Question

Here goes a SQL-Java coding style question…

How do others here deal with creating complex custom queries in Java cleanly?

I am speaking of the seemingly simple task of preparing a string which is the SQL statement to be executed.

I am aware of HQL, and also of stored procedures, but honestly I don’t really love these solutions. Perhaps I can be convinced differently. Stored procedures are annoying to deploy/maintain, and parsing performance is not such a huge issue in my case — flexibility takes precedence. HQL seems like a big leap, and has some limitations for my complex queries.

TO be clear, I am talking of super-ugly looking code like this:

    return 
        "(" + topTwenty + ")" +
        "UNION " +
        "(" + twentyBeforeMe + ")" +
        "UNION " +
        "(" + meDummyQuery + ")" +
        "UNION " +
        "(" + twentyAfterMe + ")";

Where the variables topTwenty are for example also subqueries created similarly.

I never thought I’d say this, but it was cleaner in PHP which had the multi-line string and $variable embedding in the strings.

Do people ever use a trivial templating library? How do you neatly keep the strings in the program? Or do you put them in a separate file (also seems annoying to me somehow).

Answer 1

What I do is to use String.format for table names and things that can’t be parametrized, and this class(NamedPreparedStament), which allows to use good names for bind variables instead of question marks.

String sql = "SELECT id FROM %s WHERE id > :lastInsertedYesterday ";
NamedParameterStatement p = new NamedParameterStatement(con, 
                                    String.format(sql, "table1"));
p.setInt("lastInsertedYesterday", lastOne);