这个属性在不设置的情况下是false，但是如果要设应该只能设置为true。见下面的资料。或者说是axis实现上的问题，现在webservices有很多种实现的api包，而且每家的支持力度不太一样。因此如果遇到这种问题，就要回去看看你下载的实现api的feature说明了。http://www.w3.org/TR/soap12-part1/#soapmu5.2.3 SOAP mustUnderstand Attribute
The SOAP mustUnderstand attribute information item is used to indicate whether the processing of a SOAP header block is mandatory or optional (see 2.4 Understanding SOAP Header Blocks)The mustUnderstand attribute information item has the following XML infoset properties:A [local name] of mustUnderstand .A [namespace name] of "http://www.w3.org/2003/05/soap-envelope".A [specified] property with a value of "true".The type of the mustUnderstand attribute information item is xs:boolean.Omitting this attribute information item is defined as being semantically equivalent to including it with a value of "false".SOAP senders SHOULD NOT generate, but SOAP receivers MUST accept the SOAP mustUnderstand attribute information item with a value of "false" or "0".If generating a SOAP mustUnderstand attribute information item, a SOAP sender SHOULD use the canonical representation "true" of the attribute value (see XML Schema [XML Schema Part 2]). A SOAP receiver MUST accept any valid lexical representation of the attribute value.If relaying the message, a SOAP intermediary MAY substitute "true" for the value "1", or "false" for "0". In addition, a SOAP intermediary MAY omit a SOAP mustUnderstand attribute information item if its value is "false" (see 2.7 Relaying SOAP Messages).A SOAP sender generating a SOAP message SHOULD use the mustUnderstand attribute information item only on SOAP header blocks. A SOAP receiver MUST ignore this attribute information item if it appears on descendants of a SOAP header block or on a SOAP body child element information item (or its descendents).
The SOAP mustUnderstand attribute information item is used to indicate whether the processing of a SOAP header block is mandatory or optional (see 2.4 Understanding SOAP Header Blocks)The mustUnderstand attribute information item has the following XML infoset properties:A [local name] of mustUnderstand .A [namespace name] of "http://www.w3.org/2003/05/soap-envelope".A [specified] property with a value of "true".The type of the mustUnderstand attribute information item is xs:boolean.Omitting this attribute information item is defined as being semantically equivalent to including it with a value of "false".SOAP senders SHOULD NOT generate, but SOAP receivers MUST accept the SOAP mustUnderstand attribute information item with a value of "false" or "0".If generating a SOAP mustUnderstand attribute information item, a SOAP sender SHOULD use the canonical representation "true" of the attribute value (see XML Schema [XML Schema Part 2]). A SOAP receiver MUST accept any valid lexical representation of the attribute value.If relaying the message, a SOAP intermediary MAY substitute "true" for the value "1", or "false" for "0". In addition, a SOAP intermediary MAY omit a SOAP mustUnderstand attribute information item if its value is "false" (see 2.7 Relaying SOAP Messages).A SOAP sender generating a SOAP message SHOULD use the mustUnderstand attribute information item only on SOAP header blocks. A SOAP receiver MUST ignore this attribute information item if it appears on descendants of a SOAP header block or on a SOAP body child element information item (or its descendents).
你部署完axis后用没用vadidate链接检验必须的组件？即查看Axis Happiness Page页面。
一些必须的组件如：（saaj.jar；jaxrpc.jar；axis.jar；commons-discovery-0.2.jar；commons-logging-1.0.4.jar；log4j-1.2.8.jar；wsdl4j-1.5.1.jar；javax.xml.parsers.SAXParserFactory ；activation.jar）。
我部署完之后老是提示找不到javax.xml.parsers.SAXParserFactory ，但是我已经把xercesImpl.jar；xml-apis.jar；xmlParserAPIs.jar放到了axis\WEB-INF\lib目录下了。
也就是说 axis 自己使 mustUnderstand 为 false ，却报告 false 是非法的 mustUnderstand 取值。
我甚至都怀疑是 axis 1.4 的 bug 了。到现在还是搞不懂。
你找不到 javax.xml.parsers.SAXParserFactory ，它是 JSDK 中的类。你可能是因为jsdk的 classpath 的问题造成的。