AbstractMessageAwareFiller.java

package fr.sii.ogham.core.filler;

import java.util.Map;

import fr.sii.ogham.core.builder.configuration.ConfigurationValueBuilderHelper;
import fr.sii.ogham.core.exception.filler.FillMessageException;
import fr.sii.ogham.core.message.Message;

/**
 * Base class to help to fill a particular {@link Message} type.
 * 
 * @author Aurélien Baudet
 *
 * @param <M>
 *            the type of the message that the filler is able to handle
 */
public abstract class AbstractMessageAwareFiller<M> implements MessageFiller {
    protected final Map<String, ConfigurationValueBuilderHelper<?, ?>> defaultValues;
    private final Class<M> messageType;

    /**
     * The list of properties is indexed by an alias that is known by the
     * implementation. For example, if the keys is defined like this:
     * 
     * <pre>
     * Map&lt;String, List&lt;String&gt;&gt; keys = new HashMap&lt;&gt;();
     * keys.put("to", valueBuilder.properties("ogham.email.to.default-value"));
     * keys.put("from", valueBuilder.properties("ogham.email.from.default-value", "mail.smtp.from"));
     * </pre>
     * 
     * The implementation can then retrieve real property value using map key
     * (alias):
     * 
     * <pre>
     * getProperty("from");
     * // will return either the value of "ogham.email.from.default-value" or
     * // "mail.smtp.from"
     * </pre>
     * 
     * @param defaultValues
     *            a list of property keys indexed by an alias
     * @param messageType
     *            the class of the message that this implementation can handle
     */
    protected AbstractMessageAwareFiller(Map<String, ConfigurationValueBuilderHelper<?, ?>> defaultValues, Class<M> messageType) {
        super();
        this.defaultValues = defaultValues;
        this.messageType = messageType;
    }

    @SuppressWarnings("unchecked")
    @Override
    public void fill(Message message) throws FillMessageException {
        if (messageType.isAssignableFrom(message.getClass())) {
            fill((M) message);
        }
    }

    protected abstract void fill(M message);

    /**
     * Return whether the given property alias has at least one property key
     * that is available for resolution, i.e., the value for the given key is
     * not {@code null}.
     * 
     * @param alias
     *            the property alias to resolve
     * @return true if property exists, false otherwise
     */
    protected boolean containsProperty(String alias) {
        ConfigurationValueBuilderHelper<?, ?> valueBuilder = defaultValues.get(alias);
        return valueBuilder != null && valueBuilder.getValue() != null;
    }

    /**
     * Returns the value of first property represented by the provided alias
     * that has a value (not {@code null}).
     * 
     * @param alias
     *            the property alias to resolve
     * @param valueClass
     *            the class of the resulting value
     * @param <T>
     *            the type of the resulting value
     * @return the property value or null
     */
    @SuppressWarnings("unchecked")
    protected <T> T getProperty(String alias, Class<T> valueClass) {
        ConfigurationValueBuilderHelper<?, T> valueBuilder = (ConfigurationValueBuilderHelper<?, T>) defaultValues.get(alias);
        return valueBuilder == null ? null : valueBuilder.getValue();
    }
}