19.6 Type Mapping Examples
To promote understanding of the appropriate use of the CWM Foundation’s TypeMapping package for recording mappings between
data types defined by different software systems, this section presents example instances illustrating how the CORBA IDL and
Java primitive data types can be mapped to each other and how the Java and SQL-99 primitive data types can be mapped to each
other. These mappings are obtained from relevant published standards documents: [IDL-Java], [Java-IDL] and [JDBC]. Although
the CWM Relational package supports the SQL-99 standard, the type mappings between Java and SQL are derived from the JDBC
specification which uses X/Open CLI SQL as its SQL language standard rather than SQL-99. Consequently, the Java/SQL mappings
are not exactly equivalent to those that would be needed to map to SQL-99 but should serve to illustrate the mapping techniques
required. SQL typeNumbers from the java.sql.Types file can be used to uniquely identify SQL types.
The following tables present sample type mapping instances for CORBA IDL/Java and Java/SQL-99 mappings. Because TypeMapping
instances are unidirectional, two instances -- one for each direction -- are required to indicate that a pair of data types
can be mutually interchanged. To keep the size of the tables manageable, only type mapping instances with isBestMatch = True
are shown; other, non-preferred mappings can be added as necessary to support particular implementation needs. Also, values
for the isLossy attribute of TypeMapping instances are omitted because their precise values may be implementation dependent.
Table 19-1 TypeMapping instances mapping CORBA IDL data types to Java data types
SourceType (IDL) |
TargetType (Java) |
|
|
|
|
|
|
|
|
|
|
| boolean |
boolean |
|
|
|
|
| char |
char |
|
|
|
|
| wchar |
char |
|
|
|
|
| octet |
byte |
|
|
|
|
| string |
java.lang.String |
|
|
|
|
| wstring |
java.lang.String |
|
|
|
|
| short |
short |
|
|
|
|
| unsigned short |
unsigned short |
|
|
|
|
| long |
int |
|
|
|
|
| unsigned long |
int |
|
|
|
|
| long long |
long |
|
|
|
|
| unsigned long long |
long |
|
|
|
|
| float |
float |
|
|
|
|
| double |
double |
|
|
|
|
| fixed |
java.math.BigDecimal |
|
|
|
|
Table 19-2 TypeMapping instances mapping Java data types to CORBA IDL data types Table 19-3 TypeMapping instances mapping
X/Open CLI SQL data types to Java data type
SourceType (Java) |
TargetType (IDL) |
|
|
|
|
|
|
|
|
|
|
| void |
void |
|
|
|
|
| boolean |
boolean |
|
|
|
|
| char |
wchar |
|
|
|
|
| byte |
octet |
|
|
|
|
| short |
short |
|
|
|
|
| int |
long |
|
|
|
|
| long |
long long |
|
|
|
|
| float |
float |
|
|
|
|
| double |
double |
|
|
|
|
|
|
|
|
|
|
| SourceType (X/Open CLI SQL) |
TargetType (Java) |
|
|
|
|
| CHAR |
String |
|
|
|
|
| VARCHAR |
String |
|
|
|
|
| LONGVARCHAR |
String |
|
|
|
|
| NUMERIC |
java.math.BigDecimal |
|
|
|
|
| DECIMAL |
java.math.BigDecimal |
|
|
|
|
| BIT |
boolean |
|
|
|
|
| TINYINT |
byte |
|
|
|
|
| SMALLINT |
short |
|
|
|
|
| INTEGER |
int |
|
|
|
|
| BIGINT |
long |
|
|
|
|
| REAL |
float |
|
|
|
|
| FLOAT |
double |
|
|
|
|
| DOUBLE |
double |
|
|
|
|
| BINARY |
byte[] |
|
|
|
|
| VARBINARY |
byte[] |
|
|
|
|
| LONGVARBINARY |
byte[] |
|
|
|
|
| DATE |
java.sql.Date |
|
|
|
|
| TIME |
java.sql.Time |
|
|
|
|
| TIMESTAMP |
java.sql.Timestamp |
|
|
|
|
Table 19-4 TypeMapping instances mapping Java data types to X/Open CLI SQL data types Table 19-4 TypeMapping instances mapping
Java data types to X/Open CLI SQL data types
SourceType (Java) |
TargetType (X/Open CLI SQL) |
|
|
|
|
|
|
|
|
|
|
| String |
VARCHAR (or LONGVARCHAR) |
|
|
|
|
| java.math.BigDecimal |
NUMERIC |
|
|
|
|
| Boolean |
BIT |
|
|
|
|
| Integer |
INTEGER |
|
|
|
|
| Long |
BIGINT |
|
|
|
|
| Float |
REAL |
|
|
|
|
| Double |
DOUBLE |
|
|
|
|
SourceType (Java) |
TargetType (X/Open CLI SQL) |
|
|
|
|
|
|
|
|
|
|
| byte[] |
VARBINARY (or LONGVARBINARY) |
|
|
|
|
| java.sql.Date |
DATE |
|
|
|
|
| java.sql.Time |
TIME |
|
|
|
|
| java.sql.Timestamp |
TIMESTAMP |
|
|
|
|