当辅助数据源数据库连接不可用时，Spring启动不会启动

Question

Caused by: java.lang.NullPointerException
    at org.springframework.boot.actuate.endpoint.DataSourcePublicMetrics.initialize(DataSourcePublicMetrics.java:64) ~[spring-boot-actuator-1.3.2.RELEASE.jar:1.3.2.RELEASE]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.7.0_79]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) ~[?:1.7.0_79]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.7.0_79]
    at java.lang.reflect.Method.invoke(Method.java:606) ~[?:1.7.0_79]
    at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleElement.invoke(InitDestroyAnnotationBeanPostProcessor.java:354) ~[spring-beans-4.2.4.RELEASE.jar:4.2.4.RELEASE]

I disabled the metrics too but no luck

endpoints.enabled=false
endpoints.autoconfig.enabled=false
endpoints.metrics.enabled=false

The DataSourcePublicMetrics bean always gets created, even when the metrics are disabled. This causes a NullPointerException when the database connection is unavailable, causing spring boot not to start.

Answer 1

I am using Hikari datasource and it fails to construct data source object when database is unavailable. Hence NPE from DataSourcePublicMetrics bean. I am able to circumvent the issue creating a Hikari data source that is lazy initialized with database config even when database is unavailable for later use when database becomes available. Not sure why HikariDataSource does not have a constructor for lazy init. It does have a default constructor but database config can't be set using any setter method. This is useful for applications where database is not always necessary to start them up.

public class LazyConnectionDataSource extends HikariDataSource {
    public LazyConnectionDataSource(HikariConfig config) {
        config.validate();
        config.copyState(this);
    }
}