无法使用dom4j从xml字符串解析节点

Question

I'm parsing a xml string with dom4j and I'm using xpath to select some element from it, the code is :

    String test = "<?xml version=\"1.0\" encoding=\"UTF-8\"?><epp xmlns=\"urn:ietf:params:xml:ns:epp-1.0\"><response><result code=\"1000\"><msg lang=\"en-US\">Command completed successfully</msg></result><trID><clTRID>87285586-99412370</clTRID><svTRID>52639BB8-1-ARNES</svTRID></trID></response></epp>";
    SAXReader reader = new SAXReader();
    reader.setIncludeExternalDTDDeclarations(false);
    reader.setIncludeInternalDTDDeclarations(false);
    reader.setValidation(false);
    Document xmlDoc;
    try {
        xmlDoc = reader.read(new StringReader(test));
        xmlDoc.getRootElement();
        Node nodeStatus = xmlDoc.selectSingleNode("//epp/response/result");

        System.out.print(nodeStatus.getText());
    } catch (DocumentException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

I always get null for the nodeStatus variable. I actualy nead to read the code from the result noad from the xml

<result code="1000">

This is the XML that I am reading from the String test :

<?xml version="1.0" encoding="UTF-8"?>
<epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
    <response>
        <result code="1000">
            <msg lang="en-US">Command completed successfully</msg>
        </result>
        <trID>
            <clTRID>87285586-99412370</clTRID>
            <svTRID>52639BB8-1-ARNES</svTRID>
        </trID>
    </response>
</epp>

Any hints?

Answer 1

Your XML has a namespace. DOM4J returns null because it won't find your nodes.

To make it work, you first have to register the namespaces you are using. You will need a prefix. Any one. And you will have to use that prefix in your XPath.

You could use tns for "target namespace". Then you have to create a xpath object with it like this:

XPath xpath = new DefaultXPath("/tns:epp/tns:response/tns:result");

To register the namespaces you will need to create a Map , add the namespace with the prefix you used in the xpath expression, and pass it to the setNamespaceURIs() method.

namespaces.put("tns", "urn:ietf:params:xml:ns:epp-1.0");
xpath.setNamespaceURIs(namespaces);

Now you can call selectSingleNode , but you will call it on your XPath object passing the document as the argument:

Node nodeStatus = xpath.selectSingleNode(xmlDoc);

From there you can extract the data you need. getText() won't give you the data you want. If you want the contents of the result node as XML, you can use:

nodeStatus.asXML()

Edit : to retrieve just the code, change your XPath to:

/tns:epp/tns:response/tns:result/@code

And retrieve the result with

nodeStatus.getText();

I replaced the double slash // (which means descendant-or-self) with / since the expression contains the full path and / is more efficient. But if you only have one result node in your whole file, you can use:

//result/@code

to extract the data. It will match all descendants. If there is more than one result , it will return a node-set.