I have been assigned to create a XSD schema for a proposed XML. i know what tables will be involved and what will be required fields which we always going to expect in the XML as well as optional.
I am very new to XSD and don't know where to and how to start.Can any one suggest me how to proceed so that i can start exploring something as currently i am on ground zero with the requirement.
Thanks in advance
Umesh
Best place to start off when you are at ground zero is w3schools -
http://www.w3schools.com/schema/schema_example.asp
Check this tutorial for beginners, looks good to me -
http://www.codeguru.com/java/article.php/c13529
The simplest way to start would be download a good XML editor, like XMLSpy and create schema visually. Altova has a free 30-day evaluation for their product, that should be enough for you to crank a first draft of your schema.
Depending on what you application is going to do, you might be able to generate one. For example you mention that your data is coming from (database) tables. If you intend to interact with the database using JPA entities, then you could use JAXB to generate an XML schema from the entity classes:
http://wiki.eclipse.org/EclipseLink/Examples/MOXy/JAXB/GenerateSchema
If you are using other tools to interact with the database, they may also have schema generation utilities.
Related
I am working on a project that requires the validation of many XML files against their XSD, the trouble I am having is that many of the XSD files depend on others XSDs, making the usual validation kind of troublesome, is there an elegant way to resolve this issue?
I would prefer if possible to work with those files in memory, the files are not in a concise directory structure that conforms with their importation paths.
Just to note I am working with the Java language.
Assuming here that you work with JAXP, so that you can setSchema() on either SAXParserFactory or `DocumentBuilderFactory.
One solution I was part of, was to read all XSD sources into an aggregated Schema object using SchemaFactory.newSchema(Source[] schemas). This aggregated Schema was then able to validate any XML document that referenced any "top" schema; all imported schemas had to be part of the aggregated schema. As I remember it, it was necessary to order the Source array by dependency, so that if Schema A imported Schema B, Schema B had to occur befor Schema A in the array.
Also, as I recall, <include> didn't work very well with this mechanism.
Another solution would be to set an LSResourceResolver on the ShemaFactory. You would have to implement your own LSResourceresolver that serves byte- or character streams based on the input to the resolver. I haven't personally used or researched this solution.
The first solution has of course the benefit that schema parsing and processing can be done once and reused for all validations that follows; something that will probably be difficult to achieve with the second option.
Another thing to keep in mind (depending on your context): It is a good design choice to control the whole "resolving" process (i.e. control how the parsers get access to external resources), from a performance as well as a security perspective.
I'm trying to generate flat file for test data using JAVA. Flat file has own mapping document which describes all fields of each line.
I was suggested to use XSD for mapping and I did some research on XSD. As I understood that XSD is for only validation of XML. In this case I have to randomly generate XML file based on XSD and convert it to txt or other format. Because as an output I need flat file, not XML.
It seems like using XSD i'm adding extra steps in creating the file as first create XML, validate with XSD and convert it expected format.
What would be your recommendation in my situation for following the mapping document?
Thanks in advance.
I have seen your kind of setup before. The reasons may be different than your particular scenario, but nonetheless it made sense. One thing to consider has to do with the skills and tools people have available and so whatever makes the job done quick and well, goes.
You seem to describe an offset based, "flat" data structure. In my case, people used COBOL copybooks which are very good at describing this. IBM Rational Developer had a built-in wizard which allows the creation of Java Data Bindings from a COBOL copybook. This is to say that within a minute one gets a Java class which can create a record for your flat file in no time (it comes with all the logic required to do the padding, etc.)
To get the data generated, there are tools capable of generating XML files which cover all constraints defined by an XSD (e.g. alternate content i.e. xsd:choice, enumerated values, etc.) Now, assuming you have a proper XSD describing your logical model of your flat file, one can get 10s, 100s, even 100K XML generated from an XSD spec. It takes a click, plus the time spent by the tool to create those files.
Next, to get the XML files in your generated Java class, and so avoid going through XSLT or whatever (many shops don't have the skills) it may be as simple as writing Java mapping code between a JAXB generated class and the one created above, or if matching is possible, simply annotate the generated class to support JAXB unmarshalling. This last step may take longer to code, but it would be trivial code any Java developer would know how to do it.
This could possibly give you a view into why someone may have recommended Java and XSD for this task. XSD is a modeling language with built in support for constraints, which may prove helpful in generating test data through combinatorial techniques.
What is the best tool/framework to convert classes into database schema automatically without XML mapping files?
My problem is this, I have around 20 classes with different relationships (association, inner classes, etc) to each others and I want to convert all that into a database tables to save all these data along with its relationships.
I tried to see some tutorials to Hibernate and found out that it requires building a mapping XML which is going to be very painful to my case.
Any framework to automate this?
Alternatively, you can annotate your classes instead of using XML and then generate the schema from your entities. Anyway, I strongly recommend writing the classes in a way that is easy to use with an OR mapper. It would have been best to design your model for the use of Hibernate beforehand.
I want to migrate my data from one DB to other using Java. Both DBs have different schema structure. I might also need to define some mapping / validation rule. Can anyone please guide me about any strategy, framework or any opensource project.
Thanks
Isn't in this case I have to create all the POJO to match the both schema (even by auto generating). Is there any way to avoid this thing i.e. giving schema mapping and generating POJO on fly in memory ?
Any idea?
Thanks
Yes, you need an Extract-Transform-Load (ETL) tool.
Here are some open source choices:
http://www.google.com/search?gcx=w&sourceid=chrome&ie=UTF-8&q=open+source+etl
ETL is generally used for this as in duffymo's answer.. you could also try ORM tools for this:
There is the Torque project.. http://db.apache.org/torque/
Read the data from your existing schema into java objects, then set them into the other objects for the other schema and then save them into the database. I am pretty sure hibernate also can be used, although I havent used hibernate per se. It works on the same way as torque..
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. :-)