AbstractListElementProvider.java

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package com.sun.jersey.core.provider.jaxb;

import com.sun.jersey.core.impl.provider.entity.Inflector;

import javax.ws.rs.WebApplicationException;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.ext.Providers;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.UnmarshalException;
import javax.xml.bind.Unmarshaller;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.annotation.Annotation;
import java.lang.reflect.Array;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;
import javax.ws.rs.core.Response.Status;

/**
 *
 * @author Paul.Sandoz@Sun.Com
 */
/**
 * An abstract provider for <code>T[]</code>, <code>Collection<T></code>,
 * or <code>List<T></code> where <code>T</code> is a JAXB types annotated with
 * {@link XmlRootElement}.
 * <p>
 * Implementing classes may extend this class to provide specific marshalling
 * and unmarshalling behaviour.
 * <p>
 * When unmarshalling a {@link UnmarshalException} will result in a
 * {@link WebApplicationException} being thrown with a status of 400
 * (Client error), and a {@link JAXBException} will result in a
 * {@link WebApplicationException} being thrown with a status of 500
 * (Internal Server error).
 * <p>
 * When marshalling a {@link JAXBException} will result in a
 * {@link WebApplicationException} being thrown with a status of 500
 * (Internal Server error).
 *
 * @author Paul.Sandoz@Sun.Com
 */
public abstract class AbstractListElementProvider extends AbstractJAXBProvider<Object> {

    public AbstractListElementProvider(Providers ps) {
        super(ps);
    }
    
    public AbstractListElementProvider(Providers ps, MediaType mt) {
        super(ps, mt);        
    }
    
    @Override
    public boolean isReadable(Class<?> type, Type genericType, Annotation annotations[], MediaType mediaType) {
        if (type == List.class || type == Collection.class) {
            return verifyGenericType(genericType) && isSupported(mediaType);
        } else if (type.isArray()) {
            return verifyArrayType(type) && isSupported(mediaType);
        } else
            return false;
    }
    
    @Override
    public boolean isWriteable(Class<?> type, Type genericType, Annotation annotations[], MediaType mediaType) {
        if (List.class.isAssignableFrom(type)) {
            return verifyGenericType(genericType) && isSupported(mediaType);
        } else if (type.isArray()) {
            return verifyArrayType(type) && isSupported(mediaType);
        } else
            return false;
    }

    private boolean verifyArrayType(Class type) {
        type = type.getComponentType();

        return type.isAnnotationPresent(XmlRootElement.class) ||
                type.isAnnotationPresent(XmlType.class);
    }

    private boolean verifyGenericType(Type genericType) {
        if (!(genericType instanceof ParameterizedType)) return false;

        final ParameterizedType pt = (ParameterizedType)genericType;

        if (pt.getActualTypeArguments().length > 1) return false;

        if (!(pt.getActualTypeArguments()[0] instanceof Class)) return false;

        final Class listClass = (Class)pt.getActualTypeArguments()[0];

        return listClass.isAnnotationPresent(XmlRootElement.class) ||
                listClass.isAnnotationPresent(XmlType.class);        
    }
    
    public final void writeTo(
            Object t,
            Class<?> type, 
            Type genericType, 
            Annotation annotations[], 
            MediaType mediaType, 
            MultivaluedMap<String, Object> httpHeaders,
            OutputStream entityStream) throws IOException {
        try {
            final Collection c = (type.isArray()) 
                    ? Arrays.asList((Object[])t)
                    : (Collection)t;
            final Class elementType = (type.isArray()) 
                    ? type.getComponentType()
                    : getElementClass(type, genericType);
            final Charset charset = getCharset(mediaType);
            final String charsetName = charset.name();

            final Marshaller m = getMarshaller(elementType, mediaType);
            m.setProperty(Marshaller.JAXB_FRAGMENT, true);
            if (c != UTF8)
                m.setProperty(Marshaller.JAXB_ENCODING, charsetName);
            writeList(elementType, c, mediaType, charset, m, entityStream);
        } catch (JAXBException ex) {
            throw new WebApplicationException(ex, Status.INTERNAL_SERVER_ERROR);
        }
    }

