Java Hair

You might have noticed a distinct lack of posting from me on this blog lately and I’ll tell you, it hasn’t been just your imagination.  It’s actually been over six months since the last post here.  Not acceptable, I know, and I apologize.  Things have gotten really busy around here and I was participating in quite a few projects as well as managing various aspects of the business and the lack of time for delving into some of the more interesting technical topics led to a lack of posts.

Hopefully, this year that will change.  The truth is, I started a few posts last year and just never got around to finishing them before I had to move on to the next thing.  So, at least the first technical post here will be finishing up on of those.  The work here always leads to new and interesting programming, so I’m sure that there won’t be a lack of ideas, and this year I’ll schedule in some time each week to work on those posts.

I hope 2009 was a good year for you all, let’s all have an even better 2010!

Over the last couple of years there has been a lot of talk about Ruby on Rails and Grails and how easy it is to use them to quickly build an application.  How would you like to be able to have all of that speed of development, but have it in a technology that you already know?  If you are familiar with Struts or JSF, you can use Rev to quickly build an application for you.

Rev is a code generation tool developed by Vgo Software, and it gives you the power to do that.  All you need is a database, a JDBC driver (most of the common ones are provided with Rev out of the box), a JDK of version 1.5 or better and Rev.  Using Rev you’ll be able to generate a completely functional CRUD application based on the tables that you select.  The output can be in a variety of different flavors: JSF, Struts, JSF with AJAX, JDBC, EJB, Hibernate, etc.  Rev also generates ANT build scripts for a variety of popular application servers so you can build and deploy your application directly from the tool.

What good is a CRUD application?  It all depends on what type of application you are building.  For adding testing data or building some Administration screens for a system, the Rev output may be all you need.  If you are building a more complicated system, then maybe the persistence layer is all you need and you can rework most of the UI layer.  All of the source code is available for you to modify as you see fit, so whether it is the final application itself or the basis for something bigger you will always have something to start with.

One of the unique features of Rev is the ability to customize the generation.  Not only can you easily customize the stylesheet from within Rev, but if you want to go deeper you can customize the templates that Rev uses to generate virtually whatever you’d like.  From modifying the JSP pages that get generated to creating a whole new set of templates for a completely different language, you can do it all!  In fact, included with Rev is a set of templates for generating a PHP-based application.

You can download your free trial of Rev at the Vgo Software site.  Also, be sure to sign up for the webinar I will be presenting on June 30th at 11:00 a.m. EST.  During that webinar I will demonstrate how to use Rev and talk about the various output options.

This is a new feature here on Java Hair, a book review. I was recently approached by the publisher of this book who asked if I would be interested in doing a review. The request was quite timely, I thought, since I have recently been working with XML Schema design (check out the XML category).

edfa

“Processing XML documents with Oracle JDeveloper 11g” seems more like the title to a whitepaper than a full-fledged book, but I found that the book actually covers a lot of topics that fall under the XML Processing umbrella.  That, and the fact that JDeveloper documentation can be difficult to come by makes this book a pretty handy addition to your library if you develop with JDeveloper 11g and you are working with XML.

Starting out, the book covers the parsing of XML documents using both the SAX API and the DOM API.  Information that you could get elsewhere, but as the book is JDeveloper 11g specific, it also includes information on how to set up your projects and which libraries you need to include that may or may not be included with your JDeveloper distribution.  Very handy information for someone using JDeveloper.

There is a chapter on using JDeveloper to design an XML Schema, something I could have used a few months ago, actually.  JDeveloper’s visual design feature for XML Schema’s is a great tool and comparable to anything I’ve used with Eclipse and NetBeans.  Following that is a chapter on validating your schema 3 different ways and how to create these projects in JDeveloper.

There are some chapters that I didn’t expect to see in this book, but were quite welcome.  A chapter devoted to transforming XML to PDF, another on transforming XML to MS Excel, storing XML in Oracle Berkeley DB XML and even a chapter on Oracle XML Publisher.

So all in all, despite the self-imposed limitation of XML and JDeveloper, the author, Deepak Vohra, has managed to cram in some very useful topics into his book.  Though some of it isn’t really JDeveloper specific, he does makes it relevant by walking thru setting up each project in JDeveloper as well as building and running the subsequent applications in JDeveloper.

