Spring Boot Jpa

jpa (Java Persistence API) 是 Sun 官方提出的 Java 持久化规范。它为 Java 开发人员提供了一种对象/关联映射工具来管理 Java 应用中的关系数据。它的出现主要是为了简化现有的持久化开发工作和整合 ORM 技术，结束现在 Hibernate，TopLink，JDO 等 ORM 框架各自为营的局面
现在pom.xml 配置下面代码

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>

1. 继承 JpaRepository

package com.wxx.springboot.model;

import org.springframework.data.jpa.repository.JpaRepository;

/**
 * @authorxxw
 */
public interface UserRepository extends JpaRepository<User1,Long> {
    User1 findByUserName(String userName);
    User1 findByUserNameOrEmail(String username, String email);
}

查看里面的默认方法

package org.springframework.data.jpa.repository;

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 PagingAndSortingRepository<T, ID>, QueryByExampleExecutor<T> {
    List<T> findAll();

    List<T> findAll(Sort var1);

    List<T> findAllById(Iterable<ID> var1);

    <S extends T> List<S> saveAll(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);
}

根据方法名生成SQL

  User1 findByUserName(String userName);

分页查询

    @Test
    public void testPageQuery() throws Exception {
        int page=1,size=10;
        Sort sort =  Sort.by("id");
        Pageable pageable = PageRequest.of(page, size, sort);
        userRepository.findALL(pageable);
        userRepository.findByUserName("testName", pageable);
    }

自定义sql 查询

    @Modifying
    @Query("update User u set u.userName = ?1 where u.id = ?2")
    int modifyByIdAndUserId(String  userName, Long id);

    /**
     * @Transactional 对事务的支持，查询超时的设置等
     * @Modifying 删除和修改在需要加
     * @Query 查询注解
     * @param id
     */
    @Transactional
    @Modifying
    @Query("delete from User where id = ?1")
    void deleteByUserId(Long id);

    @Transactional(timeout=10)
    @Query("select u from User u where u.emailAddress = ?1")
    User1 findByEmailAddress(String emailAddress);