    /**
     * Write a collection of JAXB objects as child elements of the root element.
     * 
     * @param elementType the element type in the collection.
     * @param t the collecton to marshall
     * @param mediaType the media type
     * @param c the charset
     * @param m the marshaller
     * @param entityStream the output stream to marshall the collection
     * @throws javax.xml.bind.JAXBException
     * @throws IOException 
     */
    public abstract void writeList(Class<?> elementType, Collection<?> t,
            MediaType mediaType, Charset c,
            Marshaller m, OutputStream entityStream)
            throws JAXBException, IOException;
    
    @Override
    public final Object readFrom(
            Class<Object> type,
            Type genericType, 
            Annotation annotations[],
            MediaType mediaType, 
            MultivaluedMap<String, String> httpHeaders, 
            InputStream entityStream) throws IOException { 
        try {
            final Class elementType = (type.isArray())
                    ? type.getComponentType()
                    : getElementClass(type, genericType);                
            final Unmarshaller u = getUnmarshaller(elementType, mediaType);            
            final XMLStreamReader r = getXMLStreamReader(elementType, mediaType, u, entityStream);
            final List l = new ArrayList();
            
            // Move to root element
            int event = r.next();
            while (event != XMLStreamReader.START_ELEMENT)
                event = r.next();

            // Move to first child (if any)
            event = r.next();
            while (event != XMLStreamReader.START_ELEMENT &&
                    event != XMLStreamReader.END_DOCUMENT)
                event = r.next();

            while (event != XMLStreamReader.END_DOCUMENT) {
                if (elementType.isAnnotationPresent(XmlRootElement.class))
                    l.add(u.unmarshal(r));
                else
                    l.add(u.unmarshal(r, elementType).getValue());

                // Move to next peer (if any)
                event = r.getEventType();
                while (event != XMLStreamReader.START_ELEMENT &&
                        event != XMLStreamReader.END_DOCUMENT)
                    event = r.next();
            }

            return (type.isArray())
                    ? createArray(l, elementType)
                    : l;
        } catch (UnmarshalException ex) {
            throw new WebApplicationException(ex, Status.BAD_REQUEST);
        } catch (XMLStreamException ex) {
            throw new WebApplicationException(ex, Status.BAD_REQUEST);
        } catch (JAXBException ex) {
            throw new WebApplicationException(ex, Status.INTERNAL_SERVER_ERROR);
        }
    }

    private Object createArray(List l, Class componentType) {
        Object array = Array.newInstance(componentType, l.size());
        for (int i = 0; i < l.size(); i++)
            Array.set(array, i, l.get(i));
        return array;
    }
    
    /**
     * Get the XMLStreamReader for unmarshalling.
     *
     * @param elementType the individual element type.
     * @param mediaType the media type.
     * @param unmarshaller the unmarshaller as a carrier of possible config options.
     * @param entityStream the input stream.
     * @return the XMLStreamReader.
     * @throws javax.xml.stream.XMLStreamException
     */
    protected abstract XMLStreamReader getXMLStreamReader(Class<?> elementType, MediaType mediaType, Unmarshaller unmarshaller,
            InputStream entityStream)
            throws XMLStreamException;

    protected Class getElementClass(Class<?> type, Type genericType) {
        ParameterizedType pt = (ParameterizedType)genericType;
        return (Class)pt.getActualTypeArguments()[0];
    }
    
    private final Inflector inflector = Inflector.getInstance();

    private final String convertToXmlName(final String name) {
        return name.replace("$", "_");
    }

    protected final String getRootElementName(Class<?> elementType) {
        if(isXmlRootElementProcessing()) {
            return convertToXmlName(inflector.pluralize(inflector.demodulize(getElementName(elementType))));
        } else {
            return convertToXmlName(inflector.decapitalize(inflector.pluralize(inflector.demodulize(elementType.getName()))));
        }
    }    

    protected final String getElementName(Class<?> elementType) {
        String name = elementType.getName();
        XmlRootElement xre = elementType.getAnnotation(XmlRootElement.class);
        if (xre != null && !xre.name().equals("##default")) {
            name = xre.name();
        }
        return name;
    }
}