ConversionService.java

/*****************************************************************************
 * Copyright 2012 Zdenko Vrabel
 *
 * 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.zdevra.guice.mvc;

import java.lang.annotation.Annotation;
import java.util.Collection;
import java.util.Map;
import java.util.Set;

import org.zdevra.guice.mvc.converters.NoConverterFactory;
import org.zdevra.guice.mvc.exceptions.NoConverterException;

import com.google.inject.Inject;
import com.google.inject.Singleton;

/**
 * The class provides conversions from incomming strings from HTTP requests 
 * to a various datatypes.
 * 
 * The class is used internally by {@link MethodInvokerImpl}.
 * 
 * You may implement and register your own converter. Just
 * implements the {@link ConversionService.Converter}, {@link ConversionService.ConverterFactory} 
 * interfaces and in your configureControllers() register the converter:
 * 
 * <pre class="prettyprint">
 * class MyModule extends MvcModule {
 * 
 *    protected void configureControllers() {
 *       ...
 *       registerConverter(MyConverterFactory.class);
 *       ...
 *    }
 * }
 * </pre>
 * 
 * All supported converters in Lime are placed in package {@link org.zdevra.guice.mvc.converters}.
 * 
 * @see ConversionService.Converter
 * @see ConversionService.ConverterFactory
 */
@Singleton
public class ConversionService {

    /** holds all registered converter factories */
    private final Collection<ConverterFactory> factories;


    /**
     * Interface for converter
     */
    public interface Converter<T> {
        public T convert(String name, Map<String, String[]> data);
    }


    /**
     * Interface for converter factory which is constructing converter impl.
     */
    public interface ConverterFactory {
        public Converter<?> createConverter(Class<?> type, Annotation[] annotations);
    }


    /**
     * Constructor
     */
    @Inject
    public ConversionService(Set<ConverterFactory> factories) {
        this.factories = factories;
    }


    /**
     * Method return right converter for type
     * 
     * @param type
     * @return
     */
    public Converter<?> getConverter(Class<?> type, Annotation[] annotations) {
        for (ConverterFactory factory : factories) {
            Converter<?> converter = factory.createConverter(type, annotations);
            if (converter != null) {
                return converter;
            }
        }

        throw new NoConverterException(type);
    }

    /**
     * Method return converter from given factory class. If factory class is {@link NoConverterFactory}, then
     * is called origin method of getConverter()
     */
    public Converter<?> getConverter(Class<? extends ConverterFactory> converterFactoryClass, Class<?> type, Annotation[] annotations) {
        if (converterFactoryClass == NoConverterFactory.class) {
            return getConverter(type, annotations);
        }

        for (ConverterFactory factory : factories) {
            if (factory.getClass() == converterFactoryClass) {
                Converter<?> converter = factory.createConverter(type, annotations);
                if (converter != null) {
                    return converter;
                }
            }
        }
        throw new NoConverterException(converterFactoryClass, type);
    }
}