/*
* Copyright (C) 2008 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.gxp.compiler.parser;
import com.google.common.base.Preconditions;
import com.google.gxp.compiler.alerts.AlertSink;
import com.google.gxp.compiler.alerts.InfoAlert;
import com.google.gxp.compiler.alerts.SourcePosition;
import com.google.gxp.compiler.fs.FileRef;
import com.google.gxp.compiler.fs.FileSystem;
import java.io.IOException;
import java.io.InputStream;
/**
* An entity resolver implementation that can resolve entities based on an
* abstract file system that interprets public ids that start with // as
* file system paths relative to the build system root, and that
* can resolve System IDs under http://gxp.googlecode.com/svn/trunk/resources/
* to a resouce available from the class path.
*/
public class FileSystemEntityResolver implements SourceEntityResolver {
/**
* prefix for files resolved using the java classloader.
*/
private static final String EXTERNAL_ENTITY_PREFIX =
"http://gxp.googlecode.com/svn/trunk/resources/";
/**
* prefix for public ids that are resolved relative to the revision control or
* project root directory
*/
private static final String SOURCE_ROOT_PUBLIC_ID_PREFIX = "//";
private final FileSystem fileSystem;
public FileSystemEntityResolver(FileSystem fileSystem) {
this.fileSystem = Preconditions.checkNotNull(fileSystem);
}
/**
* This implementation only allows systemIds which are in a predetermined
* set.
*
* @throws IOException if the protocol is recognized but the underlying file
* could not be retrieved.
* @throws UnsupportedExternalEntityException if the protocol isn't recognized
*/
public InputStream resolveEntity(SourcePosition pos, String publicId, String systemId,
AlertSink alertSink)
throws IOException {
if (systemId.startsWith(EXTERNAL_ENTITY_PREFIX)) {
InputStream stream = resolveEntityFromResource(
pos, systemId, EXTERNAL_ENTITY_PREFIX.length(), alertSink);
if (stream != null) {
return stream;
}
} else if (publicId != null &&
publicId.startsWith(SOURCE_ROOT_PUBLIC_ID_PREFIX)) {
// If the public id starts with // treat it as a path relative to
// the build system / project root.
String relPath = publicId.substring(SOURCE_ROOT_PUBLIC_ID_PREFIX.length());
if (!"".equals(relPath) && !relPath.startsWith("/")) {
// convert URI path to local file system conventions
FileRef file = fileSystem.getRoot().join(relPath);
alertSink.add(new EntityResolvedNotification(pos, publicId, file.toFilename()));
return file.openInputStream();
}
}
throw unresolved(pos, publicId, systemId, null);
}
private InputStream resolveEntityFromResource(SourcePosition pos, String systemId,
int prefixLength, AlertSink alertSink)
throws IOException {
Class<?> cls = getClass();
String resourceName = "/" + cls.getPackage().getName().replace('.', '/') +
"/" + systemId.substring(prefixLength);
alertSink.add(new EntityResolvedNotification(pos, systemId, resourceName));
return cls.getResourceAsStream(resourceName);
}
private static RuntimeException unresolved(SourcePosition pos, String publicId,
String systemId, Throwable cause) {
UnsupportedExternalEntityException error =
new UnsupportedExternalEntityException(pos, publicId, systemId);
if (cause != null) {
error.initCause(cause);
}
return error;
}
/**
* a notication that an external entity has been resolved to a resource or
* file.
*/
public static class EntityResolvedNotification extends InfoAlert {
private EntityResolvedNotification(SourcePosition entityRefPos, String id, String realPath) {
super(entityRefPos, "Resolved entity `" + id + "` to `" + realPath + "`");
}
}
}