import net.sf.saxon.trans.DynamicError;
import net.sf.saxon.value.StringValue;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.xml.transform.*;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;
import java.io.File;
import java.io.IOException;
import java.util.Enumeration;
import java.util.HashMap;
/**
* SaxonServlet. Transforms a supplied input document using a supplied stylesheet
*/
public class SaxonServlet extends HttpServlet {
public void init() throws ServletException {
super.init();
System.setProperty("javax.xml.transform.TransformerFactory", "net.sf.saxon.TransformerFactoryImpl");
}
/**
* service() - accept request and produce response<BR>
* URL parameters: <UL>
* <li>source - URL of source document</li>
* <li>style - URL of stylesheet</li>
* <li>clear-stylesheet-cache - if set to yes, empties the cache before running.
* </UL>
* @param req The HTTP request
* @param res The HTTP response
*/
public void service(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException
{
String source = req.getParameter("source");
String style = req.getParameter("style");
String clear = req.getParameter("clear-stylesheet-cache");
if (clear!=null && clear.equals("yes")) {
clearCache();
}
apply(style, source, req, res);
}
/**
* getServletInfo<BR>
* Required by Servlet interface
*/
public String getServletInfo() {
return "Calls SAXON to apply a stylesheet to a source document";
}
/**
* Apply stylesheet to source document
*/
private void apply(String style, String source,
HttpServletRequest req, HttpServletResponse res)
throws java.io.IOException {
ServletOutputStream out = res.getOutputStream();
if (style==null) {
out.println("No style parameter supplied");
return;
}
if (source==null) {
out.println("No source parameter supplied");
return;
}
try {
Templates pss = tryCache(style);
Transformer transformer = pss.newTransformer();
String mime = pss.getOutputProperties().getProperty(OutputKeys.MEDIA_TYPE);
if (mime==null) {
// guess
res.setContentType("text/html");
} else {
res.setContentType(mime);
}
Enumeration p = req.getParameterNames();
while (p.hasMoreElements()) {
String name = (String)p.nextElement();
if (!(name.equals("style") || name.equals("source"))) {
String value = req.getParameter(name);
transformer.setParameter(name, new StringValue(value));
}
}
String path = getServletContext().getRealPath(source);
if (path==null) {
throw new DynamicError("Source file " + source + " not found");
}
File sourceFile = new File(path);
transformer.transform(new StreamSource(sourceFile), new StreamResult(out));
} catch (Exception err) {
out.println(err.getMessage());
err.printStackTrace();
}
}
/**
* Maintain prepared stylesheets in memory for reuse
*/
private synchronized Templates tryCache(String url) throws TransformerException {
String path = getServletContext().getRealPath(url);
if (path==null) {
throw new DynamicError("Stylesheet " + url + " not found");
}
Templates x = (Templates)cache.get(path);
if (x==null) {
TransformerFactory factory = TransformerFactory.newInstance();
x = factory.newTemplates(new StreamSource(new File(path)));
cache.put(path, x);
}
return x;
}
/**
* Clear the cache. Useful if stylesheets have been modified, or simply if space is
* running low. We let the garbage collector do the work.
*/
private synchronized void clearCache() {
cache = new HashMap(20);
}
private HashMap cache = new HashMap(20);
}