How to lazy initialize spring-boot datasource?spring.data

I have a spring-boot application that defines a mysql DataSource:

spring.datasource.url=...
spring.datasource.username=...
spring.datasource.password=...

I run the tool as command line application triggered by a cronjob. And in 80% of all runs, I could exit the tool without having to contact the database at all:

@Controller
public class MainController {
    @Autowired
    private MyService myService;

    public void evaluate() {
           if (condition == true) myService.run();
           else System.exit(0);
    } 
}

@Service
@Lazy
public class MyService {
    @Autowired
    private JdbcTemplate jdbc;

    public void run() {
       jdbc.execute(sql);
    }
}

Problem: I want to prevent spring initializing the database at all. So, if for example the database is down or the host is unreachable (could be tested with using spring.datasource.url=localhostX), then the tool should still be runable.

Is that possible to delay the datasource initialization until it is really needed?

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]: Invocation of init method failed; nested exception is org.hibernate.service.spi.ServiceException: Unable to create requested service [org.hibernate.engine.jdbc.env.spi.JdbcEnvironment]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1778) ~[spring-beans-5.1.10.RELEASE.jar:5.1.10.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:593) ~[spring-beans-5.1.10.RELEASE.jar:5.1.10.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515) ~[spring-beans-5.1.10.RELEASE.jar:5.1.10.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320) ~[spring-beans-5.1.10.RELEASE.jar:5.1.10.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.1.10.RELEASE.jar:5.1.10.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318) ~[spring-beans-5.1.10.RELEASE.jar:5.1.10.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.1.10.RELEASE.jar:5.1.10.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1105) ~[spring-context-5.1.10.RELEASE.jar:5.1.10.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:867) ~[spring-context-5.1.10.RELEASE.jar:5.1.10.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:549) ~[spring-context-5.1.10.RELEASE.jar:5.1.10.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:744) ~[spring-boot-2.1.9.RELEASE.jar:2.1.9.RELEASE]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:391) ~[spring-boot-2.1.9.RELEASE.jar:2.1.9.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:312) ~[spring-boot-2.1.9.RELEASE.jar:2.1.9.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215) ~[spring-boot-2.1.9.RELEASE.jar:2.1.9.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1204) ~[spring-boot-2.1.9.RELEASE.jar:2.1.9.RELEASE]
Caused by: org.hibernate.service.spi.ServiceException: Unable to create requested service [org.hibernate.engine.jdbc.env.spi.JdbcEnvironment]
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.createService(AbstractServiceRegistryImpl.java:275) ~[hibernate-core-5.3.12.Final.jar:5.3.12.Final]
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:237) ~[hibernate-core-5.3.12.Final.jar:5.3.12.Final]
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:214) ~[hibernate-core-5.3.12.Final.jar:5.3.12.Final]
    at org.hibernate.id.factory.internal.DefaultIdentifierGeneratorFactory.injectServices(DefaultIdentifierGeneratorFactory.java:152) ~[hibernate-core-5.3.12.Final.jar:5.3.12.Final]
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.injectDependencies(AbstractServiceRegistryImpl.java:286) ~[hibernate-core-5.3.12.Final.jar:5.3.12.Final]
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:243) ~[hibernate-core-5.3.12.Final.jar:5.3.12.Final]
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:214) ~[hibernate-core-5.3.12.Final.jar:5.3.12.Final]
    at org.hibernate.boot.internal.InFlightMetadataCollectorImpl.<init>(InFlightMetadataCollectorImpl.java:179) ~[hibernate-core-5.3.12.Final.jar:5.3.12.Final]
    at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.complete(MetadataBuildingProcess.java:119) ~[hibernate-core-5.3.12.Final.jar:5.3.12.Final]
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.metadata(EntityManagerFactoryBuilderImpl.java:904) ~[hibernate-core-5.3.12.Final.jar:5.3.12.Final]
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:935) ~[hibernate-core-5.3.12.Final.jar:5.3.12.Final]
    at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:58) ~[spring-orm-5.1.10.RELEASE.jar:5.1.10.RELEASE]
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:365) ~[spring-orm-5.1.10.RELEASE.jar:5.1.10.RELEASE]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:391) ~[spring-orm-5.1.10.RELEASE.jar:5.1.10.RELEASE]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:378) ~[spring-orm-5.1.10.RELEASE.jar:5.1.10.RELEASE]
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.afterPropertiesSet(LocalContainerEntityManagerFactoryBean.java:341) ~[spring-orm-5.1.10.RELEASE.jar:5.1.10.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1837) ~[spring-beans-5.1.10.RELEASE.jar:5.1.10.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1774) ~[spring-beans-5.1.10.RELEASE.jar:5.1.10.RELEASE]
    ... 15 common frames omitted
Caused by: org.hibernate.HibernateException: Access to DialectResolutionInfo cannot be null when 'hibernate.dialect' not set
    at org.hibernate.engine.jdbc.dialect.internal.DialectFactoryImpl.determineDialect(DialectFactoryImpl.java:100) ~[hibernate-core-5.3.12.Final.jar:5.3.12.Final]
    at org.hibernate.engine.jdbc.dialect.internal.DialectFactoryImpl.buildDialect(DialectFactoryImpl.java:54) ~[hibernate-core-5.3.12.Final.jar:5.3.12.Final]
    at org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator.initiateService(JdbcEnvironmentInitiator.java:137) ~[hibernate-core-5.3.12.Final.jar:5.3.12.Final]
    at org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator.initiateService(JdbcEnvironmentInitiator.java:35) ~[hibernate-core-5.3.12.Final.jar:5.3.12.Final]
    at org.hibernate.boot.registry.internal.StandardServiceRegistryImpl.initiateService(StandardServiceRegistryImpl.java:94) ~[hibernate-core-5.3.12.Final.jar:5.3.12.Final]
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.createService(AbstractServiceRegistryImpl.java:263) ~[hibernate-core-5.3.12.Final.jar:5.3.12.Final]
    ... 32 common frames omitted

Solution 1:

@SpringBootApplication(exclude = HibernateJpaAutoConfiguration.class)

Somehow the hikari pool and hibernate seem to interact on startup. And if the datasource is not present, startup fails.

Using the exclusion above with @Lazy annotation delays the initialization as expected.

But that only works because I don't make use of hibernate.

Solution 2:

As said in spring doc(https://docs.spring.io/spring-boot/docs/2.1.13.RELEASE/reference/html/boot-features-sql.html):

Spring Data JPA repositories support three different modes of bootstrapping: default, deferred, and lazy. To enable deferred or lazy bootstrapping, set the spring.data.jpa.repositories.bootstrap-mode to deferred or lazy respectively.

So try the following config in your application.properties (or yaml):

spring.data.jpa.repositories.bootstrap-mode=lazy