Top 7 Rules in the ESQL Sonar Plugin You Should KnowMaintaining clean, reliable ESQL (Extended Structured Query Language) code is essential for integration projects, especially when working with IBM Integration Bus/ACE message flows. The ESQL Sonar Plugin helps teams enforce consistent standards, detect common mistakes, and reduce bugs early in development. This article examines the seven most important rules provided by the ESQL Sonar Plugin, explains why each rule matters, and gives practical examples and remediation steps you can apply immediately.
1. Avoid using GLOBAL variables
Why it matters:
- GLOBAL variables introduce hidden state that can make message flow behavior unpredictable and hard to debug, particularly in multithreaded or concurrent environments.
- They increase coupling between modules and reduce testability.
What to look for:
- Declarations using the GLOBAL keyword or implicit shared state across modules.
Example (problematic):
CREATE GLOBAL MODULE Globals BEGIN DECLARE GLOBAL myCounter INTEGER 0; END MODULE; How to fix:
- Replace GLOBAL variables with local variables, message properties, or persistent storage designed for concurrency (for example, using the ESQL Environment or database storage with proper locking).
- Pass necessary state explicitly between procedures or use message/environment tree elements scoped to the message.
2. Do not swallow exceptions silently
Why it matters:
- Catching exceptions without logging or rethrowing hides failures and makes it difficult to identify root causes. Silent failures can lead to data loss or incorrect processing results.
What to look for:
- CATCH blocks that have no logging, no rethrow, and no compensation logic.
Example (problematic):
BEGIN -- risky operation EXCEPTION WHEN SOME_EXCEPTION THEN -- nothing here END; How to fix:
- Log meaningful context (error codes, descriptions, message IDs) and decide whether to rethrow, propagate, or handle the exception safely (e.g., move message to error queue).
- Example remediation:
EXCEPTION WHEN SOME_EXCEPTION THEN SET OutputLocalEnvironment.Destination.File.Name = 'error_log'; -- Log details CALL LogError('SOME_EXCEPTION', THE_ERROR); SIGNAL; -- or rethrow/propagate as appropriate END;
3. Prefer explicit schema references over wildcard field access
Why it matters:
- Using wildcards or implicit access (e.g., referencing fields without specifying parent nodes) increases ambiguity and can result in incorrect field selection or schema drift when message structures change.
What to look for:
- Code using generic field references like InputRoot.*, or relying on position-based access instead of full hierarchical addressing.
Example (problematic):
SET OutputRoot.* = InputRoot.*; How to fix:
- Use explicit paths (InputRoot.XMLNSC.Order.Customer.Name) and map only the fields you need. This makes code clearer and safer when downstream schemas change.
4. Avoid deep nesting and long procedures — keep functions small and focused
Why it matters:
- Deeply nested logic and very long procedures increase cognitive load, make unit testing difficult, and hide logic paths that may be buggy.
What to look for:
- Procedures exceeding reasonable length (hundreds of lines), many nested IF/LOOP structures, or multiple responsibilities inside a single routine.
How to fix:
- Split large procedures into smaller, single-responsibility functions.
- Use meaningful procedure names, document inputs/outputs, and keep nesting depth shallow (prefer early returns).
Example refactor:
- Extract nested conditional branches into helper procedures like ValidateCustomer(), TransformOrder(), WriteAudit().
5. Sanitize and validate external input
Why it matters:
- Input from external systems can be malformed or malicious. Unvalidated data can cause runtime errors, incorrect business decisions, or security vulnerabilities.
What to look for:
- Direct assumptions about field existence, unguarded CASTs/conversions, and no checks for NULL or unexpected types.
Example (problematic):
SET orderQty = CAST(InputRoot.XMLNSC.Order.Quantity AS INTEGER); How to fix:
- Check for field existence, use TRY/CATCH around conversions, provide defaults, and validate ranges/formats before using values.
- Example remediation:
IF FIELDVALUE(InputRoot.XMLNSC.Order.Quantity) IS NOT NULL THEN BEGIN DECLARE q INTEGER; BEGIN SET q = CAST(InputRoot.XMLNSC.Order.Quantity AS INTEGER); IF q < 0 THEN SIGNAL USER_DEFINED_ERROR; END IF; SET orderQty = q; EXCEPTION WHEN SOME_EXCEPTION THEN -- handle invalid conversion END; END; END IF;
6. Release resources and avoid memory leaks
Why it matters:
- Long-running integration nodes can suffer from resource exhaustion if cursors, references, or large message objects are not released or trimmed. This affects performance and stability.
What to look for:
- Persistent references to large message trees, unclosed cursors in loops, or repeated allocation without cleanup.
How to fix:
- Use CLEAR, PROPAGATE appropriately, and set variables to NULL when no longer needed. Close cursors explicitly and avoid accumulating large in-memory structures.
- Example:
DECLARE c CURSOR FOR SELECT ...; OPEN c; -- process rows CLOSE c; SET myLargeBlob = NULL;
7. Follow naming conventions and keep code readable
Why it matters:
- Consistent naming and formatting make code easier to review, maintain, and onboard new team members. Sonar rules often enforce naming conventions for modules, procedures, variables, and constants.
What to look for:
- Inconsistent case, ambiguous variable names like tmp1/tmp2, or mixing naming styles in the same project.
How to fix:
- Adopt and enforce a clear naming standard (e.g., PascalCase for procedures, camelCase for local variables, UPPER_SNAKE for constants).
- Add short comments for non-obvious logic and keep line lengths reasonable.
Applying these rules in practice
- Integrate ESQL Sonar Plugin into your CI pipeline so rules run automatically at pull request time.
- Treat Sonar rule violations as actionable items: triage, assign an owner, and fix or justify exceptions.
- Combine static rules with unit tests and integration tests to catch issues that static analysis can’t detect (runtime data problems, external system behaviors).
These seven rules cover a broad set of reliability, maintainability, and security concerns that commonly surface in ESQL codebases. Applying them consistently will reduce bugs, improve code clarity, and make integration flows more robust.
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