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  • MTN WMS Implementation Story

    - by aditya.agarkar
    MTN is Africa's largest cellular phone company serving millions of customers across 21 countries. MTN uses Oracle WMS to manage its distribution activities and its sizzling growth. Just for perspective, since 2004, Africa has been the fastest growing mobile phone market in the world. If you want to know more about MTN and the WMS Project at MTN, a summarized view of MTN WMS project is here. The WMS Project at MTN was presented at Oracle Open World in 2007. The extensive automation at MTN includes interface with Conveyor for item transport, High Speed Sorter for item routing, Put to Light for packing accuracy, ASRS Carousel/Lift for inventory Security and Storage Optimization, Check Weight Scale for shipping accuracy, Automated Carton Erectors for package creation and Automated Carton Labeling. Subsequent to this presentation and their go-live in 2007, the MTN warehouse has scaled new heights. The volume has grown manifolds (as can be expected in a fast growing cellular market). Oracle WMS has been able to scale very well to the increase in volume, just as it was designed to do. Here are a couple of videos that highlight the WMS operations at MTN:  1) Video Interview with Margaretha Theart (Warehouse Manager at MTN) 2) Automation Video at MTN (Hat tip: Syed Imran) Enjoy!

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  • How can I make exception handling for all existing SQL server 2005 Stored Procedures, view and funct

    - by Space Cracker
    we have a portal that have SQL server 2005 database that contain about 1750 stored procedures , 250 view and 200 function and 95% of them not have handling exception in their code .. we search about any way that allow us making such a global exception handling in SQL that receive any exception happen in any SP,view or function and stored it in a table we made .. is there something like this in SQL server 2005 or we must write exception handling code on each item ?

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  • How to teach Exception Handling for New Programmers?

    - by Kanini
    How do you go about teaching Exception Handling to Programmers. All other things are taught easily - Data Structures, ASP.NET, WinForms, WPF, WCF - you name it, everything can be taught easily. With Exception Handling, teaching them try-catch-finally is just the syntactic nature of Exception Handling. What should be taught however is - What part of your code do you put in the try block? What do you do in the catch block? Let me illustrate it with an example. You are working on a Windows Forms Project (a small utility) and you have designed it as below with 3 different projects. UILayer BusinessLayer DataLayer If an Exception (let us say of loading an XDocument throws an exception) is raised at DataLayer (the UILayer calls BusinessLayer which in turns calls the DataLayer), do you just do the following //In DataLayer try { XDocument xd_XmlDocument = XDocument.Load("systems.xml"); } catch(Exception ex) { throw ex; } which gets thrown again in the BusinessLayer and which is caught in UILayer where I write it to the log file? Is this how you go about Exception Handling?

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  • Different callbacks for error or error as first argument?

    - by Florian Margaine
    We (and the JS SO chat room) had a talk with @rlemon some days ago about his Little-XHR library about error handling. Basically, we wanted to decide which error handling pattern should be used: xhr.get({ // Some parameters, and then success: function(data) {}, failure: function(data) {} }) Or: xhr.get({ // Some parameters, and then callback: function(err, data) {} }) One is more jQuery-like, while the other is more Node-like. Some say that the first pattern makes you think more about handling error. I think the opposite, since you may forget the other callback function, while the argument is always there on the second pattern. Any opinion/advantage/drawback about both these patterns?

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  • Aggregating customer service emails from multiple ecommerce sites for easy handling

    - by nitbuntu
    For one of my main customer help email addresses I use Mozilla Thunderbird with a combination of tags and saved searches. As the number of my e-commerce sites grows from 1 to more, customer service handling gets more tricky. Is there any simple and efficient way of handling emails from the different sites? Perhaps what I'm looking for is a way of aggregating customer service emails from different sites, into one place? Perhaps there's a way of already doing this within Thunderbird or Gmail?

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  • Aggregating customer service emails from multiple ecommerce sites for easy handling

    - by nitbuntu
    For one of my main customer help email addresses I use Mozilla Thunderbird with a combination of tags and saved searches. As the number of my e-commerce sites grows from 1 to more, customer service handling gets more tricky. Is there any simple and efficient way of handling emails from the different sites? Perhaps what I'm looking for is a way of aggregating customer service emails from different sites, into one place? Perhaps there's a way of already doing this within Thunderbird or Gmail?

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  • Introduction into handling errors in PowerShell for SQL Server tasks

    PowerShell is becoming a great tool for managing SQL Server tasks, but like most tasks that are coded there is always the need for error handling to deal with the unknown. PowerShell has several options for handling and capturing error details and in this tip we will explain these options using PowerShell for SQL Server examples. What are your servers really trying to tell you? Find out with new SQL Monitor 3.0, an easy-to-use tool built for no-nonsense database professionals.For effortless insights into SQL Server, download a free trial today.

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  • Issues with signal handling [closed]

