XPath 搜索“id”属性，给出 NPE - Java
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XPath search by "id" attribute , giving NPE - Java
提问by tomaytotomato
All,
全部，
I have multiple XML templates that I need to fill with data, to allow my document builder class to use multiple templates and insert data correctly
我有多个 XML 模板需要填充数据，以允许我的文档构建器类使用多个模板并正确插入数据
I designate the node that I want my class to insert data to by adding an attribute of:
我通过添加以下属性来指定我希望我的类向其中插入数据的节点：
id="root"
身=“根”
One example of an XML
XML 的一个示例
<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>
<SiebelMessage MessageId="07f33fa0-2045-46fd-b88b-5634a3de9a0b" MessageType="Integration Object" IntObjectName="" IntObjectFormat="Siebel Hierarchical" ReturnCode="0" ErrorMessage="">
<listOfReadAudit >
<readAudit id="root">
<recordId mapping="Record ID"></recordId>
<userId mapping="User ID"></userId>
<customerId mapping="Customer ID"></customerId>
<lastUpd mapping="Last Updated"></lastUpd>
<lastUpdBy mapping="Last Updated By"></lastUpdBy>
<busComp mapping="Entity Name"></busComp>
</readAudit>
</listOfReadAudit>
</SiebelMessage>
Code
代码
expr = xpath.compile("//SiebelMessage[@id='root']");
root = (Element) expr.evaluate(xmlDoc, XPathConstants.NODE);
Element temp = (Element) root.cloneNode(true);
Using this example: XPath to select Element by attribute value
使用此示例： XPath 按属性值选择元素
The expression is not working:
表达式不起作用：
//SiebelMessage[@id='root']
//SiebelMessage[@id='root']
Any ideas what I am doing wrong?
任何想法我做错了什么？
采纳答案by Stefan Pries
Try this:
尝试这个：
//readAudit[@id='root']
This selects all readAuditelements with the idattribute set to root(it should be just 1 element in your case).
这将选择属性设置为的所有readAudit元素（在您的情况下应该只有 1 个元素）。idroot
You could make sure it returns maximum 1 element with this:
您可以确保它返回最多 1 个元素：
//readAudit[@id='root'][1]
回答by kutschkem
What you are doing is selecting SiebelMessage nodes with the attribute id='root'.
您正在做的是选择具有属性 id='root' 的 SiebelMessage 节点。
But the SiebelMessage doesn't have an id, it's the readAudit you are after. So either do
但是 SiebelMessage 没有 id，它是您所追求的 readAudit。所以要么做
//readAudit[id='root']
or
或者
//SiebelMessage//readAudit[id='root']
