New issue. Jump to bottom. Labels in: data status: declined type: enhancement. Copy link. Keith Donald opened SPR and commented It sure would be useful if we had queryForObject variants that returned null on no row found cases vs. Affects: 3.
Collaborator Author. Keith Donald commented Maybe if instead of new methods on JdbcTemplate we add a configuration option that determines whether null is returned for empty object results?
Sometimes our requirement is not mapping results to java objects, instead we just need to process results, we can choose RowCallbackHandler in those cases. For example we need to find users whose username has less than 6 characters and write users to JSON files. PreparedStatementCreator is one of the central callback interfaces used by the JdbcTemplate class.
This interface creates a PreparedStatement given a connection, provided by the JdbcTemplate class. PreparedStatementSetter is a callback interface for JdbcTemplate class, it is used to set parameter values provided by JdbcTemplate.
We have seen several examples using JdbcTemplate. But the key difference is return type and behaviour of each callback handler method. But when you are working on large data set, you may face out of memory issues, to avoid them need to create efficient queries and apply paging or slicing on the database results.
When you call the query by providing sql query as String , JdbcTemplate takes the responsible for creating PreparedStatement object if you provided query parameters with default optimum settings. In some cases, you may need to control the PreparedStatement with specific configuration values to get results as per your requirement refer Example 5.
PreparedStatementSetter is used to set the parameter values to the PreparedStatement provided by JdbcTemplate , and also it maps the parameter java type to respective SQL type. When you have large number of parameters in query and type conversion between Java types and sql types is required, PreparedStatementSetter implementation provides full control over it.
When you run queryForObject with no parameters, JdbcTemplate creates Statement , executes query and returns single row or single column value as result. Here an example with parameters and RowMapper. When you run queryForObject with parameters JdbcTemplates creates PreparedStatement and executes query and return single row or single value as results. Java 8 Optional class provides a best way to deal with null values.
JdbcTemplate queryForList returns multiple rows results as List for single column or multiple columns. A queryForList example to get selected columns results and query with parameters. Provide parameters list Object[] and corresponding sql types in int[]. Thank you I will see you in the next post. Currently, I am working as an Associate project in an IT company. Your email address will not be published. Save my name, email, and website in this browser for the next time I comment.
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