trunk/extras/src/main/java/org/apache/struts2/views/jasperreports/OgnlValueStackDataSource.java

/*
 * $Id$
 *
 * Copyright 2006 The Apache Software Foundation.
 *
 * 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.apache.struts2.views.jasperreports;

import org.apache.struts2.util.MakeIterator;
import com.opensymphony.xwork2.util.OgnlValueStack;
import net.sf.jasperreports.engine.JRDataSource;
import net.sf.jasperreports.engine.JRException;
import net.sf.jasperreports.engine.JRField;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.util.Iterator;

/**
 * Ported to Struts.
 *
 */
public class OgnlValueStackDataSource implements JRDataSource {

    /**
     * Logger for this class
     */
    private static Log log = LogFactory.getLog(OgnlValueStackDataSource.class);


    Iterator iterator;
    OgnlValueStack valueStack;
    boolean firstTimeThrough = true;


    /**
     * Create a value stack data source on the given iterable property
     *
     * @param valueStack The value stack to base the data source on
     * @param dataSource The property to iterate over for the report
     */
    public OgnlValueStackDataSource(OgnlValueStack valueStack, String dataSource) {
        this.valueStack = valueStack;

        Object dataSourceValue = valueStack.findValue(dataSource);

        if (dataSourceValue != null) {
            if (MakeIterator.isIterable(dataSourceValue)) {
                iterator = MakeIterator.convert(dataSourceValue);
            } else {
                Object[] array = new Object[1];
                array[0] = dataSourceValue;
                iterator = MakeIterator.convert(array);
            }
        } else {
            log.warn("Data source value for data source " + dataSource + " was null");
        }
    }


    /**
     * Get the value of a given field
     *
     * @param field The field to get the value for. The expression language to get the value
     *              of the field is either taken from the description property or from the name of the field
     *              if the description is <code>null</code>.
     * @return an <code>Object</code> containing the field value or a new
     *         <code>OgnlValueStackDataSource</code> object if the field value evaluates to
     *         an object that can be iterated over.
     * @throws JRException if there is a problem obtaining the value
     */
    public Object getFieldValue(JRField field) throws JRException {
        //TODO: move the code to return a OgnlValueStackDataSource to a seperate
        //      method when and if the JRDataSource interface is updated to support
        //      this.
        String expression = field.getDescription();

        if (expression == null) {
            //Description is optional so use the field name as a default
            expression = field.getName();
        }

        Object value = valueStack.findValue(expression);

        if (log.isDebugEnabled()) {
            log.debug("field: " + field.getName() + "/" + value);
        }

        if (MakeIterator.isIterable(value)) {
            //                return new OgnlValueStackDataSource(this.valueStack, field.getName());
            return new OgnlValueStackDataSource(this.valueStack, expression);
        } else {
            return value;
        }
    }

    /**
     * Is there any more data
     *
     * @return <code>true</code> if there are more elements to iterate over and
     *         <code>false</code> otherwise
     * @throws JRException if there is a problem determining whether there
     *                     is more data
     */
    public boolean next() throws JRException {
        if (firstTimeThrough) {
            firstTimeThrough = false;
        } else {
            valueStack.pop();
        }

        if ((iterator != null) && (iterator.hasNext())) {
            valueStack.push(iterator.next());
            log.debug("Pushed next value: " + valueStack.findValue("."));

            return true;
        } else {
            log.debug("No more values");

            return false;
        }
    }
}