[FreeMarker-user] Custom directive for XML model

[Viktor Levine]

In the test below the test for map model works fine, but for XML model
breaks. The custom directive is to wire in Spring's SPEL into FM templates,
but I'm certain that the same would fail on any other directive. The reason
IMHO is this construct in DocumentModel
if (StringUtil.isXMLID(key)) {
ElementModel em = (ElementModel) NodeModel.wrap(((Document)
node).getDocumentElement());
if (em.matchesName(key, Environment.getCurrentEnvironment())) {
return em;
} else {
//HERE
return new NodeListModel(this);
}
}
which should return null where it is commented HERE. Then the caller
(Environment.getGlobalVariable(String)) would correctly pull the directive
from the shared variables.

The template is :
[#ftl]
We say [@spel]@greetingBean.printGreeting(name)[/@spel] from Freemarker in
[@spel expression="T(java.util.Locale).getDefault()"/]


The test (pardon me for the length):

public class SpelFreemarkerTemplateDirectiveTest {
private static final String XML = "<name>Felix</name>";
@Mock
private BeanFactory beanFactory;
private GreetingBean greetingBean = new GreetingBean("Hello");

@Before
public void setup() {
MockitoAnnotations.initMocks(this);
}

@Test
public void testFreemarkerSpel()
throws IOException, TemplateException {
Map<String, String> model = new HashMap<String, String>();

model.put("name", "Felix");

Configuration cfg = new Configuration();
SpelFreemarkerTemplateDirective directive = new
SpelFreemarkerTemplateDirective();

when(beanFactory.getBean("greetingBean")).thenReturn(greetingBean);
directive.setBeanFactory(beanFactory);
cfg.setSharedVariable("spel", directive);

Template tpl = cfg.getTemplate("greeting-template.ftl");

StringWriter writer = new StringWriter();

tpl.process(model, writer);

System.out.println(writer.toString());

String expected = "We say " +
greetingBean.printGreeting(model.get("name")) +
" from Freemarker in " + Locale.getDefault();

assertEquals(expected, writer.toString());
}

/**
* JAVADOC Method Level Comments
*
* @throws Exception JAVADOC.
*/
@Test
public void testXmlSpel()
throws Exception {
NodeModel model = NodeModel.parse(new InputSource(new
StringReader(XML)));
Configuration cfg = new Configuration();

SpelFreemarkerTemplateDirective directive = new
SpelFreemarkerTemplateDirective();

when(beanFactory.getBean("greetingBean")).thenReturn(greetingBean);
directive.setBeanFactory(beanFactory);
cfg.setSharedVariable("spel", directive);

Template tpl = cfg.getTemplate("greeting-template.ftl");

StringWriter writer = new StringWriter();

tpl.process(model, writer);

System.out.println(writer.toString());

String expected = "We say " + greetingBean.printGreeting("Felix") +
" from Freemarker in " +
Locale.getDefault();

assertEquals(expected, writer.toString());
}

public static class GreetingBean {
private String greeting;

public GreetingBean(String greeting) {
this.greeting = greeting;
}

public String printGreeting(String name) {
return greeting + " " + name;
}
}
}

[Viktor Levine]

And the stack trace:

FreeMarker template error:
For "@" callee: Expected a(n) user-defined directive (macro, etc.), but this
evaluated to a sequence+hash (wrapper: f.e.dom.NodeListModel):
==> spel [in template
"test/unit/com/algorithmics/pulp/spring/greeting-template.ftl" at line 2,
column 10]

The failing instruction (FTL stack trace):
----------
==> @spel [in template
"test/unit/com/algorithmics/pulp/spring/greeting-template.ftl" at line 2,
column 8]
----------

Java stack trace (for programmers):
----------
freemarker.core.UnexpectedTypeException: [... Exception message was already
printed; see it above ...]
at freemarker.core.UnifiedCall.accept(UnifiedCall.java:146)
at freemarker.core.Environment.visit(Environment.java:265)
at freemarker.core.MixedContent.accept(MixedContent.java:93)
at freemarker.core.Environment.visit(Environment.java:265)
at freemarker.core.Environment.process(Environment.java:243)
at freemarker.template.Template.process(Template.java:277)
at

[Daniel Dekany]

There problem here is that with XML models the `.` or `[]` operator
will always return a set of nodes (NodeListModel), even if there's no
match. This is crucial in the approach of the XML wapper, as further
`.` or `[]` operators are possibly applied on the result, like in
`foo.maybeMissing.bar`, also because `<#list foo.optinals as i>` has
to work even if there's 0 `optionals` in foo. So an XML model isn't
meant to be *directly* used as the data-model root. Even if it had a
setting that causes it to return null there, to fall back to the
shared variables, first it had to check that em.matchesName returns
false, which is probably not very fast (compared to, say, a
HashMap.get).