    - by user34790
    I am trying to actually study the signal handling behavior in multiprocess system. I have a system where there are three signal generating processes generating signals of type SIGUSR1 and SIGUSR1. I have two handler processes that handle a particular type of signal. I have another monitoring process that also receives the signals and then does its work. I have a certain issue. Whenever my signal handling processes generate a signal of a particular type, it is sent to the process group so it is received by the signal handling processes as well as the monitoring processes. Whenever the signal handlers of monitoring and signal handling processes are called, I have printed to indicate the signal handling. I was expecting a uniform series of calls for the signal handlers of the monitoring and handling processes. However, looking at the output I could see like at the beginning the monitoring and signal handling processes's signal handlers are called uniformly. However, after I could see like signal handler processes handlers being called in a burst followed by the signal handler of monitoring process being called in a burst. Here is my code and output #include <iostream> #include <sys/types.h> #include <sys/wait.h> #include <sys/time.h> #include <signal.h> #include <cstdio> #include <stdlib.h> #include <sys/ipc.h> #include <sys/shm.h> #define NUM_SENDER_PROCESSES 3 #define NUM_HANDLER_PROCESSES 4 #define NUM_SIGNAL_REPORT 10 #define MAX_SIGNAL_COUNT 100000 using namespace std; volatile int *usrsig1_handler_count; volatile int *usrsig2_handler_count; volatile int *usrsig1_sender_count; volatile int *usrsig2_sender_count; volatile int *lock_1; volatile int *lock_2; volatile int *lock_3; volatile int *lock_4; volatile int *lock_5; volatile int *lock_6; //Used only by the monitoring process volatile int monitor_count; volatile int usrsig1_monitor_count; volatile int usrsig2_monitor_count; double time_1[NUM_SIGNAL_REPORT]; double time_2[NUM_SIGNAL_REPORT]; //Used only by the main process int total_signal_count; //For shared memory int shmid; const int shareSize = sizeof(int) * (10); double timestamp() { struct timeval tp; gettimeofday(&tp, NULL); return (double)tp.tv_sec + tp.tv_usec / 1000000.; } pid_t senders[NUM_SENDER_PROCESSES]; pid_t handlers[NUM_HANDLER_PROCESSES]; pid_t reporter; void signal_catcher_1(int); void signal_catcher_2(int); void signal_catcher_int(int); void signal_catcher_monitor(int); void signal_catcher_main(int); void terminate_processes() { //Kill the child processes int status; cout << "Time up terminating the child processes" << endl; for(int i=0; i<NUM_SENDER_PROCESSES; i++) { kill(senders[i],SIGKILL); } for(int i=0; i<NUM_HANDLER_PROCESSES; i++) { kill(handlers[i],SIGKILL); } kill(reporter,SIGKILL); //Wait for the child processes to finish for(int i=0; i<NUM_SENDER_PROCESSES; i++) { waitpid(senders[i], &status, 0); } for(int i=0; i<NUM_HANDLER_PROCESSES; i++) { waitpid(handlers[i], &status, 0); } waitpid(reporter, &status, 0); } int main(int argc, char *argv[]) { if(argc != 2) { cout << "Required parameters missing. " << endl; cout << "Option 1 = 1 which means run for 30 seconds" << endl; cout << "Option 2 = 2 which means run until 100000 signals" << endl; exit(0); } int option = atoi(argv[1]); pid_t pid; if(option == 2) { if(signal(SIGUSR1, signal_catcher_main) == SIG_ERR) { perror("1"); exit(1); } if(signal(SIGUSR2, signal_catcher_main) == SIG_ERR) { perror("2"); exit(1); } } else { if(signal(SIGUSR1, SIG_IGN) == SIG_ERR) { perror("1"); exit(1); } if(signal(SIGUSR2, SIG_IGN) == SIG_ERR) { perror("2"); exit(1); } } if(signal(SIGINT, signal_catcher_int) == SIG_ERR) { perror("3"); exit(1); } /////////////////////////////////////////////////////////////////////////////////////// ////////////////////// Initializing the shared memory ///////////////////////////////// /////////////////////////////////////////////////////////////////////////////////////// cout << "Initializing the shared memory" << endl; if ((shmid=shmget(IPC_PRIVATE,shareSize,IPC_CREAT|0660))< 0) { perror("shmget fail"); exit(1); } usrsig1_handler_count = (int *) shmat(shmid, NULL, 0); usrsig2_handler_count = usrsig1_handler_count + 1; usrsig1_sender_count = usrsig2_handler_count + 1; usrsig2_sender_count = usrsig1_sender_count + 1; lock_1 = usrsig2_sender_count + 1; lock_2 = lock_1 + 1; lock_3 = lock_2 + 1; lock_4 = lock_3 + 1; lock_5 = lock_4 + 1; lock_6 = lock_5 + 1; //Initialize them to be zero *usrsig1_handler_count = 0; *usrsig2_handler_count = 0; *usrsig1_sender_count = 0; *usrsig2_sender_count = 0; *lock_1 = 0; *lock_2 = 0; *lock_3 = 0; *lock_4 = 0; *lock_5 = 0; *lock_6 = 0; cout << "End of initializing the shared memory" << endl; ///////////////////////////////////////////////////////////////////////////////////////////// /////////////////// End of initializing the shared memory /////////////////////////////////// ///////////////////////////////////////////////////////////////////////////////////////////// /////////////////////////////////////////////////////////////////////////////////////////// /////////////////////////////Registering the signal handlers/////////////////////////////// /////////////////////////////////////////////////////////////////////////////////////////// cout << "Registering the signal handlers" << endl; for(int i=0; i<NUM_HANDLER_PROCESSES; i++) { if((pid = fork()) == 0) { if(i%2 == 0) { struct sigaction action; action.sa_handler = signal_catcher_1; sigset_t block_mask; action.sa_flags = 0; sigaction(SIGUSR1,&action,NULL); if(signal(SIGUSR2, SIG_IGN) == SIG_ERR) { perror("2"); exit(1); } } else { if(signal(SIGUSR1 ,SIG_IGN) == SIG_ERR) { perror("1"); exit(1); } struct sigaction action; action.sa_handler = signal_catcher_2; action.sa_flags = 0; sigaction(SIGUSR2,&action,NULL); } if(signal(SIGINT, SIG_DFL) == SIG_ERR) { perror("2"); exit(1); } while(true) { pause(); } exit(0); } else { //cout << "Registerd the handler " << pid << endl; handlers[i] = pid; } } cout << "End of registering the signal handlers" << endl; ///////////////////////////////////////////////////////////////////////////////////////////////////// ////////////////////////////End of registering the signal handlers ////////////////////////////////// ///////////////////////////////////////////////////////////////////////////////////////////////////// //////////////////////////////////////////////////////////////////////////////////////////////////// ///////////////////////////Registering the monitoring process ////////////////////////////////////// //////////////////////////////////////////////////////////////////////////////////////////////////// cout << "Registering the monitoring process" << endl; if((pid = fork()) == 0) { struct sigaction action; action.sa_handler = signal_catcher_monitor; sigemptyset(&action.sa_mask); sigset_t block_mask; sigemptyset(&block_mask); sigaddset(&block_mask,SIGUSR1); sigaddset(&block_mask,SIGUSR2); action.sa_flags = 0; action.sa_mask = block_mask; sigaction(SIGUSR1,&action,NULL); sigaction(SIGUSR2,&action,NULL); if(signal(SIGINT, SIG_DFL) == SIG_ERR) { perror("2"); exit(1); } while(true) { pause(); } exit(0); } else { cout << "Monitor's pid is " << pid << endl; reporter = pid; } cout << "End of registering the monitoring process" << endl; ///////////////////////////////////////////////////////////////////////////////////////////////////// ////////////////////////End of registering the monitoring process//////////////////////////////////// ///////////////////////////////////////////////////////////////////////////////////////////////////// //Sleep to make sure that the monitor and handler processes are well initialized and ready to handle signals sleep(5); ////////////////////////////////////////////////////////////////////////////////////////////////////// //////////////////////////Registering the signal generators/////////////////////////////////////////// ///////////////////////////////////////////////////////////////////////////////////////////////////// cout << "Registering the signal generators" << endl; for(int i=0; i<NUM_SENDER_PROCESSES; i++) { if((pid = fork()) == 0) { if(signal(SIGUSR1, SIG_IGN) == SIG_ERR) { perror("1"); exit(1); } if(signal(SIGUSR2, SIG_IGN) == SIG_ERR) { perror("2"); exit(1); } if(signal(SIGINT, SIG_DFL) == SIG_ERR) { perror("2"); exit(1); } srand(i); while(true) { int signal_id = rand()%2 + 1; if(signal_id == 1) { killpg(getpgid(getpid()), SIGUSR1); while(__sync_lock_test_and_set(lock_4,1) != 0) { } (*usrsig1_sender_count)++; *lock_4 = 0; } else { killpg(getpgid(getpid()), SIGUSR2); while(__sync_lock_test_and_set(lock_5,1) != 0) { } (*usrsig2_sender_count)++; *lock_5=0; } int r = rand()%10 + 1; double s = (double)r/100; sleep(s); } exit(0); } else { //cout << "Registered the sender " << pid << endl; senders[i] = pid; } } //cout << "End of registering the signal generators" << endl; ///////////////////////////////////////////////////////////////////////////////////////////////////// //////////////////////////End of registering the signal generators/////////////////////////////////// ///////////////////////////////////////////////////////////////////////////////////////////////////// //Either sleep for 30 seconds and terminate the program or if the number of signals generated reaches 10000, terminate the program if(option = 1) { sleep(90); terminate_processes(); } else { while(true) { if(total_signal_count >= MAX_SIGNAL_COUNT) { terminate_processes(); } else { sleep(0.001); } } } } void signal_catcher_1(int the_sig) { while(__sync_lock_test_and_set(lock_1,1) != 0) { } (*usrsig1_handler_count) = (*usrsig1_handler_count) + 1; cout << "Signal Handler 1 " << *usrsig1_handler_count << endl; __sync_lock_release(lock_1); } void signal_catcher_2(int the_sig) { while(__sync_lock_test_and_set(lock_2,1) != 0) { } (*usrsig2_handler_count) = (*usrsig2_handler_count) + 1; __sync_lock_release(lock_2); } void signal_catcher_main(int the_sig) { while(__sync_lock_test_and_set(lock_6,1) != 0) { } total_signal_count++; *lock_6 = 0; } void signal_catcher_int(int the_sig) { for(int i=0; i<NUM_SENDER_PROCESSES; i++) { kill(senders[i],SIGKILL); } for(int i=0; i<NUM_HANDLER_PROCESSES; i++) { kill(handlers[i],SIGKILL); } kill(reporter,SIGKILL); exit(3); } void signal_catcher_monitor(int the_sig) { cout << "Monitoring process " << *usrsig1_handler_count << endl; } Here is the initial segment of output Monitoring process 0 Monitoring process 0 Monitoring process 0 Monitoring process 0 Signal Handler 1 1 Monitoring process 2 Signal Handler 1 2 Signal Handler 1 3 Signal Handler 1 4 Monitoring process 4 Monitoring process Signal Handler 1 6 Signal Handler 1 7 Monitoring process 7 Monitoring process 8 Monitoring process 8 Signal Handler 1 9 Monitoring process 9 Monitoring process 9 Monitoring process 10 Signal Handler 1 11 Monitoring process 11 Monitoring process 12 Signal Handler 1 13 Signal Handler 1 14 Signal Handler 1 15 Signal Handler 1 16 Signal Handler 1 17 Signal Handler 1 18 Monitoring process 19 Signal Handler 1 20 Monitoring process 20 Signal Handler 1 21 Monitoring process 21 Monitoring process 21 Monitoring process 22 Monitoring process 22 Monitoring process 23 Signal Handler 1 24 Signal Handler 1 25 Monitoring process 25 Signal Handler 1 27 Signal Handler 1 28 Signal Handler 1 29 Here is the segment when the signal handler processes signal handlers are called in a burst Signal Handler 1 456 Signal Handler 1 457 Signal Handler 1 458 Signal Handler 1 459 Signal Handler 1 460 Signal Handler 1 461 Signal Handler 1 462 Signal Handler 1 463 Signal Handler 1 464 Signal Handler 1 465 Signal Handler 1 466 Signal Handler 1 467 Signal Handler 1 468 Signal Handler 1 469 Signal Handler 1 470 Signal Handler 1 471 Signal Handler 1 472 Signal Handler 1 473 Signal Handler 1 474 Signal Handler 1 475 Signal Handler 1 476 Signal Handler 1 477 Signal Handler 1 478 Signal Handler 1 479 Signal Handler 1 480 Signal Handler 1 481 Signal Handler 1 482 Signal Handler 1 483 Signal Handler 1 484 Signal Handler 1 485 Signal Handler 1 486 Signal Handler 1 487 Signal Handler 1 488 Signal Handler 1 489 Signal Handler 1 490 Signal Handler 1 491 Signal Handler 1 492 Signal Handler 1 493 Signal Handler 1 494 Signal Handler 1 495 Signal Handler 1 496 Signal Handler 1 497 Signal Handler 1 498 Signal Handler 1 499 Signal Handler 1 500 Signal Handler 1 501 Signal Handler 1 502 Signal Handler 1 503 Signal Handler 1 504 Signal Handler 1 505 Signal Handler 1 506 Here is the segment when the monitoring processes signal handlers are called in a burst Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Why isn't it uniform afterwards. Why are they called in a burst?

