JDBC :从元数据获取数组的类型

Question

是否可以从JDBC元数据结构中获取数组列的类型？

re = openedConnection.getMetaData().getColumns(...)
while (rs.next())
{
  final String columnName = rs.getString("COLUMN_NAME");
  final int columnType = rs.getInt("DATA_TYPE");
  ...

类型返回数组但是数组是什么(int，text，数值.)？

理想情况下，数据库是独立的(Oracle和Postgres支持这一点，对于MySQL或Server并不确定)

Answer 1

使用java.sql.ResultSetMetaData.getColumnTypeName()

Oracle安装

CREATE OR REPLACE TYPE random_array IS TABLE OF VARCHAR2(42);
/

Java

Class.forName("oracle.jdbc.OracleDriver");

Connection con = DriverManager.getConnection(
    "jdbc:oracle:thin:@localhost:1521:orcl",
    "username",
    "password"
);

PreparedStatement st = con.prepareStatement(
    "SELECT random_array( 'a', 'b', 'c' ) AS array FROM DUAL"
);

ResultSet rs = st.executeQuery();
while( rs.next() )
{
  String type = rs.getMetaData().getColumnTypeName(1);
  String[] data = (String[]) rs.getArray(1).getArray();
  System.out.println( type + ": " + Arrays.toString( data ) );
}

st.close();
con.close();

输出

SCHEMA_NAME.RANDOM_ARRAY: [a, b, c]

如果您想回到Oracle并找到可以使用的集合元素的类型：

SELECT ELEM_TYPE_NAME,
       LENGTH,
       PRECISION,
       SCALE
FROM   ALL_COLL_TYPES
WHERE  TYPE_NAME = 'RANDOM_ARRAY'
AND    OWNER     = 'SCHEMA_NAME';

其中产出：

ELEM_TYPE_NAME LENGTH PRECISION SCALE
-------------- ------ --------- -----
VARCHAR2           42