Emitting Client and Server Bindings¶

To generate Java bindings for an IDL file named My.idl:

idlj My.idl

This generates the client-side bindings and is equivalent to:

idlj -fclient My.idl

The client-side bindings do not include the server-side skeleton. If you want to generate the server-side bindings for the interfaces:

idlj -fserver My.idl

Server-side bindings include the client-side bindings plus the skeleton, all of which are POA (that is, Inheritance Model) classes. If you want to generate both client and server-side bindings, use one of the following (equivalent) commands:

idlj -fclient -fserver My.idl
idlj -fall My.idl

There are two possible server-side models: the Inheritance Model and the Tie Delegation Model.

The default server-side model is the Portable Servant Inheritance Model. Given an interface My defined in My.idl, the file MyPOA.java is generated. You must provide the implementation for My and it must inherit from MyPOA.

MyPOA.java is a stream-based skeleton that extends org.omg.PortableServer.Servant @
http://docs.oracle.com/javase/7/docs/api/org/omg/PortableServer/Servant.html and implements the InvokeHandler interface and the operations interface associated with the IDL interface the skeleton implements.

The PortableServer module for the Portable Object Adapter (POA) @
http://docs.oracle.com/javase/7/docs/technotes/guides/idl/POA.html defines the native Servant type. In the Java programming language, the Servant type is mapped to the Java org.omg.PortableServer.Servant class. It serves as the base class for all POA servant implementations and provides a number of methods that may be invoked by the application programmer, as well as methods which are invoked by the POA itself and may be overridden by the user to control aspects of servant behavior.

Another option for the Inheritance Model is to use the -oldImplBase flag in order to generate server-side bindings that are compatible with versions of the Java programming language prior to J2SE 1.4. Note that using the -oldImplBase flag is non-standard: these APIs are being deprecated. You would use this flag ONLY for compatibility with existing servers written in J2SE 1.3. In that case, you would need to modify an existing MAKEFILE to add the -oldImplBase flag to the idlj compiler, otherwise POA-based server-side mappings will be generated. To generate server-side bindings that are backwards compatible:

idlj -fclient -fserver -oldImplBase My.idl
idlj -fall -oldImplBase My.idl

Given an interface My defined in My.idl, the file _MyImplBase.java is generated. You must provide the implementation for My and it must inherit from _MyImplBase.

The other server-side model is called the Tie Model. This is a delegation model. Because it is not possible to generate ties and skeletons at the same time, they must be generated separately. The following commands generate the bindings for the Tie Model:

idlj -fall My.idl
idlj -fallTIE My.idl

For the interface My, the second command generates MyPOATie.java. The constructor to MyPOATie takes a delegate. In this example, using the default POA model, the constructor also needs a poa. You must provide the implementation for delegate, but it does not have to inherit from any other class, only the interface MyOperations. But to use it with the ORB, you must wrap your implementation within MyPOATie. For instance:

    ORB orb = ORB.init(args, System.getProperties());


    // Get reference to rootpoa & activate the POAManager


    POA rootpoa = (POA)orb.resolve_initial_references("RootPOA");


    rootpoa.the_POAManager().activate();


    // create servant and register it with the ORB


    MyServant myDelegate = new MyServant();


    myDelegate.setORB(orb); 


    // create a tie, with servant being the delegate.


    MyPOATie tie = new MyPOATie(myDelegate, rootpoa);


    // obtain the objectRef for the tie


    My ref = tie._this(orb);

You might want to use the Tie model instead of the typical Inheritance model if your implementation must inherit from some other implementation. Java allows any number of interface inheritance, but there is only one slot for class inheritance. If you use the inheritance model, that slot is used up . By using the Tie Model, that slot is freed up for your own use. The drawback is that it introduces a level of indirection: one extra method call occurs when invoking a method.

