src/main/java/org/apache/commons/xml/HardeningTransformer.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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
 *
 *      https://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.
 */

package org.apache.commons.xml;

import java.util.Properties;

import javax.xml.transform.ErrorListener;
import javax.xml.transform.Result;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.transform.URIResolver;

/**
 * {@link Transformer} wrapper that rewrites the Source on every {@link Transformer#transform(Source, Result)} call through
 * {@link XmlFactories#harden(Source)} before delegating, and keeps a deny-all {@link URIResolver} floor so runtime {@code document()} calls a caller does not
 * resolve are denied rather than fetched.
 *
 * <p>The floor is installed on the delegate transformer at construction, seeded with the factory's compile-time resolver; {@link #setURIResolver(URIResolver)}
 * routes a caller's resolver through it rather than replacing it, so the block cannot be dropped.</p>
 */
final class HardeningTransformer extends Transformer {

    private final Transformer delegate;

    private final Resolvers.FallbackDenyURIResolver floor;

    HardeningTransformer(final Transformer delegate, final URIResolver uriResolver) {
        this.delegate = delegate;
        this.floor = new Resolvers.FallbackDenyURIResolver(uriResolver);
        delegate.setURIResolver(floor);
    }

    @Override
    public void setURIResolver(final URIResolver resolver) {
        floor.setDelegate(resolver);
    }

    @Override
    public URIResolver getURIResolver() {
        return floor.getDelegate();
    }

    @Override
    public void transform(final Source xmlSource, final Result outputTarget) throws TransformerException {
        try {
            delegate.transform(XmlFactories.harden(xmlSource), outputTarget);
        } catch (final TransformerConfigurationException e) {
            throw new TransformerException(e);
        }
    }

    // <editor-fold defaultstate="collapsed" desc="Trivial delegation">
    @Override
    public void clearParameters() {
        delegate.clearParameters();
    }

    @Override
    public ErrorListener getErrorListener() {
        return delegate.getErrorListener();
    }

    @Override
    public Properties getOutputProperties() {
        return delegate.getOutputProperties();
    }

    @Override
    public String getOutputProperty(final String name) {
        return delegate.getOutputProperty(name);
    }

    @Override
    public Object getParameter(final String name) {
        return delegate.getParameter(name);
    }

    @Override
    public void reset() {
        delegate.reset();
    }

    @Override
    public void setErrorListener(final ErrorListener listener) {
        delegate.setErrorListener(listener);
    }

    @Override
    public void setOutputProperties(final Properties properties) {
        delegate.setOutputProperties(properties);
    }

    @Override
    public void setOutputProperty(final String name, final String value) {
        delegate.setOutputProperty(name, value);
    }

    @Override
    public void setParameter(final String name, final Object value) {
        delegate.setParameter(name, value);
    }
    // </editor-fold>
}