Now, for the third time, I’ve run into some weird and wonderful situation where a lazy object wasn’t initialized when I was using it. When will I learn? Don’t use FetchType.LAZY unless you’re really know what you’re doing, and test carefully afterwards. The precise problem I seem to be having is that my hashCode() and equals() methods don’t work. Anyway, a word of caution!
dobesland
Dobes Vandermeer – Software Engineer, Aspiring Buddha
Please Visit My New Blog- Faster GWT startup with objects embedded in the HTML host page February 17, 2009I recently ran into an interesting article about dumping some data into the HTML host page for your GWT app to reduce the number of round trips to the server. Since my app loads a lot of little configuration items from the server on startup, I thought this would be an interesting technique and [...]Dobes
- How to workaround JPA locking limitations when using Hibernate by bypassing the EntityManager and using Session directly February 7, 2009First, the solution: private Session getSession() { return ((Session)((EntityManagerImpl)em.getDelegate()).getSession()); } Now you can call the methods on Session which handle locking using LockMode. A brief introduction to JPA’s optimistic locking system as I understand it For performance reasons, the designers of JPA decided that optimistic [...] […]Dobes
- Running Work in a Seperate Thread in Glassfish using the WorkManager February 3, 2009While working on our business accounting software, I recently learned about a very useful class in glassfish from a friendly fellow on the glassfish users mailing list. This is the WorkManager, a class that allows you to add Runnable bits of Work for glassfish to run in another thread pool. I use this to perform independent [...]Dobes
- How to parse XHTML faster by not loading DTDs from w3c.org January 4, 2009If you are reading this, you may be running into the same issues I did when parsing XHTML files, namely: Slow parsing of XHTML java.net.ConnectException: Connection refused exception when parsing XHTML code The cause of these errors is that the XML parser is loading the XHTML DTDs from w3c.org in order to resolve named “entities” like and […]Dobes
- How to use EJB Timers via the TimerService December 15, 2008Java EE provides a the TimerService to allow you to schedule actions to run at a future time. The ability to schedule timed jobs, or just delay a piece of work so it runs asynchronously, is an important part of most software systems. When I first read about the TimerService I was a bit confused [...]Dobes
- Announcing Kiyaa! - a GWT Library for Accessibility, Styling, and More! November 10, 2008Kiyaa! is a GWT toolkit for better accessibility, styling, and more! It was created in the process of making small business accounting software that I needed to be easy to use, attractive, and to maintain. It’s released under the MPL, so you can use it in your commercial applications and copy the code into other libraries [...]Dobes
- JPA Locking and Timers bit me in the arse! November 1, 2008Accidentally double-charged a bunch of credit cards this morning, had to clean up a big mess. Lessons: Learn about how JPA locking REALLY works, I thought I was getting serializable transaction isolation, in fact it’s optimistic locking. Hibernate will generate an exclusive write lock on an object row if you use em.lock() on it, other providers [...]Dobes
- Hibernate Annotations: @OneToOne with mappedBy and lazy fetch are dangerous! October 8, 2008Today I ran into a very frustrating issue with hibernate and lazy inverse @OneToOne mappings. Inverse @OneToOne mappings are mapping where you provide the mappedBy attribute to indicate that the foreign key of that relation is stored in the other table. I was using this technique as a lazy (as in, me trying to avoid work) [...]Dobes
- HQL: Be careful of using dot notation with left outer joins October 3, 2008I recently ran into a little glitch with my HQL that I thought I could share for the rest of you. I created a query that looks something like: SELECT b.c.d, a.b FROM a LEFT OUTER JOIN a.b AS b; The problem with this is that hibernate will generate an inner join to resolve b.c.d, which PostgreSQL didn’t [...]Dobes
- Just when I thought the past would disappear October 2, 2008Google brings back the old search results from 2001. Googling myself in 2001 I find the old version of dobesland.com, an old dream I had about the future of internet technology (now realized in the form of DHTML/AJAX and Cloud Computing, in a way). Back then both of these sites were hosted on a cheap [...]Dobes
- Faster GWT startup with objects embedded in the HTML host page February 17, 2009
-
Recent Comments
Robert on Glassfish: Setting the context… Terence on Eclipse J2EE Module Dependenci… Kevin on GWT: Using source-path to crea… Remy Monsen on Glassfish: Setting the context… John Fries on Python isinstance considered… bookmarks
- Clarity Accounting Blog
- My way or the highwayThese are the words I thought I would love to say when I became a boss. Once I was having an argument with my mother and she told me that the only reason why I would want to hire people is that I can tell them what to do and order them around. My first 3 [...]
