rhino_dust.java

package com.linkedin.dust.renderer;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.Writer;

import org.mozilla.javascript.Context;
import org.mozilla.javascript.JavaScriptException;
import org.mozilla.javascript.Scriptable;

public class DustEngine
{
  public static final String MODULE             = DustEngine.class.getName();
  private static Scriptable  globalScope;

  public DustEngine(InputStream dustStream)
  {
    try
    {
      Reader dustReader = new InputStreamReader(dustStream, "UTF-8");
      Context dustEngineContext = Context.enter();
      dustEngineContext.setOptimizationLevel(9);
      try
      {
        globalScope = dustEngineContext.initStandardObjects();
        dustEngineContext.evaluateReader(globalScope,
                                         dustReader,
                                         "dust-compile.js",
                                         0,
                                         null);
      }
      finally
      {
        Context.exit();
      }
    }
    catch (IOException ex)
    {
      throw new RuntimeException(" ERROR : Unable to load dust engine resource: ", ex);
    }
  }
  
  public static String compileTemplate(String name, String rawSource)
  {
    Context dustContext = Context.enter();
    try
    {
      Scriptable compileScope = dustContext.newObject(globalScope);
      compileScope.setParentScope(globalScope);
      compileScope.put("rawSource", compileScope, rawSource);
      compileScope.put("name", compileScope, name);

      try
      {
        return (String) dustContext.evaluateString(compileScope,
                                                           "(dust.compile(rawSource, name))",
                                                           "JDustCompiler",
                                                           0,
                                                           null);
      }
      catch (JavaScriptException e)
      {
        // Fail hard on any compile time error for dust templates
        throw new RuntimeException(e);
      }
    }
    finally
    {
      Context.exit();
    }
  }


  public static void loadTemplate(String name, String rawSource)
  {

    Context dustContext = Context.enter();
    try
    {
      Scriptable compileScope = dustContext.newObject(globalScope);
      compileScope.setParentScope(globalScope);
      compileScope.put("rawSource", compileScope, rawSource);
      compileScope.put("name", compileScope, name);

      try
      {
        dustContext.evaluateString(compileScope,
                                                           "(dust.loadSource(dust.compile(rawSource, name)))",
                                                           "JDustCompiler",
                                                           0,
                                                           null);
      }
      catch (JavaScriptException e)
      {
        // Fail hard on any compile time error for dust templates
        throw new RuntimeException(e);
      }
    }
    finally
    {
      Context.exit();
    }
  }

  public static void render(String name, String json, Writer writer)
  {
    Context dustContext = Context.enter();

    Scriptable renderScope = dustContext.newObject(globalScope);
    renderScope.setParentScope(globalScope);

    String renderScript =
        ("{   dust.render( name,  JSON.parse(json) , function( err, data) { if(err) { writer.write(err);} else { writer.write( data );}  } );   }");

    try
    {
      renderScope.put("writer", renderScope, writer);
      renderScope.put("json", renderScope, json);
      renderScope.put("name", renderScope, name);

      dustContext.evaluateString(renderScope,
                                       renderScript,
                                       "JDustCompiler",
                                       0,
                                       null);

    }
    catch (JavaScriptException e)
    {
      // Fail hard on any render time error for dust templates
      throw new RuntimeException(e);
    }
    finally
    {
      Context.exit();
    }
  }

}