I have a XML input
<field>
<name>id</name>
<dataType>string</dataType>
<maxlength>42</maxlength>
<required>false</required>
</field>
I am looking for a library or a tool which will take an XML instance document and output a corresponding XSD schema.
I am looking for some java library with which I can generate a XSD for the above XML structure
If all you want is an XSD so that the XML you gave conforms to it, you'd be much better off by crafting it yourself rather than using a tool.
No one knows better than you the particularities of the schema, such as which valid values are there (for instance, is the <maxlength> element required? are true and false the only valid values for <required>?).
If you really want to use a tool (I'd only advice using it if you haven't designed the XML and really can't get the real XSD - or if you designed it, double check the generated XSD), you could try Trang. It can infer an XSD Schema from a number of example XML's.
You'll have to take into account that the XSD a tool can infer you might be incomplete or inaccurate if XML samples aren't representative enough.
java -jar trang.jar sampleXML.xml inferredXSD.xsd
You can find a usage example of Trang here.
You can try with online tool called XMLGrid: http://xmlgrid.net/xml2xsd.html
You could write an XSLT to do something like that. But the problem is, a single document alone is not enough information to generate a schema. Are any of those elements optional? Is there anything missing from that document, that might appear in other instances? How many of a particular element can there be? Do they have to be in that order? There are loads of things that can be expressed in a schema, that are not immediately obvious from one instance of a document that conforms to that schema.
For the people who really want to include it in their Java code to generate an XSD and understand the perils, check out Generate XSD from XML programatically in Java
Try xmlbeans it has some tools one of them is ins2xsd you can find specifics here:
http://xmlbeans.apache.org/docs/2.0.0/guide/tools.html
Good luck
Related
I have an XML Document built programatically and waiting for serialisation (as a String). Before serialising it though, I would like to re-arrange its nodes so that they match the definition of the DTD. I should mention that my implementation prevents me to know in which order the tree will be built.
Any recommended solutions for this ?
There is some academic research to correct invalid XML:
Correction of Invalid XML Documents with Respect to Single Type Tree
Grammars
but I don't know if there is any available library for that.
So you need to do it by hand, or better rework the generation of the document so that it produces a valid instance in the first place.
There is an XML file hosted on a server that I want to parse. Normally I generate an XSD from the XML and then generate the java pojo's from this XSD. Using jackson I then parse the XML to a java object representation. Is it not more straightforward to just use xpath ? This means I do not need to generate a object hierarchy based on the XML and also I do not need to regenerate the object hierarchy if the XML changes. xpath seems much more concise and intuitive ?
Why should I use XSD , object generation instead of xpath ?
According to the XML Schema specification XSD is used for defining the structure, content and semantics of XML documents. This means that you can use XSD to validate your XML file.
Depending on your circumstances you might be able to do without generating the whole object tree if all you need is to get some values from the XML file. In this case XPath is the way to go. However, you still might want to have an XSD file in order to validate the XML file before parsing it. This way you make your software fail fast, when the structure of your XML file changes, which will suggest that you change your XPath expressions. But for this to work, you shouldn't use the XSD you generate from your XML file, instead you should have a separate pre-generated XSD file which complies with the XPath expressions.
I think both approaches are valid, depending on the circumstances.
At the end of the day, you want to extract the values from that remote xml file and do something with them.
First criteria to consider is the size of that file, and the number of data elements.
If it's just a few, then xpath extraction should be straightforward. However, if that xml file represent a sizable and/or complex data structure, then you probably want the de-serialization to a Java data structure that you can then utilize, and JAXB would be a good candidate.
JAXB is going to be easier/better if the remote server adheres or publishes an XML Schema. If it doesn't, and changes often and significantly, you're going to suffer either way, but particularly so with JAXB. There are ways to smooth things over by pre-processing that xml with XSLT to force it into a more reliable form, but that is going to be a partial solution most likely.
I need to create a javabean from xml input.There wont be any irregularities in the xml input which I give.
I know stuffs like JAXB and Apache XMLbeans work.
But here I need to autogenerate the JAVAbeanclass without using its xsd.
In short when I give any xml inputs the outputs have to be the pojo classes generated.
Any inputs for this???
I think the best solution for that is develop your own DOM (if there is many items on the XML) or SAX (if there is a lot of items) parser.
DOM takes more memory so it is not recommended for XML with many nodes (and/or many attributes).
You can use tools like wsgen to generate class files from a service.
Here is a example,
http://www.mkyong.com/webservices/jax-ws/jax-ws-wsgen-tool-example/
I am getting some information in the form of XML.
Before using that xml I want to validate that all the information is in that XML.
For this purpose I will have a master copy of XML, against which i will match all the coming documents.
How can i do this?
Looks a lot of work, but you could use XPath depending on the size and structure of your xml. Take a look at http://www.w3schools.com/xpath/default.asp.
Also there is a really good starting tutorial here:
http://www.ibm.com/developerworks/library/x-javaxpathapi.html
And if you're willing to do validation through the use of your xsd (if there is one), look at ( XML Schema (XSD) validation tool? )
A common approach for validating xml is to define a schema (xsd or dtd). A parser can validate the input xml document against all constraints that are specified in the schema document.
This is a common way if you need to make sure, that certains elements are present and that certain values are within a specified value range.
You can refer the following link to see how an xml can be validated against a dtd in java
http://www.roseindia.net/xml/dom/DOMValidateDTD.shtml
I need to generate XML and they differ only in the values, that the tags contain.
Is it possible to create a template XML and then write only the values each time? (I do not want to go the JAXB way as these are small XMLs and are not worth creating objects for them).
Is this a good approach?
Any thoughts?
You can use freemarker or velocity for templating in java -- or even just add PHP tags to a sample XML to generate from a template.
I think as a general rule, though, once you start conditionally adding elements or attributes, or looping to generate multiples, you're better of generating your XML -- though I agree sometimes getting it into a format you want (not what the generator wants) is sometimes a pain.
As long as the XML file to be produced is small, simple and mostly consistent in format, I tend to buck the trend: I simply create and write a text string.
writer.out.format("<?xml version='1.0'><root><tag1>%s</tag1></root>", value1)
kinda thing.
Despite the fact that you are against jaxb (which I have yet to use), I wish to recommend a comparable way to do this with Apache's XMLBeans.
This requires you to use an xml schema - but from my experience it worth it...