SpringBoot 中 JPA 的使用

Posted 2020-11-27 滴水穿石不是靠力，而是因为不舍昼夜。

JPA是什么? JPA(Java Persistence API)是Sun官方提出的Java持久化规范. 为Java开发人员提供了一种对象/关联映射工具来管理Java应用中的关系数据. 它的出现是为了简化现有的持久化开发工作和整合ORM技术. 结束各个ORM框架各自为营的局面.

JPA 其实是一种规范，它的实现中比较出名的是 Hibernate 框架；

1、pom 引入依赖：

     <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>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
            <version>5.1.18</version>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid-spring-boot-starter</artifactId>
            <version>1.1.10</version>
        </dependency>

2、添加配置文件

#数据库连接信息
spring.datasource.type=com.alibaba.druid.pool.DruidDataSource
spring.datasource.username=root
spring.datasource.password=521hui
spring.datasource.url=jdbc:mysql://localhost:3306/test
#JPA设置
spring.jpa.show-sql=true
spring.jpa.database=mysql
spring.jpa.database-platform=mysql
spring.jpa.hibernate.ddl-auto=update
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL57Dialect

3、编写 bean

@Entity(name = "t_book")
public class Book {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;
    private String name;
    private String author;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    @Override
    public String toString() {
        return "Book{" +
                "id=" + id +
                ", name=‘" + name + ‘‘‘ +
                ", author=‘" + author + ‘‘‘ +
                ‘}‘;
    }
}

4、编写 接口

public interface BookDao extends JpaRepository<Book,Integer> {
}

5、启动程序，数据库创建表

6、进行 CRUD 测试

   @Autowired
    BookDao bookDao;
    @Test
    void testInsert() {
        Book book = new Book();
        book.setName("孔雀翎");
        book.setAuthor("古龙");

        bookDao.save(book);
    }
    @Test
    void testupdate() {
        Book book = new Book();
        book.setName("笑傲江湖");
        book.setAuthor("金庸");
        book.setId(1);
        bookDao.saveAndFlush(book);
    }
    @Test
    void testdelete() {
        bookDao.deleteById(1);
    }

    @Test
    void testFind() {
        System.out.println(bookDao.findById(4).toString());
    }