ScriptTemplateView configuration option for JavaScript concurrency issues [SPR-13034]

[spring-projects-issues]

Sébastien Deleuze opened SPR-13034 and commented

As discussed in #16871 and on the Nashorn dev mailing list (see the reference URL), there are some concurrency issues at least with Handlebars and React, so we need to work with the Nashorn team to identify if it comes from a Nashorn bug, or if there is something on Spring side we can do to fix theses issues.

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Affects: 4.2 RC1

Reference URL: http://mail.openjdk.java.net/pipermail/nashorn-dev/2015-May/004482.html

Issue Links:

• Support JavaScript Templating [SPR-12266] #16871 Support JavaScript Templating

Referenced from: commits 34de167, d183bbb

0 votes, 6 watchers

[spring-projects-issues]

Sébastien Deleuze commented

Last update: http://mail.openjdk.java.net/pipermail/nashorn-dev/2015-May/004593.html

Basically we are trying to see if Handlebars.compile() is thread-safe, even if that seems a strange question for a Javascript library ...

[spring-projects-issues]

Sébastien Deleuze commented

See Handlebars developers feedback.

Basically, Handlerbars is not designed with concurrency in mind, but they may accept some pull requests to improve that if that means no regression for other regular users. I will try to have a look to at least identify what should be done and have an idea of the amount of work needed to fix that.

That may be also useful to be able to give some clear insights in our documentation about what are the requirements to use safely a Javascript library for server side script based template rendering.

[spring-projects-issues]

Sébastien Deleuze commented

Good news, based on this discussion, there is a ThreadLocal based solution in order to fix these concurrency issues. My tests with the script-engine-test confirms that it works, even with Handlebars (and React will be fine too)!

I am working on a commit that will make the following changes:

• Add a isThreadBound (feel free to propose a better name if any) boolean property (default to false) to ScriptTemplateView and ScriptTemplateConfigurer that will enabled getting the engine from a ThreadLocal (it is useful to keep the non ThreadLocal based mechanism for thread safe ScriptEngine implementations or thread safe JS script libraries like Mustache)
• If this property is true, ScriptTemplateView will get the ScriptEngine from a ThreadLocal<ScriptEngine> engineHolder field (the engine will have to be specified by its name in order to be instantiated for each thread, the setScriptEngine() setter will not be supported in when isThreadBound is enabled)

Another good news, with the latest Java 8 update 60 build 23, Underscore templating now works flawlessly !!!

I am likely to be able to push the commit tomorrow, just in time for 4.2 RC3 !

[spring-projects-issues]

Sébastien Deleuze commented

Resolved by this commit, using the sharedEngine property name as proposed by Juergen.