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From Rick McGuire <>
Subject Re: Should javamail be reorganized?
Date Tue, 02 May 2006 08:57:27 GMT
Alan D. Cabrera wrote:
> Rick McGuire wrote:
>> The more the geronimo javamail support is starting to get used, the 
>> more uncomfortable I'm getting with the current structure of the 
>> javamail code.  Let me level-set the situation first, so everybody 
>> understands the issues.
>> To start with, the Sun impl of javamail is not really like other jar 
>> files we consider "spec" code.  This jar files contains lots of 
>> classes in the javax.mail.* package tree, but it also contains a 
>> number of backing classes in a com.sun.mail.* tree that help 
>> implement certain features.  For example, there are various 
>> encoders/decoders used by the MimeUtility class.  These classes are 
>> undocumented, and are separate from the public javamail api classes.
>> In addition to those classes, the Sun javamail jar file contains the 
>> Sun implementations of the protocol transports and stores (smtp, 
>> pop3, and imap are supported).  In order to use the Sun version of 
>> javamail, you only need to javamail jar and the jaf (activation jar).
>> For the Geronimo implementation, things are split up a little more.  
>> The geronimo-spec-javamail jar file contains all of the javax.mail.* 
>> classes, plus whatever backing utility classes are needed to 
>> implement some of the features (with org.apache.geronimo.* package 
>> structure).  The jar does NOT however, contain any of the protocol 
>> implementations.
>> The Geronimo protocol implementations are contained in the 
>> javamail-transport module of the main Geronimo code tree.  This jar 
>> contains only the protocol implementations, plus some utility classes 
>> shared between the protocols.  In order to use the Geronimo javamail 
>> support, you need 3 jar files:  1)  the activation jar, 2) the 
>> javamail jar, and 3) the javamail-transport jar.  1) and 2) are 
>> available separately, but 3) IIUC, is only available within a 
>> Geronimo snapshot jar.
>> And just to confuse matters even more, there is another Geronimo mail 
>> module.  This module contains GBeans for configuring various mail 
>> resources.  These GBeans are independent of which javamail 
>> implementation is being used, so we can keep these out of the 
>> discussion.
> This is normal for just about all the spec implementations for 
> Geronimo.  1) spec jar, 2) impl, 3) GBean-mumbo-jumbo.  Hopefully, w/ 
> XBean, the GBean stuff will go away.
>> There is a major problem with the current Geronimo structure.  The 
>> implementation of the protocol handlers (transports and stores) is 
>> highly dependent on the version of the api they are written to.  I 
>> ran into this problem just today. Jira GERONIMO-1957 addressed the 
>> fact that changes in the geronimo 1.1 javamail spec jar broke the 1.0 
>> version of the SMTP transport.  However, the current 1.1 codebase was 
>> running with this obsolete code, so I had to back port the trunk 
>> version of the SMTP transport into the 1.1 code tree.  This also 
>> raised the question of whether we should pull back the other 
>> transport/store implementations into 1.1.
>> Now this is an issue that never arises with the Sun implementation.  
>> Since the protocol handlers are contained within the API jar, you can 
>> never get these packages out of sync.  They travel around together by 
>> definition.  In order for somebody to make use of the Geronimo 
>> javamail stack, you'd need to pull down the javamail and activation 
>> spec jars, then extract a javamail-transport jar from a Geronimo 
>> snapshot that was using a matching spec level.  Lots of opportunity 
>> for error here, and it makes it difficult for other projects to use 
>> the javamail support.  Axis is already doing this, but fortunately, 
>> they are only using the javax.mail.* stuff for Mime encoding support 
>> and are not dependent on transport or store implementations.
>> It seems, at a minimum, that the javamail-transport code should be 
>> moved from being a Geronimo module to a spec component.  Ideally, it 
>> really should be merged into the javamail spec module to mirror how 
>> the Sun implementation works.
>> Am I missing something?  Is there some compelling reason why this 
>> should be structured this way?  I really suspect we ended up at this 
>> point through a combination of ignorance and historical accident.  
>> Originally, the smtp transport code was just a sandbox component.  It 
>> was upgraded into working code because the console wanted to 
>> implement a portlet for configuring mail resouces configurations.  
>> When this code was promoted out of the sandbox, a new 
>> javamail-transport module was created because we weren't really sure 
>> where it really belonged....and we named it badly to boot.  It really 
>> should have been called javamail-protocol.  The transport portion of 
>> the name starting looking silly when we add the pop3 STORE protocol 
>> handler. 
> I look at things from a different viewpoint.  I never really 
> understood why any part of the implementation had to be bundled with 
> the JavaMail spec jar.  Folklore has it that the specification implies 
> that this must be the case.  This flies in the face of my experience 
> w/ many of the Java JSR specs that I am familiar with; I have not read 
> the spec for fear of being asked to support it.  :)  IMO, doing 
> something because Sun does it that way is not a good argument.
> Can you explain why *any* part of the implementation needs to be a 
> part of the spec jar?  My personal preference is to keep the protocol 
> handlers out of it.
I think part of my concern with javamail  is the growing desire to use 
it decoupled from Geronimo.  Axis is already doing this, but only using 
the base API classes (which are more implementation than "spec".  
There's a lot of executable code in the base API classes).  Axis is 
already doing this for their attachment support.  I hear rumblings that 
Harmony would like to use this package as well.  As currently bundled, 
there is no one place you can go to obtain just the complete Geronimo 
javamail implementation.  Right now, you need to download 2 spec jars + 
extract the javamail-transport jar from a Geronimo snapshot in order to 
do this. The code in javamail-transport has no dependencies on any other 
part of Geronimo, so that coupling is a bit artificial.

The other reason is just one of pragmatics.  Users seem to be tripping 
over this all the time, getting errors about unable to load the smtp 
protocol because the javamail-transport is missing from there 
configuration.  If the protocol handlers and the API classes are 
together, as with the Sun jars, these errors will no longer occur.

> Regards,
> Alan

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