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/*
 * Copyright 2012-2015 MarkLogic Corporation
 *
 * Licensed 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 com.marklogic.client.io;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;

import javax.xml.namespace.QName;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.w3c.dom.DOMException;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.w3c.dom.ls.DOMImplementationLS;
import org.w3c.dom.ls.LSException;
import org.w3c.dom.ls.LSInput;
import org.w3c.dom.ls.LSOutput;
import org.w3c.dom.ls.LSParser;
import org.w3c.dom.ls.LSResourceResolver;

import com.marklogic.client.MarkLogicIOException;
import com.marklogic.client.MarkLogicInternalException;
import com.marklogic.client.io.marker.BufferableHandle;
import com.marklogic.client.io.marker.ContentHandle;
import com.marklogic.client.io.marker.ContentHandleFactory;
import com.marklogic.client.io.marker.StructureReadHandle;
import com.marklogic.client.io.marker.StructureWriteHandle;
import com.marklogic.client.io.marker.XMLReadHandle;
import com.marklogic.client.io.marker.XMLWriteHandle;

/**
 * A DOM Handle represents XML content as a DOM document for reading or writing.
 */
public class DOMHandle
	extends BaseHandle
	implements OutputStreamSender, BufferableHandle, ContentHandle,
		XMLReadHandle, XMLWriteHandle,
		StructureReadHandle, StructureWriteHandle
{
	static final private Logger logger = LoggerFactory.getLogger(DOMHandle.class);

	private LSResourceResolver     resolver;
	private Document               content;
	private DocumentBuilderFactory factory;
	private XPath                  xpathProcessor;

	/**
	 * Creates a factory to create a DOMHandle instance for a DOM document.
	 * @return	the factory
	 */
	static public ContentHandleFactory newFactory() {
		return new ContentHandleFactory() {
			@Override
			public Class[] getHandledClasses() {
				return new Class[]{ Document.class };
			}
			@Override
			public boolean isHandled(Class type) {
				return Document.class.isAssignableFrom(type);
			}
			@Override
			public  ContentHandle newHandle(Class type) {
				@SuppressWarnings("unchecked")
				ContentHandle handle = isHandled(type) ?
						(ContentHandle) new DOMHandle() : null;
				return handle;
			}
		};
	}

	/**
	 * Zero-argument constructor.
	 */
	public DOMHandle() {
		super();
		super.setFormat(Format.XML);
   		setResendable(true);
	}
	/**
	 * Initializes the handle with a DOM document for the content.
	 * @param content	a DOM document
	 */
	public DOMHandle(Document content) {
		this();
		set(content);
	}

	/**
	 * Returns the resolver for resolving references while parsing the document.
	 * @return	the resolver
	 */
	public LSResourceResolver getResolver() {
		return resolver;
	}
	/**
	 * Specifies the resolver for resolving references while parsing the document.
	 * @param resolver	the reference resolver
	 */
	public void setResolver(LSResourceResolver resolver) {
		this.resolver = resolver;
	}

	/**
	 * Returns the DOM document for the content.
	 * @return	the DOM document
	 */
	@Override
	public Document get() {
		return content;
	}
	/**
	 * Assigns a DOM document as the content.
	 * @param content	a DOM document
	 */
	@Override
    public void set(Document content) {
    	this.content = content;
    }
    /**
	 * Assigns a DOM document as the content and returns the handle
	 * as a fluent convenience.
	 * @param content	a DOM document
	 * @return	this handle
     */
    public DOMHandle with(Document content) {
    	set(content);
    	return this;
    }

	/**
	 * Restricts the format to XML.
	 */
    @Override
	public void setFormat(Format format) {
		if (format != Format.XML)
			throw new IllegalArgumentException("DOMHandle supports the XML format only");
	}
	/**
	 * Specifies the mime type of the content and returns the handle
	 * as a fluent convenience.
	 * @param mimetype	the mime type of the content
	 * @return	this handle
	 */
	public DOMHandle withMimetype(String mimetype) {
		setMimetype(mimetype);
		return this;
	}

	@Override
	public void fromBuffer(byte[] buffer) {
		if (buffer == null || buffer.length == 0)
			content = null;
		else
			receiveContent(new ByteArrayInputStream(buffer));
	}
	@Override
	public byte[] toBuffer() {
		try {
			if (content == null)
				return null;

