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());
}
