org.xchain.namespaces.hibernate.GetCommand.java Source code

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Here is the source code for org.xchain.namespaces.hibernate.GetCommand.java

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/**
 *    Copyright 2011 meltmedia
 *
 *    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.xchain.namespaces.hibernate;

import java.io.Serializable;

import org.apache.commons.jxpath.JXPathContext;
import org.hibernate.Session;
import org.hibernate.metadata.ClassMetadata;
import org.xchain.annotations.Attribute;
import org.xchain.annotations.AttributeType;
import org.xchain.annotations.Element;
import org.xchain.framework.jxpath.ScopedQNameVariables;
import org.xchain.framework.jxpath.Scope;
import org.xchain.framework.hibernate.HibernateLifecycle;

/**
 * <p>The <code>get</code> command starts executes the Get method on the current session.  The <code>class-name</code> attribute identifies
 * the class to be loaded.  The <code>id</code> attribute identifies the unique identifier for the class to be loaded.</p>
 * 
 * <p>This must reference an active <code>session</code>.</p>
 * 
 * <code class="source">
 * &lt;xchain:session xmlns:xchain="http://www.xchain.org/hibernate/1.0"&gt;
 *  &lt;xchain:transaction&gt;
 *    ...
 *    &lt;xchain:get id="'1'" class-name="'my.package.entity'" variable="result" scope="request"/&gt;
 *    ...
 *  &lt;/xchain:transaction&gt;
 * &lt;/xchain:session&gt;
 * </code>
 *
 * @author Devon Tackett
 * @author Christian Trimble
 * 
 * @see SessionCommand
 * @see org.hibernate.Session#get(Class, Serializable)
 */
@Element(localName = "get")
public abstract class GetCommand extends AbstractSessionCommand {
    /**
     * ID of the entity to retrieve. 
     */
    @Attribute(localName = "id", type = AttributeType.JXPATH_VALUE)
    public abstract Serializable getId(JXPathContext context, Class type);

    public abstract boolean hasId();

    /**
     * The class of the entity to retrieve. 
     */
    @Attribute(localName = "class-name", type = AttributeType.JXPATH_VALUE)
    public abstract String getClassName(JXPathContext context);

    public abstract boolean hasClassName();

    /**
     * Where to store the retrieved entity. 
     */
    @Attribute(localName = "result", type = AttributeType.QNAME)
    public abstract String getResult(JXPathContext context);

    public abstract boolean hasResult();

    /**
     * Variable of where to store the entity.
     */
    @Attribute(localName = "variable", type = AttributeType.QNAME)
    public abstract String getVariable(JXPathContext context);

    public abstract boolean hasVariable();

    /**
     * Scope of the variable storing the entity.
     * @see Scope
     */
    @Attribute(localName = "scope", type = AttributeType.LITERAL, defaultValue = "execution")
    public abstract Scope getScope(JXPathContext context);

    protected void storeValue(JXPathContext context, Object value) throws Exception {
        if (hasResult()) {
            // TODO This should check that the path exists first.  If it doesn't exist, create it.
            context.setValue(getResult(context), value);
        } else if (hasVariable()) {
            ((ScopedQNameVariables) context.getVariables()).declareVariable(getVariable(context), value,
                    getScope(context));
        } else {
            throw new Exception("Result or Variable must be given.");
        }
    }

    /**
     * Performs a Get for the given class-name with the given id and stores the result in the given
     * result QName.
     */
    public boolean execute(JXPathContext context) throws Exception {
        if (!hasId())
            throw new Exception("A get command must have an id.");

        if (!hasClassName())
            throw new Exception("A get command must have a class-name.");

        // Get the session from the context.
        Session session = HibernateLifecycle.getCurrentSession(getName(context));

        // Get the metadata of the entity to be loaded from hibernate 
        ClassMetadata metadata = session.getSessionFactory().getClassMetadata(getClassName(context));

        storeValue(context, session.get(getClassName(context),
                getId(context, metadata.getIdentifierType().getReturnedClass())));

        // The get is executed.
        return false;
    }
}