From 5dd7436fa096d67758a25a713fdd8d70ca8d605c Mon Sep 17 00:00:00 2001
From: Peter Wu <peter@lekensteyn.nl>
Date: Wed, 23 Apr 2014 23:44:39 +0200
Subject: Catch error responses and log them

---
 src/mining/AbstractRequester.java | 31 ++++++++++++++++++++++++++++---
 src/mining/Requester.java         |  2 ++
 2 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/src/mining/AbstractRequester.java b/src/mining/AbstractRequester.java
index bfa2b6d..1e66668 100644
--- a/src/mining/AbstractRequester.java
+++ b/src/mining/AbstractRequester.java
@@ -6,6 +6,7 @@ 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;
@@ -18,17 +19,29 @@ import org.json.JSONObject;
  */
 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 {
         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 (conn.getResponseCode() != 200) {
             // TODO: print more helpful details
             throw new IOException("Unexpected response code");
         }
-        return getResponseAsJson(conn);
+        return resp;
     }
 
     protected final URL buildUrl(String resource) throws IOException {
@@ -51,6 +64,7 @@ public abstract class AbstractRequester implements Requester {
      * @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);
@@ -65,10 +79,17 @@ public abstract class AbstractRequester implements Requester {
      * @throws java.io.IOException if the response cannot be retrieved or if the
      * response does not contain well-formed JSON.
      */
-    protected final JSONObject getResponseAsJson(URLConnection conn)
+    protected final JSONObject getResponseAsJson(HttpURLConnection conn)
             throws IOException {
         StringWriter writer = new StringWriter();
-        IOUtils.copy(conn.getInputStream(), writer, Charsets.UTF_8);
+        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) {
@@ -85,4 +106,8 @@ public abstract class AbstractRequester implements Requester {
      */
     protected abstract void preconnect(URLConnection conn)
             throws IOException;
+
+    private Logger getLogger() {
+        return Logger.getLogger(getClass().getName());
+    }
 }
diff --git a/src/mining/Requester.java b/src/mining/Requester.java
index 931b0ac..df6053f 100644
--- a/src/mining/Requester.java
+++ b/src/mining/Requester.java
@@ -20,4 +20,6 @@ public interface Requester {
      * @throws java.io.IOException on error fetching the resource.
      */
     public JSONObject getJSON(String resource) throws IOException;
+
+    // TODO: retry (after sleeping) on ratelimit
 }
-- 
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