teichmann@5779: package de.intevation.flys.artifacts.datacage.templating;
teichmann@5779: 
teichmann@5779: import java.util.ArrayDeque;
teichmann@5779: import java.util.Deque;
teichmann@5779: import java.util.List;
teichmann@5779: import java.util.Map;
teichmann@5779: 
teichmann@5779: import java.sql.SQLException;
teichmann@5779: 
teichmann@5779: import javax.xml.transform.Transformer;
teichmann@5779: import javax.xml.transform.TransformerConfigurationException;
teichmann@5779: import javax.xml.transform.TransformerException;
teichmann@5779: import javax.xml.transform.TransformerFactory;
teichmann@5779: 
teichmann@5779: import javax.xml.transform.dom.DOMResult;
teichmann@5779: import javax.xml.transform.dom.DOMSource;
teichmann@5779: 
teichmann@5779: import org.apache.log4j.Logger;
teichmann@5779: 
teichmann@5779: import org.w3c.dom.Document;
teichmann@5779: import org.w3c.dom.Node;
teichmann@5779: 
teichmann@5779: /** A little round robin pool of builders to mitigate 
teichmann@5779:   * the fact the XML DOM documents are not thread safe.
teichmann@5779:   */
teichmann@5779: public class BuilderPool
teichmann@5779: {
teichmann@5779:     private static Logger log = Logger.getLogger(BuilderPool.class);
teichmann@5779: 
teichmann@5779:     private static final int DEFAULT_POOL_SIZE = 4;
teichmann@5779: 
teichmann@5779:     private static final int POOL_SIZE = Math.max(
teichmann@5779:         Integer.getInteger("flys.datacage.pool.size", DEFAULT_POOL_SIZE), 1);
teichmann@5779: 
teichmann@5779:     private Deque<Builder> pool;
teichmann@5779: 
teichmann@5779:     public BuilderPool(Document document) {
teichmann@5779:         this(document, POOL_SIZE);
teichmann@5779:     }
teichmann@5779: 
teichmann@5779:     public BuilderPool(Document document, int poolSize) {
teichmann@5779: 
teichmann@5779:         if (log.isDebugEnabled()) {
teichmann@5779:             log.debug("Create build pool with " + poolSize + " elements.");
teichmann@5779:         }
teichmann@5779: 
teichmann@5779:         pool = new ArrayDeque<Builder>(poolSize);
teichmann@5779:         for (int i = 0; i < poolSize; ++i) {
teichmann@5779:             Document doc = i > 0 // Clone all but the first.
teichmann@5779:                 ? cloneDocument(document)
teichmann@5779:                 : document;
teichmann@5779:             pool.add(new Builder(doc));
teichmann@5779:         }
teichmann@5779:     }
teichmann@5779: 
teichmann@5779:     private final static Document cloneDocument(Document document) {
teichmann@5779:         try {
teichmann@5779:             TransformerFactory tfactory = TransformerFactory.newInstance();
teichmann@5779:             Transformer xformer = tfactory.newTransformer();
teichmann@5779:             DOMSource src = new DOMSource(document);
teichmann@5779:             DOMResult dst = new DOMResult();
teichmann@5779:             xformer.transform(src, dst);
teichmann@5779:             return (Document)dst.getNode();
teichmann@5779:         }
teichmann@5779:         catch (TransformerConfigurationException tce) {
teichmann@5779:             log.error(tce);
teichmann@5779:         }
teichmann@5779:         catch (TransformerException te) {
teichmann@5779:             log.error(te);
teichmann@5779:         }
teichmann@5779: 
teichmann@5779:         log.error(
teichmann@5779:             "Returning original DOM document. " +
teichmann@5779:             "This will result in threading errors!");
teichmann@5779: 
teichmann@5779:         return document;
teichmann@5779:     }
teichmann@5779: 
teichmann@5779:     public void build(
teichmann@5779:         List<Builder.NamedConnection> connections,
teichmann@5779:         Node                          output,
teichmann@5779:         Map<String, Object>           parameters
teichmann@5779:     )
teichmann@5779:     throws SQLException
teichmann@5779:     {
teichmann@5779:         Builder builder;
teichmann@5779:         synchronized (pool) {
teichmann@5779:             try {
teichmann@5779:                 while ((builder = pool.poll()) == null) {
teichmann@5779:                     pool.wait();
teichmann@5779:                 }
teichmann@5779:             }
teichmann@5779:             catch (InterruptedException ie) {
teichmann@5779:                 log.debug("Waiting for builder interrupted. Build canceled.");
teichmann@5779:                 return;
teichmann@5779:             }
teichmann@5779:         }
teichmann@5779:         try {
teichmann@5779:             builder.build(connections, output, parameters);
teichmann@5779:         }
teichmann@5779:         finally {
teichmann@5779:             synchronized (pool) {
teichmann@5779:                 pool.add(builder);
teichmann@5779:                 pool.notify();
teichmann@5779:             }
teichmann@5779:         }
teichmann@5779:     }
teichmann@5779: }
teichmann@5779: // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf-8 :