EclipseLink MOXy helpers for better handling of namespaces.

MOXyContextResolver.java

/* Copyright 2013 Jakub Jirutka. All rights reserved.
 *
 * "THE KOFOLA-WARE LICENSE" (Revision 1):
 * Jakub Jirutka originally wrote this file. As long as you retain this notice you
 * can do whatever you want with this stuff. If we meet some day, and you think
 * this stuff is worth it, you can buy me a Kofola in return. <jakub@jirutka.cz>
 */

import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.ext.ContextResolver;
import javax.ws.rs.ext.Provider;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.Source;
import javax.xml.transform.stream.StreamSource;
import org.eclipse.persistence.jaxb.JAXBContextFactory;
import org.eclipse.persistence.oxm.NamespacePrefixMapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.InitializingBean;
import org.w3c.dom.Document;

/**
 * Context Resolver that initializes MOXy/JAXB context from OXM metadata in XML
 * mapping files.
 * 
 * @author Jakub Jirutka <jakub@jirutka.cz>
 */
@Provider
@Produces({MediaType.APPLICATION_XML, MediaType.APPLICATION_ATOM_XML, MediaType.APPLICATION_JSON})
public class MOXyContextResolver implements ContextResolver<JAXBContext>, InitializingBean {
    
    private static final Logger LOG = LoggerFactory.getLogger(MOXyContextResolver.class);

    private File[] bindingFiles;
    private NamespacePrefixMapper namespacePrefixMapper;
    private JAXBContext context;


    public void afterPropertiesSet() throws Exception {
        createContext();
    }


    public JAXBContext getContext(Class<?> type) {
        return context;
    }
    
    /**
     * Creates new instance of {@link JAXBContext} of MOXy from the given
     * OXM mapping files.
     * 
     * @throws JAXBException
     * @throws FileNotFoundException 
     */
    private void createContext() throws JAXBException, FileNotFoundException {
        ClassLoader classLoader = getClass().getClassLoader();
        List<Source> metadata = new ArrayList<Source>(bindingFiles.length);
        StringBuilder contextPath = new StringBuilder();
        
        LOG.info("Creating JAXBContext with MOXy XML bindings");

        for (int i = 0; i < bindingFiles.length; i++) {
            File file = bindingFiles[i];
            metadata.add(new StreamSource(file));
            
            if (i != 0) contextPath.append(":");
            contextPath.append(getPackageNameFromBinding(file));
        }

        Map<String, Object> props = new HashMap<String, Object>(1);
        props.put(JAXBContextFactory.ECLIPSELINK_OXM_XML_KEY, metadata);

        if (namespacePrefixMapper != null) {
            props.put(org.eclipse.persistence.jaxb.JAXBContext.NAMESPACE_PREFIX_MAPPER, namespacePrefixMapper);
        }
        context = JAXBContext.newInstance(contextPath.toString(), classLoader, props);
    }
    

    /**
     * Reads package-name from the given OXM mapping file.
     *
     * <pre>{@code
     * <xml-bindings xmlns="http://www.eclipse.org/eclipselink/xsds/persistence/oxm"
     *     ...
     *     package-name="cz.jirutka.atom.jaxb">
     *     ...
     * </xml-bindings>
     * }</pre>
     * 
     * @param bindingFile
     * @return fully qualified package name
     */
    private String getPackageNameFromBinding(File bindingFile) {
        Document doc;
        try {
            DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
            dbf.setNamespaceAware(true);
            DocumentBuilder db = dbf.newDocumentBuilder();
            doc = db.parse(bindingFile);
            
        } catch (Exception ex) {
            throw new RuntimeException(ex);
        }
        
        return doc.getDocumentElement().getAttribute("package-name");
    }


    //////// Accessors ////////

    public File[] getBindingFiles() {
        return bindingFiles;
    }

    public void setBindingFiles(File[] bindingFiles) {
        this.bindingFiles = bindingFiles;
    }

    public NamespacePrefixMapper getNamespacePrefixMapper() {
        return namespacePrefixMapper;
    }

    public void setNamespacePrefixMapper(NamespacePrefixMapper namespacePrefixMapper) {
        this.namespacePrefixMapper = namespacePrefixMapper;
    }
    