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  • Exception Handling

    - by raghu.yadav
    Here is the few links on which andre had demonstrateddifferences-of-handling-jboexception-in handling-exceptions-in-oracle-ui-shell However in this post we can see how to display exception in popup being in the same page. I use similar usecase as andre however we'll not be using Exception Handling property from taskflow, instead we use popup and invoke the same programmatically. This is a dynamic region example where user can select jobs or locations links to edit the records of corresponding tables being in the same page and click commit to save changes. To generate exception we deliberately change commit to CommitAction in commit action binding code created in the bean (same as andre) and catch the exception and add brief description of exception into #{pageFlowScope.message}. Drop Popup component after Commit button and add dialog within in popup button, bind the popup component to backing bean and invoke the same in catch clause as shown below. public String Commit() { try{ BindingContainer bindings = getBindings(); OperationBinding operationBinding = bindings.getOperationBinding("CommitAction"); Object result = operationBinding.execute(); if (!operationBinding.getErrors().isEmpty()) { return null; } }catch (NullPointerException e) { setELValue("#{pageFlowScope.message}", "NullPointerException..."); e.printStackTrace(); String popupId = this.getPopup().getClientId(FacesContext.getCurrentInstance()); PatternsPublicUtil.invokePopup(popupId); } return null; } } private void setELValue(String el, String value) { FacesContext facesContext = FacesContext.getCurrentInstance(); ELContext elContext = facesContext.getELContext(); ExpressionFactory expressionFactory = facesContext.getApplication().getExpressionFactory(); ValueExpression valueExp = expressionFactory.createValueExpression(elContext, el, Object.class); valueExp.setValue(elContext, value); } .

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  • SQL SERVER – Get Free Books on While Learning SQL Server 2012 Error Handling

    - by pinaldave
    Fans of this blog are aware that I have recently released my new books SQL Server Functions and SQL Server 2012 Queries. The books are available in market in limited edition but you can avail them for free on Wednesday Nov 14, 2012. Not only they are free but you can additionally learn SQL Server 2012 Error Handling as well. My book’s co-author Rick Morelan is presenting a webinar tomorrow on SQL Server 2012 Error Handling. Here is the brief abstract of the webinar: People are often shocked when they see the demo in this talk where the first statement fails and all other statements still commit. For example, did you know that BEGIN TRAN…COMMIT TRAN is not enough to make everything work together? These mistakes can still happen to you in SQL Server 2012 if you are not aware of the options. Rick Morelan, creator of Joes2Pros, will teach you how to predict the Error Action and control it with & without structured error handling. Register for the webinar now to learn: How to predict the Error Action and control it Nuances between successful and failing SQL statements Essential SQL Server 2012 configuration options Register for the Webinar and be present during the webinar. My co-author will announce a winner (may be more than 1 winner) during the session. If you are present during the session – you are eligible to win the book. The webinar is scheduled for 2 different times to accommodate various time zones. 1) 10am ET/7am PT 2) 1pm ET/11am PT. Each webinar will have their own winner. You can increase your chances by attending both the webinars. Do not miss this opportunity and register for the webinar right now. The recordings of the webinar may not be available. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Joes 2 Pros, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority News, SQLServer, T SQL, Technology

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  • Jump handling and gravity

    - by sprawl
    I'm new to game development and am looking for some help on improving my jump handling for a simple side scrolling game I've made. I would like to make the jump last longer if the key is held down for the full length of the jump, otherwise if the key is tapped, make the jump not as long. Currently, how I'm handling the jumping is the following: Player.prototype.jump = function () { // Player pressed jump key if (this.isJumping === true) { // Set sprite to jump state this.settings.slice = 250; if (this.isFalling === true) { // Player let go of jump key, increase rate of fall this.settings.y -= this.velocity; this.velocity -= this.settings.gravity * 2; } else { // Player is holding down jump key this.settings.y -= this.velocity; this.velocity -= this.settings.gravity; } } if (this.settings.y >= 240) { // Player is on the ground this.isJumping = false; this.isFalling = false; this.velocity = this.settings.maxVelocity; this.settings.y = 240; } } I'm setting isJumping on keydown and isFalling on keyup. While it works okay for simple use, I'm looking for a better way handle jumping and gravity. It's a bit buggy if the gravity is increased (which is why I had to put the last y setting in the last if condition in there) on keyup, so I'd like to know a better way to do it. Where are some resources I could look at that would help me better understand how to handle jumping and gravity? What's a better approach to handling this? Like I said, I'm new to game development so I could be doing it completely wrong. Any help would be appreciated.