So maybe you should just create a HashMap, and put the top-element of
the XML into it with its own name, and then use said HashMap as the
root. Or you can encapsulate the same functionality into your own
TemplateHashModel implementation that wraps a W3C DOM Document. Is
that viable?
--
Thanks,
Daniel Dekany

Post by Viktor Levine
In the test below the test for map model works fine, but for XML model
breaks. The custom directive is to wire in Spring's SPEL into FM templates,
but I'm certain that the same would fail on any other directive. The reason
IMHO is this construct in DocumentModel
if (StringUtil.isXMLID(key)) {
ElementModel em = (ElementModel) NodeModel.wrap(((Document)
node).getDocumentElement());
if (em.matchesName(key,
Environment.getCurrentEnvironment())) {
return em;
} else {
//HERE
return new NodeListModel(this);
}
}
which should return null where it is commented HERE. Then the caller
(Environment.getGlobalVariable(String)) would correctly pull the directive
from the shared variables.
[#ftl]
public class SpelFreemarkerTemplateDirectiveTest {
private static final String XML = "<name>Felix</name>";
@Mock
private BeanFactory beanFactory;
private GreetingBean greetingBean = new GreetingBean("Hello");
@Before
public void setup() {
MockitoAnnotations.initMocks(this);
}
@Test
public void testFreemarkerSpel()
throws IOException, TemplateException {
Map<String, String> model = new HashMap<String, String>();
model.put("name", "Felix");
Configuration cfg = new Configuration();
SpelFreemarkerTemplateDirective directive = new
SpelFreemarkerTemplateDirective();
when(beanFactory.getBean("greetingBean")).thenReturn(greetingBean);
directive.setBeanFactory(beanFactory);
cfg.setSharedVariable("spel", directive);
Template tpl = cfg.getTemplate("greeting-template.ftl");
StringWriter writer = new StringWriter();
tpl.process(model, writer);
System.out.println(writer.toString());
String expected = "We say " +
greetingBean.printGreeting(model.get("name")) +
" from Freemarker in " + Locale.getDefault();
assertEquals(expected, writer.toString());
}
/**
* JAVADOC Method Level Comments
*
*/
@Test
public void testXmlSpel()
throws Exception {
NodeModel model = NodeModel.parse(new InputSource(new
StringReader(XML)));
Configuration cfg = new Configuration();
SpelFreemarkerTemplateDirective directive = new
SpelFreemarkerTemplateDirective();
when(beanFactory.getBean("greetingBean")).thenReturn(greetingBean);
directive.setBeanFactory(beanFactory);
cfg.setSharedVariable("spel", directive);
Template tpl = cfg.getTemplate("greeting-template.ftl");
StringWriter writer = new StringWriter();
tpl.process(model, writer);
System.out.println(writer.toString());
String expected = "We say " +
greetingBean.printGreeting("Felix") +
" from Freemarker in " +
Locale.getDefault();
assertEquals(expected, writer.toString());
}
public static class GreetingBean {
private String greeting;
public GreetingBean(String greeting) {
this.greeting = greeting;
}
public String printGreeting(String name) {
return greeting + " " + name;
}
}
}

...

[Viktor Levine]

Daniel,

I can see your reasons. However, it renders the whole concept of custom
directives unusable in XML models out of the box. Perhaps documentation
should reflect this. We would have to avoid using custom directives in our
development. Until this functionality would be independent of the model.

Brgrds

[Daniel Dekany]

Post by Viktor Levine
Daniel,
I can see your reasons. However, it renders the whole concept of custom
directives unusable in XML models out of the box.

XML is normally not used as the data-model *root*. It was never meant
to be used like that.

Post by Viktor Levine
Perhaps documentation should reflect this. We would have to avoid
using custom directives in our development.

You can just expose the top-level XML element in the data-model with a
variable, as I have suggested.

Post by Viktor Levine
Until this functionality would be independent of the model.