Wednesday, March 14, 2012

Resolve circular dependency in Spring Autowiring

I would consider this post as best practice for using Spring in enterprise application development.

When writing enterprise web application using Spring, the amount of services in the service layer, will probably grow.
Each service in the service layer will probably consume other services, which will be injected via @Autowire .
The problem: When services number start growing, a circular dependency might occur. It does not have to indicate on design problem... It's enough that a central service, which is autowired in many services, consuming one of the other services, the circular dependency will likely to occur.

The circular dependency will cause the Spring Application Context to fail and the symptom is an error which indicate clearly about the problem:

Bean with name ‘*********’ has been injected into other beans [******, **********, **********, **********] in its raw version as part of a circular reference,

but has eventually been wrapped (for example as part of auto-proxy creation). This means that said other beans do not use the final version of the bean. This is often the result of over-eager type matching – consider using ‘getBeanNamesOfType’ with the ‘allowEagerInit’ flag turned off, for example.


 The problem in modern spring application is that beans are defined via @nnotations (and not via XML) and the option of allowEagerInit flag, simply does not exist.
The alternative solution of annotating the classes with @Lazy, simply did not work for me.

The working solution was to add default-lazy-init="true" to the application config xml file:

<?xml version="1.0" encoding="UTF-8"?>
<beans default-lazy-init="true" xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd >
    <context:component-scan base-package="com.package">
       
    </context:component-scan>
    <context:annotation-config/>
   ...
</beans>

Hope this helps.  Not sure why it is not a default configuration.
If you have suggestion why this configuration might be not ok, kindly share it with us all.

Update:
Following redesign I had, this mentioned solution simply did not do the trick.
So I designed more aggressive solution to resolve that problem in 5 steps.

Good luck!

3 comments:

  1. Hello,
    Interesting blog. It would be great if you can provide more details about it. Thanks you.

    Locum Tenens

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