简介
目的是减少模板代码。
核心接口是 Repository
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
public interface CrudRepository<T, ID extends Serializable>
extends Repository<T, ID> {
<S extends T> S save(S entity);
Optional<T> findById(ID primaryKey);
Iterable<T> findAll();
long count();
void delete(T entity);
boolean existsById(ID primaryKey);
// … more functionality omitted.
}
另外还有 JpaRepository MongoRepository
连接Mysql
使用 Spring Boot 会十分的简单。
首先添加依赖
1
2
3
4
5
6
7
8
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
</dependency>
然后添加配置 resources/application.properties
1
2
3
4
spring.jpa.hibernate.ddl-auto=none
spring.datasource.url=jdbc:mysql://192.168.0.1:3306/test
spring.datasource.username=user
spring.datasource.password=password
接着添加实体类，这里的 @Entity，@Id，@GeneratedValue 都是 javax.persistence 包下的。
1
2
3
4
5
6
7
8
9
10
11
12
13
14
@Entity
public class Bookmark {
@Id
@GeneratedValue(strategy= GenerationType.IDENTITY)
private Long id;
@Column(nullable = false)
private String title;
@Column(nullable = false,length=1024)
private String url;
private Date updateTime;
private Boolean isDelete;
// ... getter, setter and so on.
}
最后添加Repository
1
2
interface BookmarkRepository extends CrudRepository<Bookmark, Long> {
}
完成
1
Iterable<Bookmark> bookmarks = bookmarkRepository.findAll();
数据库授权
1
2
3
4
mysql> create database db_example; -- Create the new database
mysql> create user 'springuser'@'localhost' identified by 'ThePassword'; -- Creates the user
mysql> grant all on db_example.* to 'springuser'@'localhost'; -- Gives all the privileges to the new user on the newly created database
调试
在 application.properties 中添加下面配置可以在日志中输出SQL。
1
logging.level.org.hibernate.SQL=DEBUG
参考资料
reference - spring.io
accessing-data-jpa - spring.io
accessing-data-mysql - spring.io