ConvertingPropertyAccessor.java

/*
 * Copyright 2014 the original author or authors.
 *
 * 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.springframework.data.mapping.model;

import java.util.Optional;

import org.springframework.core.convert.ConversionService;
import org.springframework.data.mapping.PersistentProperty;
import org.springframework.data.mapping.PersistentPropertyAccessor;
import org.springframework.util.Assert;

/**
 * {@link PersistentPropertyAccessor} that potentially converts the value handed to
 * {@link #setProperty(PersistentProperty, Object)} to the type of the {@link PersistentProperty} using a
 * {@link ConversionService}. Exposes {@link #getProperty(PersistentProperty, Class)} to allow obtaining the value of a
 * property in a type the {@link ConversionService} can convert the raw type to.
 * 
 * @author Oliver Gierke
 */
public class ConvertingPropertyAccessor implements PersistentPropertyAccessor {

	private final PersistentPropertyAccessor accessor;
	private final ConversionService conversionService;

	/**
	 * Creates a new {@link ConvertingPropertyAccessor} for the given delegate {@link PersistentPropertyAccessor} and
	 * {@link ConversionService}.
	 * 
	 * @param accessor must not be {@literal null}.
	 * @param conversionService must not be {@literal null}.
	 */
	public ConvertingPropertyAccessor(PersistentPropertyAccessor accessor, ConversionService conversionService) {

		Assert.notNull(accessor, "PersistentPropertyAccessor must not be null!");
		Assert.notNull(conversionService, "ConversionService must not be null!");

		this.accessor = accessor;
		this.conversionService = conversionService;
	}

	/* 
	 * (non-Javadoc)
	 * @see org.springframework.data.mapping.PersistentPropertyAccessor#setProperty(org.springframework.data.mapping.PersistentProperty, java.lang.Object)
	 */
	@Override
	public void setProperty(PersistentProperty<?> property, Optional<? extends Object> value) {
		accessor.setProperty(property, convertIfNecessary(value, property.getType()));
	}

	/* 
	 * (non-Javadoc)
	 * @see org.springframework.data.mapping.PersistentPropertyAccessor#getProperty(org.springframework.data.mapping.PersistentProperty)
	 */
	@Override
	public Optional<Object> getProperty(PersistentProperty<?> property) {
		return accessor.getProperty(property);
	}

	/**
	 * Returns the value of the given {@link PersistentProperty} converted to the given type.
	 * 
	 * @param property must not be {@literal null}.
	 * @param targetType must not be {@literal null}.
	 * @return
	 */
	public <T> Optional<T> getProperty(PersistentProperty<?> property, Class<T> targetType) {

		Assert.notNull(property, "PersistentProperty must not be null!");
		Assert.notNull(targetType, "Target type must not be null!");

		return convertIfNecessary(getProperty(property), targetType);
	}

	/* 
	 * (non-Javadoc)
	 * @see org.springframework.data.mapping.PersistentPropertyAccessor#getBean()
	 */
	@Override
	public Object getBean() {
		return accessor.getBean();
	}

	/**
	 * Triggers the conversion of the source value into the target type unless the value already is a value of given
	 * target type.
	 * 
	 * @param source can be {@literal null}.
	 * @param type must not be {@literal null}.
	 * @return
	 */
	@SuppressWarnings("unchecked")
	private <T> Optional<T> convertIfNecessary(Optional<? extends Object> source, Class<T> type) {
		return source.map(it -> type.isAssignableFrom(it.getClass()) ? (T) it : conversionService.convert(it, type));
	}
}