# JSONModel.java

    /*
     * Copyright 2011 Marc Grue.
     *
     * 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.qi4j.sample.dcicargo.sample_b.infrastructure.model;

    import org.qi4j.api.value.ValueComposite;
    import org.qi4j.api.value.ValueSerializer;

    /**
     * JSONModel
     *
     * Model that can serialize/de-serialize an object to/from a JSON string.
     */
    public class JSONModel<T, U extends ValueComposite>
        extends ReadOnlyModel<T>
    {
        private Class<U> valueCompositeClass;
        private String json;
        private transient T valueComposite;

        @SuppressWarnings( "unchecked" )
        public JSONModel( T valueComposite, Class<U> valueCompositeClass )
        {
            json = module.findService( ValueSerializer.class ).get().serialize( (U) valueComposite );;
            this.valueCompositeClass = valueCompositeClass;
        }

        @SuppressWarnings( "unchecked" )
        public static <T, U extends ValueComposite> JSONModel<T, U> of( T value )
        {
            if( !( value instanceof ValueComposite ) )
            {
                throw new RuntimeException( value + " has to be an instance of a ValueComposite." );
            }

            // Get ValueComposite interface
            Class<U> valueCompositeClass = (Class<U>) qi4j.valueDescriptorFor( value ).valueType().mainType();

            return new JSONModel<T, U>( value, valueCompositeClass );
        }

        @SuppressWarnings( "unchecked" )
        public T getObject()
        {
            if( valueComposite == null && json != null )
            {
                // De-serialize
                valueComposite = (T) module.newValueFromSerializedState( valueCompositeClass, json ); // Unchecked cast
            }
            return valueComposite;
        }

        public void detach()
        {
            valueComposite = null;
        }
    }