JDBC:从元数据

时间:2017-03-21 14:21:30

标签: java oracle postgresql jdbc

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");
  ...

type返回ARRAY但是一个数组(int,text,numeric ...)?

理想情况下,数据库无关(Oracle和Postgres支持这不确定MySQL或SQL Server)

1 个答案:

答案 0 :(得分:0)

使用java.sql.ResultSetMetaData.getColumnTypeName()

Oracle安装程序

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

<强>爪哇

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();

<强>输出

SCHEMA_NAME.RANDOM_ARRAY: [a, b, c]

如果您想返回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';

哪个输出:

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