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https://issues.apache.org/jira/browse/SLING-8047?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16698664#comment-16698664
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Julian Sedding commented on SLING-8047:
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[~mundt], thanks for the test and sorry for the delay. The only other thing you
could do t help is give me some time ;)
I commented on your github branch. Could you please address the comment and
create a PR? Thanks!
I'll solicit some feedback on the mailing list, as my proposed change would be
a slight change of behaviour in a core passage of the code.
> Rendered/exported JSON requested via SlingRequestProcessor is not written to
> output stream
> ------------------------------------------------------------------------------------------
>
> Key: SLING-8047
> URL: https://issues.apache.org/jira/browse/SLING-8047
> Project: Sling
> Issue Type: Bug
> Components: Servlets
> Reporter: Philip Mundt
> Assignee: Jason E Bailey
> Priority: Major
> Attachments:
> SLING-8047-DefaultGetServlet-does-not-write-to-output-stream.patch,
> SLING-8047-ExportServlet-does-not-write-to-output-stream.patch
>
> Time Spent: 1.5h
> Remaining Estimate: 0h
>
> While trying to facilitate the {{SlingRequestProcessor}} to get a rendered or
> exported JSON representation of a resource, we ran into the problem of the
> response always being empty. The HTML rendering worked without any issue.
> (See example code of [Get the rendered HTML for an AEM resource, component or
> page|http://www.nateyolles.com/blog/2015/10/get-rendered-html-for-an-aem-resource-or-component]
> or [https://stackoverflow.com/a/34218708])
> Main, observed difference seem to be the method calls to print writer:
> h4. JsonRenderer
> {{org.apache.sling.servlets.get.impl.helpers.JsonRenderer#render}} uses
> {{#write}} method of response's print writer.
> h4. ExportServlet (via JacksonExporter)
> {{org.apache.sling.models.impl.ExportServlet#doGet}} uses {{#write}} method
> of response's print writer.
> h4. HTMLRenderer
> {{org.apache.sling.servlets.get.impl.helpers.HtmlRenderer#render}} uses
> {{#print}} and {{#println}} methods of response's print writer.
> h3. Further observations
> When the print writer's {{autoFlush}} property is set to true and one uses
> the {{#println}} method instead of {{#write}}, the {{JsonRenderer}} will
> flush the print writer's buffer to the output stream. Due to wrapping the
> response in
> {{org.apache.sling.scripting.core.impl.helper.OnDemandWriterResponse}} (where
> {{autoFlush=false}}) this does not work for the {{ExportServlet}}.
> When adding implicit {{#flush()}} calls to both classes, both request
> scenarios will work. According to the servlet specification, it should not be
> necessary to flush the print writer, as the container must immediately flush
> all remaining content to the client upon "termination of the service method
> of the servlet".
> Please find two test cases for (where implicit {{#flush()}} calls were added):
> * JsonRenderer ({{sling-org-apache-sling-servlets-get}}):
> [^SLING-8047-DefaultGetServlet-does-not-write-to-output-stream.patch]
> * ExportServlet ({{sling-org-apache-sling-models-impl}}):
> [^SLING-8047-ExportServlet-does-not-write-to-output-stream.patch]
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