We wanted to upgrade our project in order to use some up-to-date dependencies. In the moment we use jaxb for XML reading and writing. This is working very good.
In some cases we do not have an xsd or dtd in order to generate the java classes (via xjc). In those cases we use dom4j for creating xml documents or dom4j with xpath for reading xml documents.
The version 1.6.1 is over ten years old and as far as I understand, dom4j needs jaxen as the X-Path library. Jaxen 1.1.6 is also 4 years old. Also we removed from our project xerces 2.40 (also 12 years old).
What XML API is state of the art in the moment? It should support XPATH expressions and should create and read xml documents.
Also I am wondering about xerces. When we use JAXB for reading xml documents, sometimes we have an object values instead of a string, date or something else.
The reason for that is that somebody messed up the xsd and forgot do define a datatype for some elements. XJC creates simple object properties inside the generated java class. The strange thing is, that I needed to cast the object to an "ElementNSImpl" object. This object comes from the xerces project.
I am a little bit confused. Our solution for removing xerces was to define each element with a proper datatype. Unfortunately those XSDs are third party XSD and we have to fix that each time the XSD will change. But why do I have to cast the object in ElementNSImpl?
Thanks for your help.
Just because something is 'old' doesn't mean it's not useful. DOM4J is still my favorite tool for ad-hoc XML processing. dom4j has been updated since 1.6.1, but note that it is still dependent on an underying XML parser (such as Xerces).
dom4j version 1.6.1 has an XML Injection security vulnerability: https://nvd.nist.gov/vuln/detail/CVE-2018-1000632.
It appears to have been fixed in 2.1.1, released in July of 2018.
Related
I am currently working on an application that performs the task of importing or exporting some entities. The file format being used for the same is XML. JAXB is being used for XML binding.
The problem is present XSD that defines the structure of entities has no provision for versioning. How do I get started with defining versioned XSD and subsequently XML instance documents provided JAXB lies as the underlying binding framework ?
I have read that there are three possible ways of introducing versions in XSD.
1) Change the internal schema version attribute
2) Create a attribute like schemaVersion on the root element
3) Change the schema's target namespace.
Which one best suits the usecase mentioned below?
Use case: The changes made to the XSD in the next version may invalidate the existing elements. Although the schema itself may not be backward compatible but the application needs to provides support for handling all versions of schema.
XML is designed to facilitate change and flexibility in document structures. Unfortunately, JAXB isn't. The very act of compiling knowledge of document structure into your Java source code makes change to the document structure a lot more difficult.
If structural change is part of your agenda, I think you should seriously consider not using JAXB: technologies like XQuery and XSLT are much better suited to this scenario.
I have an application that receives an XML message and then parses it to perform further processing.In order to have this working in my application, after receiving the XML string, I call the JAXB marshaller to marshal it in to java POJOs and the processing takes from here after.
This thing works well till the time I have one version of XML.
Problem
But the problem comes when there are more than one versions of the same XSD. And my application has to deal with both version of messages. Clients to my application may send a old version xml or they may send a latest version XML.
For JAXB I have to convert the XSD into java pojos using JAVA XJC tool, and the problem arises when I convert the latest version of XSD it has the same class names as the previous version, but internal fields and hierarchy of the class is different. this causes problems even if i put the XJC outputs in different jars for each version.
Expected Solution
This change in version is expected to happen every 6 months and I have to make my system able to read the newer version XMLs also alongwith the old versions.
I want to know how to manage this XML processing in JAVA with JAXB or some other framework.
Shall I use SAX Parser? I have read that its not that efficient as compared to JAXB. And after working on SAX parser for last few days, i found out that it can be error prone as it involves looking for each element and getting values out of it and putting it into a java structure of our own and that is a lot of effort as compared to JAXB.
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Question
Is there any simple solution similar like JAXB ?
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Temporary Solution Used
I have used a temporary solution, with which i am not happy as a good solution. What I did is, I created a seperate jar for each XSD version using XJC tool. And created different packages ion each jar e.g.