}

MOXyNamespacePrefixMapper.java

/* Copyright 2013 Jakub Jirutka. All rights reserved.
 *
 * "THE KOFOLA-WARE LICENSE" (Revision 1):
 * Jakub Jirutka originally wrote this file. As long as you retain this notice you
 * can do whatever you want with this stuff. If we meet some day, and you think
 * this stuff is worth it, you can buy me a Kofola in return. <jakub@jirutka.cz>
 */

import java.io.File;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
import org.eclipse.persistence.oxm.NamespacePrefixMapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.util.Assert;

/**
 * Configurable mapper of XML namespaces and prefixes for MOXy.
 *
 * <p>This is very useful especially when you have many OXM mapping files
 * with common namespaces. In this situation, MOXy fails to use declared
 * default namespace.</p>
 *
 * @author Jakub Jirutka <jakub@jirutka.cz>
 */
public class MOXyNamespacePrefixMapper extends NamespacePrefixMapper {
    
    private static final Logger LOG = LoggerFactory.getLogger(MOXyNamespacePrefixMapper.class);

    private final Map<String, String> mapping;
    private String[] namespaces;


    /**
     * Creates new instance from the given XML file with declared namespace
     * prefixes. It's basically MOXy's <tt>xml-schema</tt> as the root element
     * with nested <tt>xml-ns</tt> elements, for example:
     *
     * <pre>{@code
     * <xml-schema>
     *   <xml-ns prefix="" namespace-uri="http://www.w3.org/2005/Atom" />
     *   <xml-ns prefix="osearch" namespace-uri="http://a9.com/-/spec/opensearch/1.1/" />
     *   <xml-ns prefix="xlink" namespace-uri="http://www.w3.org/1999/xlink" />
     *   <xml-ns prefix="xsi" namespace-uri="http://www.w3.org/2001/XMLSchema-instance" />
     * </xml-schema>
     * }</pre>
     *
     * @param configFile
     */
    public MOXyNamespacePrefixMapper(File configFile) {
        Assert.isTrue(configFile.canRead(), "Could not read file: " + configFile);

        LOG.trace("Parsing namespaces mapping from file: {}", configFile);
        try {
            this.mapping = parseNamespacesMapping(configFile);
            initialize();
        } catch (DocumentException ex) {
            throw new RuntimeException(ex);
        }
    }

    /**
     * Creates new instance from the given map that contains namespace URIs
     * as the keys and their prefixes as the values.
     *
     * @param namespacesMapping map of URI : prefix
     */
    public MOXyNamespacePrefixMapper(Map<String, String> namespacesMapping) {
        this.mapping = namespacesMapping;
        initialize();
    }


    public String getPreferredPrefix(String namespaceUri, String suggestion, boolean requirePrefix) {
        LOG.trace("Requesting prefix for namespace {} with suggested prefix {}",
                namespaceUri, suggestion, requirePrefix);

        if (mapping.containsKey(namespaceUri)) {
            String prefix = mapping.get(namespaceUri);
            LOG.trace("Returns preferred prefix: {}", prefix);
            return prefix;

        } else {
            LOG.trace("No preferred prefix found, returns suggested: {}", suggestion);
            return suggestion;
        }
    }

    @Override
    public String[] getPreDeclaredNamespaceUris() {
        return namespaces;
    }

    
    private void initialize() {
        this.namespaces = mapping.keySet().toArray(new String[0]);

        if (LOG.isInfoEnabled()) {
            for (Entry<String, String> entry : mapping.entrySet()) {
                LOG.info("Registering predefined namespace {} with prefix '{}'", entry.getKey(), entry.getValue());
            }
        }
    }

    /**
     * @see #MOXyNamespacePrefixMapper(java.io.File)
     *
     * @param file XML file
     * @return map of URI : prefix
     * @throws DocumentException
     */
    private Map<String, String> parseNamespacesMapping(File file) throws DocumentException {
        Map<String, String> map = new HashMap<String, String>();
        
        Document doc = new SAXReader().read(file);
        Element root = doc.getRootElement();

        for (Object node : root.elements("xml-ns")) {
            Element xmlns = (Element) node;
            String prefix = xmlns.attributeValue("prefix");
            String uri = xmlns.attributeValue("namespace-uri");
            
            map.put(uri, prefix);
        }
        return map;
    }

}