Re: [jira] Commented: (COCOON3-14) Use generics for pipeline assembly
If I only had known that this simple enhancement starts these discussions :) Now, my understanding of C3 is that it is kind of a prototype (the current code of course works perfectly and is stable, so marking this a prototype might seem wrong from this pov). We can use this as a good base for discussions, especially as this is a working solution. So I think it makes totally sense to patch/enhance parts of C3 and see where this leads us; I think it's near to impossible to discuss the whole desing theory of C3 in this mailing list, agree on something and then come up with the implementation. This would only work during a f2f get together, which seems to be out of question atm. So, again, let's use the current code as a base and discuss single points one after the other (although some points may have influence on other points). As we're still doing alpha releases, in theory we can change everything - but I don't think that this is required :) Carsten -- Carsten Ziegeler cziege...@apache.org
[jira] Commented: (COCOON3-14) Use generics for pipeline assembly
[ https://issues.apache.org/jira/browse/COCOON3-14?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=12666913#action_12666913 ] Grzegorz Kossakowski commented on COCOON3-14: - As far as I understood all the discussions it is now allowed to mix sax with stax or dom components in a pipeline, they are required to use the eventing (if you regard dom as one single big event). Is this event-based communication guaranteed at PipelineComponent level or it's left to implementation how to design it? If a user knows which type of components (s)he will use, the pipeline can be narrowed down to accept only those type of components. If the exact type is not known or a mixture of different components is to be used, using How it's possible that user is using a component and does not know what kind of input/output this component deals with? I agree with Steven's point on the need for creation of marker interfaces. If they are going to be purely marker interfaces then I'm quite concerned about this solution. Is it only my omission or this patch does not solve a problem with Pipeline results outlined by Reinhard: http://article.gmane.org/gmane.text.xml.cocoon.devel/79362 To sum up my opinion I'm -0 on this patch. In itself it's not bad (and not invading) but I think this patch tries to tweak broken foundations. I would prefer if we could agree on Pipelines and PipelineComponent fundamental design decisions and goals before we move to providing patches. There were two different approaches presented in form of patches that left on or another side unhappy so such an agreement seems to be the best solution. What about a serious discussion on this topic during ApacheCon EU this year? I don't want to suspend the whole discussion for two months, of course. Use generics for pipeline assembly -- Key: COCOON3-14 URL: https://issues.apache.org/jira/browse/COCOON3-14 Project: Cocoon 3 Issue Type: Improvement Components: cocoon-pipeline Reporter: Carsten Ziegeler Assignee: Cocoon Developers Team Attachments: generics.patch This is a simple patch to add generics to the pipeline interface and impl. With additionally introducing marker interfaces for the component types (SAX, Stax, dom) this would allow compile time checks if all components have the correct type when assembling the pipeline. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Commented: (COCOON3-14) Use generics for pipeline assembly
[ https://issues.apache.org/jira/browse/COCOON3-14?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=12666921#action_12666921 ] Steven Dolg commented on COCOON3-14: Is this event-based communication guaranteed at PipelineComponent level or it's left to implementation how to design it? The supplied patch does not change how the components interact with each other. The PipelineComponent interface remains unchanged. How it's possible that user is using a component and does not know what kind of input/output this component deals with? This is always the case when the Pipeline is assembled at runtime from a provided description, like the Sitemap. While the PipelineAPI is intended do be used with direct calls from the user's code, we should not forget that automatic pipeline construction using some kind of description is still a valid use case and that basically no assumptions about the actual components can be made in such a case (iow Generics are pretty much worthless for that) Use generics for pipeline assembly -- Key: COCOON3-14 URL: https://issues.apache.org/jira/browse/COCOON3-14 Project: Cocoon 3 Issue Type: Improvement Components: cocoon-pipeline Reporter: Carsten Ziegeler Assignee: Cocoon Developers Team Attachments: generics.patch This is a simple patch to add generics to the pipeline interface and impl. With additionally introducing marker interfaces for the component types (SAX, Stax, dom) this would allow compile time checks if all components have the correct type when assembling the pipeline. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Commented: (COCOON3-14) Use generics for pipeline assembly
[ https://issues.apache.org/jira/browse/COCOON3-14?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=12666922#action_12666922 ] Reinhard Poetz commented on COCOON3-14: --- I think this patch will be the best solution that the Java programming language can support. Grek, your ideas are interesting but I fail to see how this could ever work with Java. So here's my +1 for Carsten's patch. @Grek: We won't reach beta before Amsterdam, which means that we can still change core contracts. Use generics for pipeline assembly -- Key: COCOON3-14 URL: https://issues.apache.org/jira/browse/COCOON3-14 Project: Cocoon 3 Issue Type: Improvement Components: cocoon-pipeline Reporter: Carsten Ziegeler Assignee: Cocoon Developers Team Attachments: generics.patch This is a simple patch to add generics to the pipeline interface and impl. With additionally introducing marker interfaces for the component types (SAX, Stax, dom) this would allow compile time checks if all components have the correct type when assembling the pipeline. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Commented: (COCOON3-14) Use generics for pipeline assembly
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https://issues.apache.org/jira/browse/COCOON3-14?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=12666936#action_12666936
]
Grzegorz Kossakowski commented on COCOON3-14:
-
The supplied patch does not change how the components interact with each
other.
