# Class loader isolation and SDK module exports

*MuleSoft Platform Integration Architect Study Guide · Designing for the runtime plane technology architecture · Last updated November 13, 2026 · https://www.certifyforce.com/study-guide/mulesoft-platform-integration-architect/designing-for-the-runtime-plane-technology-architecture/class-loader-isolation-and-sdk-module-exports*

How Mule 4 isolates the runtime, applications, domains and modules behind declared APIs, how artifacts and Mule SDK modules export packages and resources, which library clashes isolation cannot prevent, and how connectors reach application dependencies.

- Certification: Salesforce MuleSoft Platform Integration Architect
- Exam section: Designing for the runtime plane technology architecture
- Study guide: https://www.certifyforce.com/study-guide/mulesoft-platform-integration-architect

**Official exam objective:**

> Design Mule applications making effective use of the implications of the Mule 4 class loader isolation of Mule modules.

## What the exam expects

- Explain why Mule 4 isolates artifacts and what an artifact's filtering class loader lets other artifacts see.
- Declare an artifact's public API with exported packages and exported resources in `mule-artifact.json`.
- Predict which packages a Java SDK module exports, and structure packages so internal classes stay hidden.
- Recognize library clashes that isolation cannot prevent, and design module signatures to avoid them.
- Choose how a connector gets access to an application dependency.

**Artifact:** an independently released unit such as the runtime, an application, a domain, a policy or an extension. **Exported package:** a Java package an artifact makes visible to others. **Filtering class loader:** the wrapper that enforces what other artifacts can see. **Mule SDK:** the Java or XML framework for building Mule 4 modules ([Class-loading Isolation](https://docs.mulesoft.com/mule-runtime/4.6/about-classloading-isolation), [SDKs Overview](https://docs.mulesoft.com/mule-sdk/latest/)).

## Key facts

| Fact | Detail | Source |
|---|---|---|
| Unexported content | Not visible from other artifacts | [Class-loading Isolation](https://docs.mulesoft.com/mule-runtime/4.6/about-classloading-isolation) |
| Export granularity | Whole packages; individual classes cannot be exported | [Export Resources](https://docs.mulesoft.com/mule-runtime/4.6/how-to-export-resources) |
| Resource export | `exportedResources` in `mule-artifact.json` | [Export Resources](https://docs.mulesoft.com/mule-runtime/4.6/how-to-export-resources) |
| SDK introspection | Configuration, connection, input and return types | [SDK isolation](https://docs.mulesoft.com/mule-sdk/latest/isolation) |
| `@Export` | Takes classes, exports their whole package | [SDK isolation](https://docs.mulesoft.com/mule-sdk/latest/isolation) |
| Duplicate export | Two modules exporting one package fail the app | [SDK isolation](https://docs.mulesoft.com/mule-sdk/latest/isolation) |
| Object return | Same-named classes from different versions still clash | [SDK isolation](https://docs.mulesoft.com/mule-sdk/latest/isolation) |
| App dependencies | Invisible to connectors unless shared or added as plugin dependencies | [Class-loading Isolation](https://docs.mulesoft.com/mule-runtime/4.6/about-classloading-isolation) |
| API versioning | Mule 4 APIs follow Semantic Versioning 2.0.0 | [Class-loading Isolation](https://docs.mulesoft.com/mule-runtime/4.6/about-classloading-isolation) |

## Check yourself

- Which three APIs does Mule 4 provide as its extension points?
- When Studio configures the connection driver for a Database connector, how does the driver reach the project?
- Why does MuleSoft suggest `.api.` and `.internal.` in package names?
- Which artifact types does the Export Resources page say hold resources that are internal unless exported?

## Sources

- [Class-loading Isolation](https://docs.mulesoft.com/mule-runtime/4.6/about-classloading-isolation)
- [Mule SDK: About Classloading Isolation](https://docs.mulesoft.com/mule-sdk/latest/isolation)
- [Export Resources](https://docs.mulesoft.com/mule-runtime/4.6/how-to-export-resources)
- [Mule SDKs Overview](https://docs.mulesoft.com/mule-sdk/latest/)

## About the full unit

The "Core concepts", "Exam traps" and "Worked scenario" sections of this unit, its 7 linked practice questions, and unlimited timed mock exams are included with the MuleSoft Platform Integration Architect pack (USD $19): https://www.certifyforce.com/practice-exams