Win a copy of The Little Book of Impediments (e-book only) this week in the Agile and Other Processes forum!
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Welcome David Jordan and Craig Russell to our Book Promotion of the Week

 
Dirk Schreckmann
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David and Craig are co-authors of Java Data Objects, which is our book promotion for this week.
Let's give them a big Welcome!
 
David O'Meara
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Welcome guys, hope you enjoy your stay!
 
John Takacs, D.P.M.
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Greetings and welcome!
This is my first book promotion, so, to the editor/webmaster, what are the rules? How does one go about asking questions?
[ June 17, 2003: Message edited by: John Takacs, D.P.M. ]
 
tormod eriksen
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I also wanna throw in a welcome!
 
Dirk Schreckmann
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This is my first book promotion, so, to the editor/webmaster, what are the rules? How does one go about asking questions?
Take a look at http://www.javaranch.com/bookpromo.jsp for the complete list of rules.
To ask a question, it may well make sense to start a new thread and just ask.
 
Amy Phillips
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Howdy guys and thanks for helping us out
 
David Jordan
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Hi,
This is my first time at the Java Ranch too.
If you would like to get a feel for the writing in the book and also for what it is like to develop with JDO, Chapter 1 is posted online:
Chapter 1 PDF
If you have been using JDBC or EJB CMP (which is probably most of you), you should check out what JDO can do for you. It lets you persist plain, ordinary Java object models without imposing any design constraints on you. You don't need to import anything from JDO and it can probably directly persist classes you already have written.
You strictly use Java syntax to navigate your objects and the JDO runtime brings objects into memory from the database on demand. You can also issue queries using your Java object model and Java operators and expressions. It is a very Java-centric API. You don't need to know SQL or go off to 2-3 of EJB training. Just a warning: once you have tried it out, you usually get hooked on it. People really like it once they have experienced it for the first time.
 
SJ Adnams
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Hi David,
JDO appears to be targeted as those people who are reacting against EJBs, be it because an EJB implementation is seen as overkill, or simply because of the learning curve.
If this is the case do you think that coders will adopt an 'Arts & Crafts' reaction? i.e. handcrafting DAO's rather than adopting (another) xml based persistence layer?
Simon
 
Steve Morrow
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Looking forward to reviewing your new book!
Welcome, and best wishes!
 
Roger Goerke
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This JDO seems a little too good to be true. There must be some price to pay for all the flexibility listed in the requirements.
Is JDO a performance killer? How does JDO get access to the private persistable attributes and how does JDO know that an object is dirty?
Any background info provided will be helpful for me to understand why I might consider using them over EJB.
 
Dirk Schreckmann
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Roger,
I started a new thread to continue the questions you posed.
This is just a howdy-do thread.
 
Dirk Schreckmann
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Simon,
I started a new thread to continue the question you posed.
This is just a howdy thread.
 
David Jordan
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JDO uses class enhancement to achieve its level of transparency. A class enhancer alters your byte code so that it intermediates field reads and updates. The byte code for a getfield is replaced by a call to a static method generated by the enhancer so it is able to ensure the field has been initialized from the datastore. When you modify a field, the JDO implementation knows that a particular field in an instance has been modified.
 
Mike Farnham
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Welcome David & Craig.
It will be good to see how it all fits together.
I know Turbine's persistence service used an object metaphor for accessing data. It was definitely very different writing SQL Queries in ObjectSpeak after having written so many SQL query commands.
Kinda like going from CommandLine interface to a GUI.
Where it always seems a little quicker sometimes to just type a command instead of dragging and dropping things here and there.
Cheers,
Mike
 
David Jordan
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In the JDO Query Language, you apply boolean filters to extents and collections. These boolean
filters are provided via a string. The filter uses the data model of the persistent Java classes. The expressions and operators are largely taken directly from Java. So the queries are very Java-centric. You can also navigate the references and collections in your object model in the queries. A JDO relational implementation will convert these queries to the datastore-specific query syntax, be it SQL or some other query language. So the queries are vendor-neutral,
which is not the case with JDBC where you have to deal with differences among the databases.
 
Mike Farnham
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Welcome David & Craig.
It will be good to see how it all fits together.
I know Turbine's persistence service used an object metaphor for accessing data. It was definitely very different writing SQL Queries in ObjectSpeak after having written so many SQL query commands.
Kinda like going from CommandLine interface to a GUI.
Where it always seems a little quicker sometimes to just type a command instead of dragging and dropping things here and there.
Cheers,
Mike
 
william nixon
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I am having problems getting front page 2000 and jdbo to work together. I am new at this and need any and all help possible.
 
Dirk Schreckmann
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Welcome to JavaRanch, william!
I'm not sure what you mean by "problems getting front page 2000 and jdbo to work together." If you've a question, let me suggest you start a new thread and just ask.
 
John Takacs, D.P.M.
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Dirk,
Isn't it better to keep all JDO book related questions in one thread? Or at least require that the subject mention "JDO book promotion"?
If I were an author looking to respond to questions, it would be better to not have to sift through scores of other posts just looking for the poor soul who wanted to ask a question related to my book and the javaranch book promotion.
Food for thought. Perhaps the current way is best.
 
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