Using an existing Java object in JRuby

Question

Could anyone say me, how should I use an existing Java object in a JRuby script?

I know how I can create a new instance of a Java class in JRuby, but in my case I have already an instance in Java and I want to check/modify some properties of it in my JRuby script.

//Java

public class MyClass 
{
private int size;

public int getSize() {
    return size;
}

public void setSize(int size) {
    this.size = size;
}
}

//...

MyClass myClass = new MyClass();
myClass.setSize(5);

//...

String script = "..????.."
ScriptingContainer rubyContainer = new ScriptingContainer();
rubyContainer.runScriptlet(script);

What should I write into the script variable to check and modify the size property like this:

if (myClass.getSize() > 3)
    myClass.setSize(10)
else
    myClass.setSize(0);

After the modification I'd like to be able to use the new value of the property in my Java code.

Thanks a lot!

JB Nizet · Accepted Answer · 2012-12-15 16:11:48Z

1

Straight from the javadoc of ScriptingContainer

The second example shows how to share variables between Java and Ruby. In this example, a local variable "x" is shared. [...]

Example 2:
    ScriptingContainer container = new ScriptingContainer();
    container.put("x", 12345);
    container.runScriptlet("puts x.to_s(2)");

answered Dec 15, 2012 at 16:11

JB Nizet

694k94 gold badges1.3k silver badges1.3k bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Anton Over a year ago

but in this case I do it from my Java code. In my case I need to know either I can get the existing Java object using only the JRuby script. Say I have a Timer and every x seconds I do rubyContainer.runScriptlet(script); to do a new check/modification without doing something else in Java.

JB Nizet Over a year ago

I don't understand the problem. Edit your question, and show the real thing that you would like to do with your Timer.

Anton Over a year ago

Suppose I have a variable in my Java code (int myInt = 5). I want to be able to achive this variable from JRuby. I initiate a ScriptingContainer and call its function runScriptlet(script). The question is what should I write into the script variable to get an access to myInt in order to check/modify it?

JB Nizet Over a year ago

Use container.put("myClass", myClass), and inside the scriptlet, modify the myClass object as you will: myClass.size = 10 for example.

Anton · Accepted Answer · 2012-12-15 18:40:34Z

1

The problem is solved, thanks a lot for your help!

It is important to set "LocalVariableBehavior.PERSISTENT" to be able to use the object during multiple evaluations. After processing of the script the value of the object in the Java code is the same as in JRuby script.

//Java

rubyContainer = new ScriptingContainer(LocalVariableBehavior.PERSISTENT);
rubyContainer.put("myClass", myClass);

String script = 
    "if myClass.getSize() > 3 then " +
    "myClass.setSize(10) " +
    "else " +
    "myClass.setSize(0)" +
    "end";

rubyContainer.runScriptlet(script);

answered Dec 15, 2012 at 18:40

Anton

4,7142 gold badges31 silver badges36 bronze badges

Collectives™ on Stack Overflow

Using an existing Java object in JRuby

2 Answers 2

4 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

4 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related