Allow default ParameterNameDiscoverer such that <constructor-arg name=".."> works by default for BeanFactory [SPR-8184]

[spring-projects-issues]

Chris Beams opened SPR-8184 and commented

See AbstractAutowireCapableBeanFactory.setParameterNameDiscoverer

I ran into some pretty unintuitive error messages today while trying to use <constructor-arg name="..." =ref="..."/> syntax for constructor argument disambiguation.

I was doing this in a unit test that uses only an XmlBeanFactory as opposed to a full ApplicationContext.

I was surprised to see that it didn't work, and after a little investigation, I realized that there is no default ParameterNameDiscoverer if you're using just a BeanFactory.

The javadoc states that there is no default in order to avoid a dependency on ASM.  Why is this important, given that .beans depends on core and .core depends on .asm?

It's true that there is no instance of a direct dependency on org.springframework.asm.* from any code in org.springframework.beans.*, yet at the same time the .beans ivy.xml does have a required compile-time dependency on .asm.

Perhaps this avoidance of .asm deps from .beans is just outdated?  If so, I can add an issue that documents the strange error, and then simply set a default for the parameterNameDiscoverer property in AbstractAutowireCapabaleBeanFactory and be done with it.

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Attachments:

• mylyn-context.zip (2.87 kB)

Referenced from: commits 4fc386a

[spring-projects-issues]

Chris Beams commented

Per ivy.xml, .beans now depends on .asm as a non-optional dependency, therefore it is reasonable to introduce this default.

Indeed, this change was introduced to support the 'name' attribute!

commit efa6b142505e9427cd1d5773d7881472a3d96999
Author: Juergen Hoeller <jhoeller@vmware.com>
Date:   Wed Jun 3 10:21:57 2009 +0000

    XML constructor-arg element allows for specifying a constructor argument by name now, with target argument names read from the class file via ASM or from Java 6's @Constructo
    
    git-svn-id: https://src.springframework.org/svn/spring-framework/trunk@1305 50f2f4bb-b051-0410-bef5-90022cba6387

diff --git org.springframework.beans/ivy.xml org.springframework.beans/ivy.xml
index d26d757..57077c1 100644
--- org.springframework.beans/ivy.xml
+++ org.springframework.beans/ivy.xml
@@ -28,6 +28,7 @@
                <dependency org="org.apache.log4j" name="com.springsource.org.apache.log4j" rev="1.2.15" conf="test->runtime"/>
                <dependency org="org.junit" name="com.springsource.org.junit" rev="4.5.0" conf="test->runtime"/>
                <dependency org="org.easymock" name="com.springsource.org.easymock" rev="2.3.0" conf="test->compile"/>
+               <dependency org="org.springframework" name="org.springframework.asm" rev="latest.integration" conf="compile->compile"/>
        </dependencies>
 
 </ivy-module>