Spring boot and Jpa Related clarification-CodePudding

Suppose i have a spring-boot application that has starter-JPA dependencies. I need to know if spring checks the connection to the db at the startup?

For example, if i have mentioned a Database that i do not have access to (like below), will the application fail to start? If yes what would be the exception?

spring.datasource.url=jdbc:postgresql://localhost:5432/postgres
spring.datasource.username=root
spring.datasource.password=root
spring.jpa.hibernate.dialect=org.hibernate.dialect.PostgreSQL94Dialect
spring.datasource.driver-class-name=org.postgresql.Driver
spring.datasource.continue-on-error=true

CodePudding user response：

For the last version of Spring Boot 2.7.2, Spring Boot doesn't check a connection itself, but gets a connection to determine some properties. Also Hibernate needs a connection to determine some properties itself (controlled by spring.jpa.properties.hibernate.temp.use_jdbc_metadata_defaults).

Also if you have spring-boot-starter-actuator as a dependency, a connection will be checked at the startup (controlled by management.health.db.enabled).

It needs to specify all automatically determined properties explicitly to not get a connection during the startup (even spring.jpa.hibernate.ddlAuto)

Add this to application.yaml

spring.jpa.hibernate.ddlAuto: "none"
spring.datasource.driver-class-name: org.postgresql.Driver
spring.jpa.database-platform: org.hibernate.dialect.PostgreSQL94Dialect

spring.jpa.properties.hibernate.temp.use_jdbc_metadata_defaults: false #Hibernate

# disable datasource check on startup
management.health.db.enabled: false #spring-boot-starter-actuator

By default Hikari is used as a connection pool. The connection pool gets all connections at the first attempt to get a connection. That's why it doesn't get the connections during the startup.

CodePudding user response：

Nothing much. Just execute your query. If the connection has died, either your JDBC driver will reconnect (if it supports it, and you enabled it in your connection string--most don't support it) or else you'll get an exception.

our best chance is to just perform a simple query against one table, e.g.:

select 1 from SOME_TABLE;