/*
* @(#)$Id: XQueryServlet.java 3619 2008-03-26 07:23:03Z yui $
*
* Copyright 2006-2008 Makoto YUI
*
* 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.
*
* Contributors:
* Makoto YUI - initial implementation
*/
package xbird.servlet.xqsp;
import java.io.*;
import java.net.URL;
import java.util.Enumeration;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import javax.servlet.ServletException;
import javax.servlet.http.*;
import xbird.util.cache.*;
import xbird.util.lang.PrintUtils;
import xbird.util.xml.SAXWriter;
import xbird.xquery.XQueryException;
import xbird.xquery.XQueryModule;
import xbird.xquery.dm.ser.SAXSerializer;
import xbird.xquery.dm.ser.Serializer;
import xbird.xquery.dm.value.Item;
import xbird.xquery.dm.value.Sequence;
import xbird.xquery.dm.value.literal.XString;
import xbird.xquery.expr.XQExpression;
import xbird.xquery.expr.var.Variable;
import xbird.xquery.expr.var.Variable.GlobalVariable;
import xbird.xquery.meta.DynamicContext;
import xbird.xquery.meta.StaticContext;
import xbird.xquery.misc.QNameUtil;
import xbird.xquery.misc.QNameTable.QualifiedName;
import xbird.xquery.parser.XQueryParser;
/**
*
* <DIV lang="en"></DIV>
* <DIV lang="ja"></DIV>
*
* @author Makoto YUI (yuin405+xbird@gmail.com)
*/
public class XQueryServlet extends HttpServlet {
private static final long serialVersionUID = -4576560807978002697L;
public static final String XQSP_NSURI = "xbird://xqsp";
private final ReadWriteLock _lock = new ReentrantReadWriteLock();
private final Cache<String, CachedQuery> _caches = CacheFactory.createCache(XQueryServlet.class.getName());
public XQueryServlet() {
super();
}
@Override
public void init() throws ServletException {
super.init();
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException,
IOException {
process(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
process(req, resp);
}
protected void process(HttpServletRequest req, HttpServletResponse resp) throws IOException {
resp.setCharacterEncoding("UTF-8");
resp.setContentType("text/html");
PrintWriter out = resp.getWriter();
String queryPath = req.getServletPath();
final CachedQuery loaded;
try {
loaded = loadQuery(queryPath);
} catch (XQueryException e) {
reportError("Query loading failed: " + queryPath, e, out);
return;
} catch (CacheException e) {
reportError("Caching failed: " + queryPath, e, out);
return;
}
XQueryModule loadedModule = loaded.queryObject;
XQExpression body = loadedModule.getExpression();
if(body == null) {
return;
}
// set parameters
Enumeration<String> paramNames = req.getParameterNames();
while(paramNames.hasMoreElements()) {
String name = paramNames.nextElement();
String value = req.getParameter(name);
QualifiedName qname = QNameUtil.parse(name, XQSP_NSURI);
Variable var = new GlobalVariable(qname, null);
var.setResult(XString.valueOf(value));
try {
loadedModule.putVariable(qname, var);
} catch (XQueryException e) {
reportError("Setting parameter failed: " + qname, e, out);
return;
}
}
// execute
final Sequence<? extends Item> result;
try {
result = body.eval(null, new DynamicContext(loaded.staticEnv));
} catch (XQueryException e) {
reportError("Execution failed: " + queryPath, e, out);
return;
}
// serialize
SAXWriter writer = new SAXWriter(out);
Serializer ser = new SAXSerializer(writer);
try {
ser.emit(result);
} catch (XQueryException e) {
reportError("Serialization failed: " + queryPath, e, out);
return;
}
}
private CachedQuery loadQuery(String path) throws IOException, XQueryException, CacheException {
URL url = getServletContext().getResource(path);
assert (url != null);
long lastModified = url.openConnection().getLastModified();
_lock.readLock().lock();
CachedQuery cached = _caches.get(path);
if(cached == null || cached.loadTimeStamp < lastModified) {
if(cached == null) {
cached = new CachedQuery();
}
// parse XQuery expression
InputStream is = url.openStream();
XQueryParser parser = new XQueryParser(is);
StaticContext staticEnv = parser.getStaticContext();
staticEnv.setBaseURI(path);
XQueryModule module = parser.parse();
_lock.readLock().unlock();
_lock.writeLock().lock();
// set query cache
cached.queryObject = module;
cached.staticEnv = staticEnv;
cached.loadTimeStamp = System.currentTimeMillis();
_caches.put(path, cached);
_lock.writeLock().unlock();
_lock.readLock().lock();
// static analysis
module.staticAnalysis(staticEnv);
}
_lock.readLock().unlock();
return cached;
}
private static void reportError(String title, Exception e, PrintWriter out) {
out.println("<h2>" + title + "</h2>");
out.println("<pre>");
String trace = PrintUtils.prettyPrintStackTrace(e);
out.println(trace);
out.println("</pre>");
}
private static final class CachedQuery {
private XQueryModule queryObject;
private StaticContext staticEnv;
private long loadTimeStamp;
private CachedQuery() {}
}
}