springboot integrated spring-jpa
The main contents:
1: spring boot and how integrated spring-jpa jpa first example query
Several commonly used as jpa annotations, lombok use annotations
2: how to set idea of adding a dependency on the pom automatically when the association.
3: integration problems encountered and solutions such as Areas, jpa lazy loading problems mysql..
We follow three-tier model MVC, DAO layer design and development, Service-layer design and development, and Controller layer.
Let's take a DAO layer design and development, Spring boot project to create a basic framework is omitted here.
This article comes from: Kaige Java (kaigejava)
"Spring boot payment programs." Kaige personal blog: www.kaigejava.com
A: add the relevant jar dependent
Because to use the mysql, mysql related to the introduction and operation of database-related jar in POM.XML file. We use here is the spring-jpa to operate the database. Specific jra as follows:
<-! Mysql related dependencies ->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
</dependency>
<-! Jpa its dependencies ->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
Teach you a idea how the coordinates entered in the pom file when Lenovo, as shown below: When the input atrifactid can think of, as shown below:
Operation: file -> settings interface, in turn found: build, execution, Deployment -> Bulid Tools -> maven -> Repositories as shown below:
Click to update it.
II: database connection configuration. We use here is yml format. FIG configured as follows:
spring:
datasource:
driver-class-name: com.mysql.cj.jdbc.Driver
username: root
password: 123456
url: jdbc:mysql://localhost/springboot-wxpay?serverTimezone=UTC&characterEncoding=utf8&useUnicode=true&useSSL=false
jpa:
show-sql: true
说明：
spring.jpa.show-sql=true.这句意思是：打印sql语句。
在url后面添加serverTimeizone=UTC是为了解决时区错误的问题。
三：创建实体及测试
3.1：创建ProductCategory实体对象。使用spring-jpa方式:
说明：
@Entity：spring-jpa实体注解
@Data: lombok注解用于自动生产get/set方法的
@Id:jpa的主键注解
@GeneratedValue：注解生成策略
3.2：创建repository接口对象
说明：使用jpa的需要继承Jparepository这个对象(有多个，这里就用简单的)
其中泛型，我们查看源码：
T：实体对象的。也就是我们上面创建的ProductCategory对象
ID：实体对象的ID类型。我们使用的事Integer类型。所以这里就写Integer。
四：创建测试类，进行测试：
在IDEA中，创建测试类快捷键：选中类名之后，ctrl+shift+t。如下图：
运行结果：
在控制台上，我们可以看到hibernate打印的sql语句以及打印出查询的结果。说明springboot继承jpa成功。
如果出现could not initialize proyx的时候，如下图错误：
在实体上面添加@Proxy(lazy = false)
说明：@ToString 是直接添加toString方法的。