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CRUD on XML using Java

I am developing a java application and i am using XML to store the settings and other data in the application.I have read about Java preferences manager API but i felt storing in XML is more convenient in my application.I started usng JAXB first but then i dint find any tutorials to modify the XML once it is created.My application involves storing the Email account details of the users.As the user adds his accounts dynamically , i need to add them to XML as well.So i dint find JAXB convenient(or rather i dint find any tutorials to update or modify the XML ).The only other option i found was DOM parser here http://docs.oracle.com/javase/tutorial/jaxp/dom/readingXML.html .But i feel it is too complicated for such a simple application.speed , memory etc doesnt matter to me.Are there any other alternatives to do this?

This can be a good (java-oriented) solution. Besides being Berkeley DB enables the development of custom data management solutions, without the overhead traditionally associated with such custom projects. yet based on XML files. It's has a very complete documentation for integration with Java lang.

With JAXB you can:
Unmarshal the XML into Java objects.
Manipulate the Java objects to modify the XML.
Marshal the objects producing a new XML document which you can use to replace the original XML.
Or:
Parse the XML into a DOM
Unmarshal the XML using a JAXB Binder
Modify the object
Use the Binder to apply the changes back to the DOM.
Write out the DOM replacing the original XML

I like to point you to XMLBeam (Disclosure: I'm affiliated with that project). This library is ideal to store configuration values in XML and while the application grows maintain the XML format without changing your Java API.
This is how IO operations look like:
Projection projection = projector.io().file(file).read(Projection.class);
projector.io().file(file).write(projection);
You get one liner IO handling and static typed access to the XML content. A pattern for configuration data would be to include a default value template in your JAR, read this if no config file was found on disk and write it back to disk on config changes. But of course you can also create documents from scratch (described in tutorials).

Java library to assist in XSD creation?

Is anyone aware of a library that makes the process of creating XSDs in Java a little easier than using something like a DocumentBuilder? Something like a helper or utility class. I came across the org.eclipse.xsd maven jar but I'm having ClassNotFoundException issues when working with it in Eclipse and I'm not entirely sure it's meant to be used as a standalone kind of thing. This is a bit difficult to Google for as well since there are lot of search results around automatic generation/translation from Java to XSD and vice versa.
Essentially what I need to do is to programmatically create an XSD from a certain source of data -- not Java classes.

Apache XMLSchema is a lightweight Java object model that can be used to manipulate and generate XML schema representations. You can use it to read XML Schema (xsd) files into memory and analyze or modify them, or to create entirely new schemas from scratch.
The fact that with this API one can create an XSD from scratch, it sounds as a starting point to achieve the ask; as to the fitness, it depends on what that "certain source of data" is.

Felxibility of data import/export feature using XML-binding

I am going to develop a database import/export feature in a Java EE application.
I plan to use XML-binding solution to convert between Java object and XML file which is import/export file.
Import feature: unmarshal the XML file to Java object in memory representation, then use JDBC to update the database.
Export feature: inverse the import process. retrieve the database to Java object and marshal the object to XML.
I think it can work fine, but it's not flexible enough. Because the XSD of XML is pre-defined, it's impossible to change XML schema and Java object definition at runtime. Say it's dynamic binding. Even I want the feature supports other file formats (You could forget it, if the format is too far at this stage).
What is your advice about the feature? Thanks!

I don't know whether this is correct answer, but if in any case it is helpful:
I have used Spring, Hibernate, JAXB where you can annotate your database entity class and its element with jaxb annotation and you are not required to write any xml schema files. In spring you can use jaxb Marshaller.
I think it should be possible in pure jaxb also, so u can look into jaxb annotation.

I think it can work fine, but it's not
flexible enough. Because the XSD of
XML is pre-defined, it's impossible to
change XML schema and Java object
definition at runtime
If you think it isn't flexible enough, go with a data interchange format which relieves you from all these fixed schema definitions (I know even JSON has a schema specification but you get the point). Is using JSON acceptable?
I would go as far to argue that if "importing to database" and "exporting from database" is the only requirement, you need not even create Java objects for this. Simply pass in a JSON string which contains the schema which would then be processed by a JSON processor which interfaces directly with your DAO layer. Similarly with the data read from the database. The downside is that "date" support in JSON is spotty at best.
Come to think of it, it need not be JSON. You can take a look at other data serialization formats like Apache Avro. But then again, if XML is your requirement which can't be changed, you can get around the "flexibility limitation" by not using a schema at all.
After all, XML is like violence. If it doesn't solve your problem, you're not using enough of it. :-)

What is best practice in converting XML to Java object?

I need to convert XML data to Java objects. What would be best practice to convert this XML data to object?
Idea is to fetch data via a web service (it doesn't use WSDL, just HTTP GET queries, so I cannot use any framework) and answers are in XML. What would be best practice to handle this situation?

JAXB is a standard API for doing this: http://java.sun.com/developer/technicalArticles/WebServices/jaxb/

Have a look at XStream. It might not be the quickest, but it is one of the most user friendly and straightforward converters in Java, especially if your model is not complex.

For a JMS project we were marshalling and unmarshalling (going from java to xml and xml to java) XML embedded in TextMessages (string property). We tried JAXB, Jibx, and XMLBeans. We found that XMLBeans worked best for us. Fast, easily configurable, good documentation, and easy Maven integration.

I have used and will continue to use JDOM -> www.jdom.org

Another option is a Sax Parser. It is procedural - i.e. a visitor pattern - but if the xml is fairly lightweight, (and even medium weight) I have found it to be very useful for this.

JAXB API which comes in Java(In built).

I have used JIBX in MQ module. It works very well. Ant config is simple. Used Xsd2Jibx converter to generate the binding files and Java beans from XML schema. Marshalling and un-marshalling allow to specify character-set parameter. It was useful in my project to handle custom character-set. But I found an issue in the binding compiler. If the Java bean has lengthier path name, it generates class file with lengthier file name which will cause issue in Windows XP(it has a maximum file length limit).
I haven't used other APIs. So I am not trying to compare with others. If you decided to use JIBX, I hope this will be helpful.
More details, please refer JIBX website

I've used XStream as well, it is easy to use and customizable. You can add your own custom converters and that was very handy for me...

So surprised more people have not mentioned Jibx. Amazing lib and i think a lot simpler to use than Jaxb. Performance is also fab!

For this you can also consider apache's bitwixt and simple framework for xml

Generating Java classes from XML file

How can I get java classes from an xml file?
In this situation, I don't have an XML schema and this way I can't use JAXB, Castor or other xml binding API as far as I know.

You can generate schema from XML file using certain tools. Then, use Apache XMLBEANS to create your classes.

XStream is great for XML -> objects and vice versa. Fast, lightweight, and works well without any schema.

Altova is also the best to generate java Classes from XML/XSD