how to validate XML using java?

I need to parse a bunch of incoming XML documents but it does not contain DOCTYPE (they all have the different DTD). DTD is created by myself. How can I validate an XML file against a DTD that is stored locally as a file? I have following requirement:

1. All DTDs (for different XML) Will be load into memory once,when incoming XML comes don't looked into an locally stored area.
2. validate incoming XML on the basis of load DTD file开发者_如何学Go.

Thanks

You need to use a local entity resolver on your SAX parser, here is an example of how to implement it:

class LocalEntityResolver implements EntityResolver {

private static final Logger LOG = ESAPI.getLogger(LocalEntityResolver.class);
private static final Map<String, String> DTDS;
static {
    DTDS = new HashMap<String, String>();
    DTDS.put("-//W3C//DTD XHTML 1.0 Transitional//EN",
            "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd");
    DTDS.put("-//W3C//ENTITIES Latin 1 for XHTML//EN",
            "http://www.w3.org/TR/xhtml1/DTD/xhtml-lat1.ent");
    DTDS.put("-//W3C//ENTITIES Symbols for XHTML//EN",
            "http://www.w3.org/TR/xhtml1/DTD/xhtml-symbol.ent");
    DTDS.put("-//W3C//ENTITIES Special for XHTML//EN",
            "http://www.w3.org/TR/xhtml1/DTD/xhtml-special.ent");
}

@Override
public InputSource resolveEntity(String publicId, String systemId)
        throws SAXException, IOException {
    InputSource input_source = null;
    if (publicId != null && DTDS.containsKey(publicId)) {
        LOG.debug(Logger.EVENT_SUCCESS, "Looking for local copy of [" + publicId + "]");

        final String dtd_system_id = DTDS.get(publicId);
        final String file_name = dtd_system_id.substring(
                dtd_system_id.lastIndexOf('/') + 1, dtd_system_id.length());

        InputStream input_stream = FileUtil.readStreamFromClasspath(
                file_name, "your/dtd/location",
                getClass().getClassLoader());
        if (input_stream != null) {
            LOG.debug(Logger.EVENT_SUCCESS, "Found local file [" + file_name + "]!");
            input_source = new InputSource(input_stream);
        }
    }

    return input_source;
}
}