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The coolest XML library for Java around. Define typesafe views (projections) to xml. Use XPath to read and write XML. Bind XML to Java collections. Requires at least Java6, supports Java8 features and has no further runtime dependencies.
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/**
 *  Copyright 2013 Sven Ewald
 *
 *  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 org.xmlbeam.io;

import java.util.HashMap;
import java.util.Map;

import java.io.IOException;

import org.w3c.dom.Document;
import org.xmlbeam.AutoMap;
import org.xmlbeam.DefaultXPathBinder;
import org.xmlbeam.XBProjector;
import org.xmlbeam.evaluation.CanEvaluate;
import org.xmlbeam.evaluation.DefaultXPathEvaluator;
import org.xmlbeam.evaluation.DocumentResolver;
import org.xmlbeam.evaluation.InvocationContext;
import org.xmlbeam.evaluation.XPathEvaluator;
import org.xmlbeam.types.XBAutoMap;
import org.xmlbeam.util.IOHelper;
import org.xmlbeam.util.intern.DocScope;
import org.xmlbeam.util.intern.ReflectionHelper;
import org.xmlbeam.util.intern.Scope;

/**
 * @author Sven Ewald
 */
public class UrlIO implements CanEvaluate {

    private final XBProjector projector;
    private final Map requestProperties = new HashMap();
    private final String url;

    /**
     * Constructor with defaults for request parameters.
     *
     * @param projector
     * @param url
     */
    public UrlIO(final XBProjector projector, final String url) {
        this.projector = projector;
        this.url = url;
        requestProperties.put("Content-Type", "text/xml");
    }

    /**
     * Create a new projection using a given URL parameter. When the URL starts with the protocol
     * identifier "resource://" the classloader of projection interface will be used to read the
     * resource from the current class path.
     *
     * @param projectionInterface
     *            A Java interface to project the data on.
     * @return a new projection instance.
     * @throws IOException
     */
    @Scope(DocScope.IO)
    public  T read(final Class projectionInterface) throws IOException {
        Class callerClass = null;
        if (IOHelper.isResourceProtocol(url)) {
            callerClass = ReflectionHelper.getDirectCallerClass();
        }
        Document document = IOHelper.getDocumentFromURL(projector.config().createDocumentBuilder(), url, requestProperties, projectionInterface, callerClass);
        return projector.projectDOMNode(document, projectionInterface);
    }

    /**
     * Post the projected document to a HTTP URL. The response is provided as a raw string.
     *
     * @param projection
     * @return response as String
     * @throws IOException
     */
    @SuppressWarnings("unchecked")
    @Scope(DocScope.IO)
    public String write(final Object projection) throws IOException {
        return IOHelper.inputStreamToString(IOHelper.httpPost(url, projection.toString(), requestProperties));
    }

    /**
     * Allows to add some request properties.
     *
     * @param params
     * @return this for convenience.
     */
    @Scope(DocScope.IO)
    public UrlIO addRequestProperties(final Map params) {
        requestProperties.putAll(params);
        return this;
    }

    /**
     * Allows to add a single request property.
     *
     * @param name
     * @param value
     * @return this for convenience.
     */
    @Scope(DocScope.IO)
    public UrlIO addRequestProperty(final String name, final String value) {
        requestProperties.put(name, value);
        return this;
    }

    /**
     * Evaluate XPath on the url document.
     *
     * @param xpath
     * @return xpath evaluator
     * @see org.xmlbeam.evaluation.CanEvaluate#evalXPath(java.lang.String)
     */
    @Override
    @Scope(DocScope.IO)
    public XPathEvaluator evalXPath(final String xpath) {
        return new DefaultXPathEvaluator(projector, new DocumentResolver() {
            @Override
            public Document resolve(final Class... resourceAwareClasses) throws IOException {
                return IOHelper.getDocumentFromURL(projector.config().createDocumentBuilder(), url, requestProperties, resourceAwareClasses);
            }
        }, xpath);
    }

    /**
     * Read complete document to a Map.
     *
     * @param valueType
     * @return Closeable map bound to complete document.
     * @throws IOException
     */
    @Scope(DocScope.IO)
    public  XBAutoMap readAsMapOf(final Class valueType) throws IOException {
        DefaultXPathBinder.validateEvaluationType(valueType);
        final Class resourceAwareClass = ReflectionHelper.getDirectCallerClass();
        Document document = IOHelper.getDocumentFromURL(projector.config().createDocumentBuilder(), url, requestProperties, resourceAwareClass);
        InvocationContext invocationContext = new InvocationContext(null, null, null, null, null, valueType, projector);
        return new AutoMap(document, invocationContext, valueType);
    }

}