diff -r 1612dbcec451 -r 639991d0808a java/cewolf-1.0/src/main/java/de/laures/cewolf/taglib/DataContainer.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/java/cewolf-1.0/src/main/java/de/laures/cewolf/taglib/DataContainer.java	Sat Feb 28 21:31:02 2009 +0100
@@ -0,0 +1,96 @@
+/*
+ * Created on 13.04.2003
+ *
+ * To change the template for this generated file go to
+ * Window>Preferences>Java>Code Generation>Code and Comments
+ */
+package de.laures.cewolf.taglib;
+
+import java.io.Serializable;
+import java.util.Date;
+import java.util.Map;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.jfree.data.general.Dataset;
+
+import de.laures.cewolf.DatasetProduceException;
+import de.laures.cewolf.DatasetProducer;
+import de.laures.cewolf.taglib.util.DatasetProductionTimeStore;
+import de.laures.cewolf.taglib.util.KeyGenerator;
+import de.laures.cewolf.util.Assert;
+
+/**
+ * @author guido
+ *
+ * To change the template for this generated type comment go to
+ * Window>Preferences>Java>Code Generation>Code and Comments
+ */
+public class DataContainer implements DataAware, Serializable {
+
+    private static transient final Log log = LogFactory.getLog(ChartImageDefinition.class);
+
+    private transient Dataset data;
+    private transient DatasetProducer producer;
+
+    private Map datasetProductionParams;
+    private long datasetProduceTime;
+    private boolean useCache = true;
+
+    public void setDataProductionConfig(DatasetProducer dsp, Map params, boolean useCache) {
+        log.debug("setDataProductionConfig");
+        producer = dsp;
+        datasetProductionParams = params;
+        this.useCache = useCache;
+        checkDataProductionNeed();
+    }
+
+    public Object getDataset() throws DatasetProduceException {
+        Assert.check(producer != null, "you need to specifiy a producer for the data of the chart.");
+        log.debug("getting data..");
+        if (data == null) {
+            log.debug("producing new dataset for " + producer.getProducerId());
+            data = (Dataset) producer.produceDataset(datasetProductionParams);
+            DatasetProductionTimeStore dataCache = DatasetProductionTimeStore.getInstance();
+            dataCache.addEntry(producer.getProducerId(), datasetProductionParams, new Date(datasetProduceTime));
+        }
+        Assert.check(data != null, "your producer of type " + producer.getClass().getName() + " produced a null dataset.");
+        return data;
+    }
+
+    /**
+     * This method checks if there has been a dataset production 
+     * for the same DatasetProvider and parameters. If so the DatasetProducer
+     * is consulted to check the expiry of this data.
+     * If the data has expired the retrieval of a cached image of this
+     * ChartDefinition is avoided by setting the datasetProduceTime to the
+     * actual time. After this the hash code of this object can not be
+     * present in the image cache and so a new image with new data will
+     * be rendered.
+     * If the data did not expire the last dataset production time is stored
+     * as a memeber to reach the same hash code for this object as the one
+     * before if possible.
+     * This method is called during serialization to ensure the same serialized
+     * representation of this and a eventually formally stored object.
+     */
+    private void checkDataProductionNeed() {
+        log.debug("checking data actuality..." + producer + ", " + datasetProductionParams);
+        final String prodId = producer.getProducerId();
+        log.debug(prodId + ", " + KeyGenerator.generateKey((Serializable)datasetProductionParams));
+        log.debug("useCache = " + useCache);
+        DatasetProductionTimeStore dataCache = DatasetProductionTimeStore.getInstance();
+        if (useCache && dataCache.containsEntry(prodId, datasetProductionParams)) {
+            Date produceTime = dataCache.getProductionTime(prodId, datasetProductionParams);
+            log.debug("cached data available.");
+            // cached data available
+            if (!producer.hasExpired(datasetProductionParams, produceTime)) {
+                log.debug("cached data is still valid.");
+                this.datasetProduceTime = produceTime.getTime();
+                return;
+            }
+            dataCache.removeEntry(prodId, datasetProductionParams);
+        }
+        datasetProduceTime = System.currentTimeMillis();
+    }
+
+}