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  • Fault Handling Slides and Q&A by Vennester

    - by JuergenKress
    Fault Handling It is one thing to architect, design, and code the “happy flow” of your automated business processes and services. It is another thing to deal with situations you do not want or expect to occur in your processes and services. This session dives into fault handling in Oracle Service Bus 11g and Oracle SOA Suite 11g, based on an order-to-cash business process. Faults can be divided into business faults, technical faults, programming errors, and faulty user input. Each type of fault needs a different approach to prevent them from occurring or to deal with them. For example, apply User Experience (UX) techniques to improve the quality of your application so that faulty user input can be prevented as much as possible. This session shows and demos what patterns and techniques can be used in Oracle Service Bus and Oracle SOA Suite to prevent and handle technical faults as well as business faults. Q&A This section lists answers to the questions that were raised during the preview event. Q: Where can retries be configured in Oracle Service Bus? The retry mechanism is used to prevent faults caused by temporary glitches such as short network interruptions. A faulted message is resend (retried) and might succeed this time since the glitch has passed. Retries are an out-of-the-box feature that can be used in Oracle Service Bus and Oracle SOA Suite using the Fault Policy framework. By default, retries are disabled in Oracle Service Bus. Read the full article. SOA & BPM Partner Community For regular information on Oracle SOA Suite become a member in the SOA & BPM Partner Community for registration please visit  www.oracle.com/goto/emea/soa (OPN account required) If you need support with your account please contact the Oracle Partner Business Center. Blog Twitter LinkedIn Mix Forum Technorati Tags: fault handling,vennester,SOA Community,Oracle SOA,Oracle BPM,Community,OPN,Jürgen Kress

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  • ASP.NET Web API Exception Handling

