java - 如何使用 XPath 检查 XML 中是否存在元素？

Question

下面是我的元素层次结构。如何检查(使用 XPath)AttachedXml 元素是否存在于 Primary Consumer

的 CreditReport 下

<Consumers xmlns="http://xml.mycompany.com/XMLSchema">
       <Consumer subjectIdentifier="Primary">
          <DataSources>
               <Credit>
                   <CreditReport>
                      <AttachedXml><![CDATA[ blah blah]]>

Answer 1

使用 boolean() XPath function

The boolean function converts its argument to a boolean as follows:

• a number is true if and only if it is neither positive or negative zero nor NaN

• a node-set is true if and only if it is non-empty

• a string is true if and only if its length is non-zero

• an object of a type other than the four basic types is converted to a boolean in a way that is dependent on that type

如果primaryConsumer的CreditReport中有AttachedXml，则返回真()。

boolean(/mc:Consumers
          /mc:Consumer[@subjectIdentifier='Primary']
            //mc:CreditReport/mc:AttachedXml)