Struts example source code file (ValueStackDataSource.java)

This example Struts source code file (ValueStackDataSource.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Struts tags/keywords

iterator, jrdatasource, jrexception, jrexception, log, no, object, object, pushed, string, string, util, valuestack, valuestackdatasource, valuestackdatasource

The Struts ValueStackDataSource.java source code

/*
 * $Id: ValueStackDataSource.java 651946 2008-04-27 13:41:38Z apetrelli $
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 java.util.Iterator;

import net.sf.jasperreports.engine.JRDataSource;
import net.sf.jasperreports.engine.JRException;
import net.sf.jasperreports.engine.JRField;

import org.apache.struts2.util.MakeIterator;

import com.opensymphony.xwork2.util.ValueStack;
import com.opensymphony.xwork2.util.logging.Logger;
import com.opensymphony.xwork2.util.logging.LoggerFactory;

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

    /**
     * Logger for this class
     */
    private static Logger LOG = LoggerFactory.getLogger(ValueStackDataSource.class);


    Iterator iterator;
    ValueStack 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 ValueStackDataSource(ValueStack 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.
     * @return an <code>Object containing the field value or a new
     *         <code>ValueStackDataSource 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 ValueStackDataSource 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 ValueStackDataSource(this.valueStack, field.getName());
            return new ValueStackDataSource(this.valueStack, expression);
        } else {
            return value;
        }
    }

    /**
     * Is there any more data
     *
     * @return <code>true if there are more elements to iterate over and
     *         <code>false 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;
        }
    }
}