    - by Fredrik N
    When I talk about exceptions in my product team I often talk about two kind of exceptions, business and critical exceptions. Business exceptions are exceptions thrown based on “business rules”, for example if you aren’t allowed to do a purchase. Business exceptions in most case aren’t important to log into a log file, they can directly be shown to the user. An example of a business exception could be "DeniedToPurchaseException”, or some validation exceptions such as “FirstNameIsMissingException” etc. Critical Exceptions are all other kind of exceptions such as the SQL server is down etc. Those kind of exception message need to be logged and should not reach the user, because they can contain information that can be harmful if it reach out to wrong kind of users. I often distinguish business exceptions from critical exceptions by creating a base class called BusinessException, then in my error handling code I catch on the type BusinessException and all other exceptions will be handled as critical exceptions. This blog post will be about different ways to handle exceptions and how Business and Critical Exceptions could be handled. Web API and Exceptions the basics When an exception is thrown in a ApiController a response message will be returned with a status code set to 500 and a response formatted by the formatters based on the “Accept” or “Content-Type” HTTP header, for example JSON or XML. Here is an example:   public IEnumerable<string> Get() { throw new ApplicationException("Error!!!!!"); return new string[] { "value1", "value2" }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The response message will be: HTTP/1.1 500 Internal Server Error Content-Length: 860 Content-Type: application/json; charset=utf-8 { "ExceptionType":"System.ApplicationException","Message":"Error!!!!!","StackTrace":" at ..."} .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   The stack trace will be returned to the client, this is because of making it easier to debug. Be careful so you don’t leak out some sensitive information to the client. So as long as you are developing your API, this is not harmful. In a production environment it can be better to log exceptions and return a user friendly exception instead of the original exception. There is a specific exception shipped with ASP.NET Web API that will not use the formatters based on the “Accept” or “Content-Type” HTTP header, it is the exception is the HttpResponseException class. Here is an example where the HttpReponseExcetpion is used: // GET api/values [ExceptionHandling] public IEnumerable<string> Get() { throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError)); return new string[] { "value1", "value2" }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The response will not contain any content, only header information and the status code based on the HttpStatusCode passed as an argument to the HttpResponseMessage. Because the HttpResponsException takes a HttpResponseMessage as an argument, we can give the response a content: public IEnumerable<string> Get() { throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent("My Error Message"), ReasonPhrase = "Critical Exception" }); return new string[] { "value1", "value2" }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   The code above will have the following response:   HTTP/1.1 500 Critical Exception Content-Length: 5 Content-Type: text/plain; charset=utf-8 My Error Message .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The Content property of the HttpResponseMessage doesn’t need to be just plain text, it can also be other formats, for example JSON, XML etc. By using the HttpResponseException we can for example catch an exception and throw a user friendly exception instead: public IEnumerable<string> Get() { try { DoSomething(); return new string[] { "value1", "value2" }; } catch (Exception e) { throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent("An error occurred, please try again or contact the administrator."), ReasonPhrase = "Critical Exception" }); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   Adding a try catch to every ApiController methods will only end in duplication of code, by using a custom ExceptionFilterAttribute or our own custom ApiController base class we can reduce code duplicationof code and also have a more general exception handler for our ApiControllers . By creating a custom ApiController’s and override the ExecuteAsync method, we can add a try catch around the base.ExecuteAsync method, but I prefer to skip the creation of a own custom ApiController, better to use a solution that require few files to be modified. The ExceptionFilterAttribute has a OnException method that we can override and add our exception handling. Here is an example: using System; using System.Diagnostics; using System.Net; using System.Net.Http; using System.Web.Http; using System.Web.Http.Filters; public class ExceptionHandlingAttribute : ExceptionFilterAttribute { public override void OnException(HttpActionExecutedContext context) { if (context.Exception is BusinessException) { throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent(context.Exception.Message), ReasonPhrase = "Exception" }); } //Log Critical errors Debug.WriteLine(context.Exception); throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent("An error occurred, please try again or contact the administrator."), ReasonPhrase = "Critical Exception" }); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   Note: Something to have in mind is that the ExceptionFilterAttribute will be ignored if the ApiController action method throws a HttpResponseException. The code above will always make sure a HttpResponseExceptions will be returned, it will also make sure the critical exceptions will show a more user friendly message. The OnException method can also be used to log exceptions. By using a ExceptionFilterAttribute the Get() method in the previous example can now look like this: public IEnumerable<string> Get() { DoSomething(); return new string[] { "value1", "value2" }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } To use the an ExceptionFilterAttribute, we can for example add the ExceptionFilterAttribute to our ApiControllers methods or to the ApiController class definition, or register it globally for all ApiControllers. You can read more about is here. Note: If something goes wrong in the ExceptionFilterAttribute and an exception is thrown that is not of type HttpResponseException, a formatted exception will be thrown with stack trace etc to the client. How about using a custom IHttpActionInvoker? We can create our own IHTTPActionInvoker and add Exception handling to the invoker. The IHttpActionInvoker will be used to invoke the ApiController’s ExecuteAsync method. Here is an example where the default IHttpActionInvoker, ApiControllerActionInvoker, is used to add exception handling: public class MyApiControllerActionInvoker : ApiControllerActionInvoker { public override Task<HttpResponseMessage> InvokeActionAsync(HttpActionContext actionContext, System.Threading.CancellationToken cancellationToken) { var result = base.InvokeActionAsync(actionContext, cancellationToken); if (result.Exception != null && result.Exception.GetBaseException() != null) { var baseException = result.Exception.GetBaseException(); if (baseException is BusinessException) { return Task.Run<HttpResponseMessage>(() => new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent(baseException.Message), ReasonPhrase = "Error" }); } else { //Log critical error Debug.WriteLine(baseException); return Task.Run<HttpResponseMessage>(() => new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent(baseException.Message), ReasonPhrase = "Critical Error" }); } } return result; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You can register the IHttpActionInvoker with your own IoC to resolve the MyApiContollerActionInvoker, or add it in the Global.asax: GlobalConfiguration.Configuration.Services.Remove(typeof(IHttpActionInvoker), GlobalConfiguration.Configuration.Services.GetActionInvoker()); GlobalConfiguration.Configuration.Services.Add(typeof(IHttpActionInvoker), new MyApiControllerActionInvoker()); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   How about using a Message Handler for Exception Handling? By creating a custom Message Handler, we can handle error after the ApiController and the ExceptionFilterAttribute is invoked and in that way create a global exception handler, BUT, the only thing we can take a look at is the HttpResponseMessage, we can’t add a try catch around the Message Handler’s SendAsync method. The last Message Handler that will be used in the Wep API pipe-line is the HttpControllerDispatcher and this Message Handler is added to the HttpServer in an early stage. The HttpControllerDispatcher will use the IHttpActionInvoker to invoke the ApiController method. The HttpControllerDipatcher has a try catch that will turn ALL exceptions into a HttpResponseMessage, so that is the reason why a try catch around the SendAsync in a custom Message Handler want help us. If we create our own Host for the Wep API we could create our own custom HttpControllerDispatcher and add or exception handler to that class, but that would be little tricky but is possible. We can in a Message Handler take a look at the HttpResponseMessage’s IsSuccessStatusCode property to see if the request has failed and if we throw the HttpResponseException in our ApiControllers, we could use the HttpResponseException and give it a Reason Phrase and use that to identify business exceptions or critical exceptions. I wouldn’t add an exception handler into a Message Handler, instead I should use the ExceptionFilterAttribute and register it globally for all ApiControllers. BUT, now to another interesting issue. What will happen if we have a Message Handler that throws an exception?  Those exceptions will not be catch and handled by the ExceptionFilterAttribute. I found a  bug in my previews blog post about “Log message Request and Response in ASP.NET WebAPI” in the MessageHandler I use to log incoming and outgoing messages. Here is the code from my blog before I fixed the bug:   public abstract class MessageHandler : DelegatingHandler { protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) { var corrId = string.Format("{0}{1}", DateTime.Now.Ticks, Thread.CurrentThread.ManagedThreadId); var requestInfo = string.Format("{0} {1}", request.Method, request.RequestUri); var requestMessage = await request.Content.ReadAsByteArrayAsync(); await IncommingMessageAsync(corrId, requestInfo, requestMessage); var response = await base.SendAsync(request, cancellationToken); var responseMessage = await response.Content.ReadAsByteArrayAsync(); await OutgoingMessageAsync(corrId, requestInfo, responseMessage); return response; } protected abstract Task IncommingMessageAsync(string correlationId, string requestInfo, byte[] message); protected abstract Task OutgoingMessageAsync(string correlationId, string requestInfo, byte[] message); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   If a ApiController throws a HttpResponseException, the Content property of the HttpResponseMessage from the SendAsync will be NULL. So a null reference exception is thrown within the MessageHandler. The yellow screen of death will be returned to the client, and the content is HTML and the Http status code is 500. The bug in the MessageHandler was solved by adding a check against the HttpResponseMessage’s IsSuccessStatusCode property: public abstract class MessageHandler : DelegatingHandler { protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) { var corrId = string.Format("{0}{1}", DateTime.Now.Ticks, Thread.CurrentThread.ManagedThreadId); var requestInfo = string.Format("{0} {1}", request.Method, request.RequestUri); var requestMessage = await request.Content.ReadAsByteArrayAsync(); await IncommingMessageAsync(corrId, requestInfo, requestMessage); var response = await base.SendAsync(request, cancellationToken); byte[] responseMessage; if (response.IsSuccessStatusCode) responseMessage = await response.Content.ReadAsByteArrayAsync(); else responseMessage = Encoding.UTF8.GetBytes(response.ReasonPhrase); await OutgoingMessageAsync(corrId, requestInfo, responseMessage); return response; } protected abstract Task IncommingMessageAsync(string correlationId, string requestInfo, byte[] message); protected abstract Task OutgoingMessageAsync(string correlationId, string requestInfo, byte[] message); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } If we don’t handle the exceptions that can occur in a custom Message Handler, we can have a hard time to find the problem causing the exception. The savior in this case is the Global.asax’s Application_Error: protected void Application_Error() { var exception = Server.GetLastError(); Debug.WriteLine(exception); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } I would recommend you to add the Application_Error to the Global.asax and log all exceptions to make sure all kind of exception is handled. Summary There are different ways we could add Exception Handling to the Wep API, we can use a custom ApiController, ExceptionFilterAttribute, IHttpActionInvoker or Message Handler. The ExceptionFilterAttribute would be a good place to add a global exception handling, require very few modification, just register it globally for all ApiControllers, even the IHttpActionInvoker can be used to minimize the modifications of files. Adding the Application_Error to the global.asax is a good way to catch all unhandled exception that can occur, for example exception thrown in a Message Handler.   If you want to know when I have posted a blog post, you can follow me on twitter @fredrikn

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  • The Koyal Group Info Mag News¦Charged building material could make the renewable grid a reality

