Problem Description : XSLT transformation creating unique namespace prefixes.
Analysis & Observation : The XSLT transformation is generating a new namespace prefix for every XML element, even when the namespace value matches that of the parent element. This leads to large XML file transformations exceeding the file size and memory limits on our systems. The behaviour in OpenJDK has remained consistent since JDK 8; however, the namespace prefix issue is not something we find optimum. During our investigation of the OpenJDK codebase, we identified defect https://bugs.openjdk.org/browse/JDK-8167179, which was intended to resolve the namespace prefix issue in the OpenJDK 8 release. However, our testing confirms that the issue persists across multiple versions, including OpenJDK 8, 11, 17, and 22. Additionally, we found an open bug report https://bugs.openjdk.org/browse/JDK-8168664 in the OpenJDK issue tracker referencing a similar problem. Notably, there has been no recent activity on this bug for several years Suggested Solution: Introduced a hashmap, and storing the unique namespace-url from root node and checking if new url namespace-url encountered then we will store it in the hashmap and increment the namespace prefix, else we will not increment the prefix. Implemented in existing function startXslElement() of src/java.xml/share/classes/com/sun/org/apache/xalan/internal/xsltc/runtime/BasisLibrary.java else { // Need to generate a prefix? if (namespace != null && namespace.length() > 0) { prefix = generatePrefix(); qname = prefix + ':' + qname; handler.startElement(namespace, qname, qname); handler.namespaceAfterStartElement(prefix, namespace); } The above code is changed to else { // Need to generate a prefix? if (namespace != null && namespace.length() > 0) { //Check if prefix needs to be incremented. if (!namespaceMap.containsKey(namespace)) { namespaceMap.put(namespace, threadLocalPrefixIndex.get().getAndIncrement()); prefix = "ns"+namespaceMap.get(namespace); qname = prefix + ':' + qname; handler.startElement(namespace, qname, qname); handler.namespaceAfterStartElement(prefix, namespace); } else { //Namespace URI already exist in map. prefix = "ns"+namespaceMap.get(namespace); qname = prefix + ':' + qname; handler.startElement(namespace, qname, qname); handler.namespaceAfterStartElement(prefix, namespace); } } Releases: OpenJDK 8, 11, 17 & 22 the issue is seen. Note: Proceeding with this approach, we will need to update the test files. For instance, we have identified one test case that validates the namespace prefix in the result - test/jaxp/javax/xml/jaxp/unittest/transform/NamespacePrefixTest.java Next steps: We want to take the above-mentioned fix to OpenJDK. Please review and suggest if the above understanding is right and we shall take the fix to OpenJDK.
