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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package sample;
import java.io.StringWriter;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
/**
* Just for fun, a little bit of magic code and utility functions to help work with XML DOM.
*/
class Xutil {
interface NodeBuilder {
Node build(Document doc);
}
/**
* Convert a name and a list of children to a document element.
*/
static Element xdom(String ns, String name, final NodeBuilder... nodes) {
return (Element)elem(ns, name, nodes).build(db.newDocument());
}
/**
* Convert a name and children to an element.
*/
static NodeBuilder elem(final String uri, final String n, final NodeBuilder... nodes) {
return new NodeBuilder() {
public Node build(Document doc) {
final Element e = doc.createElementNS(uri, n);
for(final NodeBuilder n: nodes)
e.appendChild(n.build(doc));
return e;
}
};
}
static NodeBuilder elem(final String n, final NodeBuilder... nodes) {
return elem(null, n, nodes);
}
/**
* Convert a string to a text element.
*/
static NodeBuilder text(final String t) {
return new NodeBuilder() {
public Node build(final Document doc) {
return doc.createTextNode(t);
}
};
}
private final static DocumentBuilder db = db();
private static DocumentBuilder db() {
try {
return DocumentBuilderFactory.newInstance().newDocumentBuilder();
} catch(ParserConfigurationException e) {
throw new RuntimeException(e);
}
}
/**
* Convert an element to XML.
*/
static TransformerFactory trf = TransformerFactory.newInstance();
static String xml(final Node node) {
try {
final StreamResult r = new StreamResult(new StringWriter());
trf.newTransformer().transform(new DOMSource(node), r);
return r.getWriter().toString();
} catch(TransformerException e) {
throw new RuntimeException(e);
}
}
/**
* Evaluate an xpath expression.
*/
private static XPathFactory xpf = XPathFactory.newInstance();
static String xpath(final String expr, final Node node) {
final XPath xp = xpf.newXPath();
try {
return (String)xp.evaluate(expr, node, XPathConstants.STRING);
} catch(XPathExpressionException e) {
throw new RuntimeException(e);
}
}
/**
* A pure Java FP-style alternative to xpath for DOM.
*/
interface Mapper<T> {
T map(final Element e);
}
static Mapper<Element> identity = new Mapper<Element>() {
public Element map(Element e) {
return e;
};
};
interface Reducer<T> {
T reduce(final T accum, final Element e);
}
static Reducer<String> print = new Reducer<String>() {
public String reduce(String accum, Element e) {
return accum + e.getTextContent();
}
};
/**
* Apply a mapper to a list of elements.
*/
static <T> List<T> xmap(final Mapper<T> f, final Iterable<Element> l) {
final List<T> v = new ArrayList<T>();
for(Element e: l)
v.add(f.map(e));
return v;
}
/**
* Apply a filter to a list of elements.
*/
static List<Element> xfilter(final Mapper<Boolean> f, final Iterable<Element> l) {
final List<Element> v = new ArrayList<Element>();
for(Element e: l)
if(f.map(e))
v.add(e);
return v;
}
/**
* Perform a reduction over a list of elements.
*/
static <T> T xreduce(final Reducer<T> f, final T initial, final Iterable<Element> l) {
T accum = initial;
for(Element e: l)
accum = f.reduce(accum, e);
return accum;
}
/**
* Return a filter that selects elements by name.
*/
static Mapper<Boolean> select(final String name) {
return new Mapper<Boolean>() {
public Boolean map(Element e) {
return name.equals(e.getLocalName());
}
};
}
/**
* Return the child elements of a node.
*/
static Iterable<Element> elems(final Node parent) {
final List<Element> l = new ArrayList<Element>();
for (Node n: children(parent))
if (n instanceof Element)
l.add((Element)n);
return l;
}
/**
* An iterable over the children of a node.
*/
private static Iterable<Node> children(Node parent) {
final NodeList l = parent.getChildNodes();
final int n = l.getLength();
return new Iterable<Node>() {
public Iterator<Node> iterator() {
return new Iterator<Node>() {
int i = 0;
public boolean hasNext() {
return i < n;
}
public Node next() {
return l.item(i++);
}
public void remove() {
}
};
}
};
}
}
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