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package io;
import com.google.gson.JsonElement;
import com.google.gson.JsonParser;
import java.io.FileNotFoundException;
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.Level;
import java.util.logging.Logger;
import org.apache.commons.io.Charsets;
import org.apache.commons.io.IOUtils;
/**
* Performs an API Request.
*
* @author Peter Wu
*/
public abstract class AbstractRequester implements Requester {
private static final String API_URL = "https://api.twitter.com/";
@Override
public Response getJSON(String resource) throws IOException {
HttpURLConnection conn = open(buildUrl(resource));
try {
preconnect(conn);
JsonElement resp = getResponseAsJson(conn);
if(resp.isJsonObject() && resp.getAsJsonObject().has("errors")) {
/* print response to stderr for debugging */
String errors = resp.getAsJsonObject().get("errors").toString();
getLogger().log(Level.INFO, "Request failed: {0}", errors);
}
// TODO: what if there is an internal server error? Technically we
// should always treat that as "don't know what the server thinks".
if (conn.getResponseCode() != 200) {
// TODO: print more helpful details
throw new IOException("Unexpected response code");
}
int rateLimit = Integer.parseInt(conn.getHeaderField("X-Rate-Limit-Limit"));
int rateLimitRemaining = Integer.parseInt(conn.getHeaderField("X-Rate-Limit-Remaining"));
int rateLimitReset = Integer.parseInt(conn.getHeaderField("X-Rate-Limit-Reset"));
return new Response(resp, rateLimit, rateLimitRemaining, rateLimitReset);
} finally {
conn.disconnect();
}
}
protected final URL buildUrl(String resource) throws IOException {
String spec = API_URL;
String[] split = resource.split("\\?", 2);
boolean isPreV1;
isPreV1 = resource.startsWith("oauth/") || resource.startsWith("oauth2/");
if (!isPreV1 && !resource.startsWith("1")) {
// manual inspection shows that at least oauth/ and oauth2/ do not
// have a version prefixed. Do not add version if already given
// (e.g. "1/account/rate_limit_status").
spec += "1.1/";
}
// path part
spec += split[0];
if (!isPreV1) {
// not sure about the history, but oauth{,2}/ don't have this.
spec += ".json";
}
// append parameters after path
if (split.length >= 2) {
spec += "?" + split[1];
}
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().log(Level.FINE, "Opening: {0}", 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 JsonElement getResponseAsJson(HttpURLConnection conn)
throws IOException {
StringWriter writer = new StringWriter();
InputStream is;
try {
is = conn.getInputStream();
} catch (FileNotFoundException ex) {
/* 404 (FileNotFoundException) */
is = conn.getErrorStream();
}
// this could happen if the URL was severly malformed
if (is == null) {
throw new IOException("Failed to fetch response");
}
IOUtils.copy(is, writer, Charsets.UTF_8);
JsonParser parser = new JsonParser();
return parser.parse(writer.toString());
}
/**
* 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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