The PipelineComponent interface remains unchanged.
I didn't formulate my question clearly: what is our intention. Do we want a
generic API for event exchange or each pair of components will be dealing with
this in it's implementation by doing some of instanceof checks?
This is always the case when the Pipeline is assembled at runtime from a
provided description, like the Sitemap.
While the PipelineAPI is intended do be used with direct calls from the
user's code, we should not forget that automatic pipeline
construction using some kind of description is still a valid use case and
that basically no assumptions about
the actual components can be made in such a case (iow Generics are pretty
much worthless for that)
It's not entirely true that generics are worhtless at runtime. Take a look at
quick prototype:
PipelineComponent.java
package test;
public interface PipelineComponentT, U {
U execute(T event);
}
TestComponent.java
package test;
import java.util.LinkedList;
import java.util.List;
public class TestCompoent implements PipelineComponentString, ListString {
public ListString execute(String event) {
ListString list = new LinkedListString();
list.add(event);
return list;
}
}
main.java
package test;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
public class main {
public static void main(String[] args) {
Type[] interfaces = TestCompoent.class.getGenericInterfaces();
for (Type i : interfaces) {
if (i instanceof ParameterizedType) {
ParameterizedType pt = (ParameterizedType)i;
if
(pt.getRawType().equals(PipelineComponent.class)) {
Type[] typeArguments =
pt.getActualTypeArguments();
Type input = typeArguments[0];
Type output = typeArguments[1];
System.out.println(TestCompoent.class +
is +
PipelineComponent + input + , +
output + );
}
}
}
}
}
This gives me following output:
class test.TestCompoent is PipelineComponentclass java.lang.String,
java.util.Listjava.lang.String
My point is that Pipeline *can* and *should* check if it's valid (given
components can be combined). Of course this will work only if one component
accepts one type of input and produces one type of output but I don't see this
as a problem.
Use generics for pipeline assembly
--
Key: COCOON3-14
URL: https://issues.apache.org/jira/browse/COCOON3-14
Project: Cocoon 3
Issue Type: Improvement
Components: cocoon-pipeline
Reporter: Carsten Ziegeler
Assignee: Cocoon Developers Team
Attachments: generics.patch
This is a simple patch to add generics to the pipeline interface and impl.
With additionally introducing marker interfaces for the component types (SAX,
Stax, dom)
this would allow compile time checks if all components have the correct type
when assembling the pipeline.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
[jira] Commented: (COCOON3-14) Use generics for pipeline assembly
[ https://issues.apache.org/jira/browse/COCOON3-14?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=12666938#action_12666938 ] Grzegorz Kossakowski commented on COCOON3-14: - Looks like our JIRA set-up sucks and JIRA does not follow comment formatting. I'm moving with discussion to mailing list. Use generics for pipeline assembly -- Key: COCOON3-14 URL: https://issues.apache.org/jira/browse/COCOON3-14 Project: Cocoon 3 Issue Type: Improvement Components: cocoon-pipeline Reporter: Carsten Ziegeler Assignee: Cocoon Developers Team Attachments: generics.patch This is a simple patch to add generics to the pipeline interface and impl. With additionally introducing marker interfaces for the component types (SAX, Stax, dom) this would allow compile time checks if all components have the correct type when assembling the pipeline. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
Re: [jira] Commented: (COCOON3-14) Use generics for pipeline assembly
Reinhard Poetz (JIRA) pisze: I think this patch will be the best solution that the Java programming language can support. Grek, your ideas are interesting but I fail to see how this could ever work with Java. It might be that I'm not making myself clearly enough. When I'm talking about about fundamental design decisions I have in mind questions like: 1. Should component take one type of input and produce one type of output or more? 2. Is it component's concern to check if other components fit it (it's tightly coupled with first point) or it's Pipeline concern? 3. Do we want to mix components accepting different types in one pipeline? I'm asking more about our goals, basic principles and boundaries. Answering this kind of questions has nothing to do with Java capabilities even if implementation of fulfiling these goals will be affected by Java capabilities. My little example posted to this issue shows that certain operations can be done using plain Java 1.5. I would like to find out what are real limitations of Java so we can be sure that we exploit maximum we can from this language for our needs. I ask for that because this can be a starting point for doing some research on my side that I'm inserted in doing in my limited spare time. So here's my +1 for Carsten's patch. @Grek: We won't reach beta before Amsterdam, which means that we can still change core contracts. Good to know that doors are not closed entirely. -- Best regards, Grzegorz Kossakowski
