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https://issues.apache.org/jira/browse/CAMEL-24406?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18106136#comment-18106136
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mayur mohan commented on CAMEL-24406:
-------------------------------------
Summary:
* Invalid / non-XML content does *not* just produce a clean exception – it
forces expensive DOM construction first.
* Retries multiply the cost because the same stream objects are rebuilt on
every attempt.
* Under load or with large bad payloads this becomes a significant heap-memory
and GC problem, even though the final outcome is always a parse failure.
*Mitigation* (until an upstream Camel improvement exists): perform a cheap
prefix + size check on the raw byte[] / InputStream *before* any type
conversion or CXF binding runs. This rejects the payload early and avoids the
DOM allocation entirely.
> camel-xml-jaxp: XmlConverter.toDOMDocument throws SAXParseException for
> non-XML content (Content is not allowed in prolog)
> --------------------------------------------------------------------------------------------------------------------------
>
> Key: CAMEL-24406
> URL: https://issues.apache.org/jira/browse/CAMEL-24406
> Project: Camel
> Issue Type: Improvement
> Components: camel-core-xml
> Reporter: mayur mohan
> Priority: Major
>
> h2. Problem
> When a ByteArrayInputStreamCache (or byte[]) carrying a non-XML response body
> (empty body, JSON error page, plain-text HTTP response, BOM-only) is passed
> to XmlConverter.toDOMDocument, the JDK XML parser throws:
> {noformat}
> org.xml.sax.SAXParseException; lineNumber: 1; columnNumber: 1; Content is not
> allowed in prolog.
> {noformat}
> Surfaced as:
> {noformat}
> Cannot read from xml stream. Reason: Error during type conversion from type:
> org.apache.camel.converter.stream.ByteArrayInputStreamCache to the required
> type: org.w3c.dom.Document ... due to org.xml.sax.SAXParseException: Content
> is not allowed in prolog.
> {noformat}
> h2. Stack Trace
> {noformat}
> org.xml.sax.SAXParseException; lineNumber: 1; columnNumber: 1; Content is not
> allowed in prolog.
> at
> java.xml/com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.createSAXParseException(ErrorHandlerWrapper.java:204)
> at
> java.xml/com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.fatalError(ErrorHandlerWrapper.java:178)
> at
> java.xml/com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:400)
> at
> java.xml/com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:978)
> at
> java.xml/javax.xml.parsers.DocumentBuilder.parse(DocumentBuilder.java:122)
> at
> org.apache.camel.converter.jaxp.XmlConverter.toDOMDocument(XmlConverter.java:661)
> at
> org.apache.camel.converter.jaxp.CamelXmlJaxpBulkConverterLoader.doConvertTo(CamelXmlJaxpBulkConverterLoader.java:317)
> at
> org.apache.camel.converter.jaxp.CamelXmlJaxpBulkConverterLoader.convertTo(CamelXmlJaxpBulkConverterLoader.java:51)
> at
> org.apache.camel.spi.BulkTypeConverters.convertTo(BulkTypeConverters.java:122)
> at
> org.apache.camel.component.cxf.converter.CxfPayloadConverter.convertTo(CxfPayloadConverter.java:165)
> at
> org.apache.camel.component.cxf.converter.CxfPayloadConverterLoader.lambda(CxfPayloadConverterLoader.java:68)
> at
> org.apache.camel.support.SimpleTypeConverter.convertTo(SimpleTypeConverter.java:101)
> at
> org.apache.camel.impl.converter.CoreTypeConverterRegistry.doConvertTo(CoreTypeConverterRegistry.java:516)
> at
> org.apache.camel.impl.converter.CoreTypeConverterRegistry.convertTo(CoreTypeConverterRegistry.java:203)
> at
> org.apache.camel.core.osgi.OsgiTypeConverter.convertTo(OsgiTypeConverter.java:138)
> at org.apache.camel.support.MessageSupport.getBody(MessageSupport.java:96)
> at
> org.apache.camel.component.cxf.DefaultCxfBinding.getBodyFromCamel(DefaultCxfBinding.java:1019)
> at
> org.apache.camel.component.cxf.DefaultCxfBinding.populateCxfResponseFromExchange(DefaultCxfBinding.java:461)
> at
> org.apache.camel.component.cxf.CxfConsumer.CxfConsumerInvoker.setResponseBack(CxfConsumer.java:324)
> at
> org.apache.camel.component.cxf.CxfConsumer.CxfConsumerInvoker.syncInvoke(CxfConsumer.java:248)
> {noformat}
> h2. Root Cause
> XmlConverter.toDOMDocument(byte[], Exchange) and toDOMDocument(StreamCache,
> Exchange) pass the content directly to DocumentBuilder.parse() without first
> checking whether it could plausibly be XML. Any content whose first
> non-whitespace byte is not < causes an immediate SAXParseException deep
> inside the JDK parser.
> h2. Fix
> Add a cheap static looksLikeXml(byte[]) helper that inspects only the first
> few bytes (handles UTF-8 BOM, UTF-16 BE/LE BOM, leading whitespace). Guard
> the two toDOMDocument overloads that take byte[] and StreamCache to return
> null when content is definitely not XML. Use @Converter(allowNull = true) so
> the Camel type-converter framework falls through gracefully.
> h2. Files Changed
> core/camel-xml-jaxp/src/main/java/org/apache/camel/converter/jaxp/XmlConverter.java
> core/camel-xml-jaxp/src/test/java/org/apache/camel/converter/jaxp/XmlConverterPrologTest.java
> (new, 13 tests)
> h2. Test Results
> {noformat}
> Tests run: 13, Failures: 0, Errors: 0, Skipped: 0 [JDK 21 / Maven 3.9]
> BUILD SUCCESS
> {noformat}
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