The writing style is very dry, much like you’d probably expect from a reference book, and it should be treated as such, it isn’t something that you are going to want to sit down and read in one sitting.  However, if you have work to do in XML and you are considering using or already using JDeveloper as your IDE, I would definitely recommend picking it up.

You can find the book on virtually any online bookstore or on the publisher’s website: Packt Publishing.

Animals In The Dark

If you haven’t heard William Elliott Whitmore before, you really ought to give his new album, Animals in the Dark, a listen to.  He’s an old soul in a not-so-old body with a voice that makes him sound decades older than he is.  He’s been compared to Tom Waits many a time.  His style has been described as Folk, Country, Alt-Country, Punk, and Soul.  He definitely sings with a lot of soul, has a punk attitude, and musically sounds a lot like folk, playing a lone acoustic guitar or banjo.

I just started listening to him recently, but he has been around for a while.  I haven’t had the chance to see him live yet, but hopefully sometime after he gets back from his tour in Europe I’ll be able to catch him somewhere.

Animals in the Dark is a politically charged album which is pretty self evident on tracks like “Mutiny”, “Old Devils” and “Johnny Law”.  If that isn’t your thing, don’t let that deter you, there really is some great music on this album.  If you like this one, be sure to check out “Songs of the Blackbird”, I’m not sure if I like it more than “Animals”, but it certainly has grown on me since I snagged it from the iTunes store.  That purchase, btw, marks my first purchase of music from the iTunes store, now that it isn’t DRM’d and I can use play it anywhere, I no longer have a good reason to not buy my music there.  I still am a little annoyed by the lack of mp3 support, but being able to purchase and download directly on my iPhone really seems to make up for that.

As Whitmore syas, “I don’t want to be set, I just want to be free.”

More about William Elliott Whitmore:

The Official Site

MySpace

This is Part 3 of a 3 part series on XML Schema Design.  Check out Part 1 or Part 2.

I recently helped complete a project for a large enterprise and this series was inspired by that work and some of the questions that were raised during that process. This last part of the series covers some ways to make your schema design more flexible.

Reasons to make it more flexible were covered in Part 1, but the basic idea is adopted from evolution. If your solution is extendable and adaptable, it will encourage more people in your organization to use it., ensuring its survival. Ideally different applications within the enterprise will be able to make use of the schema without requiring an updated release of the XSD to adapt to the application’s specific needs.

Extendability

In order to achieve expandability within a single version of the schema it becomes necessary to have the types and elements within the schema allow the addition of different elements and even different attributes. This would allow a user of the schema to add their own elements to the schema without violating the schema definition and would therefore promote the schema’s use within the organization.

To provide extensibility to the schema, named complex types could have the following elements added to their definition:

<xsd:any namespace="##targetNamespace" processContents="strict" minOccurs="0" maxOccurs="unbounded" />
<xsd:any namespace="##other" processContents="lax" minOccurs="0" maxOccurs="unbounded" />

These element definitions will render the schema invalid if there are options elements appearing before their declaration. To prevent this from being an error, add a new element to encompass those generic elements. Your final definition would look like:

   <xsd:complexType name="ExtraData">
       <xsd:sequence>

           <xsd:any namespace="##targetNamespace" processContents="strict" minOccurs="0" maxOccurs="unbounded" />
           <xsd:any namespace="##other" processContents="lax" minOccurs="0" maxOccurs="unbounded" />
       </xsd:sequence>
   </xsd:complexType>

The addition of these two element definitions allow for any other elements of the target namespace to be added to the type as well as any other elements from any other namespace to be added to the type. Finally to allow for any other attributes to be added the following attribute definition could be added to named complex types:

<xsd:anyAttribute namespace="##any" processContents="skip" />

A Better Approach?

This method of expandibility works but does so by allowing for almost any XML constructs to be added to XML files in that ExtraData element. This may not always be what you want. Instead, by being careful to abstract out just enough to make the schema flexible, you may be able to achieve the same thing.

