SpringDataJPA 入门教程

Updated Time 2024-05-22
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SpringData JPA

项目介绍

环境准备

Application.yml

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/database
    username: MYSQL_USER
    password: MYSQL_PWD
    driver-class-name: com.mysql.cj.jdbc.Driver
  jpa:
    hibernate:
      ddl-auto: create-drop
    show-sql: true
    properties:
      hibernate:
        dialect: org.hibernate.community.dialect.MySQLDialect
        format_sql: true
spring:
  datasource:
    url: jdbc:postgresql://localhost:5432/postgres
    username: postgres
    password: your_password
    driver-class-name: org.postgresql.Driver
  jpa:
    hibernate:
      ddl-auto: create-drop
    show-sql: true
    properties:
      hibernate:
        dialect: org.hibernate.community.dialect.SQLiteDialect
        format_sql: true
spring:
  datasource:
    url: DB_PATH
    driver-class-name: com.p6spy.engine.spy.P6SpyDriver
  jpa:
    hibernate:
      ddl-auto: create-drop
    show-sql: true
    properties:
      hibernate:
        dialect: org.hibernate.community.dialect.SQLiteDialect
        format_sql: true

pom.xml

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

    <dependency>
        <groupId>com.mysql</groupId>
        <artifactId>mysql-connector-j</artifactId>
        <scope>runtime</scope>
    </dependency>

    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
</dependencies>
<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <dependency>
        <groupId>org.postgresql</groupId>
        <artifactId>postgresql</artifactId>
        <scope>runtime</scope>
    </dependency>

    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
</dependencies>
<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <dependency>
        <groupId>p6spy</groupId>
        <artifactId>p6spy</artifactId>
        <version>3.9.1</version>
    </dependency>

    <dependency>
        <groupId>org.xerial</groupId>
        <artifactId>sqlite-jdbc</artifactId>
        <version>3.45.3.0</version>
    </dependency>

    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
</dependencies>

项目编写

实体类

@Data
@AllArgsConstructor
@NoArgsConstructor
@Builder
@ToString
@Entity(name = "Author") // 用于将一个普通的 Java 类标识为一个 JPA 实体（entity）
public class Author {
    @Id
    // MySQL 下的主键自增，如果是 PostgreSQL 需要配置序列生成器
    @GeneratedValue(
            strategy = GenerationType.IDENTITY
    )
    private Long id;
    @Column(
            name = "first_name",
            nullable = false
    )
    private String firstName;
    @Column(
            name = "last_name",
            nullable = false
    )
    private String lastName;
    @Column(
            name = "email",
            unique = true,
            nullable = false
    )
    private String email;
    @Column(
            name = "age",
            nullable = false
    )
    private Integer age;
}
@Data
@AllArgsConstructor
@NoArgsConstructor
@Builder
@ToString
@Entity(name = "Book")
public class Book {
    @Id
    @GeneratedValue(
            strategy = GenerationType.IDENTITY
    )
    private Long id;
//    private Long authorId; // Book 与 Author 为一对多关系
    @Column(
            name = "title",
            nullable = false
    )
    private String title;
    @Column(
            name = "type"
    )
    @Enumerated(EnumType.STRING)
    private BookType type;
}
@Data
@AllArgsConstructor
@NoArgsConstructor
@Builder
@ToString
@Entity(name = "IdCard")
public class IdCard {
    @Id
    @GeneratedValue(
            strategy = GenerationType.IDENTITY
    )
    private Long id;
    @Column(
            name = "number",
            unique = true
    )
    private String number;
    @Column(
            name = "sex"
    )
    private Integer sex;
    @Column(
            name = "address",
            nullable = false
    )
    private String address;
}
@Data
@AllArgsConstructor
@NoArgsConstructor
@Builder
@ToString
@Entity(name = "Publisher")
public class Publisher {
    @Id
    @GeneratedValue(
            strategy = GenerationType.IDENTITY
    )
    private Long id;
    @Column(
            name = "address",
            nullable = false
    )
    private String address;
    @Column(
            name = "contact",
            unique = true
    )
    private String contact;
}
@Getter
@RequiredArgsConstructor
public enum BookType {
    FICTION("FIC", "Fiction"),
    NON("NF", "Non-Fiction"),
    SCIENCE("SCI", "Science"),
    HISTORY("HIS", "History"),
    FANTASY("FAN", "Fantasy"),
    BIOGRAPHY("BIO", "Biography");

    private final String code;
    private final String description;

    private static final Map<String, BookType> BY_CODE = new HashMap<>();

    static {
        for (BookType bookType : values()) {
            BY_CODE.put(bookType.code, bookType);
        }
    }

    public static BookType valueOfCode(String code) {
        return BY_CODE.get(code);
    }

}

关联关系

OneToOne

表示对象之间的一对一关系，可以放在字段上面。 - 如果配置双向关联，维护关联关系的是拥有外键的一方，另一方必须配置 mappedBy。 - 如果配置单向关联，直接配置在拥有外键的一方即可。

测试数据

使用 faker 来生成一些数据写入数据库： 

<dependency>
    <groupId>com.github.javafaker</groupId>
    <artifactId>javafaker</artifactId>
    <version>1.0.2</version>
</dependency>

在 MainApplication.java 中编写如下代码： 

@Bean
CommandLineRunner commandLineRunner(AuthorRepository authorRepository) {
    return args -> {
        genFakerData(authorRepository);
    };
}

private void genFakerData(AuthorRepository authorRepository) {
    Faker faker = new Faker();
    for (int i = 0; i < 10; i++) {
        Author author = Author.builder()
                .id(null)
                .firstName(faker.name().firstName())
                .lastName(faker.name().lastName())
                .email(faker.internet().emailAddress())
                .age(faker.number().numberBetween(20, 80))
                .build();
        authorRepository.save(author);
    }
}

附录

Docker 创建容器

以命令方式：

docker run --name my-mysql \
  -e MYSQL_ROOT_PASSWORD=123456 \
  -p 3306:3306 \
  -d mysql:latest
# TODO 待补充
  1. 1. SpringData JPA
    1. 1.1. 项目介绍
    2. 1.2. 环境准备
      1. 1.2.1. Application.yml
      2. 1.2.2. pom.xml
  2. 2. 项目编写
    1. 2.1. 实体类
    2. 2.2. 关联关系
      1. 2.2.1. OneToOne
    3. 2.3. 测试数据
  3. 3. 附录
    1. 3.1. Docker 创建容器
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