Some Java / MySQL IBATIS gotchas

Posted: 20091022

Wow. I had a funny day. First of all, I was happy to be back in the eclipse java world, as compared to grails (Intellij). Secondly, discovering iBATIS was an eye-opener, especially with regard to startup times for integration tests (I use JUnit4 for this). Compared to anything hibernate based... f.e. grails (grails has its own merits anyway).

iBATIS has a cool plugin called iBATOR. It analyzes an existing table structure, and creates CRUD DAO classes you can use, among with the iBATIS SQL map file and the Java Pojo domain models themselves. And the DAO classes have cool features such as Criteria classes which enable you to query by example like this:

BlogEntryExample example = new BlogEntryExample();
example.createCriteria().andAuthorIsLike('%Amanjit%').andYearIsEqualTo(2007L);
List<BlogEntry> entries = dao.selectByExample(example);

which will return all Blog Entries from an author like "Amanjit" in the year 2007. Nice stuff. Of course, the BlogEntry table (could be called TABLE_BLOG_ENTRY) contains the columns called year and author. Generated query class are huge but the feature is useful. The whole stuff is autogenerated. you also get update, delete and create DAO methods out of the box. You can have custom SQLMap entries in a file, on regenerating from a changed DB model iBATIS won't override your queries / resultmap config. Nice.

Of course, hand crafted hand optimized SQL is one of the main reasons people use IBATIS. But, I have to say, you are still free to do anyway, and regarding the 1:n, m:n joining stuff you probably have to :-)

DELETE FROM BlogEntry WHERE year=2007                          # works
DELETE FROM BlogEntry table_blog WHERE table_blog.year=2007    # does not work. toasted.

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