Package groovy.text

Class SimpleTemplateEngine

java.lang.Object
groovy.text.TemplateEngine
groovy.text.SimpleTemplateEngine
public class SimpleTemplateEngine extends TemplateEngine
Processes template source files substituting variables and expressions into placeholders in a template source text to produce the desired output.

The template engine uses JSP style <% %> script and <%= %> expression syntax or GString style expressions. The variable 'out' is bound to the writer that the template is being written to.

Frequently, the template source will be in a file but here is a simple example providing the template as a string: 

 def binding = [
     firstname : "Grace",
     lastname  : "Hopper",
     accepted  : true,
     title     : 'Groovy for COBOL programmers'
 ]
 def engine = new groovy.text.SimpleTemplateEngine()
 def text = '''\
 Dear <%= firstname %> $lastname,

 We <% if (accepted) print 'are pleased' else print 'regret' %> \
 to inform you that your paper entitled
 '$title' was ${ accepted ? 'accepted' : 'rejected' }.

 The conference committee.
 '''
 def template = engine.createTemplate(text).make(binding)
 println template.toString()
This example uses a mix of the JSP style and GString style placeholders but you can typically use just one style if you wish. Running this example will produce this output: 
 Dear Grace Hopper,

 We are pleased to inform you that your paper entitled
 'Groovy for COBOL programmers' was accepted.

 The conference committee.
The template engine can also be used as the engine for groovy.servlet.TemplateServlet by placing the following in your web.xml file (plus a corresponding servlet-mapping element): 
 <servlet>
   <servlet-name>SimpleTemplate</servlet-name>
   <servlet-class>groovy.servlet.TemplateServlet</servlet-class>
   <init-param>
     <param-name>template.engine</param-name>
     <param-value>groovy.text.SimpleTemplateEngine</param-value>
   </init-param>
 </servlet>
In this case, your template source file should be HTML with the appropriate embedded placeholders.

  • Constructor Details

    • SimpleTemplateEngine

      public SimpleTemplateEngine()
      Creates an engine that parses template scripts with the default Groovy class loader.

    • SimpleTemplateEngine

      public SimpleTemplateEngine(boolean verbose)
      Creates an engine with optional debug output enabled.
      Parameters:
      verbose - true to print generated script source while compiling templates

    • SimpleTemplateEngine

      public SimpleTemplateEngine(ClassLoader parentLoader)
      Creates an engine that uses a GroovyShell built from the supplied parent loader.
      Parameters:
      parentLoader - class loader used to compile generated template scripts

    • SimpleTemplateEngine

      public SimpleTemplateEngine(GroovyShell groovyShell)
      Creates an engine backed by the supplied GroovyShell.
      Parameters:
      groovyShell - shell used to compile generated template scripts

  • Method Details

    • createTemplate

      public Template createTemplate(Reader reader) throws CompilationFailedException, IOException
      Compiles template source from the supplied reader.
      Specified by:
      createTemplate in class TemplateEngine
      Parameters:
      reader - template source
      Returns:
      a compiled template instance
      Throws:
      CompilationFailedException - if Groovy fails to compile the generated template script
      IOException - if reading the template source fails

    • setVerbose

      public void setVerbose(boolean verbose)
      Parameters:
      verbose - true if you want the engine to display the template source file for debugging purposes

    • isVerbose

      public boolean isVerbose()
      Indicates whether generated template scripts are printed during compilation.
      Returns:
      true if debug output is enabled

    • isEscapeBackslash

      public boolean isEscapeBackslash()
      Indicates whether backslashes are escaped while parsing template source.
      Returns:
      true if backslash escaping is enabled

    • setEscapeBackslash

      public void setEscapeBackslash(boolean escapeBackslash)
      Controls whether backslashes in template source should be preserved using the legacy GROOVY-4585 behavior.
      Parameters:
      escapeBackslash - true to escape backslashes while parsing the template