The Holy Java

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Posts Tagged ‘xml’

Creating dynamic EMF model from XSDs and loading its instances from XML as SDOs

Posted by Jakub Holý on January 3, 2011

This post describes how to read a dynamic EMF model from a set of XML schema files (XSDs) and how to use that model to transform XMLs to SDO DataObjects or EMF EObjects, all this in a stand-alone environment. Read the rest of this entry »

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EMF: Reading a model from XML – how to correctly declare its namespace – variants

Posted by Jakub Holý on January 3, 2011

When you use the Eclipse Modeling Framework (EMF) to read a model instance from an XML file, such as a webservice call message payload, it’s essential for EMF to be able to match the root XML element with the model’s “ePackage” that should be used for (re)constructing the model instance from the XML and this is done by matching the root element’s and the ePackage’s namespaces (as in XSD). So it’s very important to have proper configuration of EMF and proper content of the XML. Since there ale multiple variations of both, there are more ways to get it wrong than right. To learn what I’ve discovered regarding the valid combinations suitable at different situations, read on. Read the rest of this entry »

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Howto: JAX-WS service with XML Source input instead of JAXB-produced POJOs (similar to JAX-RPC with SOAPElement input)

Posted by Jakub Holý on December 29, 2010

Sometimes you may want to create a JAX-WS webservice with its input defined by a proper, structured XSD yet accessing the input as raw XML object and not as POJOs produced by JAXB, similarly as with a JAX-RPC webservice having input of the type SOAPElement. This is possible using @WebServiceProvider with javax.xml.ws.Service.Mode.PAYLOAD.

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Most interesting links of November

Posted by Jakub Holý on November 30, 2010

This month has been quite interesting, among others I ‘ve picked up several blogs by Adam Bien. I really like his brief, practical and insightful posts :-)

Java, Jave EE, architecture etc.

  • EJB 3.1 + Hessian = (Almost) Perfect Binary Remoting – “With hessian it is very easy to expose existing Java-interfaces with almost no overhead. Hessian is also extremely (better than IIOP and far better than SOAP) fast and scalable.” See also the discussion regarding a “DynamicHessianServlet” (which would be more comfortable then creating a new servlet for each service).
  • Binary XML – Fast Infoset performance results – FI is the name of a standard for binary XML encoding and also of its OSS implementation; according to these measurements (with default settings, compared to Xerces 2.7.1), on average: The FI SAX parser  is about 5 times faster than the Xerces SAX parser, the FI DOM serializer (using default settings) is 25% to 30% faster than the Xerces DOM XMLSerializer, and FI documents are 40% to 60% smaller than XML documents (i.e. it can provide modest to good compression). And: “The use of external vocabularies can be a very effective way to increase the efficiency of parsing, serializing and size at the expense of the fast infoset documents no longer being self-describing … .”
    For the interested ones: FI is built on ASN.1, a standard for describing data structures in a way that is independent of machine architecture and implementation language, it also includes a selection on different binary encoding rules, e.g. DER (triplets tag id – length – value).
  • EJB 3.1 And REST – The Lightweight Hybrid – Why to use @Stateless – there have been recently discussion about Spring vs. EJB and whether @Stateless is of any use. According to this article, the added value of EJB (though some are provided also by Spring) include injection capabilities, transactions, single threading model (for why that is good see #2 on Why I like EJB 3.0/3.1), visibility in JMX, concurrency restriction via thread/bean pools.
  • Why Service Isn’t A ServiceFacade, But ServiceFacade Is Sometimes A Service…
  • Experiences from migrating Hyperic 4.5 from EJB/JBoss to Spring/Tomcat, what good has it brought – simplified unit and integration tests, simplified code thanks to Jdbc/JmsTemplate, … (My comment: EJB 3.1 would certainly bring at least some of the advantages too.)

Performance – large JVM heaps are very much feasible

  • Tuning the IBM JVM for large heaps – tuning 64b IBM JVM 6 with 100GB heap to have acceptable GC times (~ 1/2s as opposed to 25s with the default settings)
  • BigMemory: Heap Envy – there have been recently a lot of fuss about Terracotta’s new BigMemory, a  GC-resistent many GB cache space (using NIO byte buffer). This post discusses it’s disadvantages and compares it with a solution based on ConcurrentHashMap, comming to the conclusion that the old good ConcurrentHashMap outperforms BigMemory considerably.

Other

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SOAP/SAAJ/XML Issues When Migrating to Java 6 (with Axis 1.2)

Posted by Jakub Holý on November 19, 2010

When you migrate an application using Apache Axis 1.2 from Java 4 or 5 to Java 6 (JRE 1.6) you will most likely encounter a handful of strange SOAP/SAAJ/XML errors and ClassCastExceptions. This is due to the fact that Sun’s implementation of SAAJ 1.3 has been integrated directly into the 1.6 JRE. Due to this integration it’s loaded by the bootstrap class loader and thus cannot see various classes that you might be referencing in your old code.

As mentioned on Spring pages:

Java 1.6 ships with SAAJ 1.3, JAXB 2.0, and JAXP 1.4 (a custom version of Xerces and Xalan). Overriding these libraries by putting different version on the classpath will result in various classloading issues, or exceptions in org.apache.xml.serializer.ToXMLSAXHandler. The only option for using more recent versions is to put the newer version in the endorsed directory (see above).

Fortunately, there is a simple solution, at least for Axis 1.2. Read the rest of this entry »

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