{"id":758,"date":"2017-09-12T10:00:55","date_gmt":"2017-09-12T10:00:55","guid":{"rendered":"http:\/\/smartfoxserver.com\/blog\/?p=758"},"modified":"2017-09-12T10:00:55","modified_gmt":"2017-09-12T10:00:55","slug":"better-ways-of-logging-exceptions-in-sfs2x","status":"publish","type":"post","link":"https:\/\/smartfoxserver.com\/blog\/better-ways-of-logging-exceptions-in-sfs2x\/","title":{"rendered":"Better ways of logging Exceptions in SFS2X"},"content":{"rendered":"

A recent discussion on our support forum brought up the struggle of sending\u00a0enough details to the log files when an Exception is caught on the\u00a0server side. In this article we\u00a0provide a few options to improve error reporting in your Extensions and avoid those puzzling,\u00a0single-line errors.<\/p>\n

\u00bb The problem<\/h3>\n

Let’s consider this example:<\/p>\n

\r\ntry\r\n{\r\n\tCreateRoomSettings crs = new CreateRoomSettings();\r\n\tcrs.setName("The Lobby");\r\n\tcrs.setGame(false);\r\n\tcrs.setMaxUsers(60);\r\n\t\r\n\tgetApi().createRoom(getParentZone(), crs, null);\r\n}\r\ncatch(SFSCreateRoomException ex)\r\n{\r\n\ttrace("Room creation failure: " + ex);\r\n}\r\n<\/pre>\n
If an error occurs in the API call, this is what we will get in the log files:<\/p>\n
10:14:15,712 INFO  [main] Extensions     - {javaTest}: Room creation failure: com.smartfoxserver.v2.exceptions.SFSCreateRoomException: Room creation error. A room with the same name already exists: The Lobby, { Zone: BasicExamples }, null<\/pre>\n
(scroll horizontally to read the full error message)<\/sup><\/p>\n
While the description is clear\u00a0and tells you exactly what problem has occurred we have no stack trace to understand where exactly in our code this happened. If this operation is wrapped in a method called by multiple classes it will be pretty difficult to understand where this exception is generated.<\/p>\n
In these cases having a full stack trace would help substantially, so let’s see how we can improve our error reporting accordingly.<\/p>\n
1)\u00a0Using the inherited logger<\/h4>\n
The SFSExtension base class provides access to the underlying logging system via the getLogger()<\/strong> method. With one line of code we can immediately add a stack trace to our error reporting:<\/p>\n
\r\ntry\r\n{\r\n\t\/\/ Potentially "dangerous" code\r\n}\r\ncatch(Exception ex)\r\n{\r\n\tgetLogger().warn("My custom message", ex);\r\n}\r\n<\/pre>\n
This in turn will generate an output like this in the log files:<\/p>\n
10:45:47,965 WARN  [Thread-3] Extensions     - Room creation error\r\ncom.smartfoxserver.v2.exceptions.SFSCreateRoomException: Room creation error. A room with the same name already exists: The Lobby, { Zone: BasicExamples }, null\r\n\tat com.smartfoxserver.v2.api.SFSApi.createRoom(SFSApi.java:776)\r\n\tat sfs2x.extension.logging.CustomLoggerExtension.init(CustomLoggerExtension.java:24)\r\n\tat com.smartfoxserver.v2.entities.managers.SFSExtensionManager.createExtension(SFSExtensionManager.java:303)\r\n\tat com.smartfoxserver.v2.entities.managers.SFSExtensionManager.reloadExtension(SFSExtensionManager.java:533)\r\n\tat com.smartfoxserver.v2.entities.managers.SFSExtensionManager$ExtensionFileChangeListener.fileChanged(SFSExtensionManager.java:111)\r\n\tat org.apache.commons.vfs.events.ChangedEvent.notify(ChangedEvent.java:34)\r\n\tat org.apache.commons.vfs.provider.AbstractFileSystem.fireEvent(AbstractFileSystem.java:519)\r\n\tat org.apache.commons.vfs.provider.AbstractFileSystem.fireFileChanged(AbstractFileSystem.java:487)\r\n\tat org.apache.commons.vfs.impl.DefaultFileMonitor$FileMonitorAgent.check(DefaultFileMonitor.java:647)\r\n\tat org.apache.commons.vfs.impl.DefaultFileMonitor$FileMonitorAgent.access$200(DefaultFileMonitor.java:418)\r\n\tat org.apache.commons.vfs.impl.DefaultFileMonitor.run(DefaultFileMonitor.java:373)\r\n\tat java.lang.Thread.run(Thread.java:745)\r\n<\/pre>\n
2)\u00a0ExceptionMessageComposer<\/h4>\n
If you want an even more flexible and fine grained system, SFS2X provides a custom helper class called ExceptionMessageComposer<\/strong>, which can be imported from\u00a0com.smartfoxserver.v2.exceptions<\/em><\/p>\n
The class adds the ability to attach multiple lines of info to every reported error and provide a better description of the issue in a readable format.<\/p>\n
Let’s take a look at an example:<\/p>\n
\r\ntry\r\n{\r\n   \/\/ some code\r\n}\r\ncatch(IllegalStateException ex)\r\n{\r\n\tExceptionMessageComposer emc = new ExceptionMessageComposer(ex);\r\n\temc.setDescription("Unexpected error during game turn");\r\n\temc.addInfo("Player 1 State: " + player1.getState());\r\n\temc.addInfo("Player 2 State: " + player2.getState());\r\n\temc.addInfo("Last P1 position: " + player1.getPosition());\r\n\temc.addInfo("Last P2 position: " + player2.getPosition());\r\n\temc.addInto("Pieces on board: " + board.countPieces());\r\n\r\n\t  \/\/ ...\r\n  \r\n\tlog.warn(emc.toString());\r\n}\r\n<\/pre>\n