Spring Jdbc Template-优快云博客

本文介绍使用JdbcTemplate进行数据库查询的方法，包括单条记录查询、多条记录查询及三种回调方式：ResultSetExtractor、RowMapper和RowCallbackHandler。这些技巧有助于开发者更高效地处理数据库查询任务。

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1. Only one single result/row.
int queryForInt(String sql)
int queryForInt(String sql, Object[] args)
long queryForLong(String sql)
long queryForLong(String sql, Object[] args)
Object queryForObject(String sql, Class requiredType)
Object queryForObject(String sql, Object[] args, Class requiredType)
Map queryForMap(String sql)
Map queryForMap(String sql, Object[] args)

2. Multiple rows
List queryForList(String sql)
List queryForList(String sql, Object[] args)

3. Three types of callback
1) ResultSetExtractor
List customerList = (List)jdbcTemplate.query("select * from customer", new ResultSetExtractor(){
public Object extractData(ResultSet rs) throws Exception
{
List customers = new ArrayList();
while(rs.next())
{
Customer customer = new Customer();
customer.setFirstName(rs.getString(1));
customer.setLastName(rs.getString(2));
...
customers.add(customer);
}
return customers;
}});

2) RowMapper
List customerList = jdbcTemplate.query("select * from customer", new RowMapper(){
public Object mapRow(ResultSet rs, int rowNumber) throws SQLException {
Customer customer = new Customer();
customer.setFirstName(rs.getString(1));
customer.setLastName(rs.getString(2));
...
return customer;
}});

3) RowCallbackHandler
final List customerList = new ArrayList();
jdbcTemplate.query("select * from customer", new RowCallbackHandler(){
public void processRow(ResultSet rs) throws SQLException {
Customer customer = new Customer();
customer.setFirstName(rs.getString(1));
customer.setLastName(rs.getString(2));
...
customerList.add(customer);
}});