SpringBoot2.3整合Spring Data JPA实现基本操作

Spring Data JPA是Spring基于ORM框架、JPA规范的基础上封装的一套JPA应用框架，可以使开发者用极简的代码即可对数据库的访问合操作，它提供了包括增删改查等在内的常用功能，且易于扩展、提高开发效率。

    org.springframework.boot
    spring-boot-starter-web


    org.springframework.boot
    spring-boot-starter-data-jpa


    mysql
    mysql-connector-java

server:
  port: 8105
spring:
  application:
    name: springboot-jpa
  datasource:
    #type: com.zaxxer.hikari.HikariDataSource
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://xx.xx.xx.xx:3306/springboot?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&useSSL=true&serverTimezone=GMT%2B8
    username: 用户名
    password: 密码
    hikari:
      minimum-idle: 10 #最小空闲连接，默认10
      maximum-pool-size: 20 #最大连接数
      idle-timeout: 600000 #空闲连接超时时间，默认600000(10分钟)
      max-lifetime: 540000 #连接最大存活时间，默认30分钟
      connection-timeout: 60000 #连接超时时间，默认30秒
      connection-test-query: SELECt 1 #测试连接是否可用查询语句
  jpa:
    hibernate:
      ddl-auto: update #数据库表生成策略
    database-platform: org.hibernate.dialect.MySQL5InnoDBDialect
    show-sql: true #控制台显示sql语句
    database: mysql
  jackson:
    date-format: yyyy-MM-dd HH:mm:ss
    time-zone: GMT+8

@Repository
public interface SysUserRepository extends JpaRepository, JpaSpecificationExecutor {

    @Query(value = "from sys_user user where user.userName = ?1")
    SysUser findUserByUserName(String userName);

    @Query(value = "update sys_user set userName = ?2 where id = ?1")
    @Modifying
    int updateUserById(Long id, String userName);

    @Query(value = "select * from sys_user where user_code = :userCode", nativeQuery = true)
    SysUser findUserByUserCode(String userCode);
}

说明：JpaRepository接口用于实现基本增删改查操作，JpaSpecificationExecutor接口用于实现复杂查询(分页查询)
Spring Data JPA可以使用接口定义的方式查询，也支持JPQL方式和SQL语句查询

public interface SysUserService {

    
    SysUser insertUser(SysUser user);

    
    SysUser updateUser(SysUser user);

    
    SysUser selectUserById(Long id);

    
    Optional findById(Long id);

    
    List findAll();

    
    void deleteById(Long id);

    
    SysUser findUserByUserName(String userName);

    
    SysUser findUserByUserCode(String userCode);

    
    int updateUserById(Long id, String userName);

    
    List selectUserBySpecification(String userName);

    
    Page selectPageUserBySpecification(int pageNum, int pageSize, String userName);
}

@Service
public class SysUserServiceImpl implements SysUserService {

    @Autowired
    private SysUserRepository userRepository;

    @Override
    public SysUser insertUser(SysUser user) {
        return userRepository.save(user);
    }

    @Override
    public SysUser updateUser(SysUser user) {
        return userRepository.save(user);
    }

    @Override
    public SysUser selectUserById(Long id) {
        return userRepository.getOne(id);
    }

    @Override
    public Optional findById(Long id) {
        return userRepository.findById(id);
    }

    @Override
    public List findAll() {
        return userRepository.findAll();
    }

    @Override
    public void deleteById(Long id) {
        userRepository.deleteById(id);
    }

    @Override
    public SysUser findUserByUserName(String userName) {
        return userRepository.findUserByUserName(userName);
    }

    @Override
    public SysUser findUserByUserCode(String userCode) {
        return userRepository.findUserByUserCode(userCode);
    }

    @Override
    @Transactional(rollbackFor = Exception.class)
    public int updateUserById(Long id, String userName) {
        return userRepository.updateUserById(id, userName);
    }

    @Override
    public List selectUserBySpecification(String userName) {
        Specification specification = new Specification() {
            @Override
            public Predicate toPredicate(Root root, CriteriaQuery criteriaQuery, CriteriaBuilder criteriaBuilder) {
                return criteriaBuilder.like(root.get("userName").as(String.class), "%" + userName + "%");
            }
        };
        return userRepository.findAll(specification);
    }

    @Override
    public Page selectPageUserBySpecification(int pageNum, int pageSize, String userName) {
        Specification specification = new Specification() {
            @Override
            public Predicate toPredicate(Root root, CriteriaQuery criteriaQuery, CriteriaBuilder criteriaBuilder) {
                List predicateList = new ArrayList<>();
                if (StringUtils.hasLength(userName)) {
                    predicateList.add(criteriaBuilder.like(root.get("userName").as(String.class), "%" + userName + "%"));
                }
                return criteriaBuilder.and(predicateList.toArray(new Predicate[predicateList.size()]));
            }
        };
        Pageable pageable = PageRequest.of(pageNum, pageSize);
        return userRepository.findAll(specification, pageable);
    }
}

只需要按照Spring Data JPA提供的方法命名规则定义方法的名称，就可以完成查询工作。Spring Data JPA在程序执行的时候会根据方法名称进行解析，并自动生成查询语句进行查询。