- Resources for working capitalThere are three stages in the life of an active business: 1) startup, 2) operating, and 3) growth. Each of these stages has needs for capital (cash) and appropriate sources for available funds are different for each stage. Having a sound strategy for obtaining and maintaining your cash position is the key to having a [...]
- Business Cash CycleComplete and up-to-date records for your business finances are imperative to keep your business solvent and profitable. Understanding your finances and utilizing the accurate reports generated by your comprehensive business accounting application should be your primary focus. Your business will be at risk if your capital, which is the fuel that runs your bus […]
- Cash is still kingIn today’s electronic age, unless your business is primarily retail, you may rarely see actual “cash money”. Most service or information businesses and all online businesses conduct their transactions entirely through the Internet. The bookkeeping, accounting, and invoicing functions are performed with an online accounting software, and mos […]
- Personal vs Business FinancesAs a small business owner, you should ensure that your personal accounts are kept separate from your business accounts. At the start-up of your business, you will need to set aside six to twelve months of income to keep your family solvent while your business becomes profitable. Depending on your business structure, the way you [...]
- Are you an accidental entrepreneur?In today’s challenging economic environment of companies downsizing or closing and retirement accounts decimated, many people find themselves deciding to start a business. For many, becoming an entrepreneur was the farthest thing from their minds, but with shrinking employment options, some people feel they have no choice. Whether you always wanted to […]
- Fall into good accounting practicesOf course keeping up with your business accounting tasks is FUN-isn’t it? Well OK, with a little regular “financial discipline” and regular use of your business accounting software, it can certainly be less “not fun”! Consistent completion of smaller tasks can keep you from having one big task (and headache) at the end of each [ […]
- Bookkeeper or AccountantBookkeeper or Accountant? What’s the difference? Although many of the tasks of a bookkeeper are done by an accountant and vice versa, technically, there are differences between bookkeeping and accounting. The bookkeeper is the person who actually records the transactions while the accountant analyzes, verifies, and reports the results. The accountant h […]
- It’s What You GETYou’ve heard it before: “It’s not what you make, it’s what you keep!” While that is certainly true, when you are a SOHO (Small Office Home Office), it is also “It’s not just what you make, it’s what you GET!” In other words, working hard for yourself is useless if you don’t get paid! Make sure [...]
- October 15 will soon arrive…October 15 will soon be here! It will be October 15 or 15 October all over the world, but if you are in the United States, October 15 means Quarterly Tax Time! If you have been consistent about keeping track of your finances with your business accounting software, AND you have been diligently depositing your [...]
- My way or the highway
January 7, 2008 at 2:24 am |
Are you sure you did not close or clear the session or transaction before try to navigate your lazy object ? This is usually the typical trouble with lazy objects I also encountered with when first using HIbernate. In case of pure EJB (JPA), you can get the same behavior when returning lazy object as a result of EJB bean method.
January 7, 2008 at 10:09 am |
Yeah, I’m in a transaction – it’s one EJB using another one. I’m using reflection to fetch properties of an entity and comparing them using equals() and, for whatever reason, equals() returned false when I compared an object to itself! Weird!
During debugging, I saw that the object was a lazy proxy, and that it was not loaded, so I changed FetchType.LAZY to FetchType.EAGER and suddenly it worked!
I made sure my equals() method wasn’t accessing members directly – it was using getter methods. So, I have no idea why this was not working this way.
Some kind of issue with accessing members with reflection? Or something else?
I guess I just don’t feel like I have time to debug these weird hibernate behaviors when I can just not use lazy fields.
After making this post, though, I did switch some of my inverse relationships back to LAZY because they were causing all kinds of extra things to be fetched that I didn’t need… hopefully I won’t get burned by that too soon.
June 4, 2009 at 1:29 am |
There are 2 possible solutions.
Choose for the opensessioninview-pattern.
Manually initialize collections in dao-calls, where you need them: Hibernate.initialize(…)
Eager fetching by default is the root of all evil.