    - by Chyler Tilton
    What if your cell phone didn’t come with a battery? Imagine, instead, if the material from which your phone was built was a battery. The promise of strong load-bearing materials that can also work as batteries represents something of a holy grail for engineers. And in a letter published online in Nano Letters last week, a team of researchers from Vanderbilt University describes what it says is a breakthrough in turning that dream into an electrocharged reality. The researchers etched nanopores into silicon layers, which were infused with a polyethylene oxide-ionic liquid composite and coated with an atomically thin layer of carbon. In doing so, they created small but strong supercapacitor battery systems, which stored electricity in a solid electrolyte, instead of using corrosive chemical liquids found in traditional batteries. These supercapacitors could store and release about 98 percent of the energy that was used to charge them, and they held onto their charges even as they were squashed and stretched at pressures up to 44 pounds per square inch. Small pieces of them were even strong enough to hang a laptop from—a big, fat Dell, no less. Although the supercapacitors resemble small charcoal wafers, they could theoretically be molded into just about any shape, including a cell phone’s casing or the chassis of a sedan. They could also be charged—and evacuated of their charge—in less time than is the case for traditional batteries. “We’ve demonstrated, for the first time, the simple proof-of-concept that this can be done,” says Cary Pint, an assistant professor in the university’s mechanical engineering department and one of the authors of the new paper. “Now we can extend this to all kinds of different materials systems to make practical composites with materials specifically tailored to a host of different types of applications. We see this as being just the tip of a very massive iceberg.” Pint says potential applications for such materials would go well beyond “neat tech gadgets,” eventually becoming a “transformational technology” in everything from rocket ships to sedans to home building materials. “These types of systems could range in size from electric powered aircraft all the way down to little tiny flying robots, where adding an extra on-board battery inhibits the potential capability of the system,” Pint says. And they could help the world shift to the intermittencies of renewable energy power grids, where powerful batteries are needed to help keep the lights on when the sun is down or when the wind is not blowing. “Using the materials that make up a home as the native platform for energy storage to complement intermittent resources could also open the door to improve the prospects for solar energy on the U.S. grid,” Pint says. “I personally believe that these types of multifunctional materials are critical to a sustainable electric grid system that integrates solar energy as a key power source.”

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  • Any learning/studying material for C/C++ that use game programming as learning context out there?

    - by mac
    As most of game programming is done - I read on this very site - in C/C++ I was wondering if there is any learning/studying material for C/C++ that would target specifically game programming. I am not looking for material about "developing games" or "software architecture for games", but rather for material that uses "game programming" as the CONTEXT for introducing and illustrating C/C++ features, idioms, programming techniques, etc... With a simile: think to the GOF book on design patterns. There, they used "developing a text-editor" as a context for introducing design patterns, but the book is most definitively not a book about "developing text-editors". Thanks in advance for your time and advice! PS: My background: I am a programmer with a solid experience in OO scripting languages and only some experience in C and Assembler (on AVR microcontrollers), so I am thinking to mid-to-advanced level material, rather than tutorials for beginners, although it might be interesting to take a look to the latter ones if nothing else is available.

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  • ASP.NET MVC 3 Hosting :: Error Handling and CustomErrors in ASP.NET MVC 3 Framework