[jira] Commented: (COCOON3-14) Use generics for pipeline assembly
[ https://issues.apache.org/jira/browse/COCOON3-14?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=12666957#action_12666957 ] Steven Dolg commented on COCOON3-14: This gives me following output: class test.TestCompoent is PipelineComponentclass java.lang.String, java.util.Listjava.lang.String Of course you can do this and use the generic parameters to check for compatibility. But I don't see how this is any difference than the instanceof check, we have now. IMO an component instanceof StAXConsumer is just as good as an firstComponent.getOutputType() == lastComponent.getInputType(). Of course the latter one looks much more sophisticated but basically you're just checking for some specific class. And I also don't see what's the advantage in having one class performing the compatibility check (and supporting all the little exceptions from the common case which might be necessary over time) instead of letting the components do it themselves. I'm still wondering what the input and output type of the SAX components would be and how the callbacks should be integrated/defined in the PipelineComponent interface. Maybe we can have an example, so that this can become less speculative. Use generics for pipeline assembly -- Key: COCOON3-14 URL: https://issues.apache.org/jira/browse/COCOON3-14 Project: Cocoon 3 Issue Type: Improvement Components: cocoon-pipeline Reporter: Carsten Ziegeler Assignee: Cocoon Developers Team Attachments: generics.patch This is a simple patch to add generics to the pipeline interface and impl. With additionally introducing marker interfaces for the component types (SAX, Stax, dom) this would allow compile time checks if all components have the correct type when assembling the pipeline. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Commented: (COCOON3-14) Use generics for pipeline assembly
[ https://issues.apache.org/jira/browse/COCOON3-14?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=12666523#action_12666523 ] Andreas Pieber commented on COCOON3-14: --- I'm still the opinion that this would not work at pipeline level. The problem is that components themself decide which consumer/producer they accept (depends on the component type). The first time you come into the situation where components have to be mixed (eg. xml and picture components) the pipeline-compile-check would fail. Think about the following situation: A *.xhtml is inserted in the pipe with some pictures in it. According to the description in it the pictures could be transformed, saved to some place and the urls in the xhtml replaced. In this case the pipeline would look like: X-X-X-XP-P-P-P-PX-X-X Where X stands for XML-Components and P for picture-Component and XP,PX for the Translators (Starter and Finisher are not relevant for the example). This situation will work at the moment, but will fail with generic pipes. Taking the wrong components would fail the first time you create the pipeline with a SetupException so that IMO its not a real life problem at all, and more an academic problem. If there really have to be a compile-check it may have to be happen at component-level. Does the type of the Producer matches my Consumer (or the other way round). At least there's still the option to create a plugin for the different IDEs checking this at compile time. Best Regards, Andreas Use generics for pipeline assembly -- Key: COCOON3-14 URL: https://issues.apache.org/jira/browse/COCOON3-14 Project: Cocoon 3 Issue Type: Improvement Components: cocoon-pipeline Reporter: Carsten Ziegeler Assignee: Cocoon Developers Team Attachments: generics.patch This is a simple patch to add generics to the pipeline interface and impl. With additionally introducing marker interfaces for the component types (SAX, Stax, dom) this would allow compile time checks if all components have the correct type when assembling the pipeline. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Commented: (COCOON3-14) Use generics for pipeline assembly
[ https://issues.apache.org/jira/browse/COCOON3-14?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=12666527#action_12666527 ] Carsten Ziegeler commented on COCOON3-14: - Why does your example from above not work with generics? Use generics for pipeline assembly -- Key: COCOON3-14 URL: https://issues.apache.org/jira/browse/COCOON3-14 Project: Cocoon 3 Issue Type: Improvement Components: cocoon-pipeline Reporter: Carsten Ziegeler Assignee: Cocoon Developers Team Attachments: generics.patch This is a simple patch to add generics to the pipeline interface and impl. With additionally introducing marker interfaces for the component types (SAX, Stax, dom) this would allow compile time checks if all components have the correct type when assembling the pipeline. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Commented: (COCOON3-14) Use generics for pipeline assembly
