Just Spring Data Access

Chapter 2. Advanced Concepts

The Spring framework has provided extensive APIs to work with the database. We’ve covered the basics of the framework in the last chapter, especially using the versatile JdbcTemplate class. This chapter elaborates on advanced concepts, including other templates, callbacks, and batch operations.

NamedParameterJdbcTemplate

In our queries, we define the bind variables using a ? operator as shown in the following snippet:

select count(*) from TRADES 
  where account = ? and security = ?

If we have a handful of these parameters, it would be an eyesore to read a query with ? all over the place. Spring has defined a new NamedParameterJdbcTemplate class that comes handy in eliminating these placeholder variables. This class basically encapsulates the JdbcTemplate by providing the enhanced functionality of declaring the bind variables using named parameters.

The same query can be tweaked as shown below using appropriate names instead of ? variables:

select count(*) from TRADES 
  where account = :account and security = :security 

The :account and :security names indicate that these variables will be passed in by some means. Note the colon (:) before the variable; this is the syntax you must follow.

There are two ways of setting these variables. One is to use a simple Map with the variables as the keys, and the other is to use SqlParameterSource, a utility provided by the framework.

Using Map

The following snippet shows how to set the variables by using a map with keys:

public ...