			ByteArrayOutputStream buffer = new ByteArrayOutputStream();
			write(buffer);

			return buffer.toByteArray();
		} catch (IOException e) {
			throw new MarkLogicIOException(e);
		}
	}
	/**
	 * Returns the DOM document as an XML string.
	 */
	@Override
	public String toString() {
		try {
			byte[] buffer = toBuffer();
			if ( buffer == null ) return null;
			else return new String(buffer,"UTF-8");
		} catch (UnsupportedEncodingException e) {
			throw new MarkLogicIOException(e);
		}
	}

	/**
	 * Returns the factory for building DOM documents.
	 * @return	the document factory
	 */
	public DocumentBuilderFactory getFactory() throws ParserConfigurationException {
		if (factory == null)
			factory = makeDocumentBuilderFactory();
		return factory;
	}
	/**
	 * Specifies the factory for building DOM documents.
	 * @param factory	the document factory
	 */
	public void setFactory(DocumentBuilderFactory factory) {
		this.factory = factory;
	}
	protected DocumentBuilderFactory makeDocumentBuilderFactory() throws ParserConfigurationException {
		DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
		factory.setNamespaceAware(true);
		factory.setValidating(false);
		// TODO: XInclude

		return factory;
	}

	/**
	 * Get the processor used to evaluate XPath expressions.
	 * You might get the XPath processor to configure it. For instance,
	 * you can configure the XPath processor to declare namespace
	 * bindings or to set a function or variable resolver.
	 * @see com.marklogic.client.util.EditableNamespaceContext
	 * @return	the XPath expression processor
	 */
	public XPath getXPathProcessor() {
		if (xpathProcessor == null)
			xpathProcessor = makeXPathProcessorFactory().newXPath();
		return xpathProcessor;
	}
	/**
	 * Specifies the processor used to evaluate XPath expressions against
	 * the document.
	 * @param xpathProcessor	the XPath expression processor
	 */
	public void setXPathProcessor(XPath xpathProcessor) {
		this.xpathProcessor = xpathProcessor;
	}
	protected XPathFactory makeXPathProcessorFactory() {
		return XPathFactory.newInstance();
	}

	/**
	 * Evaluate a string XPath expression against the retrieved document.
	 * An XPath expression can return a Node or subinterface such as
	 * Element or Text, a NodeList, or a Boolean, Number, or String value.
	 * @param xpathExpression	the XPath expression as a string
	 * @param as	the type of the value 
	 * @return	the value produced by the XPath expression
	 */
	public  T evaluateXPath(String xpathExpression, Class as)
	throws XPathExpressionException {
		return evaluateXPath(xpathExpression, get(), as);
	}
	/**
	 * Evaluate a string XPath expression relative to a node such as a node
	 * returned by a previous XPath expression.
	 * An XPath expression can return a Node or subinterface such as
	 * Element or Text, a NodeList, or a Boolean, Number, or String value.
	 * @param xpathExpression	the XPath expression as a string
	 * @param context	the node for evaluating the expression
	 * @param as	the type of the value 
	 * @return	the value produced by the XPath expression
	 */
	public  T evaluateXPath(String xpathExpression, Node context, Class as)
	throws XPathExpressionException {
		checkContext(context);
		return castAs(
				getXPathProcessor().evaluate(xpathExpression, context, returnXPathConstant(as)),
				as
				);
	}
	/**
	 * Compile an XPath string expression for efficient evaluation later.
	 * @param xpathExpression	the XPath expression as a string
	 * @return	the compiled XPath expression
	 */
	public XPathExpression compileXPath(String xpathExpression)
	throws XPathExpressionException {
		return getXPathProcessor().compile(xpathExpression);
	}
	/**
	 * Evaluate a compiled XPath expression against the retrieved document.
	 * An XPath expression can return a Node or subinterface such as
	 * Element or Text, a NodeList, or a Boolean, Number, or String value.
	 * @param xpathExpression	an XPath expression compiled previously
	 * @param as	the type of the value 
	 * @return	the value produced by the XPath expression
	 */
	public  T evaluateXPath(XPathExpression xpathExpression, Class as)
	throws XPathExpressionException {
		return evaluateXPath(xpathExpression, get(), as);
	}
	/**
	 * Evaluate a compiled XPath expression relative to a node such as a node
	 * returned by a previous XPath expression.
	 * An XPath expression can return a Node or subinterface such as
	 * Element or Text, a NodeList, or a Boolean, Number, or String value.
	 * @param xpathExpression	an XPath expression compiled previously
	 * @param context	the node for evaluating the expression
	 * @param as	the type of the value 
	 * @return	the value produced by the XPath expression
	 */
	public  T evaluateXPath(XPathExpression xpathExpression, Node context, Class as)
	throws XPathExpressionException {
		checkContext(context);
		return castAs(
				xpathExpression.evaluate(context, returnXPathConstant(as)),
				as
				);
	}
	protected void checkContext(Node context) {
		if (context == null) {
			throw new IllegalStateException("Cannot process empty context");
		}
	}
	protected QName returnXPathConstant(Class as) {
		if (as == null) {
			throw new IllegalArgumentException("cannot execute XPath as null");
		} else if (Node.class.isAssignableFrom(as)) {
			return XPathConstants.NODE;
		} else if (NodeList.class.isAssignableFrom(as)) {
			return XPathConstants.NODESET;
		} else if (String.class.isAssignableFrom(as)) {
			return XPathConstants.STRING;
		} else if (Number.class.isAssignableFrom(as)) {
			return XPathConstants.NUMBER;
		} else if (Boolean.class.isAssignableFrom(as)) {
			return XPathConstants.BOOLEAN;
		}
		throw new IllegalArgumentException("cannot execute XPath as "+as.getName());
	}
	protected  T castAs(Object result, Class as) {
		if (result == null) {
			return null;
		}
		if (!as.isAssignableFrom(result.getClass())) {
			throw new IllegalArgumentException("cannot cast "+result.getClass().getName()+" to "+as.getName());
		}
		@SuppressWarnings("unchecked")
		T typedResult = (T) result;
		return typedResult;
	}