    - by C. Miller
    So, what else is new in MVC 3? MVC 3 now has a GlobalFilterCollection that is automatically populated with a HandleErrorAttribute. This default FilterAttribute brings with it a new way of handling errors in your web applications. In short, you can now handle errors inside of the MVC pipeline. What does that mean? This gives you direct programmatic control over handling your 500 errors in the same way that ASP.NET and CustomErrors give you configurable control of handling your HTTP error codes. How does that work out? Think of it as a routing table specifically for your Exceptions, it's pretty sweet! Global Filters The new Global.asax file now has a RegisterGlobalFilters method that is used to add filters to the new GlobalFilterCollection, statically located at System.Web.Mvc.GlobalFilter.Filters. By default this method adds one filter, the HandleErrorAttribute. public class MvcApplication : System.Web.HttpApplication {     public static void RegisterGlobalFilters(GlobalFilterCollection filters)     {         filters.Add(new HandleErrorAttribute());     } HandleErrorAttributes The HandleErrorAttribute is pretty simple in concept: MVC has already adjusted us to using Filter attributes for our AcceptVerbs and RequiresAuthorization, now we are going to use them for (as the name implies) error handling, and we are going to do so on a (also as the name implies) global scale. The HandleErrorAttribute has properties for ExceptionType, View, and Master. The ExceptionType allows you to specify what exception that attribute should handle. The View allows you to specify which error view (page) you want it to redirect to. Last but not least, the Master allows you to control which master page (or as Razor refers to them, Layout) you want to render with, even if that means overriding the default layout specified in the view itself. public class MvcApplication : System.Web.HttpApplication {     public static void RegisterGlobalFilters(GlobalFilterCollection filters)     {         filters.Add(new HandleErrorAttribute         {             ExceptionType = typeof(DbException),             // DbError.cshtml is a view in the Shared folder.             View = "DbError",             Order = 2         });         filters.Add(new HandleErrorAttribute());     }Error Views All of your views still work like they did in the previous version of MVC (except of course that they can now use the Razor engine). However, a view that is used to render an error can not have a specified model! This is because they already have a model, and that is System.Web.Mvc.HandleErrorInfo @model System.Web.Mvc.HandleErrorInfo           @{     ViewBag.Title = "DbError"; } <h2>A Database Error Has Occurred</h2> @if (Model != null) {     <p>@Model.Exception.GetType().Name<br />     thrown in @Model.ControllerName @Model.ActionName</p> }Errors Outside of the MVC Pipeline The HandleErrorAttribute will only handle errors that happen inside of the MVC pipeline, better known as 500 errors. Errors outside of the MVC pipeline are still handled the way they have always been with ASP.NET. You turn on custom errors, specify error codes and paths to error pages, etc. It is important to remember that these will happen for anything and everything outside of what the HandleErrorAttribute handles. Also, these will happen whenever an error is not handled with the HandleErrorAttribute from inside of the pipeline. <system.web>  <customErrors mode="On" defaultRedirect="~/error">     <error statusCode="404" redirect="~/error/notfound"></error>  </customErrors>Sample Controllers public class ExampleController : Controller {     public ActionResult Exception()     {         throw new ArgumentNullException();     }     public ActionResult Db()     {         // Inherits from DbException         throw new MyDbException();     } } public class ErrorController : Controller {     public ActionResult Index()     {         return View();     }     public ActionResult NotFound()     {         return View();     } } Putting It All Together If we have all the code above included in our MVC 3 project, here is how the following scenario's will play out: 1.       A controller action throws an Exception. You will remain on the current page and the global HandleErrorAttributes will render the Error view. 2.       A controller action throws any type of DbException. You will remain on the current page and the global HandleErrorAttributes will render the DbError view. 3.       Go to a non-existent page. You will be redirect to the Error controller's NotFound action by the CustomErrors configuration for HTTP StatusCode 404. But don't take my word for it, download the sample project and try it yourself. Three Important Lessons Learned For the most part this is all pretty straight forward, but there are a few gotcha's that you should remember to watch out for: 1) Error views have models, but they must be of type HandleErrorInfo. It is confusing at first to think that you can't control the M in an MVC page, but it's for a good reason. Errors can come from any action in any controller, and no redirect is taking place, so the view engine is just going to render an error view with the only data it has: The HandleError Info model. Do not try to set the model on your error page or pass in a different object through a controller action, it will just blow up and cause a second exception after your first exception! 2) When the HandleErrorAttribute renders a page, it does not pass through a controller or an action. The standard web.config CustomErrors literally redirect a failed request to a new page. The HandleErrorAttribute is just rendering a view, so it is not going to pass through a controller action. But that's ok! Remember, a controller's job is to get the model for a view, but an error already has a model ready to give to the view, thus there is no need to pass through a controller. That being said, the normal ASP.NET custom errors still need to route through controllers. So if you want to share an error page between the HandleErrorAttribute and your web.config redirects, you will need to create a controller action and route for it. But then when you render that error view from your action, you can only use the HandlerErrorInfo model or ViewData dictionary to populate your page. 3) The HandleErrorAttribute obeys if CustomErrors are on or off, but does not use their redirects. If you turn CustomErrors off in your web.config, the HandleErrorAttributes will stop handling errors. However, that is the only configuration these two mechanisms share. The HandleErrorAttribute will not use your defaultRedirect property, or any other errors registered with customer errors. In Summary The HandleErrorAttribute is for displaying 500 errors that were caused by exceptions inside of the MVC pipeline. The custom errors are for redirecting from error pages caused by other HTTP codes.

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  • What is the best way to go about testing that we handle failures appropriately?

    - by Earlz
    we're working on error handling in an application. We try to have fairly good automated test coverage. One big problem though is that we don't really know of a way to test some of our error handling. For instance, we need to test that whenever there is an uncaught exception, a message is sent to our server with exception information. The big problem with this is that we strive to never have an uncaught exception(and instead have descriptive error messages). So, how do we test something what we never want to actually happen?

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  • Event Handling in jQuery

    - by bipinjoshi
    In the previous part of this series I discussed how HTML DOM can be manipulated using jQuery. Now let's proceed with one of the most common task you do in JavaScript - handling events. jQuery streamlines the JavaScript event handling mechanism by providing you a uniform and easy way to wire events with their handlers without bothering about the cross browser issues. As an example we will create a custom context menu (shortcut menu or right click menu) that displays some options specific to our website instead of the normal context menu of the browser.http://www.bipinjoshi.net/articles/fc9bf7fb-4b81-48cf-9b2d-cee10d2de2f9.aspx

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  • Pattern for loading and handling resources

    - by Enoon
    Many times there is the need to load external resources into the program, may they be graphics, audio samples or text strings. Is there a patten for handling the loading and the handling of such resources? For example: should I have a class that loads all the data and then call it everytime I need the data? As in: GraphicsHandler.instance().loadAllData() ...//and then later: draw(x,y, GraphicsHandler.instance().getData(WATER_IMAGE)) //or maybe draw(x,y, GraphicsHandler.instance().WATER_IMAGE) Or should I assign each resource to the class where it belongs? As in (for example, in a game): Graphics g = GraphicsLoader.load(CHAR01); Character c = new Character(..., g); ... c.draw(); Generally speaking which of these two is the more robust solution? GraphicsHandler.instance().getData(WATER_IMAGE) //or GraphicsHandler.instance().WATER_IMAGE //a constant reference

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  • 3D Location Handling

    - by tgrosinger
    I am thinking about making a simulator type game that will involve having lots of small objects in a 3D space. What is the typical solution for handling these objects? The first thing that comes to mind is a 3D Array, but I can't help but think there is a more efficient solution. Another idea that comes to mind is objects having possession of smaller items. For example a House possesses a Table which possesses a Cup and Bowl. The final way I can think of handling this is just having an array of "objects" that each have an x, y, z value. While this would make storing them easy I do not understand how you would detect collisions without just looking at every possible object and checking to see if it is in the way. Are there other ways of holding onto these objects that is more efficient?

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  • kernel software trap handling

    - by Tony
    I'm reading a book on Windows Internals and there's something I don't understand: "The kernel handles software interrupts either as part of hardware interrupt handling or synchronously when a thread invokes kernel functions related to the software interrupt." So does this mean that software interrupts or exceptions will only be handled under these conditions: a. When the kernel is executing a function from said thread related to the software exception(trap) b. when it is already handling a hardware trap Is my understanding of this correct? The next bit: "In most cases, the kernel installs front-end trap handling functions that perform general trap handling tasks before and after transferring control to other functions that field the trap." I don't quite understand what it means by 'front-end trap handling functions' and 'field the trap'? Can anyone help me?

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