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I have a Spring project (not using Spring Boot, if that's relevant) that I'm trying to connect to a local database using the Postgres JDBC driver. (The local database is actually Yugabyte, but that should be fully compatible with the Postgres driver.)

When starting the application, I get this error message:

java.lang.IllegalArgumentException: An AbstractMessageProducingMessageHandler may only be referenced once (org.springframework.integration.config.SplitterFactoryBean#0) - use scope="prototype"
    at org.springframework.util.Assert.isTrue(Assert.java:118)
    at org.springframework.integration.config.AbstractStandardMessageHandlerFactoryBean.checkReuse(AbstractStandardMessageHandlerFactoryBean.java:168)
    at org.springframework.integration.config.AbstractStandardMessageHandlerFactoryBean.createHandler(AbstractStandardMessageHandlerFactoryBean.java:137)
    at org.springframework.integration.config.AbstractSimpleMessageHandlerFactoryBean.createHandlerInternal(AbstractSimpleMessageHandlerFactoryBean.java:186)
    at org.springframework.integration.config.AbstractSimpleMessageHandlerFactoryBean.getObject(AbstractSimpleMessageHandlerFactoryBean.java:174)
    at org.springframework.integration.config.AbstractSimpleMessageHandlerFactoryBean.getObject(AbstractSimpleMessageHandlerFactoryBean.java:59)
    at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:171)
    ... 52 more

I can't place this error at all. There is one similar question on Stack Overflow, but there the asker seems to actually know what they're doing and how this is related to spring integration. I, however, am not aware at all that I'm trying to 'reuse' anything. The referenced question also doesn't seem to be related to database configuration.

My setup/configuration is a bit involved, so I'll try to quote the parts that seem relevant.

I have a dao layer project that has the following gradle dependencies (among others):

implementation("org.springframework:spring-context:5.2.2.RELEASE")
implementation("org.springframework:spring-jdbc:5.2.2.RELEASE")
implementation("org.jooq:jooq-kotlin:3.14.11")
runtimeOnly("org.postgresql:postgresql:42.2.19.jre7")

In the same project, I have some configuration (in Kotlin):

@Configuration
open class Config {
    @Bean
    open fun jdbcTemplate(dataSource: DataSource): JdbcTemplate = JdbcTemplate(dataSource)

    @Bean
    open fun dslContext(): DSLContext = DefaultDSLContext(SQLDialect.POSTGRES)

    @Configuration
    @Profile("!unittest")
    open inner class NonTestConfig {
        @Bean
        open fun dataSource(): DataSource {
            return DriverManagerDataSource().apply {
                // Hardcoded properties to be replaced by values from property file
                setDriverClassName("org.postgresql.Driver")
                url = "jdbc:postgresql://localhost:5433/demo"
                username = "yugabyte"
                password = "yugabyte"
            }
        }
    }
}

(Notes: the DSLContext bean is used for JOOQL, included for completeness' sake. The inner class config is there because there is also a separate unit testing config for an embedded database - that one works fine!)

Now, the above project is used in my top-level project that contains the actual application. It's a maven runtime dependency there. I import the config class in this project's XML configuration, using this method:

<context:annotation-config />
<bean class="my.package.Config" />

Then trying to start the application produces the error message.

Merlin's Beard
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  • You show fully not relevant information. The error is indeed about some Spring Integration `splitter` configuration when you use the same `AbstractMessageProducingHandler` instance in different places. You should share more info about your Spring Integration configuration. The database stuff is misleading and fully not related to the problem. – Artem Bilan Jun 14 '21 at 16:59
  • The thing is, this is a large existing project that worked just fine until I added the dependency to this dao project with this database config. Therefore I concluded that _something_ in the config that I quoted causes Spring to reuse an `AbstractMessageProducingHandler` instance (after all, that's the only thing that changed). Are you saying that _nothing_ in the code above could produce the error? Alternatively, would you know of a method to figure out where these duplicate handlers originate? – Merlin's Beard Jun 14 '21 at 18:24
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    There is probably some `` configuration with an `id` which is used somewhere else. It might even be the problem with duplicate `id` when by default the last bean wins and therefore a wrong bean reference is used somewhere you would expect a different one. You need to search your project for what is going on around splitters and their bean names. – Artem Bilan Jun 14 '21 at 18:36

1 Answers1

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I figured out what the problem was, but I still don't know how it relates to a <splitter>.

The problem was that the Config class, apart from the database stuff, also included a bean to encrypt data. It turned out that this bean was also defined in another library used by the top-level project. Fixing this duplicate bean problem made the error go away.

I discovered this in a roundabout way: I included the dao project and its configuration in a different top-level project that uses Spring Boot. This led to a clear error message about the encryptor bean having two definitions.

If anyone can explain why the error message is so cryptic in the non-Boot case, that would be a nice complementary answer.

Merlin's Beard
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