Chapter 11: Creating CORBA Java Components

Choose implementation datatypes

EAServer provides two component types for Java components. These component types are functionally equivalent, except that they use different mappings between IDL datatypes and the Java datatypes that are required in your implementation class. The choices are:

Java with IDL datatypes The component’s method declarations use the type mappings that are specified by the CORBA document, IDL to Java Language Mapping Specification (formal/99-07-53). To use these type mappings, specify Java - CORBA as the component type in the EAServer Manager Component Properties dialog box.
Java with JDBC datatypes Predefined EAServer datatypes and IDL base types are mapped to types in the java.lang and java.sql packages. User-defined exceptions are not supported. User-defined IDL parameter and return types are mapped to Java datatypes using the standard CORBA IDL-to-Java mappings. Components that were developed for some earlier EAServer versions may use these type mappings. Components that throw com.sybase.jaguar.util.JException must use these mappings. To use these type mappings, specify Java - JDBC as the component type in the EAServer Manager Component Properties dialog box.

Use IDL types for new development Java-JDBC type mappings are supported to provide backward compatibility with earlier EAServer versions. For new development, use the Java-CORBA types. Components using Java-JDBC type mappings cannot raise user-defined IDL exceptions; all exceptions must be thrown as the generic jaguar.util.JException class. If you import a Java class that uses jaguar.util.JException, the importer generates a Java-JDBC component.

The sections below describe the mappings in detail.

Java - CORBA component datatype mappings

The following table lists the datatypes displayed in EAServer Manager, the equivalent CORBA IDL types, and the Java datatypes used in Java/IDL component methods.

**Table 11-1: EAServer Manager, CORBA IDL, and Java datatype equivalence**
EAServer Manager display datatype	CORBA IDL type	Java type (input parameter or return value)	Java type (inout or out parameter)
integer<16>	short	short	org.omg.CORBA.ShortHolder
integer<32>	long	int	org.omg.CORBA.IntHolder
integer<64>	long long	long	org.omg.CORBA.LongHolder
float	float	float	org.omg.CORBA.FloatHolder
double	double	double	org.omg.CORBA.DoubleHolder
boolean	boolean	boolean	org.omg.CORBA.BooleanHolder
char	char	char	org.omg.CORBA.CharHolder
byte	octet	byte	org.omg.CORBA.ByteHolder
string	string	java.lang.String	org.omg.CORBA.StringHolder
binary	BCD::Binary	byte[]	BCD.Binary
decimal	BCD::Decimal	BCD.Decimal	BCD.DecimalHolder
money	BCD::Money	BCD.Money	BCD.MoneyHolder
date	MJD::Date	MJD.Date	MJD.DateHolder
time	MJD::Time	MJD.Time	MJD.TimeHolder
timestamp	MJD::Timestamp	MJD.Timestamp	MJD.TimestampHolder
ResultSet	TabularResults:: ResultSet	TabularResults.ResultSet	TabularResults.ResultSetHolder
ResultSets	TabularResults:: ResultSets	TabularResults.ResultSet[ ]	TabularResults.ResultSetsHolder

Binary, Fixed-Point, and Date/Time types The BCD and MJD IDL modules define types to represent common database column types such as binary data, fixed-point numeric data, dates, times. The BCD::Binary CORBA type maps to a Java byte array. The other BCD and MJD types map to data representations that are optimized for network transport.

To convert between the IDL-mapped datatypes and from core java.* classes, use these classes from the com.sybase.CORBA.jdbc11 package:

Class	Description
SQL	Contains methods to convert from BCD.* and MJD.* types to java.* types
IDL	Contains methods to convert from java.* types to BCD.* and MJD.* types

Chapter 1, “Java Classes and Interfaces,” in the EAServer API Reference provides reference pages for these classes.

Result set types The TabularResults IDL module defines types used to represent tabular data. Result sets are typically used only as return types, though you can pass them as parameters.

“Return result sets” describes how to create and return result sets.

User-defined IDL types A user-defined type is any type that is:

Not in the set of datatypes that is not predefined by EAServer’s read-only repository modules and
Not one of the CORBA IDL base types.

If a method definition includes user-defined types, the Java component method will use the equivalent Java datatype as specified by the CORBA Java language mappings specification. See “Overview” for more information on this document.

CORBA Any and TypeCode support EAServer’s Java ORB supports the CORBA Any and TypeCode datatypes. Refer to the OMG CORBA 2.3 specification and IDL to Java Language Mapping Specification (formal/99-07-53) for information on using these types.

Holder classes for IDL types All IDL-mapped Java types have an accompanying holder class that is used for passing parameters by reference. Each holder class has the following structure:

public class <Type>Holder {
    // Current value
    public <type> value;
    // Default constructor
    public <Type>Holder() {}
    // Constructor that sets initial value
    public <Type>Holder(<type> v) {
      this.value = v;
    }
}

This structure is defined by the CORBA Java-language bindings specification.

Java - JDBC component datatype mappings

Java-JDBC type mappings are supported to provide backward compatibility with earlier EAServer versions. For new development, use the Java-CORBA types. Components using Java-JDBC type mappings cannot raise user-defined IDL exceptions; all exceptions must be thrown as the generic jaguar.util.JException class.

The table below shows the datatypes displayed in the EAServer Manager, the datatypes used by Java components, and the argument modes (in, inout, out for parameter passing modes and return to indicate the type is used for method return values).

inout and out parameters for these datatypes are passed in holder classes from the com.sybase.jaguar.util and com.sybase.CORBA.jdbc11 packages. For more information on these packages, see the reference pages in Chapter 1, “Java Classes and Interfaces,” in the EAServer API Reference.

**Table 11-2: Java - JDBC component datatype mappings**
EAServer Manager datatype	IDL type	Mode	Java type
boolean	boolean	input, return inout, out	boolean BooleanHolder
binary	BCD::Binary	input, return inout, out	byte[ ] BytesHolder
byte	octet	input inout, out	byte ByteHolder
date	MJD::Date	input, return inout, out	java.sql.Date com.sybase.jaguar.util.jdbc11.DateHolder
decimal	BCD::Decimal	input, return inout, out	java.math.BigDecimal com.sybase.jaguar.util.jdbc11.BigDecimalHolder
double	double	input, return inout, out	double DoubleHolder
float	float	input, return inout, out	float FloatHolder
integer<16>	short	input, return inout, out	short ShortHolder
integer<32>	long	input, return inout, out	int IntegerHolder
integer<64>	long long	input, return inout, out	long LongHolder
money	BCD::Money	input, return inout, out	java.math.BigDecimal com.sybase.jaguar.util.jdbc11.BigDecimalHolder
string	string	input, return inout, out	java.lang.String StringHolder
time	MJD::Time	input, return inout, out	java.sql.Time com.sybase.jaguar.util.jdbc11.TimeHolder
timestamp	MJD:: Timestamp	input, return inout, out	java.sql.Timestamp com.sybase.jaguar.util.jdbc11.TimestampHolder

User-defined IDL types in a method declaration are mapped to the same Java classes as for a Java/IDL component. See “User-defined IDL types” for more information.

Methods in a Java-JDBC component do not return result sets explicitly. If the IDL method definition indicates a result set or result sets are returned, the Java method must be declared to return void, and the implementation must use the EAServer JServerResultSet and JServerResultSetMetaData interfaces to send result sets back to the client.

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