Calling Groovy scripts from Java and refreshing the Groovy scripts periodically

Question

I want to call the Groovy scripts from Java and refresh the Groovy scripts periodically. For example ,

public class AppTest {
   public static void main(String args[]) throws Exception {
      TestVO test = new TestVO();
      AnotherInput input = new AnotherInput();
      test.setName("Maruthi");
      input.setCity("Newark");
      GroovyClassLoader loader = new GroovyClassLoader(AppTest.class.getClassLoader());
      Class groovyClass = loader.parseClass(new File("src/main/resources/groovy/MyTestGroovy.groovy"));
      GroovyObject groovyObject = (GroovyObject) groovyClass.newInstance();
      Object[] inputs = {test,null};
      Map<String,String> result = (Map<String, String>)groovyObject.invokeMethod("checkInput", inputs);
      System.out.println(result);
   }
}

And my Groovy script is

class MyTestGroovy {

   def x = "Maruthi";
   def checkInput = { TestVO input,AnotherInput city ->

      if(input.getName().equals(x)) {
         input.setName("Deepan");
         println "Name changed Please check the name";
      } else {
         println "Still Maruthi Rocks";
      }

      Map<String, String> result = new HashMap<String,String>();
      result.put("Status", "Success");

      if(city != null && city.getCity().equalsIgnoreCase("Newark")) {
         result.put("requested_State", "Newark");
      }

      return result;
   }

   def executeTest = {  
      println("Test Executed");
   }
}

How efficient my memory would be managed when I create multiple instances of groovy script and execute the script. Is it advisable to use a number of Groovy scripts as my customized rule engine. Please advise.

blackdrag blackdrag · Accepted Answer · 2014-07-07T09:07:56

It is usually better to have several instances of the same script, than parsing the class every time you want to create an instance. Performance wise that is because compiling the script takes some time, you have to pay in addition to creating an instance. Memory wise you use up the number of available classes up faster. Even if old classes are collected, if you have many scripts active, it can happen... though that normally means hundreds or even thousands of them (depends on the jvm version and your memory settings)

Of course, once the script changed, you will have to recompile the class anyway. So if in your scenario you will have only one instance of the class active at the same time, and a new instance is only required after a change to the source, you can recompile every time.

I mention that especially, because you might even be able to write the script in a way, that let's you reuse the same instance. But it is of course beyond the scope of this question.

Calling Groovy scripts from Java and refreshing the Groovy scripts periodically

1 Answers