For instance, consider an XML Schema that contains many different discreet data points. Let take a simple user profile type definition for instance:

   <xsd:complexType name="UserProfileType">
       <xsd:sequence>
           <xsd:element name="FirstName" type="xsd:string"></xsd:element>
           <xsd:element name="LastName" type="xsd:string"></xsd:element>
           <xsd:element name="AccountCreated" type="xsd:dateTime"></xsd:element>
       </xsd:sequence>
       <xsd:attribute name="userId" type="xsd:string"/>
   </xsd:complexType>

An example of an instance of an XML document that is validates against this schema definition might be:

  <Profile userid="rjava">
     <FirstName>Rob</FirstName>
     <LastName>Java</LastName>
     <AccountCreated>2009-05-26T09:00:00</AccountCreated>
  </Profile>

This might work fine for a while, but what happens when you want to keep track of the last time the user accessed the site? You would have to change the schema definition. The solution discussed above would work, but what if we create a generic data type:

   <xsd:complexType name="DataType">
       <xsd:sequence>
           <xsd:element name="Description" type="xsd:string" minOccurs="0"/>
           <xsd:element name="StringValue" type="xsd:string" minOccurs="0"/>
           <xsd:element name="DateValue" type="xsd:dateTime" minOccurs="0"/>
       </xsd:sequence>
       <xsd:attribute name="name" type="xsd:string" />
   </xsd:complexType>

We could use this generic data type inside our UserProfileType:

   <xsd:complexType name="UserProfileType">
       <xsd:sequence>
           <xsd:element name="Data" type="tns:DataType" minOccurs="0" maxOccurs="unbounded"></xsd:element>
       </xsd:sequence>
       <xsd:attribute name="userId" type="xsd:string"/>
   </xsd:complexType>

We could now represent the same data using an XML document like this:

  <Profile userid="rjava">
     <Data name="FirstName">
        <StringValue>Rob</StringValue>
     </Data>
     <Data name="LastName">
        <StringValue>Java</StringValue>
     </Data>
     <Data name="AccountCreated">
        <DateValue>2009-05-26T09:00:00</DateValue>
     </Data>
     <Data name="Email">
        <StringValue>rob@java-hair.com</StringValue>
     </Data>
  </Profile>

So now we have made the UserProfileType very fluid, maybe too fluid depending on what you want to accomplish.  It is exapandable simply by adding whatever instances of Data into the UserProfileType element in your XML Document, but it doesn’t require any fields or even suggest any.  A better use may be to combine the first two examples.  That way you could enforce the required fields and make optional some of the more common fields, but still leave room for other elements that new applications may require.

Conclusion

It is very important that the Canonical XML Schema be as easy as possible to understand while still maintaining re usability and flexibility.  A Canonical XML Schema is only going to be as good as it’s user-base is large.  There isn’t much point in investing in one if the organization as a whole is not going to adopt it.

Hopefully this series of articles has given you some ideas on how to design an XML Schema that your organization can make use of.  Getting the business as a whole to adopt something like this isn’t going to be easy, especially if you don’t have an immediate need for one.  My suggestion would be to start small, start with new applications that requires an XML Schema.  Prove the value in a proper enterprise-wide design by showing how the time and effort for enhancements and changes can be reduced and you will go a long way it getting it adopted.

Now that we’ve gotten the whats and whys out of the way, we can start to talk about the guidelines themselves.

Naming Conventions
Naming conventions should be used in order to provide the understandability required in any good schema.

Names for all elements, attributes and types should be explicit.  Abbreviations should only be used where such abbreviations are obvious to anyone familiar with the domain. Any XML Types should be suffixed by the word Type. Elements should not include any suffix.

UpperCamelCase should be used in naming XML Elements and Types. This means that the first letter of each word that makes up the name will be capitalized included the first letter of the name. For example: CompanyName, AddressType, FirstName could all be valid names within the schema.

XML Attributes should be named using LowerCamelCase in which the first letter of the name is in lowercase and each additional word within the name will start with an uppercase letter.

The truth is, you can use any naming convention you want as long as it is consistent.  Consistency is the foundation of any good design and XML Schemas are no exception.

Elements Versus Attributes

Since the XML Specification allows for the same types of information to be stored as values for attributes or values for elements, a long standing debate is whether one should prefer attributes over elements for content and vice-versa. For a Canonical XML Design that requires flexibility and the ability to expand in the future, it is recommended that elements be created for most content and that attributes are only used to provide descriptors for those elements when necessary.

