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• Spotlight on mkyong

  - by MarkH

  Occasionally, I'd like to share a blog I've discovered or that someone has passed along to me. Criteria are few, but in a nutshell, it must be: Java-related. (Doh!) Interesting. A good blog is exciting to read at some level, whether due to perspective, eye-catching writing, or technical insight. It doesn't have to read like a Stephen King novel, but it should grab you somehow. Technically deep or technically broad. A site that dives deeply, quickly is a great reference for particular topics/tasks. On the other hand, one that covers a lot of ground at a high-but-still-technical level can be a handy site to visit occasionally as well. Both are what I consider "bookmarkable", but for different reasons. Drumroll, please... With that in mind, this Blog Spotlight is cast upon mkyong.com, a site I stumbled across that offers a little bit of everything for various Java dev audiences. The title indicates the site is for "Java web development tutorials", and indeed it does have these: JSF, Spring, Struts, Hibernate, JAX-WS, JAX-RS, and numerous other topics are addressed to varying degrees. The site isn't devoted exclusively to server-side tutorials, though. Recent posts include mobile development topics, and the links at the bottom of the page connect you to reference pages and other useful sites. I've poked around through a couple of the tutorials and, while they won't take you from "zero to hero", they do seem to provide a nice overview of the subject at hand. They also offer an occasional explanatory comment that is missing from far too many texts, sites, and doc pages. It's not a perfect site, but I like it. The Bottom Line mkyong.com offers a nice "summary site" of server-side tutorials, mobile dev posts, and reference links. Check it out! All the best,Mark 

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• NetBeans, JSF, and MySQL Primary Keys using AUTO_INCREMENT

  - by MarkH

  I recently had the opportunity to spin up a small web application using JSF and MySQL. Having developed JSF apps with Oracle Database back-ends before and possessing some small familiarity with MySQL (sans JSF), I thought this would be a cakewalk. Things did go pretty smoothly...but there was one little "gotcha" that took more time than the few seconds it really warranted. The Problem Every DBMS has its own way of automatically generating primary keys, and each has its pros and cons. For the Oracle Database, you use a sequence and point your Java classes to it using annotations that look something like this: @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="POC_ID_SEQ") @SequenceGenerator(name="POC_ID_SEQ", sequenceName="POC_ID_SEQ", allocationSize=1) Between creating the actual sequence in the database and making sure you have your annotations right (watch those typos!), it seems a bit cumbersome. But it typically "just works", without fuss. Enter MySQL. Designating an integer-based field as PRIMARY KEY and using the keyword AUTO_INCREMENT makes the same task seem much simpler. And it is, mostly. But while NetBeans cranks out a superb "first cut" for a basic JSF CRUD app, there are a couple of small things you'll need to bring to the mix in order to be able to actually (C)reate records. The (RUD) performs fine out of the gate. The Solution Omitting all design considerations and activity (!), here is the basic sequence of events I followed to create, then resolve, the JSF/MySQL "Primary Key Perfect Storm": Fire up NetBeans. Create JSF project. Create Entity Classes from Database. Create JSF Pages from Entity Classes. Test run. Try to create record and hit error. It's a simple fix, but one that was fun to find in its completeness. :-) Even though you've told it what to do for a primary key, a MySQL table requires a gentle nudge to actually generate that new key value. Two things are needed to make the magic happen. First, you need to ensure the following annotation is in place in your Java entity classes: @GeneratedValue(strategy = GenerationType.IDENTITY) All well and good, but the real key is this: in your controller class(es), you'll have a create() function that looks something like this, minus the comment line and the setId() call in bold red type:     public String create() {         try {             // Assign 0 to ID for MySQL to properly auto_increment the primary key.             current.setId(0);             getFacade().create(current);             JsfUtil.addSuccessMessage(ResourceBundle.getBundle("/Bundle").getString("CategoryCreated"));             return prepareCreate();         } catch (Exception e) {             JsfUtil.addErrorMessage(e, ResourceBundle.getBundle("/Bundle").getString("PersistenceErrorOccured"));             return null;         }     } Setting the current object's primary key attribute to zero (0) prior to saving it tells MySQL to get the next available value and assign it to that record's key field. Short and simple…but not inherently obvious if you've never used that particular combination of NetBeans/JSF/MySQL before. Hope this helps! All the best, Mark

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• How to Plug a Small Hole in NetBeans JSF (Join Table) Code Generation