1. Pojos for version 1.2 are in a jar with base package com.cgs.v_12
2. Pojos for version 2.0 are in a different jar with base package com.cgs.v_20
i have added both as a maven dependancy to my system and using them for processing different versions.
For JAXB/ any other solution that maps between XSD -> POJOs, this will be a 1-1 mapping, especially if the POJOs are generated.
Do you have to
(1) map the entire XML to POJO, or
(2) a subset of that XML to a static/ fixed POJO model?
If (1), since the changes in the subsequent versions cannot be anticipated, I believe the solution for the above will be use a strategy pattern to select the correct JAXB artifacts based on the version
If (2), you can explore using XPATH, defining XPATH mappings per version.
I am starting a new project where I have third party XSD. My Java application needs to generate, and readm XML messages that conform to this XSD. In the past I have used Apache XMLBeans for this. It looks like XMLBeans has been retired.
What is a good replacement for XMLBeans now that it has been retired? I have used XStream on other projects but I don't recall that XStream has the ability to generate Java classes from an XSD so I am thinking that it is not a good choice over XMLBeans for this use case. I have hundreds of types defined in the XSD and would really prefer not to have to create the hundreds of Java classes to represent them in Java by hand.
In other words, using the XStream example, I have a Person type (and 99 others) defined in the XSD. Using XMLBeans I can generate the Java classes to represent these objects, but using XStream I would need to create the Java classes (e.g. Person) by hand or using some other tool. What tool should I use in this case?
Have you looked at JAXB? I haven't done anything with either of these, but googling for "alternative to XMLBeans" brings up lots of references to this package. Here's an article that compares them...
http://blog.bdoughan.com/2012/01/how-does-jaxb-compare-to-xmlbeans.html
XMLBeans has been unretired:
The Apache POI project has unretired the XMLBeans codebase and is maintaining it as a sub-project. Until now the XMLBeans codebase was held in the Apache Attic where former Apache projects are kept for the public good.
The latest release as of August 2020 is:
3.1.0 (March 26, 2019)
Having said that, I am not sure I would recommend using it, based on its history of retirement. Other solutions, such as JAXB, might be prefered since it will probably be better maintained in the future.
I have been looking at ways to parse XML Schema files for metadata of types defined in those files and get other information, and build the type hierarchy to be shown to the user.
I found a number of candidates:
Apache WS Commons XMLSchema API
Apache Xerces XML Schema API
XSOM
XMLBeans
XMLSchema API and Xerces XML Schema API seem the two best suited.
While XMLSchema API was easier to use, it is not as well documented, and Xerces seems to be the one with much more support. However, I have been unable to locate any resources which might help me get started with the Xerces XML Schema API, except their FAQ's which have proved to be highly inadequate.
So my question is twofold - Which is the better choice for parsing and querying Schema files, and there any resources for these two to get started quickly?
take a look at Xstream, it's a good instrument for serialization, but you also can use it for parsing. Here is two minute tutorial.
Another option you might consider is Saxon's SCM format, which is an XML representation of the schema component model. Both SCM and XSOM are closely based on the schema component model defined in the W3C specs, and rely heavily on the user understanding that model; they don't repeat the documentation of the component model in the API definitions.
Is there an XML serialization framework for Java that does not use reflection, but instead generates static serialization code (Java source) from XSD ?
I've never seen anything that does exactly what you are asking for: generating serialization code from XSD. However, if you're not stuck with an existing XSD schema, Modello may satisfy your requirements.
Modello is used by Maven for parsing pom.xml and settings.xml files. It reads a .mdo file (like this description of the Maven project model), and can generate a Java object model; an XML Schema (XSD) file; and serialisation/de-serialisation code. The serialisation/deserialisation code can use one of a number of XML parser APIs (e.g. JDOM, StAX, etc.). The XML parser API used by Maven itself is xpp3.
Modello can also generate code to convert one version of the model to another. It can generate HTML documentation about your XML format.
If you have an existing XSD, it might be too much work to use modello. But, if you're creating your own XML format, it could be worth starting with modello and generating the XSD.