This project contains utilities to simplify JDBC data access code.
The JdbcTemplate dramatically simplifies common JDBC usage and enforces the correct usage of the API. For example, performing a query to obtain a value can be done like this:
int value = jdbcTemplate.selectOne("SELECT value FROM table WHERE id = ?;",
(rs, rowNum) -> rs.getInt("value"), JDBC.string("0101101011")).get();
This example makes use of the RowMapper interface, by which a row from a ResultSet can be converted to any arbitrary value as desired (such as mapping into an object).
The ResultSetHandler interface can be used if processing the ResultSet as a whole.
The JdbcTemplate avoids SQL injection by recommending the use of query parameters and the ParameterValue interface. ParameterValue implementations are aware of how to apply themselves to a PreparedStatement. Implementations are provided in the JDBC utility class for many of the JDBC standard types.
Database-specifc extensions are also supported. The net.josephbeard.jdbc.postgres package includes several that are available when using a PostgreSQL JDBC driver.
Multiple calls can be performed in the same transaction.
jdbcTemplate.doInTransaction(c -> {
jdbcTemplate.insert(c, "INSERT INTO t1 (id, value) VALUES (?,?);", JDBC.string("0101101011"), JDBC.integer(5));
jdbcTemplate.insert(c, "INSERT INTO t2 (id, value) VALUES (?,?);", JDBC.string("0101101011"), PostgreSQL.json("[1, \"2\", 3.14]"));
throw new SQLException("Transaction will be automatically rolled back!");
});
This example also demonstrates the use of JDBC extensions (in this case, support for the PostgreSQL JSON datatype).