  - by MarkH

  I was asked recently to provide an assist with designing and building a small-but-vital application that had at its heart some basic CRUD (Create, Read, Update, & Delete) functionality, built upon an Oracle database, to be accessible from various locations. Working from the stated requirements, I fleshed out the basic application and database designs and, once validated, set out to complete the first iteration for review. Using SQL Developer, I created the requisite tables, indices, and sequences for our first run. One of the tables was a many-to-many join table with three fields: one a primary key for that table, the other two being primary keys for the other tables, represented as foreign keys in the join table. Here is a simplified example of the trio of tables: Once the database was in decent shape, I fired up NetBeans to let it have first shot at the code. NetBeans does a great job of generating a mountain of essential code, saving developers what must be millions of hours of effort each year by building a basic foundation with a few clicks and keystrokes. Lest you think it (or any tool) can do everything for you, however, occasionally something tosses a paper clip into the delicate machinery and makes you open things up to fix them. Join tables apparently qualify.  :-) In the case above, the entity class generated for the join table (New Entity Classes from Database) included an embedded object consisting solely of the two foreign key fields as attributes, in addition to an object referencing each one of the "component" tables. The Create page generated (New JSF Pages from Entity Classes) worked well to a point, but when trying to save, we were greeted with an error: Transaction aborted. Hmm. A quick debugger session later and I'd identified the issue: when trying to persist the new join-table object, the embedded "foreign-keys-only" object still had null values for its two (required value) attributes...even though the embedded table objects had populated key attributes. Here's the simple fix: In the join-table controller class, find the public String create() method. It will look something like this:     public String create() {        try {            getFacade().create(current);            JsfUtil.addSuccessMessage(ResourceBundle.getBundle("/Bundle").getString("JoinEntityCreated"));            return prepareCreate();        } catch (Exception e) {            JsfUtil.addErrorMessage(e, ResourceBundle.getBundle("/Bundle").getString("PersistenceErrorOccured"));            return null;        }    } To restore balance to the force, modify the create() method as follows (changes in red):     public String create() {         try {            // Add the next two lines to resolve:            current.getJoinEntityPK().setTbl1id(current.getTbl1().getId().toBigInteger());            current.getJoinEntityPK().setTbl2id(current.getTbl2().getId().toBigInteger());            getFacade().create(current);            JsfUtil.addSuccessMessage(ResourceBundle.getBundle("/Bundle").getString("JoinEntityCreated"));            return prepareCreate();        } catch (Exception e) {            JsfUtil.addErrorMessage(e, ResourceBundle.getBundle("/Bundle").getString("PersistenceErrorOccured"));            return null;        }    } I'll be refactoring this code shortly, but for now, it works. Iteration one is complete and being reviewed, and we've met the milestone. Here's to happy endings (and customers)! All the best,Mark

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• Extreme Portability: OpenJDK 7 and GlassFish 3.1.1 on Power Mac G5!

  - by MarkH

  Occasionally you hear someone grumble about platform support for some portion or combination of the Java product "stack". As you're about to see, this really is not as much of a problem as you might think. Our friend John Yeary was able to pull off a pretty slick feat with his vintage Power Mac G5. In his words: Using a build script sent to me by Kurt Miller, build recommendations from Kelly O'Hair, and the great work of the BSD Port team... I created a new build of OpenJDK 7 for my PPC based system using the Zero VM. The results are fantastic. I can run GlassFish 3.1.1 along with all my enterprise applications. I recently had the opportunity to pick up an old G5 for little money and passed on it. What would I do with it? At the time, I didn't think it would be more than a space-consuming novelty. Turns out...I could have had some fun and a useful piece of hardware at the same time. Maybe it's time to go bargain-hunting again. For more information about repurposing classic Apple hardware and learning a few JDK-related tricks in the process, visit John's site for the full article, available here. All the best,Mark

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• Quick Fix for GlassFish/MySQL NoPasswordCredential Found

  - by MarkH

  Just the other day, I stood up a GlassFish 3.1.2 server in preparation for a new web app we've developed. Since we're using MySQL as the back-end database, I configured it for MySQL (driver) and created the requisite JDBC resource and supporting connection pool. Pinging the finished pool returned a success, and all was well. Until we fired up the app, that is -- in this case, after a weekend. Funny how things seem to break when you leave them alone for a couple of days. :-) Strangely, the error indicated "No PasswordCredential found". Time to re-check that pool. All the usual properties and values were there (URL, driverClass, serverName, databaseName, portNumber, user, password) and were populated correctly. Yes, the password field, too. And it had pinged successfully. So why the problem? A bit of searching online produced enough relevant material to offer promise. I didn't take notes as I was investigating the cause (note to self), but here were the general steps I took to resolve the issue: First, per some guidance I had found, I tried resetting the password value to nothing (using () for a value). Of course, this didn't fix anything; the database account requires a password. And when I tried to put the value back, GlassFish politely refused. Hmm. I'd seen that some folks created a new pool to replace the "broken" one, and while that did work for them, it seemed to simply side-step the issue. So I deleted the password property - which GlassFish allowed me to do - and restarted the domain. Once I was back in, I re-added the password property and its value, saved it, and pinged...success! But now to the app for the litmus test. The web app worked, and everything and everyone was now happy. Not bad for a Monday.  :-D Hope this helps, Mark

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• All sites give Error 500 under Sharepoint Foundation (SP2010)

  - by MarkH

  I've just installed Sharepoint Foundatuion on my W2008 64bit server and got it up and running as far as being able to access the Central Admin etc just fine. I did have to disable 32 bit apps in the application pools for all the SP sites and also, following a tip on here, add a config option for bitness64 as a prerequisite for the services. However whenever I try to access the "Sharepoint - 80" site itself (or another site collection I created in the admin tool), I am getting an unhelpful 500 error. The log doesn't add anything - I can't find anything to give me a clue as to what it's complaining about. The server is a hosted VPS and all services like SQL are running locally (and are OK). Any ideas where I look next? M

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