/**
* Copyright 2009 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.step2.discovery;
import com.google.step2.http.FetchException;
import com.google.step2.http.FetchRequest;
import com.google.step2.http.FetchResponse;
import com.google.step2.http.HttpFetcher;
import org.apache.http.HttpStatus;
import org.apache.http.client.HttpResponseException;
import java.io.IOException;
import java.io.InputStream;
import java.net.URI;
import java.net.URISyntaxException;
/**
* Super-class for implementations of HostMetaFetcher that fetch a host-meta
* file from a certain URL. A subclass of this class can merely indicate which
* URL the host-meta should be fetched from, and this class will then take
* care of the actual fetching of the bits, and the parsing of the file.
*/
public abstract class UrlHostMetaFetcher implements HostMetaFetcher {
private final HttpFetcher fetcher;
/**
* Constructor. An UrlHostMetaFetcher is a HostMetaFetcher that needs
* an HttpFetcher to do its job.
*/
protected UrlHostMetaFetcher(HttpFetcher fetcher) {
this.fetcher = fetcher;
}
public HostMeta getHostMeta(String host) throws HostMetaException {
InputStream responseStream = null;
try {
URI uri = getHostMetaUriForHost(host);
FetchRequest request = FetchRequest.createGetRequest(uri);
FetchResponse response = fetcher.fetch(request);
int status = response.getStatusCode();
responseStream = response.getContentAsStream();
if (status != HttpStatus.SC_OK) {
throw new HttpResponseException(status, "fetching host-meta from " +
host + " return status " + status);
}
return HostMeta.parseFromStream(responseStream);
} catch (FetchException e) {
throw new HostMetaException(e);
} catch (URISyntaxException e) {
throw new HostMetaException(e);
} catch (HttpResponseException e) {
throw new HostMetaException(e);
} catch (IOException e) {
throw new HostMetaException(e);
} finally {
if(responseStream != null) {
try {
responseStream.close();
} catch(IOException ex) {
// ignored
}
}
}
}
/**
* Given a host, returns the URL from which to download the host-meta for
* that host.
*/
protected abstract URI getHostMetaUriForHost(String host)
throws URISyntaxException;
}