Spring Boot – Integrate JPA

JPA introduction

JPA (Java Persistence API)

Integrate JPA

Jap rely on

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
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Of course, you need to add spring-boot-starter-JDBC and mysql-connector-Java database dependencies

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <scope>runtime</scope>
</dependency>
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The core concept

The core interface of JPA is Repository. The Repository interface has two generic parameters

, where T is the entity object we need to operate on, and ID is the unique primary key field of our database entity object. In JPA, Interface CrudRepository inherits the Repository interface to provide us with sophisticated CRUD capabilities.
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The next code is CrudRepository

@NoRepositoryBean
public interface CrudRepository<T.ID> extends Repository<T.ID> {
    <S extends T> S save(S var1);

    <S extends T> Iterable<S> saveAll(Iterable<S> var1);

    Optional<T> findById(ID var1);

    boolean existsById(ID var1);

    Iterable<T> findAll(a);

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

    long count(a);

    void deleteById(ID var1);

    void delete(T var1);

    void deleteAll(Iterable<? extends T> var1);

    void deleteAll(a);
}
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On the basis of interface CrudRepository, JPA provides PagingAndSortingRepository interface are used to implement sorting and paging.

@NoRepositoryBean
public interface PagingAndSortingRepository<T.ID> extends CrudRepository<T.ID> {
    Iterable<T> findAll(Sort var1);

    Page<T> findAll(Pageable var1);
}
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Query data where page = 1 and pageSize = 20

 repository.findAll(PageRequest.of(1.20));
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Jpa provides us with JpaRepository, an interface we can rely on directly when using Jpa for database operations.

@NoRepositoryBean
public interface JpaRepository<T.ID> extends PagingAndSortingRepository<T.ID>, QueryByExampleExecutor<T> {
    List<T> findAll(a);

    List<T> findAll(Sort var1);

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

    <S extends T> List<S> saveAll(Iterable<S> var1);

    void flush(a);

    <S extends T> S saveAndFlush(S var1);

    void deleteInBatch(Iterable<T> var1);

    void deleteAllInBatch(a);

    T getOne(ID var1);

    <S extends T> List<S> findAll(Example<S> var1);

    <S extends T> List<S> findAll(Example<S> var1, Sort var2);
}
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The actual operation

Define the Entity

Create s_user table

CREATE TABLE `s_user` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `user_name` varchar(30) NOT NULL COMMENT 'Username'.`password` varchar(50) NOT NULL COMMENT 'password'.`real_name` varchar(30) NOT NULL COMMENT 'User real name'.`mnemonic_code` varchar(30) DEFAULT NULL COMMENT 'mnemonic code'.`sex` varchar(30) DEFAULT NULL COMMENT 'Sex 0 male 1 female'.`created_by` int(11) DEFAULT NULL COMMENT 'Founder'.`created_time` datetime(6) DEFAULT NULL COMMENT 'Creation time'.`last_modified_by` int(11) DEFAULT NULL COMMENT 'Update person'.`last_modified_time` datetime(6) DEFAULT NULL COMMENT 'Update Time',
  PRIMARY KEY (`id`))ENGINE=InnoDB DEFAULT CHARSET=utf8;
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Entity

@Data
@Entity
@Table(name = "s_user")
public class SUser {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;
    @Column(name = "user_name")
    private String userName;
    @Column(name = "pass_word")
    private String passWord;
    @Column(name = "real_name")
    private String realName;
    @Column(name = "mnemonic_code")
    private String mnemonicCode;
    @Column(name = "sex")
    private String sex;
    @Column(name = "created_by")
    private Integer createdBy;
    @Column(name = "created_time",updatable = false)
    private Date createdTime;
    @Column(name = "last_modified_by")
    private Integer lastModifiedBy;
    @Column(name = "last_modified_time")
    private Date lastModifiedTime;
}
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Commonly used annotations in Entity

@IdIndicates that this field is the database primary key

@GeneratedValueIndicates the primary key value generation policy

@CloumnField notes

• nameThe field name
• uniqueWhether or not the only
• nullableWhether is empty
• lengthThe length of the
• columnDefinitionColumn definitions such as TEXT

Repository

@Repository
public interface UserRepository extends JpaRepository<SUser.Integer> {}Copy the code