[jboss-jira] [JBoss JIRA] (JBEE-183) NullPointerException happens at ELEvaluator.parseExpressionString() due to a concurrency issue

NullPointerException happens at ELEvaluator.parseExpressionString() due to a concurrency issue ---------------------------------------------------------------------------------------------- Key: JBEE-183 URL: https://issues.jboss.org/browse/JBEE-183 Project: JBoss JavaEE Spec APIs Issue Type: Bug Components: jboss-jstl-api Environment: - JBoss EAP 7.0.8 - jboss-jstl-api_1.2_spec-1.1.3.Final Reporter: Masafumi Miura Attachments: byteman-script.btm, example.zip The following NullPointerException happens at ELEvaluator.parseExpressionString() due to a concurrency issue. Once this NPE happens, you will see same NPE every time when accessing the failed JSP. (If development="true" is configured in <jsp-config>, recompile can happen in the next access, so NPE can disappear after successful compilation in the next access.) {code} ERROR [io.undertow.request] (default task-4) UT005023: Exception handling request to /dsl/g/clsys/cl/nop-constind/CNC001.jsp: org.apache.jasper.JasperException: JBWEB004001: Unable to compile class for JSP at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:667) [jastow-2.0.0.Final-redhat-1.jar:2.0.0.Final-redhat-1] at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:358) [jastow-2.0.0.Final-redhat-1.jar:2.0.0.Final-redhat-1] at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:402) [jastow-2.0.0.Final-redhat-1.jar:2.0.0.Final-redhat-1] at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:346) [jastow-2.0.0.Final-redhat-1.jar:2.0.0.Final-redhat-1] at javax.servlet.http.HttpServlet.service(HttpServlet.java:790) [jboss-servlet-api_3.1_spec-1.0.0.Final-redhat-1.jar:1.0.0.Final-redhat-1] ...(snip)... ... Caused by: java.lang.NullPointerException at org.apache.taglibs.standard.lang.jstl.ELEvaluator.parseExpressionString(ELEvaluator.java:276) [jboss-jstl-api_1.2_spec-1.1.3.Final-redhat-1.jar:1.1.3.Final-redhat-1] at org.apache.taglibs.standard.lang.jstl.Evaluator.validate(Evaluator.java:71) [jboss-jstl-api_1.2_spec-1.1.3.Final-redhat-1.jar:1.1.3.Final-redhat-1] at org.apache.taglibs.standard.lang.support.ExpressionEvaluatorManager.validate(ExpressionEvaluatorManager.java:131) [jboss-jstl-api_1.2_spec-1.1.3.Final-redhat-1.jar:1.1.3.Final-redhat-1] at org.apache.taglibs.standard.tlv.el.ValidationUtil.validateExpression(ValidationUtil.java:26) [jboss-jstl-api_1.2_spec-1.1.3.Final-redhat-1.jar:1.1.3.Final-redhat-1] at org.apache.taglibs.standard.tlv.el.JstlELCoreTLV.validateExpression(JstlELCoreTLV.java:26) [jboss-jstl-api_1.2_spec-1.1.3.Final-redhat-1.jar:1.1.3.Final-redhat-1] at org.apache.taglibs.standard.tlv.JstlCoreTLV$Handler.startElement(JstlCoreTLV.java:158) [jboss-jstl-api_1.2_spec-1.1.3.Final-redhat-1.jar:1.1.3.Final-redhat-1] at org.apache.xerces.parsers.AbstractSAXParser.startElement(AbstractSAXParser.java:498) at org.apache.xerces.parsers.AbstractXMLDocumentParser.emptyElement(AbstractXMLDocumentParser.java:180) at org.apache.xerces.impl.XMLNSDocumentScannerImpl.scanStartElement(XMLNSDocumentScannerImpl.java:275) at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl$FragmentContentDispatcher.dispatch(XMLDocumentFragmentScannerImpl.java:1653) at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:324) at org.apache.xerces.parsers.XML11Configuration.parse(XML11Configuration.java:875) at org.apache.xerces.parsers.XML11Configuration.parse(XML11Configuration.java:798) at org.apache.xerces.parsers.XMLParser.parse(XMLParser.java:108) at org.apache.xerces.