CREATE JAVA ACTION: AS $$ block generates uncompilable Java (imports in method body)

[engalar]

Problem

CREATE JAVA ACTION ... AS $$ ... $$ generates Java files that fail to compile, because the $$ code is placed verbatim into the executeAction() method body (BEGIN USER CODE region) without handling imports.

Per Mendix official docs:

Only the following code will be retained when actions are regenerated:

• the import list
• the code between BEGIN USER CODE and END USER CODE
• the code between BEGIN EXTRA CODE and END EXTRA CODE

Imports are a separate preserved region at file top level, but mxcli has no mechanism to populate it.

Reproduction

CREATE JAVA ACTION MyModule.ReadCSV(File: System.FileDocument) RETURNS String
AS $$
IContext context = this.getContext();
InputStream is = Core.getFileDocumentContent(context, File.getMendixObject());
BufferedReader reader = new BufferedReader(new InputStreamReader(is, "UTF-8"));
String line = reader.readLine();
reader.close();
return line;
$$;

Generated Java file only has default imports:

import com.mendix.systemwideinterfaces.core.IContext;
import com.mendix.systemwideinterfaces.core.UserAction;
import com.mendix.systemwideinterfaces.core.IMendixObject;

Core, InputStream, BufferedReader, InputStreamReader are all unresolved → compilation error.

What happens when AI agents write the code

AI agents naturally prepend import statements inside $$:

AS $$
import com.mendix.core.Core;
import java.io.*;
// actual code...
$$;

These end up inside the method body, which is illegal Java:

public String executeAction() throws Exception {
    // BEGIN USER CODE
    import com.mendix.core.Core;     // ← syntax error
    import java.io.*;                 // ← syntax error
    // ...
}

This happened to all 3 Java Actions in our project (CreateOrdersFromCSV, ParseCSVFile, ReadResourceFile).

Root cause

AS $$ only writes to BEGIN USER CODE. The generated .java file has no mechanism to receive additional imports.

Suggested fixes

Option A: Strip import lines from $$ and move to file header (minimal, backward-compatible)

If $$ block contains lines matching ^\s*import\s+[\w.*]+;\s*$, extract them and place in the import section instead of the method body. This makes AI-generated code "just work".

Option B: Add IMPORT clause to MDL syntax

CREATE JAVA ACTION MyModule.ReadCSV(File: System.FileDocument) RETURNS String
IMPORT com.mendix.core.Core, java.io.*, java.util.*
AS $$
// can use short names
$$;

Option C: Auto-detect types and inject imports

Scan $$ code for known type references and auto-add imports. A reasonable default mapping:

Type	Import
Core	com.mendix.core.Core
IContext	com.mendix.systemwideinterfaces.core.IContext
IMendixObject	com.mendix.systemwideinterfaces.core.IMendixObject
IMendixIdentifier	com.mendix.systemwideinterfaces.core.IMendixIdentifier
InputStream	java.io.InputStream
BufferedReader	java.io.BufferedReader
InputStreamReader	java.io.InputStreamReader
BigDecimal	java.math.BigDecimal
List, ArrayList	java.util.List, java.util.ArrayList
Map, HashMap	java.util.Map, java.util.HashMap
ILogNode	com.mendix.logging.ILogNode

Bonus: Support BEGIN EXTRA CODE

Consider an EXTRA $$...$$ block for helper methods:

CREATE JAVA ACTION MyModule.MyAction() RETURNS String
AS $$
return helper();
$$
EXTRA $$
private String helper() { return "ok"; }
$$;

Also: skill doc java-actions.md references removed API

The Core API Reference table in java-actions.md lists:

Core.retrieveXPathQuery(context, xpath)

This method does not exist in Mendix 10+/11. The correct API per official docs is:

Core.createXPathQuery(xpath).execute(context)

This causes AI agents to generate code that compiles but fails with method not found.

Environment

• mxcli: 0.1.0
• Mendix: 11.6.4
• Platform: Windows 11