	@Override
	protected Class receiveAs() {
		return InputStream.class;
	}
	@Override
	protected void receiveContent(InputStream content) {
		if (content == null) {
			this.content = null;
			return;
		}

		try {
			if (logger.isInfoEnabled())
				logger.info("Parsing DOM document from input stream");

			DocumentBuilderFactory factory = getFactory();
			if (factory == null) {
				throw new MarkLogicInternalException("Failed to make DOM document builder factory");
			}

			DOMImplementationLS domImpl = (DOMImplementationLS) factory.newDocumentBuilder().getDOMImplementation();

			LSParser parser = domImpl.createLSParser(DOMImplementationLS.MODE_SYNCHRONOUS, null);
			if (resolver != null) {
				parser.getDomConfig().setParameter("resource-resolver", resolver);
			}

			LSInput domInput = domImpl.createLSInput();
			domInput.setEncoding("UTF-8");
			domInput.setByteStream(content);

			this.content = parser.parse(domInput);
		} catch (ParserConfigurationException e) {
			logger.error("Failed to parse DOM document from input stream",e);
			throw new MarkLogicInternalException(e);
		} finally {
			try {
				content.close();
			} catch (IOException e) {
				//ignore
			}
			
		}
	}
	@Override
	protected OutputStreamSender sendContent() {
		if (content == null) {
			throw new IllegalStateException("No document to write");
		}

		return this;
	}
	@Override
	public void write(OutputStream out) throws IOException {
		try {
			if (logger.isInfoEnabled())
				logger.info("Serializing DOM document to output stream");

			DocumentBuilderFactory factory = getFactory();
			if (factory == null) {
				throw new MarkLogicInternalException("Failed to make DOM document builder factory");
			}

			DOMImplementationLS domImpl = (DOMImplementationLS) factory.newDocumentBuilder().getDOMImplementation();
			LSOutput domOutput = domImpl.createLSOutput();
			domOutput.setEncoding("UTF-8");
			domOutput.setByteStream(out);
			domImpl.createLSSerializer().write(content, domOutput);
		} catch (DOMException e) {
			logger.error("Failed to serialize DOM document to output stream",e);
			throw new MarkLogicInternalException(e);
		} catch (LSException e) {
			logger.error("Failed to serialize DOM document to output stream",e);
			throw new MarkLogicInternalException(e);
		} catch (ParserConfigurationException e) {
			logger.error("Failed to serialize DOM document to output stream",e);
			throw new MarkLogicInternalException(e);
		}
	}
}




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