Java

This post involves a slightly edge case scenario that I encountered a couple of months ago, so hopefully I get all the details right the first time. Essentially, I had a JPA2 project using Hibernate 3.6.10 as the ORM. This project had a requirement of some native SQL being used for dynamic table creation, so to achieve this I would call Query q = em.createNativeQuery(sql); and the proceed to call q.setParameter(...). This worked fine for both setting columns to a value, and setting them to null, at least on H2 and MySQL. However, if you tried to set to null when using SQLServer you’d get the following: ...

A quick note about using the BindingResult to detect and report errors in a form. One gotcha that got me was the need to set a name on the @ModelAttribute in order to properly relate the form:form commandName and the validation object. Essentially, if you don’t set a name then @ModelAttribute will get the command name from the name of the argument, and BindingResult will get the command name from the type of the argument, meaning that when you go to use form:errors nothing will be displayed. ...

It is often handy to be able to extract the Maven version of your project at run time, either for displaying in an about box, or in debugging information. One option is to read /META-INF/maven/${groupId}/${artifactId}/pom.properties. However, this file is only available in the packaged version of your project, so during development the method will fail. The approach I’ve taken to fulfil this requirement is to create a text (properties) file in the project resources, and have Maven process this. This allows Maven to inject the version number during compile. The following snippets need to be configured. ...

I recently had an issue using the Apache HTTP Client pooling library where after a while threads would just block when trying to open connections. It didn’t take too much to figure out that the thread pool was being exhausted, a quick thread dump revealed all the threads were waiting for a connection from the pool. The issue was, which method was not releasing the connection? In the Apache HC library a connection is released to the pool when the response.getEntity().getContent() is closed (provided it isn’t already null). This is what EntityUtils.consume does - it checks if getContent() is null and if not then it calls .close(). ...

Sometimes in a webapp you will be in a situation where a filter/app/container other than Spring will be responsible for authenticating a user and setting the user principal, leaving the authz to the Spring webapp. A portlet container is a typical example. There is a few examples floating around showing how to do this in Spring 2.x, but it appears some thing (packages, etc) have changed for Spring 3.x, so here is how to make it work. Use the following in your applicationContext.xml ...

Recounting a strange little compatibility issue I had between ZSI 2.0 and CXF 2.0.x. I was using CXF as the server, running from Maven using Jetty, and ZSI as the client. The parameters from the ZSI were arriving at the service implementation as null. With the web services logging turned on I could see that the SOAP packet was arriving OK, and looked good. A little bit of digging round the web turned up this message. The issue was that ZSI wasn’t explicitly namespacing the elements, and so CXF was not seeing them. The solution was to add elementFormDefault=“qualified” to my WSDL definition, and rebuild the ZSI stubs. ...

After programming for Zope3/Plone for the past year I’ve come to really admire the flexibility and elegance that their implementation of the adapter pattern gives us. And, after Martin Aspeli put the call out almost a year ago, and it has not yet been answered, I thought it was time to give it a go. How hard could it be. So, what I’ve developed is a very simple, no dependency, maven available library which should greatly improve the flexibility of your code. ...

The problem I’ve been address in my most recent work block has been to develop an interface to a relational data store which can be used either as a local DB, or via webservices. The concept is quite straight forward, we want CRUD operations on a set of data objects. The schema is fairly straight forward too, with a core hierarchy of elements with a few enumerated lists. As well as a few cuts across the hierarchy. ...

Recently I had need to deploy some Spring webapps which required predeploy configuration. Being the first time I had to find a serious answer I looked to the mythical JNDI for an answer. This document is meant to complement other Spring JNDI documents out there. Essentially the problem is this. We need to deploy a webapp. The webapp needs configurations (database and webservice endpoint locations). Editing properties files or XML config within the webapp isn’t nice, because on a redeploy the config will be lost. Inside containers like Tomcat I am not aware of a way to easily add extra items to the classpath which won’t get nuked unexpectedly, so solutions like PropertyPlaceholderConfigurer don’t really fly as the properties file will end up within the webapp. And I don’t like the idea of setting environment variables for to locate such things. ...

Here’s a very weird Maven/Java issue. The error message (below) occurs in my build phase where JaxB is called to produce some Java objects from XML. JaxB calls HyperJaxB, and on some systems it crashes. [ERROR] XJC while compiling schema(s): org.apache.commons.logging.LogConfigurationException: org.apache.commons.logging.LogConfigurationException: org.apache.commons.logging.LogConfigurationException: Class org.apache.commons.logging.impl.Log4JLogger does not implement Log Caused by: org.apache.commons.logging.LogConfigurationException: org.apache.commons.logging.LogConfigurationException: org.apache.commons.logging.LogConfigurationException: Class org.apache.commons.logging.impl.Log4JLogger does not implement Log Caused by: org.apache.commons.logging.LogConfigurationException: org.apache.commons.logging.LogConfigurationException: Class org.apache.commons.logging.impl.Log4JLogger does not implement Log Caused by: org.apache.commons.logging.LogConfigurationException: Class org.apache.commons.logging.impl.Log4JLogger does not implement Log ...