thymeleaf - passing a Selection Variable Expression *{foo} to an Expression Utility Object

Question

I have a spring backed form with a model object Foo that contains Bar

<form action="#" th:action="@{/some/action}" th:object="${foo}" method="post">

now, I would like to do something like this:

<input type="text" id="bar.createdAt" name="bar.createdAt" th:value="*{bar.createdAt} ? ${#dates.format(bar.createdAt, #messages.msg('app.dateformat.datetime'))}"/>

but the following parsing exeption is thrown:

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is org.thymeleaf.exceptions.TemplateProcessingException: Exception evaluating SpringEL expression: "#dates.format(bar.createdAt, #messages.msg('app.dateformat.datetime'))" (registration:93)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:973)
    org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:852)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
root cause

org.thymeleaf.exceptions.TemplateProcessingException: Exception evaluating SpringEL expression: "#dates.format(bar.createdAt, #messages.msg('app.dateformat.datetime'))" (registration:93)
    org.thymeleaf.spring4.expression.SpelVariableExpressionEvaluator.evaluate(SpelVariableExpressionEvaluator.java:161)
    org.thymeleaf.standard.expression.VariableExpression.executeVariable(VariableExpression.java:154)
    org.thymeleaf.standard.expression.SimpleExpression.executeSimple(SimpleExpression.java:59)
root cause

org.springframework.expression.spel.SpelEvaluationException: EL1007E:(pos 7): Property or field 'createdAt' cannot be found on null
    org.springframework.expression.spel.ast.PropertyOrFieldReference.readProperty(PropertyOrFieldReference.java:211)
    org.springframework.expression.spel.ast.PropertyOrFieldReference.getValueInternal(PropertyOrFieldReference.java:85)
    org.springframework.expression.spel.ast.PropertyOrFieldReference.access$000(PropertyOrFieldReference.java:43)
    org.springframework.expression.spel.ast.PropertyOrFieldReference$AccessorLValue.getValue(PropertyOrFieldReference.java:341)

I've already tried: ...#dates.format(*{bar.createdAt}..., ...#dates.format(__*{bar.createdAt}__...but none has worked out.

the same without the form (directly accessing view model object) works fine.

Any idea what would be the right construct? Thanks in advance!!!

Answer 1

Instead of :

${#dates.format(bar.createdAt, #messages.msg('app.dateformat.datetime'))}

Change it to :

*{#dates.format(bar.createdAt, #messages.msg('app.dateformat.datetime'))}

So that the utility object will work on the bar property of the last selected object which is the form backing object, ${foo}, in your case.