How to create sample entities on app startup in a Spring Boot project?-CodePudding

I was wondering how can I create sample entities on startup to test my front end with in a Spring Boot application. Right now I'm trying to use a CommandLineRunner but I get this error:

    java.lang.IllegalStateException: Failed to execute CommandLineRunner
    at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:798) ~[spring-boot-2.5.0.jar:2.5.0]
    at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:779) ~[spring-boot-2.5.0.jar:2.5.0]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:344) ~[spring-boot-2.5.0.jar:2.5.0]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1336) ~[spring-boot-2.5.0.jar:2.5.0]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1325) ~[spring-boot-2.5.0.jar:2.5.0]
    at it.uniroma3.siw.SiwSpringSecurityApplication.main(SiwSpringSecurityApplication.java:24) ~[classes/:na]
Caused by: org.springframework.dao.InvalidDataAccessApiUsageException: org.hibernate.TransientPropertyValueException: object references an unsaved transient instance - save the transient instance before flushing : it.uniroma3.siw.spring.model.Intervento.meccanico -> it.uniroma3.siw.spring.model.Meccanico; nested exception is java.lang.IllegalStateException: org.hibernate.TransientPropertyValueException: object references an unsaved transient instance - save the transient instance before flushing : it.uniroma3.siw.spring.model.Intervento.meccanico -> it.uniroma3.siw.spring.model.Meccanico

.... .... ....

Any solution to this error? Or maybe any other way to create sample (test) entities in the database?

CodePudding user response：

In regards, to the error, it is possibly because the cascade relationships on your entities are not set properly. Do refer to the article below for help on the issue:

https://www.baeldung.com/hibernate-unsaved-transient-instance-error

There are multiple ways to load initial data into your application. Using the command-line runner is a valid approach. For more alternative ways refer to the article below:

https://www.baeldung.com/spring-boot-data-sql-and-schema-sql