Another best practice to follow is to use an element to represent data that can stand on its own, independent of any parent element and use attributes to represent properties or meta-data of that element. For example. a Contact element may have a type attributed to it that tells the user what kind of contact information is provided, i.e. e-mail address or phone number, etc.

As you begin the process of abstracting elements to allow for expandability, you may find that it may make sense to store use elements in cases where you had used attributes before.  That is okay.  More on that when we discuss abstracting the schema.

Types Versus Elements

Another decision that needs to be made in designing an XML Schema is when to use types and when to use elements. In the case of a Canonical XML Schema, XML Types should be used extensively to make the schema easier to understand and easier to re-use. In cases where a generic XML Type could be used, the need to create a type is obvious. However, in cases where the element or type will most likely not be reused, it is not normally necessary to create a type. Having an explicit type definition will allow potential users of the schema to more easily interpret the design. So as a general rule, do not use anonymous complex types.

Data Types

User-derived types are composites (Complex) or subsets (Simple) of existing types. The extensions are used to consistently constrain the schema so that its use becomes easier. For example, a CurrencyAmount type can be created so that whenever a currency amount is needed in the schema, the generic type can be used. This way if the definition of the type changes, it can be changed in one place.  It also means that the developer of extensions to the schema does not need to think about how currency amounts will be constrained because it has already been done.

Use of Simple Types

Simple user-derived types are subsets of existing types. These types constrain the lexical or value space of the parent type. An example of a simple type is a type that limits the value of an element to a list of values. A use for this may be in limiting the Currency type values to standard iso currency types.

Use of Complex Types

Complex Types are user-derived types that allow various elements to be combined and represented as a whole. A Complex Type is also necessary if you wish to create a type that uses an attribute. To continue our example from above, the CurrencyAmount may be a Complex Type that includes both the type of currency (i.e., US Dollar or Euro) and the amount (i.e. 123,000) as elements within it.

In order to provide a grouping of elements an xml sequence is used. This sequence contains the elements included in the type and the order in which they are included. Elements within the list have two important attributes, minOccurs and maxOccurs which are used to indicate if the element is required and how many times it may appear in the sequence.

File Structure

When a large schema is being created, it is best to use references to include the various complex types of the schema in one definition. This allows the definition to be split up among multiple files and makes the reading of those definitions much easier. It also becomes easier to reuse portions of the schema because you can reference the subset of complex types or elements that you wish to include.

Stay Tuned for Part 3…

Part 3 will discuss some ideas on making the schema extendable via abstraction and walking the line between extendable and understandable.

If you haven’t already, check out Part 1 of the series.

As a Java developer who does a lot of work with Oracle products including Jdeveloper and ADF, my head is still spinning a little from the news that Oracle is buying Sun Microsystems.

Oracle buying BEA hurt a little, though it was completely expected and a great move on Oracle’s part, I was a little sad to see the application server competition field drop by one but I was very happy that Oracle was smart enough to choose Weblogic.  At that point it was really the only the decision they could make.

With Oracle buying Sun there is a lot of synergy, there are many technologies that are duplicated among both companies.  Oracle owning both should make those technologies better and enable them to compete with the leaders in those respective areas.  The big ones that stick out for me:

!. Oracle’s JDeveloper and Sun’s NetBeans

Could they really afford to drop NetBeans, probably not, but can they afford to drop JDeveloper, no, not really.  Here the only thing that really makes sense is to merge the two, probably adding in the ADF wizards and goodies like that into NetBeans.  At least, that is what I hope they do.  JDeveloper isn’t bad, but I only ever use it to develop ADF projects and I bet many, many people are in that same boat.  Combining the two could end up giving Eclipse a run for it’s money, hopefully the competition just spurs both to be better.

2. Oracle’s Oracle VM and Sun’s Virtual Box

I haven’t had much experience with Oracle VM, but I have lately become a huge fan of Sun’s Virtual Box.  It’s a great product and it lets me do everything I want for free.  Will this continue to be the case?  I don’t know.  I’m not an expert on virtualization in the enterprise, I use it for desktop VMs, but I hadn’t seen much about Virtual Box working in that space.  I would imagine Oracle VM is all about virtualizing the network and competing with VMWare on that level.  With the two together VMWare’s got some competition.