[ https://issues.apache.org/jira/browse/COCOON3-14?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=12666534#action_12666534 ] Andreas Pieber commented on COCOON3-14: --- Of course it would work using a general Pipeline. But it wont work using a PipelineStAX|SAX|Dom (whatever). I simply wanted to point out that its possible with this generic construction to forbid completely valid constructions... Use generics for pipeline assembly -- Key: COCOON3-14 URL: https://issues.apache.org/jira/browse/COCOON3-14 Project: Cocoon 3 Issue Type: Improvement Components: cocoon-pipeline Reporter: Carsten Ziegeler Assignee: Cocoon Developers Team Attachments: generics.patch This is a simple patch to add generics to the pipeline interface and impl. With additionally introducing marker interfaces for the component types (SAX, Stax, dom) this would allow compile time checks if all components have the correct type when assembling the pipeline. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Commented: (COCOON3-14) Use generics for pipeline assembly
[ https://issues.apache.org/jira/browse/COCOON3-14?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=12666541#action_12666541 ] Carsten Ziegeler commented on COCOON3-14: - Hmm I still don't so :) As far as I understood all the discussions it is now allowed to mix sax with stax or dom components in a pipeline, they are required to use the eventing (if you regard dom as one single big event). Use generics for pipeline assembly -- Key: COCOON3-14 URL: https://issues.apache.org/jira/browse/COCOON3-14 Project: Cocoon 3 Issue Type: Improvement Components: cocoon-pipeline Reporter: Carsten Ziegeler Assignee: Cocoon Developers Team Attachments: generics.patch This is a simple patch to add generics to the pipeline interface and impl. With additionally introducing marker interfaces for the component types (SAX, Stax, dom) this would allow compile time checks if all components have the correct type when assembling the pipeline. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Commented: (COCOON3-14) Use generics for pipeline assembly
[ https://issues.apache.org/jira/browse/COCOON3-14?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=12666545#action_12666545 ] Steven Dolg commented on COCOON3-14: Although we cannot prevent every misconfiguration of a pipeline with this patch, I think it still makes a lot of sense. If a user knows which type of components (s)he will use, the pipeline can be narrowed down to accept only those type of components. If the exact type is not known or a mixture of different components is to be used, using PipelinePipelineComponent pipeline = ... will yield exactly the same behavior we have now. IMO that is the most important aspect of this patch: we do not limit the possibilities, while still providing the option to have compile-time checks. The only drawback I can think of is that we will need a marker interface for every content type that is to be used. While we certainly won't need more than one (maybe two) per module, this adds another interface to the hierarchy. Now there were some objections that the number of interfaces already is high (or at least higher than expected), but IMO this is absolutely worth it. Usually I don't bother with the Pipeline module when working on a content type specific module. And declaring my own marker interface for my components (instead of using PipelineComponent) is actually a sound approach. This might also be used to clearly indicate which components are compatible - although this would rather be something to be encouraged and probably cannot be enforced, since it is only a marker interface. Use generics for pipeline assembly -- Key: COCOON3-14 URL: https://issues.apache.org/jira/browse/COCOON3-14 Project: Cocoon 3 Issue Type: Improvement Components: cocoon-pipeline Reporter: Carsten Ziegeler Assignee: Cocoon Developers Team Attachments: generics.patch This is a simple patch to add generics to the pipeline interface and impl. With additionally introducing marker interfaces for the component types (SAX, Stax, dom) this would allow compile time checks if all components have the correct type when assembling the pipeline. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
[jira] Commented: (COCOON3-14) Use generics for pipeline assembly
[ https://issues.apache.org/jira/browse/COCOON3-14?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=1210#action_1210 ] Carsten Ziegeler commented on COCOON3-14: - Yes, even with this patch it's still possible to mix different component types and yes, we have to introduce new marker interfaces :) (and yes it was me how mentioned that there are too many interfaces already...), but if you're just interested in one component type, e.g. sax, then it's just one additional interface. So if noone objects I'll apply the patch in the next days. Use generics for pipeline assembly -- Key: COCOON3-14 URL: https://issues.apache.org/jira/browse/COCOON3-14 Project: Cocoon 3 Issue Type: Improvement Components: cocoon-pipeline Reporter: Carsten Ziegeler Assignee: Cocoon Developers Team Attachments: generics.patch This is a simple patch to add generics to the pipeline interface and impl. With additionally introducing marker interfaces for the component types (SAX, Stax, dom) this would allow compile time checks if all components have the correct type when assembling the pipeline. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.
