Java? ???? Spring Data ?? ?????? ??? ??????? ???? ??

??:
??? ????? ?? ???? ??????? ???? ? ? ?????. ??????? ?????? ???? ?? ?? ??? ???? ?? ??? ????. ?? ???? ?? ??? ????? ?? Spring Data? ??????. Spring Data? ??? ??? ???? ???? ??? ??? ?? ?? ??????? ?? ???? ???? ????????.

? ????? Java? ???? Spring Data ?? ?????? ??? ??????? ???? ??? ?????. MySQL? ??????? ???? Spring Data JPA? ?? ??? ??? ??? ?????.

1??: ?? ?? ??

1. Java JDK ? ?????? MySQL? ???? ?? ?? ??? ?????.

2. ??? Maven ????? ???? ?? ???? ???? Spring Data ? MySQL? ?? ??? ?????. ????? pom.xml ??? ?? ???? ?????.

   <dependencies>
    <!-- Spring Data JPA -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>
    
    <!-- MySQL驅(qū)動 -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.26</version>
    </dependency>
   </dependencies>

3. Spring Boot ?????? ?? ???? ???? ??? ?? ?? ??? ?????.

   @SpringBootApplication
   public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
   }

2??: ?????? ?? ??
Spring Boot?? ?? ?? application.properties?? ??????? ?? ??? ??? ?? ?????.

spring.datasource.url=jdbc:mysql://localhost:3306/testdb
spring.datasource.username=root
spring.datasource.password=root
spring.jpa.database-platform=org.hibernate.dialect.MySQL8Dialect

??? ??????? URL, ??? ??, ????? ???? MySQL8 ??? ???? ???? ?????.

3??: ??? ??? ???
??????? ???? ??? ???? ??? ???? ????. ? ???? ??? ?? id, name, age?? ? ?? ??? ???? User ??? ???? ?????.

@Entity
@Table(name = "user")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    @Column(name = "name")
    private String name;
    
    @Column(name = "age")
    private Integer age;
    
    // getter和setter方法
}

????? JPA ??? ???? ??? ???? ?? ?? ?? ??? ?????.

4??: ??? ??? ????? ??
??????? ?? ??? ???? ?????? ?????. ? ???? ??? ?? Spring Data JPA? CrudRepository ?????? ???? UserRepository ?????? ?????.

public interface UserRepository extends CrudRepository<User, Long> {
    List<User> findByName(String name);
}

????? CrudRepository ?????? ???? ?? ??? ???? ???? ?? ??? ?????.

5??: ??? ?? ??
?????? ??? ???? ???? ??? ??? ??? ???. ? ???? ??? ?? UserService ???? ???? UserRepository? ???? ??? ??? ??? ?????.

@Service
public class UserService {
    @Autowired
    private UserRepository userRepository;
    
    public User save(User user) {
        return userRepository.save(user);
    }
    
    public User findById(Long id) {
        return userRepository.findById(id).orElse(null);
    }
    
    public List<User> findByName(String name) {
        return userRepository.findByName(name);
    }
}

????? Autowired ??? ???? UserRepository? ???? ???? ID ???? ???? ???? ???? ??? ?????. ???? ???? ?? ??? ???? ???? ????.

6??: ?????? ??
?? ???? ?? ????? Spring Boot ??????? ?????.

public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

? ???? ??????? ???? http://localhost:8080? ????? ??????? ???? ? ????.

??:
? ????? Java? ???? Spring Data ?? ?????? ??? ??????? ???? ??? ?????. ??? Spring Data JPA? ???? MySQL ??????? ?? ???? ???? ??? ???, ??? ??? ????? ? ??? ??? ???? ??? ??????. Spring Data? ???? ??? ?? ?? ?? ??? ???? ?? ???? ?? ??? ???? ? ????. ? ??? ??? ??? ????!

? ??? Java? ???? Spring Data ?? ?????? ??? ??????? ???? ??? ?? ?????. ??? ??? PHP ??? ????? ?? ?? ??? ?????!