3.  Oracle’s Unbreakable Linux and Sun Solaris

Oracle had a great jumpstart to their linux platform basing it on the RedHat codebase way back when.  Solaris was my first exposure to any type of Unix (Solaris and AIX, actually) and it has been around forever.  If the adoption of Linux has hurt anything, it’s probably been Solaris and through that, sales of Sun’s hardware.  Oracle says that their owning of Solaris will enable them to tune the Oracle Database software to run even better on it, and since according to Oracle, most of their database customers are using Solaris, I think they’ll probably do that.  I have no idea what will have to Unbreakable Linux though.  Who has to look out with this one?  I’d say IBM.  Buying Sun probably would have been good for them in the products space, I think the only area IBM is going to be competing in future is going to be services.  RedHat has Ubuntu to worry about on the desktop side and now a bigger threat from Oracle and Sun on the server-side, they have their work cut out for them.

4.  Oracle Database and Sun’s MySQL

MySQL has a huge customer base, most of them probably non-paying.  I think with this one, Oracle just adds it to their ever increasing repetoire of niche databases.  It won’t go away, but I see less adoption in the future, maybe a boost for PostgreSQL if they can get their act together.

5. Sun’s Java and Oracle’s ADF

Oracle has always been a big player in the specifications for the Java language.  I’m sure someone else will go into all the details, because I honestly don’t know them off the top of my head, but I do know that many technologies and ideas that ADF is based on where either approved JSR’s or close to approved JSR’s.  Does Oracle’s acquisition of Sun and Java mean that they will be better equipted to push trhough whatever they want to add to the language?  Well, I don’t think it will be quite that easy, but I’m sure it makes it easier.

I’ve always been a Java guy at heart, I work with Oracle technology sometimes, and I think they have really come a long way, but Oracle owning Java does kind of scare me a little.  One thing Oracle does really well, and JDeveloper is great at this, is making complex technologies easy to use.  It is what Microsoft does really well.  .NET makes easy the things that Java makes hard.  ADF actually does a lot of the same.  The combination of ADF and Java together could pose a big threat to Microsoft’s .NET if Oracle does it right.

My first thought about Oracle owning Java is that many developers are going to jump up and down about it and complain.  Some will probably jump ship, maybe to .NET but probably to Ruby or PHP or something else.  I don’t think many coroporations are going to change the direction of their IT departments though, so for them, it will be .NET or Java as it always has.  In the end, I thnk most Java developers are going to remain Java developers and hopefully Oracle’s backing of Java will just end up making it a better language to work with.

Microsoft might have more to worry about with Oracle owning Open Office now also.  I hope that Oracle continues to invest in it, or it’ll end up being Microsoft Office vs. Google Apps and that’s about it.  I’m all for cutting edge, but Gmail hasn’t come out of Beta yet and I’d like to see Microsoft have some competiion in this area.

So I wanted to get my thoughts out there while they were floating around in my head and hopefully yours so I could hear your opinions on the topic.  Please let me know what you think about this acquistion and what you think it means to the future of technology and competition in the field.

I finally found the answer to one of life’s most difficult questions — why is it that everytime I redeploy a WAR file in Tomcat it fails?  The answer is that in Windows, Tomcat will hold a lock on certain files in the web application.  There is a simple fix to this dilemna, edit the context.xml file in your TOMCAT_HOME\conf directory.

Add 2 attributes to the Context element in the file, so that the element description looks like this:

<Context antiResourceLocking=”true” antiJARResource=”true”>

Problem solved.  You should be able to just copy a new version of the war file on top of the old one in the webapps directory of Tomcat and it will redeploy.

This works for me on Windows XP using apache-tomcat-6.0.18.

Introduction

This post and the posts that follow are to provide some of my guidelines and best practices for creating and utilizing an enterprise-wide XML Schema.  I will start off with some background in this post, then move on to the guidelines and best practices in future posts.  Jack Van Hoof has a great article about Canonical Data Models (CDMs) and what they are good for on his blog.  This enterprise-wide XML Schema is an implementation of a CDM and will hereafter be referred to as a Canonical XML Schema.

