java - 是否可以从 Java 代码获取嵌套表/数组的元数据？

Question

通常对于用户定义的类型，我可以简单地执行以下操作(简化但实用的示例):

//Create table
create type myType1 as object( a char(2), b char(2) );
create type myTable1 as table of myType1;

//Java code
ArrayDescriptor  des  = ArrayDescriptor.createDescriptor( "MYTABLE1", con);
StructDescriptor sDes = StructDescriptor.createDescriptor( des.getBaseName(), con);

//Populte the metadata
String  columnName = sDes.getColumnName(0);
int     oracleType = sDes.getColumnType(0);
int     maxSize    = sDes.getColumnDisplaySize(0);
boolean isNullable = sDes.isNullable(0)>0;

除了现在我有一个用原始类型而不是结构定义的表，而且我似乎无法访问元数据。我当前的代码是:

//Create table
create or replace type myTable2 as table of char(2);

//Java code
ArrayDescriptor descriptor = ArrayDescriptor.createDescriptor( "MYTABLE2", con);
//This next line would throw an exception, as CHAR type is not a structure
//StructDescriptor sDes = StructDescriptor.createDescriptor( des.getBaseName(), con);

//Populte the metadata    
int     oracleType = descriptor.getBaseType(); // This Works
String  columnName = "COLUMN_VALUE";           // This Works (I think)
int     maxSize    = ????                      // How do I access the '2'?
boolean isNullable = ????                      // How do I access isNullable?

Answer 1

希望我没听错。如果您可以获得列信息，您可以尝试以下代码。

DatabaseMetaData databaseMetaData = connection.getMetaData();

ResultSet columns = databaseMetaData.getColumns(null,null, tableName, null);
while(columns.next())
{
    String columnName = columns.getString("COLUMN_NAME");
    String datatype = columns.getString("DATA_TYPE");
    String columnsize = columns.getString("COLUMN_SIZE");
    String decimaldigits = columns.getString("DECIMAL_DIGITS");
    String isNullable = columns.getString("IS_NULLABLE");
    String is_autoIncrment = columns.getString("IS_AUTOINCREMENT");
}