1 files changed, 135 insertions, 0 deletions
diff --git a/config-model/src/main/java/com/yahoo/config/model/builder/xml/XmlHelper.java b/config-model/src/main/java/com/yahoo/config/model/builder/xml/XmlHelper.java
new file mode 100644
index 00000000000..924d888b0d0
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+++ b/config-model/src/main/java/com/yahoo/config/model/builder/xml/XmlHelper.java
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+// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.config.model.builder.xml;
+
+import com.yahoo.component.ComponentId;
+import com.yahoo.component.ComponentSpecification;
+import com.yahoo.log.LogLevel;
+import com.yahoo.text.XML;
+import org.w3c.dom.Document;
+import org.w3c.dom.Element;
+import org.xml.sax.InputSource;
+import org.xml.sax.SAXException;
+
+import javax.xml.parsers.DocumentBuilder;
+import javax.xml.parsers.DocumentBuilderFactory;
+import javax.xml.parsers.ParserConfigurationException;
+import java.io.IOException;
+import java.io.Reader;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import java.util.logging.Logger;
+
+
+/**
+ * Static methods for helping dom building
+ *
+ * @author <a href="mailto:bratseth@yahoo-inc.com">Jon Bratseth</a>
+ */
+public final class XmlHelper {
+    private static final Logger log = Logger.getLogger(XmlHelper.class.getPackage().toString());
+
+
+    private static final String idReference = "idref";
+    // Access to this needs to be synchronized (as it is in getDocumentBuilder() below)
+    public static final DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
+
+    static {
+        XmlHelper.factory.setNamespaceAware(true);
+        // if use jdom and jaxen this will fail badly:
+        XmlHelper.factory.setXIncludeAware(true);
+    }
+
+    private XmlHelper() {}
+
+    public static String nullIfEmpty(String attribute) {
+        if (attribute.isEmpty())
+            return null;
+        else
+            return attribute;
+    }
+
+    /**
+     * For searchers inside search chains, the id may be both a reference and an id at once, or just a reference.
+     * In other cases, it is clear which one it is from context, so I think the difference is not worth bothering users
+     * with, unless they are XML purists in which case they will have the option of writing this correctly.
+     * - Jon
+     */
+    public static String getIdString(Element element) {
+        String idString = element.getAttribute("id");
+        if (idString == null || idString.trim().equals(""))
+            idString = element.getAttribute(idReference);
+        if (idString == null || idString.trim().equals(""))
+            idString = element.getAttribute("ident");
+        return idString;
+    }
+
+    public static ComponentId getId(Element element) {
+        return new ComponentId(getIdString(element));
+    }
+
+    public static ComponentSpecification getIdRef(Element element) {
+        return new ComponentSpecification(getIdString(element));
+    }
+
+    public static Document getDocument(Reader reader) {
+        Document doc;
+        try {
+            doc = getDocumentBuilder().parse(new InputSource(reader));
+        } catch (SAXException | IOException e) {
+            throw new IllegalArgumentException(e);
+        }
+        return doc;
+    }
+
+    public static List<String> splitAndDiscardEmpty(String field, String regex) {
+        List<String> ret = new ArrayList<>();
+        for (String t : field.split(regex)) {
+            if (!t.isEmpty()) {
+                ret.add(t);
+            }
+        }
+        return ret;
+    }
+
+    public static List<String> spaceSeparatedSymbols(String field) {
+        return splitAndDiscardEmpty(field, " ");
+    }
+
+    public static Collection<String> spaceSeparatedSymbolsFromAttribute(Element spec, String name) {
+        return spaceSeparatedSymbols(spec.getAttribute(name));
+    }
+
+    public static Collection<String> valuesFromElements(Element parent, String elementName) {
+        List<String> symbols = new ArrayList<>();
+        for (Element symbol : XML.getChildren(parent, elementName)) {
+            symbols.add(XML.getValue(symbol).trim());
+        }
+        return symbols;
+    }
+
+    public static boolean isReference(Element element) {
+        return element.hasAttribute(idReference);
+    }
+
+    /**
+     * Creates a new XML document builder.
+     *
+     * @return A new DocumentBuilder instance, or null if we fail to get one.
+     */
+    public static synchronized DocumentBuilder getDocumentBuilder() {
+        try {
+            DocumentBuilder docBuilder = factory.newDocumentBuilder();
+            log.log(LogLevel.DEBUG, "XML parser now operational!");
+            return docBuilder;
+        } catch (ParserConfigurationException e) {
+            log.log(LogLevel.WARNING, "No XML parser available - " + e);
+            return null;
+        }
+    }
+
+    public static Optional<String> getOptionalAttribute(Element element, String name) {
+        return Optional.ofNullable(element.getAttribute(name)).filter(s -> !s.isEmpty());
+    }
+}