Collaborating on Java objects within Rhino's Javascript

Question

Collaborating on Java objects within Rhino's Javascript

Admitting that I am a JavaScript novice, I must acknowledge that my question might be lacking in clarity and detail.

Background

Within my organization, we use an internal Eclipse-based IDE for JavaScript development. The IDE allows us to write scripts in JavaScript and execute them directly. From what I have observed in stack traces of exceptions, it seems like the IDE uses Rhino.

The code I am working with is spread across 3 ".js" files:

Script-1: Declares global variables and instantiates Java objects

importClass(java.util.HashMap);
var hmTCResult = new HashMap();

Script-2: Performs actions using the global variables defined in Script-1

Script-2.prototype.run = function() {
hmTCResult.put("Result", "Fail");
};

changeStatus = function(strStatus){
hmTCResult.put("Result", strStatus);
};

Script-3: Calls a function from Script-2 which utilizes the global variables

changeStatus("Pass")

Problem Definition

When I call the function from Script-3 that interacts with the global variables in Script-2, it fails to recognize the instance variables and throws an exception stating "hmTCResult not set to the instance of an object." It's important to note that the same variable works perfectly fine within Script-1.

I have tried to understand the concept of Scope and Context in JavaScript by reading up on it, but I haven't been able to find explicit information about these concepts in the IDE. If needed, I can provide additional information for better clarification.

java javascript rhino

Answer 1

Answer №1

Make sure to juggle your scopes and set up prototype search properly for everything to work smoothly:

Context cx = Context.enter();
try {
    // Cache and reuse:
    ScriptableObject sealedSharedScope = cx.initStandardObjects(null,
            true);
    // Load necessary LiveConnect components.
    String loadMe = "RegExp; getClass; java; Packages; JavaAdapter;";
    cx.evaluateString(sealedSharedScope, loadMe, "preLoadLazyLoad", 0,
            null);

    cx.evaluateString(sealedSharedScope, "varInRoot = 'blah';",
            "setVarInRoot", 0, null);

    // Additional cx.evaluateString calls can be added here to customize the environment (e.g., hmTCResult)

    // Create a new throw-away scope within the hierarchy, with local variables:
    Scriptable scope = cx.newObject(sealedSharedScope);
    // Ensure that definitions in the root scope are accessible
    scope.setPrototype(sealedSharedScope);
    // Make sure new global variables are created in this scope (avoid using var)
    scope.setParentScope(null);

    cx.evaluateString(scope, "localVar = varInRoot;", "mySource", 0,
            null);
    assertEquals("blah", scope.get("localVar", scope).toString());
    // Check for variable not in root:
    assertEquals(ScriptableObject.NOT_FOUND,
            sealedSharedScope.get("localVar", scope));
} finally {
    Context.exit();
}

Note that scope.get does not automatically search the prototype chain - you need to do it manually!

Remember that scopes are separate from Context and persist even after Context.exit().

Answer 2

Make sure to juggle your scopes and set up prototype search properly for everything to work smoothly:

Context cx = Context.enter();
try {
    // Cache and reuse:
    ScriptableObject sealedSharedScope = cx.initStandardObjects(null,
            true);
    // Load necessary LiveConnect components.
    String loadMe = "RegExp; getClass; java; Packages; JavaAdapter;";
    cx.evaluateString(sealedSharedScope, loadMe, "preLoadLazyLoad", 0,
            null);

    cx.evaluateString(sealedSharedScope, "varInRoot = 'blah';",
            "setVarInRoot", 0, null);

    // Additional cx.evaluateString calls can be added here to customize the environment (e.g., hmTCResult)

    // Create a new throw-away scope within the hierarchy, with local variables:
    Scriptable scope = cx.newObject(sealedSharedScope);
    // Ensure that definitions in the root scope are accessible
    scope.setPrototype(sealedSharedScope);
    // Make sure new global variables are created in this scope (avoid using var)
    scope.setParentScope(null);

    cx.evaluateString(scope, "localVar = varInRoot;", "mySource", 0,
            null);
    assertEquals("blah", scope.get("localVar", scope).toString());
    // Check for variable not in root:
    assertEquals(ScriptableObject.NOT_FOUND,
            sealedSharedScope.get("localVar", scope));
} finally {
    Context.exit();
}

Note that scope.get does not automatically search the prototype chain - you need to do it manually!

Remember that scopes are separate from Context and persist even after Context.exit().

Answer 3

Answer №2

When trying to run a JavaScript script in Java, you can use the following steps:

ScriptEngine engine = new ScriptEngineManager().getEngineByMimeType( "text/javascript" );
Bindings bindings = engine.getBindings( ScriptContext.GLOBAL_SCOPE );
bindings.put( "varname", ... );
bindings.put( ... );
engine.put( ScriptEngine.FILENAME, script.toString());
engine.eval( new FileReader( script ));

If all 3 scripts are loaded into the same engine and bindings, everything works fine. However, if a new engine is created specifically for executing script3, the context will be cleared.

This message doesn't exactly provide an answer, but it's too lengthy to be just a comment.

Answer 4

When trying to run a JavaScript script in Java, you can use the following steps:

ScriptEngine engine = new ScriptEngineManager().getEngineByMimeType( "text/javascript" );
Bindings bindings = engine.getBindings( ScriptContext.GLOBAL_SCOPE );
bindings.put( "varname", ... );
bindings.put( ... );
engine.put( ScriptEngine.FILENAME, script.toString());
engine.eval( new FileReader( script ));

If all 3 scripts are loaded into the same engine and bindings, everything works fine. However, if a new engine is created specifically for executing script3, the context will be cleared.

This message doesn't exactly provide an answer, but it's too lengthy to be just a comment.

Answer 5

Answer №3

Based on the information provided and assuming the accuracy of your edited transcripts, it seems likely that your scripts are running in isolated scopes with the global scope as the parent.

It appears that the changeStatus function works in the third script because it is not declared with the keyword var, making it a variable in the global scope shared by all three scripts.

On the other hand, the hmTCResult variable may not work as expected because it is declared using var, indicating a local variable specific to each script's scope. This can cause issues when trying to access the variable from different scripts operating in separate scopes.

Answer 6

Based on the information provided and assuming the accuracy of your edited transcripts, it seems likely that your scripts are running in isolated scopes with the global scope as the parent.

It appears that the changeStatus function works in the third script because it is not declared with the keyword var, making it a variable in the global scope shared by all three scripts.

On the other hand, the hmTCResult variable may not work as expected because it is declared using var, indicating a local variable specific to each script's scope. This can cause issues when trying to access the variable from different scripts operating in separate scopes.

Collaborating on Java objects within Rhino's Javascript

Background

Problem Definition

Answer №1

Answer №2

Answer №3

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