菜鸟学Spring Boot——简单到令人发指的CRUD

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/liushuijinger/article/details/83063010

前情提要

上回书说到，用Spring Boot写了一个Hello World小例子，那么今天就来完成上篇结尾留下的增删改查的实例。

软件环境

• Windows 10
• JDK 11
• IDEA 2018.2
• Maven 3.5.4
• MySQL 8.0.12

代码

pom文件中需要添加一下依赖：

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
	<groupId>mysql</groupId>
	<artifactId>mysql-connector-java</artifactId>
	<version>8.0.12</version>
</dependency>
<dependency>
	<groupId>org.javassist</groupId>
	<artifactId>javassist</artifactId>
	<version>3.23.1-GA</version>
</dependency>
<dependency>
	<groupId>org.projectlombok</groupId>
	<artifactId>lombok</artifactId>
</dependency>

yml文件：

server:
  port: 8080
  servlet:
    path: /hello

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/helloboot?serverTimezone=Asia/Shanghai&allowPublicKeyRetrieval=true&useSSL=false
    username: root
    password: root
  jpa:
    show-sql: true

Controller：

@RestController()
public class UserController {

    @Autowired
    private UserRepository userRepository;

    @PostMapping("/user")
    public User save(User user) {
        return userRepository.save(user);
    }

    @PutMapping("/user")
    public User update(User user) {
        return userRepository.save(user);
    }

    @GetMapping("/user/{id}")
    public User findById(@PathVariable("id") Integer id) {
        return userRepository.findById(id).get();
    }

    @DeleteMapping("/user/{id}")
    public void delete(@PathVariable("id") Integer id) {
        userRepository.deleteById(id);
    }
}

由于过于简单，就省去Service层了。

Dao层：

public interface UserRepository extends JpaRepository<User, Integer> {
}

Dao层简单到令人发指！完成一个基本的CRUD只需要定义一个接口，不需要写任何实现和SQL。

实体

@Entity
@Data
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;
    private String name;
    private Integer age;
}

如果想要实现更多功能，依然简单到爆炸，只需要按照下表的规则，就能实现各种查询操作，不需要写任何实现和SQL。
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内置关键字：

Keyword	Sample	JPQL snippet
And	findByLastnameAndFirstname	… where x.lastname = ?1 and x.firstname = ?2
Or	findByLastnameOrFirstname	… where x.lastname = ?1 or x.firstname = ?2
Is,Equals	findByFirstname,findByFirstnameIs,findByFirstnameEquals	… where x.firstname = ?1
Between	findByStartDateBetween	… where x.startDate between ?1 and ?2
LessThan	findByAgeLessThan	… where x.age < ?1
LessThanEqual	findByAgeLessThanEqual	… where x.age <= ?1
GreaterThan	findByAgeGreaterThan	… where x.age > ?1
GreaterThanEqual	findByAgeGreaterThanEqual	… where x.age >= ?1
After	findByStartDateAfter	… where x.startDate > ?1
Before	findByStartDateBefore	… where x.startDate < ?1
IsNull	findByAgeIsNull	… where x.age is null
IsNotNull,NotNull	findByAge(Is)NotNull	… where x.age not null
Like	findByFirstnameLike	… where x.firstname like ?1
NotLike	findByFirstnameNotLike	… where x.firstname not like ?1
StartingWith	findByFirstnameStartingWith	… where x.firstname like ?1 (parameter bound with appended %)
EndingWith	findByFirstnameEndingWith	… where x.firstname like ?1 (parameter bound with prepended %)
Containing	findByFirstnameContaining	… where x.firstname like ?1 (parameter bound wrapped in %)
OrderBy	findByAgeOrderByLastnameDesc	… where x.age = ?1 order by x.lastname desc
Not	findByLastnameNot	… where x.lastname <> ?1
In	findByAgeIn(Collection ages)	… where x.age in ?1
NotIn	findByAgeNotIn(Collection ages)	… where x.age not in ?1
True	findByActiveTrue()	… where x.active = true
False	findByActiveFalse()	… where x.active = false
IgnoreCase	findByFirstnameIgnoreCase	… where UPPER(x.firstame) = UPPER(?1)