While using the SimpleTemplateEngine to process a template with a “$package” expression I got an error. Rename this expression to “$pack” and it works.
Puzzling. Then I looked at the source code for the template engine. Oops, forgot that Groovy uses script parsing of text to implement many powerful features, like templates. Kind of like extreme EYODF*. Thus, a snippet of the source code for SimpleTemplateEngine shown in listing 1 below, the word “package” is interpreted as the Java language keyword “package“.
try {
template.script = groovyShell.parse(script, "SimpleTemplateScript" + counter++ + ".groovy");
} catch (Exception e) {
throw new GroovyRuntimeException("Failed to parse template script (your template may contain an error or be trying to use expressions not currently supported): " + e.getMessage());
}
Listing 1
Below is an example of this.
def templateText = '''package $package;''' def engine = new groovy.text.SimpleTemplateEngine(true) def template = engine.createTemplate(templateText) def binding = ['package':'a/b/c'] def s = template.make(binding) println s
Listing 2
Results in:
Caught: groovy.lang.GroovyRuntimeException: Failed to parse template script (your template may contain an error or be trying to use expressions not currently supported): startup failed:
SimpleTemplateScript1.groovy: 1: unexpected token: package @ line 1, column 23.
out.print("""package $package;""");
^
1 error
Now change the expression to $pack:
def templateText = '''package $pack;''' def engine = new groovy.text.SimpleTemplateEngine() // pass in true to see debug output def template = engine.createTemplate(templateText) def binding = ['pack':'a/b/c'] def s = template.make(binding) println s
Listing 3
And, the result is:
package a/b/c;
Environment
- Groovy Version: 2.2.2 JVM: 1.7.0_25 Vendor: Oracle Corporation OS: Windows 7
- Eclipse 4.3
- Groovy-Eclipse Feature: 2.9.0.xx-20140228-1800-e43-SNAPSHOT
Some links
EYODF*: “Eat Your Own Dog Food”
