Asked by
Amit Dubey
in
Computers & Technology
at
10:22 PM on December 08, 2008
ayisha's Answer
The JdbcTemplate class is the central class in the JDBC core package. It simplifies the use of JDBC since it handles the creation and release of resources. This helps to avoid common errors such as forgetting to always close the connection. It executes the core JDBC workflow like statement creation and execution, leaving application code to provide SQL and extract results. This class executes SQL queries, update statements or stored procedure calls, imitating iteration over ResultSets and extraction of returned parameter values. It also catches JDBC exceptions and translates them to the generic, more informative, exception hierarchy defined in the org.springframework.dao package.
Code using the JdbcTemplate only need to implement callback interfaces, giving them a clearly defined contract. The PreparedStatementCreator callback interface creates a prepared statement given a Connection provided by this class, providing SQL and any necessary parameters. The same is true for the CallableStatementCreator interface which creates callable statement. The RowCallbackHandler interface extracts values from each row of a ResultSet.
The JdbcTemplate can be used within a DAO implementation via direct instantiation with a DataSource reference, or be configured in a Spring IOC container and given to DAOs as a bean reference. Note: the DataSource should always be configured as a bean in the Spring IoC container, in the first case given to the service directly, in the second case to the prepared template.
Finally, all of the SQL issued by this class is logged at the 'DEBUG' level under the category corresponding to the fully qualified class name of the template instance (typically JdbcTemplate, but it may be different if a custom subclass of the JdbcTemplate class is being used).
Answered at
11:00 PM on December 08, 2008
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