DefaultValueExpression.java

/*
 * (C) Copyright 2013 Nuxeo SA (http://nuxeo.com/) and contributors.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the GNU Lesser General Public License
 * (LGPL) version 2.1 which accompanies this distribution, and is available at
 * http://www.gnu.org/licenses/lgpl-2.1.html
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * Contributors:
 *     Anahide Tchertchian
 */
package org.nuxeo.ecm.platform.ui.web.binding;

import java.util.Collection;

import javax.el.ELContext;
import javax.el.PropertyNotFoundException;
import javax.el.ValueExpression;

/**
 * Value expression holding a default value expression for resolve on get, when
 * original value expression defaults to null.
 * <p>
 * Accepts a null original value expression in case default value should be
 * resolved even if no mapping should be done.
 *
 * @since 5.7.3
 */
public class DefaultValueExpression extends ValueExpression {

    private static final long serialVersionUID = 1L;

    protected final ValueExpression originalExpression;

    protected final ValueExpression defaultExpression;

    public DefaultValueExpression(ValueExpression originalExpression,
            ValueExpression defaultExpression) {
        super();
        this.originalExpression = originalExpression;
        this.defaultExpression = defaultExpression;
    }

    @Override
    public Class<?> getExpectedType() {
        if (originalExpression != null) {
            return originalExpression.getExpectedType();
        } else {
            return defaultExpression.getExpectedType();
        }
    }

    @Override
    public Class<?> getType(ELContext arg0) throws PropertyNotFoundException {
        if (originalExpression != null) {
            return originalExpression.getType(arg0);
        } else {
            return defaultExpression.getType(arg0);
        }
    }

    @Override
    @SuppressWarnings("rawtypes")
    public Object getValue(ELContext arg0) throws PropertyNotFoundException {
        Object value = null;
        if (originalExpression != null) {
            value = originalExpression.getValue(arg0);
        }
        if (value == null
                || ((value instanceof Object[]) && ((Object[]) value).length == 0)
                || ((value instanceof Collection) && ((Collection) value).size() == 0)) {
            value = defaultExpression.getValue(arg0);
        }
        return value;
    }

    @Override
    public boolean isReadOnly(ELContext arg0) throws PropertyNotFoundException {
        if (originalExpression != null) {
            return originalExpression.isReadOnly(arg0);
        } else {
            return true;
        }
    }

    @Override
    public void setValue(ELContext arg0, Object arg1)
            throws PropertyNotFoundException {
        if (originalExpression != null) {
            originalExpression.setValue(arg0, arg1);
        }
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (!(obj instanceof DefaultValueExpression)) {
            return false;
        }
        DefaultValueExpression other = (DefaultValueExpression) obj;
        if (originalExpression != null) {
            return originalExpression.equals(other.originalExpression)
                    && defaultExpression.equals(other.defaultExpression);
        } else {
            return defaultExpression.equals(other.defaultExpression);
        }
    }

    @Override
    public String getExpressionString() {
        if (originalExpression != null) {
            return originalExpression.getExpressionString();
        }
        return null;
    }

    @Override
    public int hashCode() {
        if (originalExpression != null) {
            return originalExpression.hashCode() + defaultExpression.hashCode();
        } else {
            return defaultExpression.hashCode();
        }
    }

    @Override
    public boolean isLiteralText() {
        return (originalExpression != null && originalExpression.isLiteralText())
                || (defaultExpression != null && defaultExpression.isLiteralText());
    }
}