Testing database access - JUnit in Action - page 346

L OGGING
Earlier on we said that DbUnit would warn us about the missing column in the XML
issue, but if you run the testNULL() method, it fails without any warning. If that hap-
pens, it means DbUnit logging is somehow disabled.
There's no API or DbUnit configuration file to explicitly enable logging. Instead,
you must configure SLF4J in your project. It isn't the intent of this topic to explain how
SLF4J works or why the DbUnit chose this tool (until release 2.2, DbUnit used no log-
ging framework at all). Briefly, you need to add to the project's classpath a JAR con-
taining a real SL4J implementation. In our cases we didn't see any log because the
project's Ant script is explicitly using sl4j-nop.jar, which doesn't log anything (this is
also the default implementation included in your Maven project if you just add
DbUnit as a project dependency).
If your project already uses a logging framework (like log4j or Java's java.util.
logging ), chances are there's an SLF4J provider for that framework, so you can just
include its JAR (such as sl4j-log4j12.jar) in the classpath. If you don't use any logging
framework, the easiest solution (the one that requires no extra configuration) is to
add sl4j-simple.jar. This provider sends info messages to System.out , sends warnings
and errors to System.err , and ignores all other logging levels (like debug and trace).
Adding sl4j-simple.jar to the classpath and running the test case again, we get the
aforementioned warning:

474 [main] WARN org.dbunit.dataset.xml.FlatXmlProducer - Extra columns on
➥

line 2. Those columns will be ignored.
474 [main] WARN org.dbunit.dataset.xml.FlatXmlProducer - Please add the
➥

extra columns to line 1, or use a DTD to make sure the value of those
➥

columns are populated or specify 'columnSensing=true' for your
➥

FlatXmlProducer.
474 [main] WARN org.dbunit.dataset.xml.FlatXmlProducer - See FAQ for more
➥

details.
Whenever you're facing problems that sound like a DbUnit bug or usage issue, try
enabling the lower logging levels 9 like debug or trace. DbUnit will output a lot of
debugging information, which will hopefully help you resolve the issue.

17.6 Creating datasets from existing database data

So far in the examples, we created dataset XML files from scratch, in a bottom-up
approach. This is the ideal situation when you're doing pure TDD , but often you need
to create these files from the data already in the database.
For instance, you might be working on a big project, where the database develop-
ment is done by a separate team of DBA s and a QA team maintains a database instance
full of testing data. Typically in these situations, your Java code (and test cases) will
have to deal with complex scenarios, like tables with dozens of columns and many for-
eign key relationships. It would be unpractical and error prone to create the datasets

9

Notice that you'll need a better SL4J implementation than sl4j-simple in this case.