JDBC -- DBUtils

DBUtils framework:

　　Constructor:

　　　　QueryRunner(); 

　　　　QueryRunner(DataSource dataSource);

　　Method:

　　　　batch:

　　　　　　batch(Connection conn, String sql, Object[][] params);  ----->  when you use the default constructor

　　　　　　batch(String sql, Object[][] params);  ----->  high dimensionality: the amount of statement low dimensionality: the parameter each statement needs

　　　　query:

　　　　　　<T> T query(String sql, ResultSetHandler<T> rsh, Object... params);

　　　　　　<T> T query(Connection conn, String sql, ResultSetHandler<T> rsh, Object... params);

　　　　update:

　　　　　　update(String sql, Object... parmas);

　　　　　　update(Connection conn, String sql, Object... params);

　　　　When you want to call the update method for several times, pleas use update(Connection conn, String sql, Object... parmas), and the default constructor is needed.

ResultSetHandler of DBUtils:

　　ArrayHandler: used when the result set has only one result in the set, the return value is Object[], the records in the list is the data of every column.

　　ArrayListHandler: used when the result set has many results in the set, the return value is List<Object[]> , the records are encapsulated in the List, every Object[] represents one row of data.

　　BeanHandler: return one JavaBean record 

　　BeanListHandler: return a List of JavaBean record

　　ColumnListHandler: used when want to query one column, the return value is List<Object>, the value in the List is the column's values.

　　KeyedHandler: used when the result set has many records, the return value is Map<Object,Map<String,Object>>

　　MapHandler: used when the result set has only one record, the return value is Map<String,Object>, key is the filed name, value is the filed value.

　　MapListHandler: ... the return value is List<Map<String,Object>>

　　ScalarHandler: used when the result has only one row and one column, the return value is Object