How to extract details from the xml files using java?

问题

I have the following type of XML file,

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE eSummaryResult PUBLIC "-//NLM//DTD eSummaryResult, 29 October 2004//EN" "http://www.ncbi.nlm.nih.gov/entrez/query/DTD/eSummary_041029.dtd">
<eSummaryResult>
<DocSum>
    <Id>224589801</Id>
    <Item Name="Caption" Type="String">NC_000010</Item>
    <Item Name="Title" Type="String">Homo sapiens chromosome 10, GRCh37.p10 Primary Assembly</Item>
    <Item Name="Extra" Type="String">gi|224589801|gnl|ASM:GCF_000001305|10|ref|NC_000010.10||gpp|GPC_000000034.1||gnl|NCBI_GENOMES|10[224589801]</Item>
    <Item Name="Gi" Type="Integer">224589801</Item>
    <Item Name="CreateDate" Type="String">2002/08/29</Item>
    <Item Name="UpdateDate" Type="String">2012/10/30</Item>
    <Item Name="Flags" Type="Integer">544</Item>
    <Item Name="TaxId" Type="Integer">9606</Item>
    <Item Name="Length" Type="Integer">135534747</Item>
    <Item Name="Status" Type="String">live</Item>
    <Item Name="ReplacedBy" Type="String"/>
    <Item Name="Comment" Type="String"><![CDATA[  ]]></Item>
</DocSum>

</eSummaryResult>

How to extract the details from node="Item" based on the name value it has? And also is it good to use the standard java dom xml or better to use any other xml parser library for this purpose?

回答1:

I suggest StAX, try this (javax.xml.stream.*)

    XMLInputFactory f = XMLInputFactory.newInstance();
    XMLStreamReader rdr = f.createXMLStreamReader(new FileReader("test.xml"));
    while (rdr.hasNext()) {
        if (rdr.next() == XMLStreamConstants.START_ELEMENT) {
            if (rdr.getLocalName().equals("Item")) {
                System.out.println(rdr.getAttributeValue("", "Name"));
                System.out.println(rdr.getElementText());
            }
        }
    }

StAX must be always the first thing to consider. See http://en.wikipedia.org/wiki/StAX you will know why

回答2:

Try the below code

/* Create a Document object (doc) from the xml */
NodeList list = doc.getElementsByTagName("Item");

for(int i=0;i<list.getLength();i++)
{
    Node node = list.item(i);
    NamedNodeMap namedNodeMap = node.getAttributes();
    if(namedNodeMap.getNamedItem("Name").getTextContent().equalsIgnoreCase("Caption"))
    {
         System.out.println(node.getTextContent());
    }
}

The output should be NC_000010

回答3:

If only using standard Java, XPath is the way to go:

private URL xml = getClass().getResource("/example.xml");

@Test
public void testExamples() throws Exception {
    //assertEquals("NC_000010", extractUsingDom("Caption"));
    assertEquals("NC_000010", extractUsingXPath("Caption"));
}

public String extractUsingXPath(final String name) throws XPathExpressionException, IOException {
    // XPathFactory class is not thread-safe so we do not store it
    XPath xpath = XPathFactory.newInstance().newXPath();
    return xpath.evaluate(
        String.format("/eSummaryResult/DocSum/Item[@Name='%s']", name), // xpath expression
        new InputSource(xml.openStream()));                             // the XML Document
}

回答4:

Maybe use XPath?

Document dom = ...;
XPath xpath = XPathFactory.newInstance().newXPath();
String result = xpath.evaluate("/eSummaryResult/DocSum/Item[@Name='Title']", dom);

来源：https://stackoverflow.com/questions/13762881/how-to-extract-details-from-the-xml-files-using-java

标签

java

xml

xml-parsing