NonStringException in FreeMarker template when output_format is set

Question

I have a FreeMarker template where I want to specify the output format in order to escape some characters in my XML files. The template example looks as below:

<#ftl output_format="XML">
<#assign field1>
   TestField&1&
</#assign>
<#assign field2>
   <#if field1?trim?length == 0>
      TestField&1&
   <#else>
      TestField&2&
   </#if>
</#assign>
<?xml version="1.0" encoding="UTF-8"?>
<FIELD2>${field2}</FIELD2>

The transformation works fine (except the escaping), unless I put the <#ftl output_format="XML"> directive in my template. After that I get a NonStringException:

freemarker.core.NonStringException: For "?trim" left-hand operand: Expected a string or something automatically convertible to string (number, date or boolean), but this has evaluated to a markup_output (wrapper: f.c.TemplateXMLOutputModel): ==> field1 [in template "Test.ftl" at line 6, column 9]

Basically field1?trim?length does not work, because field1 is not evaluated as a string anymore.

Without the output format directive everything woks as expected.
FreeMarker version I'm using is 2.3.26-incubating.

score 1 · Accepted Answer · answered Feb 23 '21 at 15:06

1

You can use the markup_string builtin, which returns the markup stored inside a markup output value as string.

<#ftl output_format="XML">
<#assign field1>
    TestField&1&
</#assign>
<#assign field2>
    <#if field1?markup_string?trim?length == 0>
        TestField&1&
    <#else>
        TestField&2&
    </#if>
</#assign>
<?xml version="1.0" encoding="UTF-8"?>
<FIELD2>${field2}</FIELD2>

answered Feb 23 '21 at 15:06

obourgain

8,856
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Thank you very much, this solution works - appreciate you assistance here! – DimaSan Feb 24 '21 at 09:30

Ori Marko · Answer 2 · 2021-02-21T09:55:07.577

0

To prevent this error with XML outputformat you can assign field1 with string value:

<#ftl output_format="XML">
<#assign field1 ="TestField&1&"/>

edited Feb 21 '21 at 09:55

answered Feb 21 '21 at 08:55

Ori Marko

56,308
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Thank you for the suggestion, but unfortunately it does not work neither. The result of such assignment is `org.xmlunit.XMLUnitException: The entity name must immediately follow the '&' in the entity reference` – DimaSan Feb 23 '21 at 12:53
@DimaSan this is XML issue, do you mean to use &? see https://stackoverflow.com/questions/16303779/the-entity-name-must-immediately-follow-the-in-the-entity-reference – Ori Marko Feb 23 '21 at 12:58
@DimaSan Does that `XMLUnitException` occur after you did `${field2}`? Then maybe auto escaping is turned off there, which is not recommended. (Or, `XMLUnit` tries to validate the template itself as XML? Although then it would choke on `<#` as well.) – ddekany Mar 11 '21 at 08:12

NonStringException in FreeMarker template when output_format is set

2 Answers2