Add API error handler to log unexpected errors/exceptions

Fixed /admin/uptime to return text/plain instead of application/json
 as response is only a simple long.
Ditto /admin/stop.

src/main/java/org/qora/api/ApiErrorHandler.java

@@ -0,0 +1,36 @@
+package org.qora.api;
+
+import java.io.IOException;
+
+import javax.servlet.RequestDispatcher;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.eclipse.jetty.server.Request;
+import org.eclipse.jetty.server.handler.ErrorHandler;
+
+public class ApiErrorHandler extends ErrorHandler {
+
+	private static final Logger LOGGER = LogManager.getLogger(ApiErrorHandler.class);
+
+	@Override
+	public void handle(String target, Request baseRequest, HttpServletRequest request, HttpServletResponse response) throws IOException {
+		String requestURI = request.getRequestURI();
+
+		String queryString = request.getQueryString();
+		if (queryString != null)
+			requestURI += "?" + queryString;
+
+		Throwable th = (Throwable) request.getAttribute(RequestDispatcher.ERROR_EXCEPTION);
+		if (th != null) {
+			LOGGER.error(String.format("Unexpected %s during request %s", th.getClass().getCanonicalName(), requestURI));
+		} else {
+			LOGGER.error(String.format("Unexpected error during request %s", requestURI));
+		}
+
+		super.handle(target, baseRequest, request, response);
+	}
+
+}

src/main/java/org/qora/api/ApiService.java

@@ -6,6 +6,7 @@ import org.eclipse.jetty.rewrite.handler.RedirectPatternRule;
 import org.eclipse.jetty.rewrite.handler.RewriteHandler;
 
 import org.eclipse.jetty.server.Server;
+import org.eclipse.jetty.server.handler.ErrorHandler;
 import org.eclipse.jetty.server.handler.InetAccessHandler;
 import org.eclipse.jetty.servlet.DefaultServlet;
 import org.eclipse.jetty.servlet.FilterHolder;
@@ -33,6 +34,10 @@ public class ApiService {
 		// Create RPC server
 		this.server = new Server(Settings.getInstance().getApiPort());
 
+		// Error handler
+		ErrorHandler errorHandler = new ApiErrorHandler();
+		this.server.setErrorHandler(errorHandler);
+
 		// IP address based access control
 		InetAccessHandler accessHandler = new InetAccessHandler();
 		for (String pattern : Settings.getInstance().getApiWhitelist()) {
@@ -49,10 +54,11 @@ public class ApiService {
 		context.setContextPath("/");
 		rewriteHandler.setHandler(context);
 
-		FilterHolder filterHolder = new FilterHolder(CrossOriginFilter.class);
-		filterHolder.setInitParameter("allowedOrigins", "*");
-		filterHolder.setInitParameter("allowedMethods", "GET, POST");
-		context.addFilter(filterHolder, "/*", null);
+		// Cross-origin resource sharing
+		FilterHolder corsFilterHolder = new FilterHolder(CrossOriginFilter.class);
+		corsFilterHolder.setInitParameter("allowedOrigins", "*");
+		corsFilterHolder.setInitParameter("allowedMethods", "GET, POST, DELETE");
+		context.addFilter(corsFilterHolder, "/*", null);
 
 		// API servlet
 		ServletContainer container = new ServletContainer(config);

src/main/java/org/qora/api/resource/AdminResource.java

@@ -59,7 +59,7 @@ public class AdminResource {
 		responses = {
 			@ApiResponse(
 				description = "uptime in milliseconds",
-				content = @Content(schema = @Schema(type = "number"))
+				content = @Content(mediaType = MediaType.TEXT_PLAIN, schema = @Schema(type = "number"))
 			)
 		}
 	)
@@ -75,7 +75,7 @@ public class AdminResource {
 		responses = {
 			@ApiResponse(
 				description = "\"true\"",
-				content = @Content(schema = @Schema(type = "string"))
+				content = @Content(mediaType = MediaType.TEXT_PLAIN, schema = @Schema(type = "string"))
 			)
 		}
 	)