如何使用未准备好的数据库启动 Spring-Boot webapp + Spring-Batch？答案

【问题标题】：How to start Spring-Boot webapp + Spring-Batch with an unready database?如何使用未准备好的数据库启动 Spring-Boot webapp + Spring-Batch？
【发布时间】：2019-05-15 13:38:40
【问题描述】：

按照“十二因素应用程序”的建议，我的所有 Spring Boot 应用程序都能够在没有数据库的情况下启动，只有当数据库可用时，健康端点状态才会变为健康。那挺好的。但是我的新 spring-boot 应用程序包含 spring-batch，它破坏了这个特性。

这个问题很容易重现，重用这个project

使用 postgresql 驱动程序将其转换为 Web 应用程序，并添加：

     <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-web</artifactId>
     </dependency>
     <dependency>
         <groupId>org.postgresql</groupId>
         <artifactId>postgresql</artifactId>
         <version>42.2.5</version>
     </dependency>

添加 application.properties 文件：

spring.datasource.url=jdbc:postgresql://localhost:5432/exp_sesame
spring.datasource.driver-class-name=org.postgresql.Driver
spring.datasource.username=ADMIN
spring.datasource.password=ADMIN
spring.batch.initialize-schema=always

然后，如果您启动此应用程序，它将失败。

org.postgresql.util.PSQLException: Connection to localhost:5432 refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections.
    at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:280) ~[postgresql-42.2.5.jar:42.2.5]
    at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:49) ~[postgresql-42.2.5.jar:42.2.5]
    at org.postgresql.jdbc.PgConnection.<init>(PgConnection.java:195) ~[postgresql-42.2.5.jar:42.2.5]
    at org.postgresql.Driver.makeConnection(Driver.java:454) ~[postgresql-42.2.5.jar:42.2.5]
    at org.postgresql.Driver.connect(Driver.java:256) ~[postgresql-42.2.5.jar:42.2.5]
    at com.zaxxer.hikari.util.DriverDataSource.getConnection(DriverDataSource.java:136) ~[HikariCP-3.2.0.jar:na]
    at com.zaxxer.hikari.pool.PoolBase.newConnection(PoolBase.java:369) ~[HikariCP-3.2.0.jar:na]
    at com.zaxxer.hikari.pool.PoolBase.newPoolEntry(PoolBase.java:198) ~[HikariCP-3.2.0.jar:na]
    at com.zaxxer.hikari.pool.HikariPool.createPoolEntry(HikariPool.java:467) [HikariCP-3.2.0.jar:na]
    at com.zaxxer.hikari.pool.HikariPool.checkFailFast(HikariPool.java:541) [HikariCP-3.2.0.jar:na]
    at com.zaxxer.hikari.pool.HikariPool.<init>(HikariPool.java:115) [HikariCP-3.2.0.jar:na]
    at com.zaxxer.hikari.HikariDataSource.getConnection(HikariDataSource.java:112) [HikariCP-3.2.0.jar:na]
    at org.springframework.jdbc.datasource.DataSourceUtils.fetchConnection(DataSourceUtils.java:157) [spring-jdbc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils.java:115) [spring-jdbc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:78) [spring-jdbc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.jdbc.core.JdbcTemplate.execute(JdbcTemplate.java:323) [spring-jdbc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.boot.jdbc.EmbeddedDatabaseConnection.isEmbedded(EmbeddedDatabaseConnection.java:123) [spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
    at org.springframework.boot.autoconfigure.jdbc.DataSourceInitializer.isEmbedded(DataSourceInitializer.java:140) [spring-boot-autoconfigure-2.1.4.RELEASE.jar:2.1.4.RELEASE]
    at org.springframework.boot.autoconfigure.jdbc.DataSourceInitializer.isEnabled(DataSourceInitializer.java:132) [spring-boot-autoconfigure-2.1.4.RELEASE.jar:2.1.4.RELEASE]
    at org.springframework.boot.autoconfigure.jdbc.DataSourceInitializer.createSchema(DataSourceInitializer.java:98) [spring-boot-autoconfigure-2.1.4.RELEASE.jar:2.1.4.RELEASE]
    at org.springframework.boot.autoconfigure.jdbc.DataSourceInitializerInvoker.afterPropertiesSet(DataSourceInitializerInvoker.java:64) [spring-boot-autoconfigure-2.1.4.RELEASE.jar:2.1.4.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1837) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1774) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:593) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:224) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveNamedBean(DefaultListableBeanFactory.java:1115) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveBean(DefaultListableBeanFactory.java:407) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:341) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:335) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.boot.autoconfigure.jdbc.DataSourceInitializerPostProcessor.postProcessAfterInitialization(DataSourceInitializerPostProcessor.java:55) ~[spring-boot-autoconfigure-2.1.4.RELEASE.jar:2.1.4.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsAfterInitialization(AbstractAutowireCapableBeanFactory.java:429) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1782) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:593) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:277) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1247) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1167) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:593) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:90) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:374) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1411) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:592) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:392) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1321) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1160) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:555) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:277) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1247) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1167) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:593) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:90) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:374) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1411) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:592) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) [spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:849) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:877) ~[spring-context-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:549) ~[spring-context-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:142) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:775) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:316) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1260) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1248) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
    at hello.Application.main(Application.java:10) ~[classes/:na]

Spring-Batch 和数据库有很强的耦合，我理解，但它应该在没有它的情况下启动（惰性初始化）。

当前解决方法

我将 spring-batch bean 移动到不会自动启动的子上下文中。在主 spring 上下文中，我有一个调度程序，它以编程方式检查数据库运行状况执行器，并在数据库启动时创建子上下文。

有人对此有意见吗？

谢谢各位

【问题讨论】：

标签： database spring-boot web-applications spring-batch

【解决方案1】：

好点！这实际上并不特定于 Spring Batch 本身，因为 Spring Batch 需要一个 DataSource bean，就像任何其他应用程序一样。

关键是DataSource 应该准备好“十二因素”（如果这有意义的话）并在数据库关闭或尚未启动时重试获取连接。

Spring Boot 中有一个关于此功能的未解决问题：请参阅 issue #4779。可以找到使用spring-retry 的示例here 来使用此重试功能装饰数据源。

FTR，我推荐 Kelsey Hightower 的 12 Fractured Apps 文章，他在其中解决了同样的问题（参见 Eliminate the need to deploy services in a specific order 部分）。代码示例是用golang编写的，但思路是一样的。

希望这会有所帮助。

【讨论】：

谢谢，我已经看过 #4779 不明白为什么不关闭。因为，在我没有 spring-batch 用例的情况下，它可以工作：我的 spring boot 应用程序在没有数据库的情况下启动。即使使用 spring-data 等...所以，#4779 并没有关闭，因为这个问题是关于一个低级别的解决方案，例如使用数据源代理......好吧，这很有意义......