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Date: Wed, 10 May 2017 07:55:04 +0000 (UTC)
From: "Lorenzo Bernacchioni (JIRA)" <jira@apache.org>
To: issues@struts.apache.org
Message-ID: <JIRA.13047236.1488359160000.173731.1494402904326@Atlassian.JIRA>
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Subject: [jira] [Commented] (WW-4749) Buffer/Flush behaviour in
 FreemarkerResult
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archived-at: Wed, 10 May 2017 07:55:11 -0000


    [ https://issues.apache.org/jira/browse/WW-4749?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16004244#comment-16004244 ] 

Lorenzo Bernacchioni commented on WW-4749:
------------------------------------------

Left this comment in Github

Now that {{useBufferedWriter}} has been changed with {{writeIfCompleted}} for backward compatibility, just for the sake of code readability, I would change the name of the local variable {{willUseBufferedWriter}} with {{willWriteIfCompleted}}

> Buffer/Flush behaviour in FreemarkerResult
> ------------------------------------------
>
>                 Key: WW-4749
>                 URL: https://issues.apache.org/jira/browse/WW-4749
>             Project: Struts 2
>          Issue Type: Improvement
>          Components: Core Results
>    Affects Versions: 2.3.31, 2.5.1
>            Reporter: Lorenzo Bernacchioni
>            Assignee: Lukasz Lenart
>            Priority: Minor
>             Fix For: 2.5.next
>
>
> Scenario: the application use freemarker with a {{TemplateExceptionHandler.RETHROW_HANDLER}} policy, but occasionally needs to produce large XML (20~200Mb) and goes out of memory.
> In [FreemarkerResult|http://grepcode.com/file/repo1.maven.org/maven2/org.apache.struts/struts2-core/2.5-BETA1/org/apache/struts2/views/freemarker/FreemarkerResult.java#191] there are two possible behaviours (line 191):
>  * *Buffer-behaviour*: the whole template is processed and if everything is OK it is flushed to the output, otherwise an exception is thrown and handled at higher level before any output has been sent. This is intended to be used when {{TemplateExceptionHandler.RETHROW_HANDLER}} is active
> * *Flush-behaviour*: template is processed and flushed according to freemarker library policies, used with any other {{TemplateExceptionHandler}}
> Since {{TemplateExceptionHandler}} cannot be switched for a given request (it is a global configuration embedded in {{FreemarkerManager}}) there is no way to force a Flush-behaviour. (you can only force a Buffer-behaviour using {{isWriteIfCompleted}})
> I implemented a more flexible solution that let you force the behaviour in both ways:
> {code:title=FreemarkerResult.java|borderStyle=solid}
>     final boolean willUsebufferedWriter;
>     if (useBufferedWriter != null){
>         willUsebufferedWriter = useBufferedWriter;
>     }else{
>         willUsebufferedWriter = configuration.getTemplateExceptionHandler() == TemplateExceptionHandler.RETHROW_HANDLER;
>     }
>                 
>     if (willUsebufferedWriter){
>     ...
>     }else{
>     ...
>     }       
> {code}
> where {{useBufferedWriter}} is a parameter that can be modified per request
> {code}
> <result type="freemarker">
>     <param name="location">big_feed.ftl</param>
>     <param name="contentType">text/xml</param>
>     <param name="useBufferedWriter">false</param>
> </result>
> {code}


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