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https://issues.apache.org/jira/browse/MIME4J-72?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12638384#action_12638384
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Markus Wiederkehr commented on MIME4J-72:
-----------------------------------------
There are two issues that are somewhat related.
1) With Oleg's version the visitor cannot decide how deep it wants to go into
the message hierarchy. To give you an example let's assume you are interested
in processing multipart/mixed messages but you wish to ignore
multipart/alternative or multipart/related. Or assume you want to process PDF
attachments but not in inner (forwarded) messages.
With my implementation the visitor decides whether to visit inner Bodies /
Entities or not. Oleg's version gives the visitor no choice because the
traversal is hard-coded into Message / Multipart.
2) Regardless of RFC 1521 Message/Multipart/BodyPart/Body is the structure of a
Mime4j Message object. Let's assume you wanted to copy a message. It could be
done like this:
class CopyVisitor extends AbstractEntityVisitor {
private Stack stack = new Stack();
public void beginMessage(Message message) {
Message copy = new Message();
copyHeader(message, copy);
if (!stack.isEmpty())
((Entity) stack.peek()).setBody(copy);
stack.push(copy);
}
public void endMessage(Message message) {
stack.pop();
}
// analogous for Multipart and BodyPart.
public void visitBody(Body body) {
// called for all body implementations except Message and Multipart
Body copy = copyBody(body);
((Entity) stack.peek()).setBody(copy);
}
private Header copyHeader(Entity source, Entity target) { ... }
private Body copyBody(Body body) { ... }
}
You could also write visitors that copy certain bodies of a message, remove
other bodies or replace certain bodies with post-processed versions.
Of course this could also be done with a visitor that distinguishes between
Entity and Body alone. But it would require a lot more is-instanceof checks..
> Provide a means to dispose a Message
> ------------------------------------
>
> Key: MIME4J-72
> URL: https://issues.apache.org/jira/browse/MIME4J-72
> Project: JAMES Mime4j
> Issue Type: Improvement
> Affects Versions: 0.5
> Reporter: Markus Wiederkehr
> Assignee: Robert Burrell Donkin
> Attachments: entityvisitor.patch, mime4j-disposable.patch,
> mime4j-dispose-finalize.patch, mime4j-dispose-no-clutter.patch,
> mime4j-dispose-visitor.patch
>
>
> Currently an org.apache.james.mime4j.message.Message uses temporary files to
> store text and binary attachments of the message. Unfortunately a Message
> cannot be disposed of explicitly. Even when it eventually gets garbage
> collected the temp files continue to exist until the VM exits.
> If the VM runs for a long time and a lot of e-mails get processed this can
> become a major problem.
> For this reason I think that class Entity and interface Body should both have
> a method to dispose of the object. Multipart should dispatch a dispose-call
> to its list of body parts. A BodyPart should dispose of its body and concrete
> Body implementation such as TempFileTextBody should ultimately invoke
> delete() on the backing TempFile.
> Last but not least SimpleTempStorage$SimpleTempFile should not silently
> ignore delete-calls.
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