基于SpringBoot3和JDK17，集成H2数据库和jpa

基于SpringBoot3和JDK17，集成H2数据库和jpa

学会用H2数据库，为了快速写出需要处理数据关系的demo。

工程配置

完整demo：https://download.csdn.net/download/weixin_43820556/89385337

pom.xml文件

<?xml version="1.0" encoding="UTF-8"?><projectxmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>3.2.6</version><relativePath/></parent><groupId>com.donny.demo</groupId><artifactId>h2</artifactId><version>0.0.1-SNAPSHOT</version><name>h2</name><description>Demo project for Spring Boot</description><properties><java.version>17</java.version></properties><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-actuator</artifactId></dependency><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.springframework.boot</groupId><artifactId>spring-boot-devtools</artifactId><scope>runtime</scope><optional>true</optional></dependency><dependency><groupId>com.h2database</groupId><artifactId>h2</artifactId><scope>runtime</scope></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-configuration-processor</artifactId><optional>true</optional></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><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId><configuration><excludes><exclude><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId></exclude></excludes></configuration></plugin></plugins></build></project>

application.properties文件

spring.application.name=h2 spring.jpa.show-sql=true spring.jpa.hibernate.ddl-auto=update spring.jpa.database-platform=org.hibernate.dialect.H2Dialect spring.datasource.driver-class-name=org.h2.Driver# 内存模式#spring.datasource.url=jdbc:h2:mem:test# 文件持久化模式spring.datasource.url=jdbc:h2:./db/testdb;AUTO_SERVER=TRUE;spring.datasource.username=saspring.datasource.password=sa#spring.sql.init.schema-locations=classpath:db/schema.sqlspring.h2.console.path=/h2spring.h2.console.enabled=truelogging.config=classpath:logback-spring.xmlmanagement.endpoints.web.exposure.include=loggers

练习H2数据库的操作

h2数据库的建表

/*学生*/DROPTABLEIFEXISTS`student`;CREATETABLE`student`(`id`INTEGERauto_incrementprimarykey,`name`varchar(50)notnull);/*老师,一个老师可以交好几个班级*/DROPTABLEIFEXISTS`teacher`;CREATETABLE`teacher`(`id`INTEGERauto_incrementprimarykey,`name`varchar(50)notnull,`subject`varchar(50)notnull);/*班级，一个学生只能在一个班级，一个班级有多名老师和学生*/DROPTABLEIFEXISTS`grade`;CREATETABLE`grade`(`id`INTEGERauto_incrementprimarykey,`student_id`INTEGER,`teacher_id`INTEGER,`name`varchar(50));-- ------------------------------ Records of student-- ----------------------------INSERTINTO`student`VALUES(0,'张三');INSERTINTO`student`VALUES(1,'少杰');INSERTINTO`student`VALUES(10,'赵子龙');-- ------------------------------ Records of student-- ----------------------------INSERTINTO`teacher`VALUES(0,'张老师','语文');INSERTINTO`teacher`VALUES(1,'王老师','数学');INSERTINTO`teacher`VALUES(2,'陈老师','英语');-- ------------------------------ Records of student-- ----------------------------INSERTINTO`grade`VALUES(1,0,0,'1班');INSERTINTO`grade`VALUES(2,1,2,'2班');INSERTINTO`grade`VALUES(3,10,1,'Z班');

自增主键控制

如果单独插入了数据，则不会与JPA的数据插入时主键相关联，例如，在建表的同时，写入了id为1的数据，则JPA在新增的时候，也会不会新增id为2的数据，还是新增id为1的数据，此时即报错。本人并未解决这种问题，而是将插入数据的操作，全部交由JPA来做，是实现主键自增的统一，如果有网友可以解决此问题，可以留言。

通过JPA来操作数据库

多对多关系，建议拆解成多个1对多的关系，进行表设计。
通过注解控制外键关系

@OneToOne：双向关系，实体键的关系是一对一，此注解用在单端上 @ManyToOne：双向关系，实体键的关系是多对一，此注解用在单端上

练习动态调整日志

引入依赖

<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-actuator</artifactId></dependency>

打开管理api（application.properties）

management.endpoints.web.exposure.include=loggers

查看类的目前的日志级别

GET请求：http://127.0.0.1:8080/actuator/loggers/com.donny.demo.h2.controller.LogController

结果

{"effectiveLevel":"DEBUG"}

修改类的日志级别

POST请求：

http://127.0.0.1:8080/actuator/loggers/com.donny.demo.h2.controller.LogController 请求体{"configuredLevel":"info"}

重新查询

{"configuredLevel":"ERROR","effectiveLevel":"ERROR"}

结果会是在LogController中增加一个配置项。若要取消configuredLevel，只要将请求体改为{"configuredLevel":null}

测试类

packagecom.donny.demo.h2.controller;importlombok.extern.slf4j.Slf4j;importorg.springframework.web.bind.annotation.GetMapping;importorg.springframework.web.bind.annotation.RequestMapping;importorg.springframework.web.bind.annotation.RestController;/** * @author 1792998761@qq.com * @version 1.0 */@RestController@RequestMapping("/log")@Slf4jpublicclassLogController{@GetMapping("/logger")publicStringloggerLevel(){log.trace("logger level is trace");log.info("logger level is info");log.debug("logger level is debug");log.warn("logger level is warn");log.error("logger level is error");return"success";}}

开启日志级别为debug时，输出的是[2024-06-01 15:24:25,180][http-nio-8080-exec-5][ERROR][com.donny.demo.h2.controller.LogController:23] logger level is error。说明生效了。