groovyTemplateEngine.writeTo(out) throws nullpointer when executed ASYNC (in a task)

[cdaoust]

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Task List

• Steps to reproduce provided
• Stacktrace (if present) provided
• Example that reproduces the problem uploaded to Github
• Full description of the issue provided (see below)

Full description

We have code that processes GSP templates from a database for emails so they can be edited regularly. When using the GroovyPagesTemplateEngine within ASYNC code a nullpointer is thrown from the method writeTo(). Outside of a promise task everything works fine.

There is no stacktrace.

Steps to Reproduce

1. take mrhaki example from blog
   http://mrhaki.blogspot.com/2010/05/grails-goodness-use-gsp-template-engine.html
   and execute within futures task

2. Code to reproduce issue

Example service with test method that displays issue:

class TestService {
def groovyPagesTemplateEngine
void test() {
def p1 = task{

    def templateText = '''\

GSP Template Engine

This is just a sample with template text.

<g:if test="${show}">

We can use taglibs in our template!

</g:if>

• ${item}

''' def output = new StringWriter() groovyPagesTemplateEngine.createTemplate(templateText, 'sample').make([show: true, items: ['Grails','Groovy']]).writeTo(output) output.toString() } p1.onComplete{ results -> log.info(results) } } }

Expected Behaviour

nullpointer not thrown when executed async.

Actual Behaviour

nullpointer is thrown from groovyPagesTemaplteEngine.writeTo() when executed from within promise.

Environment Information

• Operating System: Mac OS/X
• Grails Version: 3.2.11
• JDK Version: 1.8
• Container Version (If Applicable): N/A

Example Application

• the entire example code is within this issue in steps to reproduce.

I am copying it here as well.

class TestService {
def groovyPagesTemplateEngine
void test() {
def p1 = task{

    def templateText = '''\

GSP Template Engine

This is just a sample with template text.

<g:if test="${show}">

We can use taglibs in our template!

</g:if>

• ${item}

''' def output = new StringWriter() groovyPagesTemplateEngine.createTemplate(templateText, 'sample').make([show: true, items: ['Grails','Groovy']]).writeTo(output) output.toString() } p1.onComplete{ results -> log.info(results) } } }

[cdaoust]

A little more info - I spent some time debugging the grails/groovy code and the issue is that this is not running in the context of a web request (its scheduled) and the GSP template code is looking for the web request context/binding. So this goes back to my question I posed on the Grails slack channel - should one be able to process GSP templates outside of a web request? Perhaps I have to switch to simpler template engine?