/*
 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package com.sun.tools.internal.xjc;

import java.net.URL;

import javax.xml.validation.Schema;
import javax.xml.validation.SchemaFactory;
import javax.xml.validation.ValidatorHandler;

import com.sun.xml.internal.bind.v2.util.XmlFactory;
import javax.xml.XMLConstants;
import org.xml.sax.SAXException;

import static com.sun.xml.internal.bind.v2.util.XmlFactory.allowExternalAccess;

/**
 * Wraps a JAXP {@link Schema} object and lazily instantiate it.
 *
 * This object is thread-safe. There should be only one instance of
 * this for the whole VM.
 *
 * @author Kohsuke Kawaguchi
 */
public final class SchemaCache {

    private Schema schema;

    private final URL source;

    public SchemaCache(URL source) {
        this.source = source;
    }

    public ValidatorHandler newValidator() {
        synchronized(this) {
            if(schema==null) {
                try {
                    // do not disable secure processing - these are well-known schemas
                    SchemaFactory sf = XmlFactory.createSchemaFactory(XMLConstants.W3C_XML_SCHEMA_NS_URI, false);
                    schema = allowExternalAccess(sf, "file", false).newSchema(source);
                } catch (SAXException e) {
                    // we make sure that the schema is correct before we ship.
                    throw new AssertionError(e);
                }
            }
        }

        ValidatorHandler handler = schema.newValidatorHandler();
        return handler;
    }

}