integer age)

　　　　findByNameOrAddress(String name) 等...

• 基于@Query注解的查询和更新

 /**
     * SQL nativeQuery的值是true 执行的时候不用再转化
     * @param name
     * @return
     */
    @Query(value = "SELECT * FROM table_user WHERE name = ?1", nativeQuery = true)
    List<User> findByUsernameSQL(String name);

　　//基于HQL

    /**
     * 基于HQL
     * @param name
     * @param id
     * @return
     */
    @Query("Update User set name = ?1 WHERE id = ?2")
    @Modifying
    int updateNameAndId(String name, Integer id);

CrudReposiroty ： 继承了Repository

/*
 * Copyright 2008-2017 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.util.Optional;

/**
 * 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 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 must not be {@literal null}.
     * @return the saved entity will never be {@literal null}.
     */
    <S extends T> S save(S entity);

    /**
     * Saves all given entities.
     * 
     * @param entities must not be {@literal null}.
     * @return the saved entities will never be {@literal null}.
     * @throws IllegalArgumentException in case the given entity is {@literal null}.
     */
    <S extends T> Iterable<S> saveAll(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 Optional#empty()} if none found
     * @throws IllegalArgumentException if {@code id} is {@literal null}.
     */
    Optional<T> findById(ID id);

    /**
     * Returns whether an entity with the given id exists.
     * 
     * @param id must not be {@literal null}.
     * @return {@literal true} if an entity with the given id exists, {@literal false} otherwise.
     * @throws IllegalArgumentException if {@code id} is {@literal null}.
     */
    boolean existsById(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> findAllById(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 deleteById(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 deleteAll(Iterable<? extends T> entities);

    /**
     * Deletes all entities managed by the repository.
     */
    void deleteAll();
}

CrudRepository

Crud主要是添加了对数据的增删改查的方法

PagingAndSortingRepository： 继承了Repository

/*
 * 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 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 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);
}

PagingAndSortingRepository

/**
 * 继承了Repository,缺点只能对所有的数据进行排序或者分页
 */
@Repository
public interface UserPagingAndSortingReposiroty extends PagingAndSortingRepository<User, Integer> {
}

 @Test
    public void TestSort(){
        //定义排序规则
        Sort.Order order = new Sort.Order(Sort.Direction.DESC, "name");
        Sort.Order order1 = new Sort.Order(Sort.Direction.DESC, "id");
        //Sort
        Sort sort = new Sort(order, order1);
        List<User> users = (List<User>)userPagingAndSortingReposiroty.findAll(sort);
        System.out.println(users);
    }

测试排序

-------------------未完待续