don't depend on docs.javacord.org

add fallback javadoc.io docs to use if docs.javacord.org doesn't work
use ci.javacord.org for getting the version

src/main/java/org/javacord/bot/Constants.java

@@ -35,7 +35,17 @@ public final class Constants {
     /**
      * The API URL where to obtain the latest release version for Javacord.
      */
-    public static final String LATEST_VERSION_URL = "https://docs.javacord.org/rest/latest-version/release";
+    public static final String LATEST_VERSION_URL = "https://ci.javacord.org/app/rest/builds/buildType:(id:Javacord_Release),status:SUCCESS?guest=1";
+
+    /**
+     * The URL to the Javacord docs on docs.javacord.org, with a placeholder for api/core.
+     */
+    public static final String JAVACORD_DOCS_URL_1 = "https://docs.javacord.org/%s/";
+
+    /**
+     * The URL to the Javacord docs on javadoc.io, with a placeholder for api/core and another for the version.
+     */
+    public static final String JAVACORD_DOCS_URL_2 = "https://javadoc.io/static/org.javacord/javacord-%s/%s/";
 
     private Constants() { /* nope */ }
 

src/main/java/org/javacord/bot/util/LatestVersionFinder.java

@@ -4,6 +4,7 @@
 import com.fasterxml.jackson.databind.ObjectMapper;
 import okhttp3.OkHttpClient;
 import okhttp3.Request;
+import okhttp3.Request.Builder;
 import okhttp3.ResponseBody;
 import org.javacord.api.DiscordApi;
 import org.javacord.api.util.logging.ExceptionLogger;
@@ -49,25 +50,30 @@ public CompletableFuture<String> findLatestVersion() {
     private String getAndUpdateVersionSync() {
         Request request = new Request.Builder()
                 .url(Constants.LATEST_VERSION_URL)
+                .header("Accept", "application/json")
                 .build();
+
         try (ResponseBody body = client.newCall(request).execute().body()) {
             if (body == null) {
                 throw new RuntimeException("Error while requesting the latest version: No response body.");
             }
+
             JsonNode response = mapper.readTree(body.charStream());
-            // Response format is a JSON object {"version":"x.y.z"}
+
+            // Response format is a JSON object {"number":"x.y.z (#n)", ...}
             if (!response.isObject()) {
                 throw new AssertionError("Latest Version API result differs from expectation");
             }
-            String latestVersion = response.get("version").asText();
-            if (latestVersion == null || latestVersion.isEmpty()) {
+
+            String latestVersion = response.get("number").asText();
+            if (latestVersion == null || latestVersion.isEmpty() || !latestVersion.contains(" ")) {
                 throw new AssertionError("Latest Version API result differs from expectation");
             }
-            // Set cached version
-            this.latestVersion = latestVersion;
+
+            this.latestVersion = latestVersion.split(" ", 2)[0]; //converts "x.y.z (#n)" to "x.y.z"
             // Eventually clean up update task
             return latestVersion;
-        } catch (NullPointerException | IOException e) {
+        } catch (IOException e) {
             throw new RuntimeException("Error while requesting the latest version", e);
         }
     }

src/main/java/org/javacord/bot/util/javadoc/parser/JavadocParser.java

@@ -7,6 +7,8 @@
 import okhttp3.Response;
 import okhttp3.ResponseBody;
 import org.javacord.api.DiscordApi;
+import org.javacord.bot.Constants;
+import org.javacord.bot.util.LatestVersionFinder;
 
 import java.io.IOException;
 import java.util.HashSet;
@@ -43,7 +45,7 @@ public JavadocParser(DiscordApi api, String url) {
      * @return The latest JavaDoc link.
      */
     public static CompletableFuture<String> getLatestJavaDocs(DiscordApi api) {
-        return getJavadocUrl(api, "https://docs.javacord.org/api/");
+        return getJavadocUrl(api, "api");
     }
 
     /**
@@ -53,21 +55,27 @@ public static CompletableFuture<String> getLatestJavaDocs(DiscordApi api) {
      * @return The latest core JavaDoc link.
      */
     public static CompletableFuture<String> getLatestCoreJavaDocs(DiscordApi api) {
-        return getJavadocUrl(api, "https://docs.javacord.org/core/");
+        return getJavadocUrl(api, "core");
     }
 
-    private static CompletableFuture<String> getJavadocUrl(DiscordApi api, String url) {
+    private static CompletableFuture<String> getJavadocUrl(DiscordApi api, String type) {
         return CompletableFuture.supplyAsync(() -> {
             try {
                 Request request = new Request.Builder()
-                        .url(url)
+                        .url(String.format(Constants.JAVACORD_DOCS_URL_1, type))
                         .build();
 
                 try (Response response = client.newCall(request).execute()) {
                     return response.request().url().toString();
                 }
             } catch (Exception e) {
-                throw new CompletionException(e);
+                try {
+                    return String.format(Constants.JAVACORD_DOCS_URL_2, type,
+                            new LatestVersionFinder(api).findLatestVersion().join());
+                } catch (Exception ignored) {
+                    //Just handle first exception, because it is more important.
+                    throw new CompletionException(e);
+                }
             }
         }, api.getThreadPool().getExecutorService());
     }