Monday, November 15, 2010

Jeans - Running Java Servlet and JSP Webapp in ASP.NET/IIS - Part 4

Retrieving a database connection is one of the most popular problem in software development. Usually, we specify the connection string in a configure file and create the database connection with the connection string. The Java way is wrapping connection string in a javax.sql.DataSource interface and put in the application server config. The application server will put the DataSource instance into a JNDI context. So, this is what should be supported.

Bring in the Unity
Microsoft has a Dependency Injection container called Unity. Even though I am not doing dependency injection, I'd like to configure how to instantiate the data source in web.config. Instead of writing my own configuration classes, Unity is a good alternative as an object builder.

Before doing any configuration, the JDBC driver has to be compiled into .Net assembly since it will be loaded by Unity instead of the Java class loader.

Method Injection
When configuring Unity, we could specify the methods to be called during the instance initialization. The first attempt:
<method name="setURL">
    <param name="url" value="..." />

However, Unity was smart enough to know there is no such parameter name. I fired-off the object explorer to look the actual parameter name. It seemed that IKVM compiled all parameter name with str, str1, str2, etc. The configuration has to be like this:

<method name="setURL">
    <param name="str" value="..." />

JNDI Context
Having known that a data source with the name jdbc/testDS is the same as java:comp/env/jdbc/testDS, I tried to mimic the behavior with the reference of this article. It turned out the result is an exception:
javax.persistence.PersistenceException: Exception [EclipseLink-7060] (Eclipse Persistence Services - 2.0.2.v20100323-r6872): org.eclipse.persistence.exceptions.ValidationException
Exception Description: Cannot acquire data source [jdbc/testDS].
Internal Exception: javax.naming.NameNotFoundException: Name jdbc is not bound in this Context
    at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy(

So, I reverted to the simpliest way by just creating the jdbc subcontext in the initial context.

The configuration was set. Time to run the test. It did not work:
javax.persistence.PersistenceException: Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.0.2.v20100323-r6872): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: Login failed for user 'jsptest'.
Error Code: 18456
    at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy(

Well, the password was copied from persistence and very simple:
<method name="setPassword">
    <param name="str" value="passw0rd" />

Not sure what happened but when the user and password were put in the URL, it worked.

The new source code has been checked-in in The persistence.xml has changed to use the <non-jta-data-source>jdbc/testDS</non-jta-data-source>.

Note: sqljdbc4.jar has been removed from the source repository. Please download it from Microsoft and compile it with IKVM to run the JSP demo site.

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