Troubleshooting XML Module | MuleSoft Documentation
# Troubleshooting XML Module
To troubleshoot XML module, become familiar with the information about enabling verbose logging and interpreting commonly thrown messages.
## Enable Verbose Logging
To get a better understanding of why an application’s interaction with the XML Module is failing, temporarily enable verbose logging for XML module.
Remember to always disable the enhanced verbosity after troubleshooting because it affects your Mule application performance.
To enable verbose logging:
  1. Access Anypoint Studio and navigate to the **Package Explorer** view.
  2. Open your application’s project name.
  3. Open the `src/main/resources` path folder.
  4. Open the `log4j2.xml` file inside the folder.
  5. Add an `<AsyncLogger>` tag inside the `<Loggers>` tag:
```
			<Loggers>
				...
				<AsyncLogger name="org.mule.module.xml" level="DEBUG"/>
				...
			</Loggers>
```

  6. Save your application changes.
  7. Click the project name in **Package Explorer** and then click **Run** > **Run As** > **Mule Application**.


## Troubleshoot Validation Against Schema Issues
When using the XML module to validate against a schema that has references to other local schema files, the validation can fail with the error:
```
The supplied schemas were not valid. schema_reference: Failed to read schema document schemadocumentname.xsd, because file access is not allowed due to restriction set by the accessExternalSchema property
```

In the Studio Console, the error looks like this:
```
ERROR 2021-03-25 18:42:34,499 [[MuleRuntime].uber.03: [bug-xsd-schema-not-found-support].bug-xsd-schema-not-foundFlow.CPU_INTENSIVE @52ec9ec0] [processor: ; event: 026a10a0-8db3-11eb-80a6-3c22fb270222] org.mule.runtime.core.internal.exception.DefaultSystemExceptionStrategy:
********************************************************************************
Message        : The supplied schemas were not valid. schema_reference: Failed to read schema document 'schemadocumentname.xsd', because 'file' access is not allowed due to restriction set by the accessExternalSchema property.
Element        : bug-xsd-schema-not-foundFlow/processors/2 @ bug-xsd-schema-not-found-support:main.xml:16 (Validate schema)
Element DSL      : <xml-module:validate-schema schemas="ref/despatchAdviceMessages/despatchAdviceMessage.xsd"></xml-module:validate-schema>
Error type      : XML-MODULE:INVALID_SCHEMA
FlowStack       : at bug-xsd-schema-not-foundFlow(bug-xsd-schema-not-foundFlow/processors/2 @ bug-xsd-schema-not-found-support:main.xml:16 (Validate schema))
 (set debug level logging or '-Dmule.verbose.exceptions=true' for everything)
********************************************************************************
```

This error occurs because the access was restricted in the XML module global element configuration by setting the **Expand entities** field to the default value of **NEVER**. This value prevents XXE (XML External Entity) and DoS (Denial of Service) attacks.
To resolve this issue, set the **Expand entities** field to **INTERNAL** :
  1. In Studio, open your project and access your Mule app flow.
  2. Navigate to the **Global Element** tab.
  3. Select the **XML Config** configuration and click **Edit**.
  4. In the **Global Element Properties** window, set the **Expand entities** field to **INTERNAL**.
  5. Click **OK**.


In the **Configuration XML** editor, the `<expandEntities>` configuration looks like this:
```
<xml-module:config name="XML_Config" expandEntities="INTERNAL"/>
```

## Understand Common Throws
Here is a list of common throw messages and how to interpret them:
  * XML-MODULE:INVALID_INPUT_XML
```
The input document is not a valid XML.
```

  * XML-MODULE:INVALID_SCHEMA
```
The supplied schema is invalid.
```

  * XML-MODULE:INVALID_XPATH_EXPRESSION
```
The supplied XPath expression is invalid.
```

  * XML-MODULE:NULL_CONTEXT_PROPERTY
```
A context property with a null value was supplied.
```

  * XML-MODULE:SCHEMA_NOT_HONOURED
```
The input XML document does not honor its schema.
```

  * XML-MODULE:SCHEMA_NOT_FOUND
```
The schema could not be found.
```

  * XML-MODULE:TRANSFORMATION
```
There was an error transforming an XML document.
```

  * XML-MODULE:SCHEMA_INPUT_ERROR


The Validate schema operation failed because both the Schema and the Schema Content fields were used at the same time during the operation’s execution. You can only use one of these fields to validate schema XSD content.
## See Also
  * XML Module Reference
  * MuleSoft Help Center
  *