LinkageError: Loader Constraints Violated When Linking javax/xml/namespace/QName in WebSphere 6.1 Using Resteasy
If you are working with WebSphere 6.1 and using Resteasy, you may come across a common error known as "LinkageError: Loader Constraints Violated". This error occurs when trying to link the javax/xml/namespace/QName in your code. In this article, we will discuss what this error means and how to resolve it.
What is a LinkageError?
A LinkageError is a type of Java error that occurs when there is a conflict between two classes or interfaces. This error is usually caused by a mismatch in the class definitions or when there are different versions of the same class being used. In the case of WebSphere 6.1 and Resteasy, the LinkageError occurs when trying to link the javax/xml/namespace/QName class.
Understanding javax/xml/namespace/QName
The javax/xml/namespace/QName class is a part of the Java API for XML Processing (JAXP) specification. It is used to represent a qualified name in an XML document. This class is used by many Java libraries, including Resteasy, to handle XML data.
Why does the error occur in WebSphere 6.1 and Resteasy?
WebSphere 6.1 uses its own implementation of the JAXP specification, which may be different from the one used by Resteasy. This can cause conflicts when trying to link the javax/xml/namespace/QName class, resulting in the LinkageError.
How to resolve the LinkageError in WebSphere 6.1 and Resteasy
To resolve this error, you will need to make some changes to your code and the WebSphere 6.1 configuration. Follow these steps:
1. Check your code: The first step is to check your code and make sure you are not using any other versions of the javax/xml/namespace/QName class. If you are using any other versions, remove them from your code.
2. Update the WebSphere 6.1 configuration: WebSphere 6.1 has a default setting to use its own implementation of the JAXP specification. To resolve the LinkageError, you will need to change this setting to use the JAXP implementation provided by your application. To do this, go to the WebSphere administrative console and navigate to Applications > Application Types > WebSphere enterprise applications > your application. Click on the class loader link and change the class loader order to Classes loaded with parent class loader first.
3. Add the JAXP implementation to your application: Finally, you will need to add the JAXP implementation jar file to your application. This can be done by editing your application's deployment descriptor (web.xml) and adding the following code:
<listener>
<listener-class>org.jboss.resteasy.plugins.server.servlet.ResteasyBootstrap</listener-class>
</listener>
This will ensure that Resteasy uses the JAXP implementation provided by your application instead of the one used by WebSphere.
Conclusion
The LinkageError: Loader Constraints Violated error can be a frustrating obstacle when working with WebSphere 6.1 and Resteasy. However, by following the steps outlined in this article, you can resolve this error and continue working on your project. Remember to always check your code and make sure you are using the correct versions of classes to avoid any conflicts
