ExtendedBeanInfo raises 'type mismatch' error with covariant property types [SPR-8806]

[spring-projects-issues]

Paul Nardone opened SPR-8806 and commented

Transcribed by cbeams from Paul's original comment on #12995

I am experiencing an issue with ExtendedBeanInfo and covariante propertytypes i've yet to isolate a simple test but it appears to be due using JDK PropertyDescriptor and the long standing JDK bug that are the cause resulting in

java.beans.IntrospectionException: type mismatch between read and write methods
at java.beans.PropertyDescriptor.findPropertyType(PropertyDescriptor.java:603)
at java.beans.PropertyDescriptor.setWriteMethod(PropertyDescriptor.java:270)
at java.beans.PropertyDescriptor.<init>(PropertyDescriptor.java:117)
at org.springframework.beans.ExtendedBeanInfo.addOrUpdatePropertyDescriptor(ExtendedBeanInfo.java:260)
at org.springframework.beans.ExtendedBeanInfo.addOrUpdatePropertyDescriptor(ExtendedBeanInfo.java:178)
at org.springframework.beans.ExtendedBeanInfo.<init>(ExtendedBeanInfo.java:95)
at org.springframework.beans.CachedIntrospectionResults.<init>(CachedIntrospectionResults.java:224)
... 124 more

---

Attachments:

• testspringprops_1.zip (10.74 kB)

Issue Links:

• Regression - Introspection with BeanUtils started failing for java.awt.Component derived classes [SPR-8491] #13137 Regression - Introspection with BeanUtils started failing for java.awt.Component derived classes ("is duplicated by")
• Review ExtendedBeanInfo implementation [SPR-8347] #12995 Review ExtendedBeanInfo implementation
• Overhaul non-void JavaBean write method support [SPR-10029] #14663 Overhaul non-void JavaBean write method support

[spring-projects-issues]

Chris Beams commented

Hi Paul,

Are you seeing this behavior against 3.1 RC1?

You mention a 'well-known JDK bug' - could you provide a link to that issue?

You also mentioned that you've had a hard time reproducing this - chances are that we will too. We'd certainly like to work it out for RC2, however. If there's any way you can reproduce this, we'll certainly look into it asap.

By the way, you may find the spring-framework-issues project helpful in putting together a simple reproduction test case. See https://github.com/SpringSource/spring-framework-issues#readme

[spring-projects-issues]

Paul Nardone commented

Hi Chris,

Yes I'm seeing this in 3.1 RC1 on Java 1.6

this is the bug I was thinking of when I was searching for possible causes

http://bugs.sun.com/view_bug.do?bug_id=6422403

I have now produced a testcase that reproduces this bug, the class hierarchy and needs to be such to reproduce the error

[spring-projects-issues]

Chris Beams commented

Thanks for the repro project, Paul. I've added this to the issues repository and am looking into it now.

spring-attic/spring-framework-issues@660a47d

[spring-projects-issues]

Chris Beams commented

Paul, this is resolved. Please give it a shot against 3.1.0.BUILD-SNAPSHOT and let us know, thanks!

commit f8f741d0e99531540cec179761407db0983e2060
Author: Chris Beams <cbeams@vmware.com>
Date:   Sat Nov 19 21:07:10 2011 +0000

    Avoid 'type mismatch' errors in ExtendedBeanInfo
    
    Certain edge cases around return type covariance can trigger an
    IntrospectionException when trying to create a new PropertyDescriptor;
    particularly around the addition of write methods with parameter types
    that do not match read method return types.
    
    These type mismatch exceptions are raised during normal Introspector
    operations as well (i.e. without ExtendedBeanInfo in the mix), but
    the Introspector intentionally supresses them. In covariance cases,
    there is often already a suitable write method present, e.g. discovered
    in a supertype or superinterface, that, with the benefit of bridge
    methods works just fine in practice at runtime.  That is to say, in
    these suppression cases, the rejection of the write method is 'OK' in
    that there is already a write method present that can handle a call.
    
    ExtendedBeanInfo now mirrors this suppression behavior, but does issue
    a WARN-level log message to let the user know.
    
    An important effect of this change is that ExtendedBeanInfo now modifies
    the delegate BeanInfo object, whereas previously it did not. In practice
    this probably matters very little, but it is a design change worth
    noting. The reason for this change was to avoid the need to create new
    PropertyDescriptors wherever possible. It was discovered that by updating
    existing PDs, one can avoid these IntrospectionExceptions a greater
    percentage of the time.
    
    Issue: SPR-8806

[spring-projects-issues]

Chris Beams commented

A general note to watchers of ExtendedBeanInfo-related issues: #14663 is a major refactoring of ExtendedBeanInfo and overall support for non-void returning setter methods.

If you have submitted a reproduction project with this issue, we have run it through its paces against these new changes, but we would like to ask you to do the same against your actual applications.

Please consider updating your dev or test builds to work against 3.1.4.BUILD-SNAPSHOT and/or 3.2.0.BUILD-SNAPSHOT to verify, and we would appreciate any feedback, even if it's to let us know that all is well. So that we can consolidate feedback, please add your comments to #14663, and mention the original issue(s) that you were watching.

Thanks!

Note also that testing against 3.1.4 is preferable to 3.2.0 because ExtendedBeanInfo is always in the code path in the latter, while in 3.2.0 we've optimized things such that ExtendedBeanInfo is only in play for bean classes that have one or more non-void returning setter methods.