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1198) at org.apache.xerces.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:564) at org.apache.taglibs.standard.tlv.JstlBaseTLV.validate(JstlBaseTLV.java:158) [jboss-jstl-api_1.2_spec-1.1.3.Final-redhat-1.jar:1.1.3.Final-redhat-1] at org.apache.taglibs.standard.tlv.JstlCoreTLV.validate(JstlCoreTLV.java:97) [jboss-jstl-api_1.2_spec-1.1.3.Final-redhat-1.jar:1.1.3.Final-redhat-1] at org.apache.jasper.compiler.TagLibraryInfoImpl.validate(TagLibraryInfoImpl.java:552) [jastow-2.0.0.Final-redhat-1.jar:2.0.0.Final-redhat-1] at org.apache.jasper.compiler.Validator.validateXmlView(Validator.java:1856) [jastow-2.0.0.Final-redhat-1.jar:2.0.0.Final-redhat-1] at org.apache.jasper.compiler.Validator.validateExDirectives(Validator.java:1825) [jastow-2.0.0.Final-redhat-1.jar:2.0.0.Final-redhat-1] at org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:218) [jastow-2.0.0.Final-redhat-1.jar:2.0.0.Final-redhat-1] at org.apache.jasper.compiler.Compiler.compile(Compiler.java:354) [jastow-2.0.0.Final-redhat-1.jar:2.0.0.Final-redhat-1] at org.apache.jasper.compiler.Compiler.compile(Compiler.java:334) [jastow-2.0.0.Final-redhat-1.jar:2.0.0.Final-redhat-1] at org.apache.jasper.compiler.Compiler.compile(Compiler.java:321) [jastow-2.0.0.Final-redhat-1.jar:2.0.0.Final-redhat-1] at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:652) [jastow-2.0.0.Final-redhat-1.jar:2.0.0.Final-redhat-1] ... 61 more {code} - https://github.com/jboss/jboss-jstl-api_spec/blob/jboss-jstl-api_1.2_spec... {code} 252 public Object parseExpressionString(String pExpressionString) 253 throws ELException { 254 // See if it's an empty String 255 if (pExpressionString.length() == 0) { 256 return ""; 257 } 258 259 if (!(mBypassCache) && (sCachedExpressionStrings == null)) { 260 createExpressionStringMap(); 261 } 262 263 // See if it's in the cache 264 Object ret = 265 mBypassCache ? 266 null : 267 sCachedExpressionStrings.get(pExpressionString); 268 269 if (ret == null) { 270 // Parse the expression 271 Reader r = new StringReader(pExpressionString); 272 ELParser parser = new ELParser(r); 273 try { 274 ret = parser.ExpressionString(); 275 if (!mBypassCache) { 276 sCachedExpressionStrings.put(pExpressionString, ret); // <- NPE occurred at here 277 } 278 } 279 catch (ParseException exc) { 280 throw new ELException 281 (formatParseException(pExpressionString, 282 exc)); 283 } 284 catch (TokenMgrError exc) { 285 // Note - this should never be reached, since the parser is 286 // constructed to tokenize any input (illegal inputs get 287 // parsed to <BADLY_ESCAPED_STRING_LITERAL> or 288 // <ILLEGAL_CHARACTER> 289 throw new ELException(exc.getMessage()); 290 } 291 } 292 return ret; 293 } {code} - https://github.com/jboss/jboss-jstl-api_spec/blob/jboss-jstl-api_1.2_spec... {code} ~~~ 51 /** 52 * The singleton instance of the evaluator * 53 */ 54 static ELEvaluator sEvaluator = 55 new ELEvaluator 56 (new JSTLVariableResolver()); : 62 /** 63 * Translation time validation of an attribute value. This method 64 * will return a null String if the attribute value is valid; 65 * otherwise an error message. 66 */ 67 public String validate(String pAttributeName, 68 String pAttributeValue) { 69 try { 70 sEvaluator.setBypassCache(true); // <-- mBypassCache is set to true before invoking parseExpressionString() 71 sEvaluator.parseExpressionString(pAttributeValue); 72 sEvaluator.setBypassCache(false); 73 return null; 74 } 75 catch (ELException exc) { {code}