{"id":258,"date":"2018-12-14T09:27:31","date_gmt":"2018-12-14T09:27:31","guid":{"rendered":"https:\/\/jan.schnasse.org\/blog\/?p=258"},"modified":"2018-12-14T09:27:31","modified_gmt":"2018-12-14T09:27:31","slug":"process-parts-of-xml-with-xpath-in-java","status":"publish","type":"post","link":"https:\/\/jan.schnasse.org\/blog\/2018\/12\/14\/process-parts-of-xml-with-xpath-in-java\/","title":{"rendered":"Process parts of XML with XPath in Java"},"content":{"rendered":"

This shows you how to<\/p>\n

1. Read in an XML file to a DOM<\/span>
\n2. Filter out a set of Nodes<\/span> with XPath<\/span>
\n3. Perform a certain action on each of the extracted Nodes<\/span>.<\/p>\n

We will call the code with the following statement<\/p>\n

processFilteredXml(xmlIn, xpathExpr,(node) -> {\/*Do something...*\/;});<\/pre>\n
In our case we want to print some creatorNames<\/span> from a book.xml<\/span> using „\/\/book\/creators\/creator\/creatorName“<\/span> as xpath to perform a printNode<\/span> action on each Node that matches the XPath<\/span>.<\/p>\n
Full code<\/strong><\/p>\n
@Test\npublic void printXml() {\n    try (InputStream in = readFile(\"book.xml\")) {\n        processFilteredXml(in, \"\/\/book\/creators\/creator\/creatorName\", (node) -> {\n            printNode(node, System.out);\n        });\n    } catch (Exception e) {\n        throw new RuntimeException(e);\n    }\n}\n\nprivate InputStream readFile(String yourSampleFile) {\n    return Thread.currentThread().getContextClassLoader().getResourceAsStream(yourSampleFile);\n}\n\nprivate void processFilteredXml(InputStream in, String xpath, Consumer<Node> process) {\n    Document doc = readXml(in);\n    NodeList list = filterNodesByXPath(doc, xpath);\n    for (int i = 0; i < list.getLength(); i++) {\n        Node node = list.item(i);\n        process.accept(node);\n    }\n}\n\npublic Document readXml(InputStream xmlin) {\n    try {\n        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();\n        DocumentBuilder db = dbf.newDocumentBuilder();\n        return db.parse(xmlin);\n    } catch (Exception e) {\n        throw new RuntimeException(e);\n    }\n}\n\nprivate NodeList filterNodesByXPath(Document doc, String xpathExpr) {\n    try {\n        XPathFactory xPathFactory = XPathFactory.newInstance();\n        XPath xpath = xPathFactory.newXPath();\n        XPathExpression expr = xpath.compile(xpathExpr);\n        Object eval = expr.evaluate(doc, XPathConstants.NODESET);\n        return (NodeList) eval;\n    } catch (Exception e) {\n        throw new RuntimeException(e);\n    }\n}\n\nprivate void printNode(Node node, PrintStream out) {\n    try {\n        Transformer transformer = TransformerFactory.newInstance().newTransformer();\n        transformer.setOutputProperty(OutputKeys.INDENT, \"yes\");\n        transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, \"yes\");\n        transformer.setOutputProperty(\"{http:\/\/xml.apache.org\/xslt}indent-amount\", \"2\");\n        StreamResult result = new StreamResult(new StringWriter());\n        DOMSource source = new DOMSource(node);\n        transformer.transform(source, result);\n        String xmlString = result.getWriter().toString();\n        out.println(xmlString);\n    } catch (Exception e) {\n        throw new RuntimeException(e);\n    }\n}<\/pre>\n
Prints<\/strong><\/p>\n
<creatorName>Fosmire, Michael<\/creatorName>\n\n<creatorName>Wertz, Ruth<\/creatorName>\n\n<creatorName>Purzer, Senay<\/creatorName><\/pre>\n
For book.xml<\/p>\n
<book>\n  <creators>\n    <creator>\n      <creatorName>Fosmire, Michael<\/creatorName>\n      <givenName>Michael<\/givenName>\n      <familyName>Fosmire<\/familyName>\n    <\/creator>\n    <creator>\n      <creatorName>Wertz, Ruth<\/creatorName>\n      <givenName>Ruth<\/givenName>\n      <familyName>Wertz<\/familyName>\n    <\/creator>\n    <creator>\n      <creatorName>Purzer, Senay<\/creatorName>\n       <givenName>Senay<\/givenName>\n       <familyName>Purzer<\/familyName>\n    <\/creator>\n  <\/creators>\n  <titles>\n    <title>Critical Engineering Literacy Test (CELT)<\/title>\n  <\/titles>\n<\/book><\/pre>\n
See also<\/strong><\/p>\n
https:\/\/stackoverflow.com\/a\/52736526\/1485527<\/a><\/p>\n
https:\/\/github.com\/jschnasse\/overflow\/tree\/master\/src\/test\/java\/stack52720162<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
This shows you how to 1. Read in an XML file to a DOM 2. Filter out a set of Nodes with XPath 3. Perform a certain action on each of the extracted Nodes. We will call the code with the following statement processFilteredXml(xmlIn, xpathExpr,(node) -> {\/*Do something…*\/;}); In our case we want to print […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6,9],"tags":[],"class_list":["post-258","post","type-post","status-publish","format-standard","hentry","category-development","category-java"],"_links":{"self":[{"href":"https:\/\/jan.schnasse.org\/blog\/wp-json\/wp\/v2\/posts\/258","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/jan.schnasse.org\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/jan.schnasse.org\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/jan.schnasse.org\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/jan.schnasse.org\/blog\/wp-json\/wp\/v2\/comments?post=258"}],"version-history":[{"count":0,"href":"https:\/\/jan.schnasse.org\/blog\/wp-json\/wp\/v2\/posts\/258\/revisions"}],"wp:attachment":[{"href":"https:\/\/jan.schnasse.org\/blog\/wp-json\/wp\/v2\/media?parent=258"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/jan.schnasse.org\/blog\/wp-json\/wp\/v2\/categories?post=258"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/jan.schnasse.org\/blog\/wp-json\/wp\/v2\/tags?post=258"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}