// Copyright (C) 2007 Google Inc.
//
// 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.
package com.google.caja.plugin;
import java.util.List;
import com.google.caja.CajaException;
import com.google.caja.lexer.ExternalReference;
import com.google.caja.lexer.FetchedData;
import com.google.caja.reporting.Message;
import com.google.caja.reporting.MessagePart;
import com.google.common.collect.Lists;
/**
* Specifies how the cajoler resolves external resources such as scripts and
* stylesheets in the code being cajoled.
*
* @author mikesamuel@gmail.com
*/
public interface UriFetcher {
/**
* Loads an external resource such as the {@code src} of a {@code script}
* tag or a stylesheet.
*
* @return non-null resource
* @throws UriFetchException if the resource could not be loaded
*/
FetchedData fetch(ExternalReference ref, String mimeType)
throws UriFetchException;
/** A fetcher that will not load any URI. */
public static final UriFetcher NULL_NETWORK = new DataUriFetcher();
public static class UriFetchException extends CajaException {
private static final long serialVersionUID = -7915784512753732116L;
public final ExternalReference ref;
public final String expectedMimeType;
public UriFetchException(
ExternalReference ref, String mimeType, Throwable cause) {
super(
new Message(
PluginMessageType.FAILED_TO_LOAD_EXTERNAL_URL,
ref.getReferencePosition(),
MessagePart.Factory.valueOf(ref.getUri().toString())),
cause);
this.ref = ref;
this.expectedMimeType = mimeType;
}
public UriFetchException(
ExternalReference ref, String mimeType, List<Throwable> causes) {
this(ref, mimeType, causes.isEmpty() ? null : causes.get(0));
}
public UriFetchException(ExternalReference ref, String mimeType) {
this(ref, mimeType, (Throwable) null);
}
}
/**
* Chains one of more uri fetchers in order and returns the first
* successfully loaded resource
*/
public final static class ChainingUriFetcher {
public static UriFetcher make(final UriFetcher... fetchers) {
return new UriFetcher() {
List<Throwable> causes = Lists.newArrayList();
public FetchedData fetch(ExternalReference ref, String mimeType)
throws UriFetchException {
for (UriFetcher fetcher : fetchers) {
try {
return fetcher.fetch(ref, mimeType);
} catch (UriFetchException e) {
causes.add(e);
}
}
// None of the fetchers succeeded
throw new UriFetchException(ref, mimeType, causes);
}
};
}
}
}