Background
The primary requirement of a Canonical XML Schema and the related data model is to provide a standard format for which all content will be distributed thereby requiring applications to adhere to this common format.  If a new application is added to the platform, only a transformation between the Canonical XML Schema will be needed to allow it to produce or consume the required content.

In addition, 5 criteria should be considered:

1. Completeness – The entirety of elements in the source schemas should be present in the new schema.
2. Minimalism – Each element should be defined only once.
3. Expandability - The schema should be able to anticipate data that may not have originally been found in any of the source schemas, that is, it should allow its use to grow and not hinder the use of it in the future.
4. Comprehension – The schema should be formulated in a way the allows for easy browsing and querying.
5. Performance - Understanding how the content in the XML documents supported by the schema will be used can help in determining some of the structure within the schema.  For instance, if one intended use of the produced XML is to provide rapid searching, then the schema should be structured to support fast searches.

Keep in mind that these criteria are often at odds with one another.  For example, designs that emphasize expandability do so at the risk of deemphasizing performance and comprehension.

Why Guidelines?

A current problem with the XML content that is currently being produced and consumed by various applications within many enterprises is a lack of standards and guidelines for the creation of such content.  A Canonical XML Schema will enforce adherence to a singular structure thereby enforcing adherence to the guidelines and best practices set forth by the schema itself.  In addition, the Canonical XML Schema must be built following guidelines and best practices.  The guidelines and best practices need to be documented to allow producers and consumers of XML content to understand why the model is designed the way it is and how to expand upon that design when it is necessary to do so.

Think about a group of systems that have grown over the years and are communicating with each other via XML (or even without XML). Once there are more than 2 systems talking to each other, it makes sense to develop as much of a generic communication pipeline as possible and a Canonical XML Schema will help you do that.

Communication without a Canonical XML Schema

You can see in the picture above, that in the enterprise described there are 9 translations of data being performed, one for each pairing of applications. As applications are added, the number of translations grows exponentially.

Communication using a Canonical XML Schema

In the second diagram, only 6 translations are being performed and the number of translations that need to be performed as new systems are put online grows in a linear fashion.  As new applications are added, only one translation of data needs to be performed, either from the new application to the Canonical XML Schema (if it’s a producer) or from the Canonical XML Schema to the new application (if it’s a consumer).

Next…

Part 2 will describe some of the best practices and guidelines and Part 3 will go into more depth around abstraction of elements and walking the thin line between expandable and understandable.

First, let me tell you why VirtualBox doesn’t rock, it’s that copying VMs really seems to be more work that it needs to be. VMWare is much easier this way.

However, VirtualBox does rock, and I’m sometimes more clueless than I think I am.

As it turns out, VirtualBox has a feature (and has had it for some time now, hence the clueless part!) wherein the guest OS can run seamlessly on the host OS. Basically this means that instead of having to open a separate desktop that has the guest OS in it, you can open applications directly onto the desktop of the host operating system. Check out the picture of my desktop at home, it is Windows Vista running a VirtualBox VM with Ubuntu 8.10 installed.

VirtualBox Seamless Integration (Vista and Ubuntu)

I don’t know why I feel so strongly about this, but this is one of those small things that really makes me happy to be alive in this day and age. It is just plain cool. It would be cooler if I could transfer files from the VM to the Host just by dragging and dropping, but for now I’ll settle for being able to cut and paste between the two (yes, you can do that!).

How do you accomplish this, you ask? It’s straightforward actually.

1. Download VirtualBox from Sun.
2. Install it.
3. Create a VM.
4. On the guest OS, install the VirtualBox tools.
5. Restart the guest OS.
6. Click on Machine->Seamless.
7. Enjoy.

In my few days of experimenting I found that with Windows Vista as the host and Ubuntu as the guest, it worked practically flawlessly. With Ubuntu as the host and Windows xP as the guest, it was a little slow moving into seamless mode and has more graphical hiccups. It could be the graphics card in this desktop though. Even with the hiccups, it is pretty sweet however.

So it is official, VirtualBox is right up there with Synergy as the two tools that really make me happy and, in fact, more productive in my day-to-day.