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package mining;
import java.io.IOException;
import java.io.InputStream;
import java.io.StringWriter;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.util.logging.Logger;
import org.apache.commons.io.Charsets;
import org.apache.commons.io.IOUtils;
import org.json.JSONException;
import org.json.JSONObject;
/**
* Performs an API Request.
*
* @author Peter Wu
*/
public abstract class AbstractRequester implements Requester {
private static final Logger LOGGER
= Logger.getLogger(AbstractRequester.class.getName());
private static final String API_URL = "https://api.twitter.com/";
@Override
public JSONObject getJSON(String resource) throws IOException {
return getJSON(resource, true);
}
@Override
public JSONObject getJSONRelax(String resource) throws IOException {
return getJSON(resource, false);
}
private JSONObject getJSON(String resource, boolean checkStatusCode)
throws IOException {
HttpURLConnection conn = open(buildUrl(resource));
preconnect(conn);
JSONObject resp = getResponseAsJson(conn);
/* print response to stderr for debugging */
if (resp.has("errors")) {
try {
String errors = resp.get("errors").toString();
getLogger().fine("Request failed: " + errors);
} catch (JSONException ex) {
}
}
if (checkStatusCode && conn.getResponseCode() != 200) {
// TODO: print more helpful details
throw new IOException("Unexpected response code");
}
return resp;
}
protected final URL buildUrl(String resource) throws IOException {
String spec = API_URL;
if (!resource.startsWith("oauth/") && !resource.startsWith("oauth2/")) {
// manual inspection shows that at least oauth/ and oauth2/ do not
// have a version prefixed.
spec += "1.1/";
}
spec += resource;
spec += ".json";
return new URL(spec);
}
/**
* Opens a connection to the URL.
*
* @param url The URL to open a connection to.
* @return a connection that can be used for sending requests.
* @throws java.io.IOException on failure to open a connection.
*/
protected final HttpURLConnection open(URL url) throws IOException {
getLogger().fine("Opening: " + url);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
// set default param: fail if no response within 5 seconds
conn.setReadTimeout(5000);
return conn;
}
/**
* Reads the response body from a connection (in JSON format).
*
* @param conn An open connection to which a request was already made.
* @return A JSON object as parsed from the response.
* @throws java.io.IOException if the response cannot be retrieved or if the
* response does not contain well-formed JSON.
*/
protected final JSONObject getResponseAsJson(HttpURLConnection conn)
throws IOException {
StringWriter writer = new StringWriter();
InputStream is;
try {
is = conn.getInputStream();
} catch (IOException ex) {
/* 404 (FileNotFoundException) */
is = conn.getErrorStream();
}
IOUtils.copy(is, writer, Charsets.UTF_8);
try {
return new JSONObject(writer.toString());
} catch (JSONException ex) {
// treat JSON errors as if an I/O error occurred
throw new IOException(ex);
}
}
/**
* Prepare the request before it gets send.
*
* @param conn A connection for the request.
* @throws java.io.IOException on failing to prepare the request.
*/
protected abstract void preconnect(URLConnection conn)
throws IOException;
private Logger getLogger() {
return Logger.getLogger(getClass().getName());
}
}
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