[英]XPath in java won't accept variable in expression
Can someone be kind enough to explain me why 有人能对我解释一下吗
xPath.evaluate("/MEMBER_LIST/MEMBER[1]/ADDRESS", nodeMemberList, XPathConstants.STRING) Returns the value I'm looking for and why xPath.evaluate("/MEMBER_LIST/MEMBER[" + i + "]/ADDRESS", nodeMemberList, XPathConstants.STRING) Returns an empty String? xPath.evaluate(“ / MEMBER_LIST / MEMBER [1] / ADDRESS”,nodeMemberList,XPathConstants.STRING)返回我要查找的值以及为什么xPath.evaluate(“ / MEMBER_LIST / MEMBER [” + i +“] / ADDRESS “,nodeMemberList,XPathConstants.STRING)返回空字符串? I have to do these in a for loop so here "i" is an int representing the current entry. 我必须在for循环中执行这些操作,因此这里的“ i”是一个表示当前条目的整数。
Does your for loop start at 1? 您的for循环是否从1开始? The expression /MEMBER_LIST/MEMBER[0]
isn't a valid XPath expression because XPath indexes start at 1. Also, accessing an index which exceeds the total number of nodes is invalid. /MEMBER_LIST/MEMBER[0]
表达式不是有效的XPath表达式,因为XPath索引从1开始。而且,访问超出节点总数的索引也是无效的。 For example, executing /MEMBER_LIST/MEMBER[5]
when there are only 3 MEMBER
elements. 例如,当只有3个MEMBER
元素时,执行/MEMBER_LIST/MEMBER[5]
。
You can also use the XPathConstants.NODESET constant. 您还可以使用XPathConstants.NODESET常量。 This will return a list of all elements that match the given expression. 这将返回与给定表达式匹配的所有元素的列表。 You can then iterate over the list. 然后,您可以遍历列表。
NodeList nodeList = (NodeList)xPath.evaluate("/MEMBER_LIST/MEMBER/ADDRESS", nodeMemberList, XPathConstants.NODESET);
for (int i = 0; i < nodeList.getLength(); ++i){
Node node = nodeList.item(i);
String address = node.getTextContent();
}
如果i==0
则答案将为空,因为XPath索引从1开始。
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