To generate server-side, Tie model bindings that are compatible with versions of the IDL to Java language mapping in versions prior to J2SE 1.4.

idlj -oldImplBase -fall My.idl
idlj -oldImplBase -fallTIE My.idl

For the interface My, this will generate My_Tie.java. The constructor to My_Tie takes a impl. You must provide the implementation for impl, but it does not have to inherit from any other class, only the interface HelloOperations. But to use it with the ORB, you must wrap your implementation within My_Tie. For instance:

    ORB orb = ORB.init(args, System.getProperties());


    // create servant and register it with the ORB


    MyServant myDelegate = new MyServant();


    myDelegate.setORB(orb); 


    // create a tie, with servant being the delegate.


    MyPOATie tie = new MyPOATie(myDelegate);


    // obtain the objectRef for the tie


    My ref = tie._this(orb);

Specifying Alternate Locations for Emitted Files¶

If you want to direct the emitted files to a directory other than the current directory, invoke the compiler as:

idlj -td /altdir My.idl

For the interface My, the bindings will be emitted to /altdir/My.java, etc., instead of ./My.java.

Specifying Alternate Locations for Include Files¶

If My.idl included another idl file, MyOther.idl, the compiler assumes that MyOther.idl resides in the local directory. If it resides in /includes, for example, then you would invoke the compiler with the following command:

idlj -i /includes My.idl

If My.idl also included Another.idl that resided in /moreIncludes, for example, then you would invoke the compiler with the following command:

idlj -i /includes -i /moreIncludes My.idl

Since this form of include can become irritatingly long, another means of indicating to the compiler where to search for included files is provided. This technique is similar to the idea of an environment variable. Create a file named idl.config in a directory that is listed in your CLASSPATH. Inside of idl.config, provide a line with the following form:

includes=/includes;/moreIncludes

The compiler will find this file and read in the includes list. Note that in this example the separator character between the two directories is a semicolon (;). This separator character is platform dependent. On the Windows platform, use a semicolon, on the Unix platform, use a colon, etc. For more information on includes, see the Setting the Classpath @
http://docs.oracle.com/javase/7/docs/technotes/tools/index.html#general.

Emitting Bindings for Include Files¶

By default, only those interfaces, structs, etc, that are defined in the idl file on the command line have Java bindings generated for them. The types defined in included files are not generated. For example, assume the following two idl files:

My.idl

#include <MyOther.idl>
interface My
{
};

MyOther.idl

interface MyOther
{
};

The following command will only generate the java bindings for My:

idlj My.idl

To generate all of the types in My.idl and all of the types in the files that My.idl includes (in this example, MyOther.idl), use the following command:

idlj -emitAll My.idl

There is a caveat to the default rule. #include statements which appear at global scope are treated as described. These #include statements can be thought of as import statements. #include statements which appear within some enclosing scope are treated as true #include statements, meaning that the code within the included file is treated as if it appeared in the original file and, therefore, Java bindings are emitted for it. Here is an example:

My.idl

#include <MyOther.idl>
interface My
{


  #include <Embedded.idl>
};

MyOther.idl

interface MyOther
{
};

Embedded.idl

enum E {one, two, three};

Running the following command:

idlj My.idl

will generate the following list of Java files:

Notice that MyOther.java was not generated because it is defined in an import-like #include. But E.java was generated because it was defined in a true #include. Also notice that since Embedded.idl was included within the scope of the interface My, it appears within the scope of My (that is,in MyPackage).

If the -emitAll flag had been used in the previous example, then all types in all included files would be emitted.

Inserting Package Prefixes¶

Suppose that you work for a company named ABC that has constructed the following IDL file:

Widgets.idl

module Widgets
{


  interface W1 {...};


  interface W2 {...};
};

Running this file through the IDL-to-Java compiler will place the Java bindings for W1 and W2 within the package Widgets. But there is an industry convention that states that a company's packages should reside within a package named com.<company name>. The Widgets package is not good enough. To follow convention, it should be com.abc.Widgets. To place this package prefix onto the Widgets module, execute the following:

idlj -pkgPrefix Widgets com.abc Widgets.idl

If you have an IDL file which includes Widgets.idl, the -pkgPrefix flag must appear in that command also. If it does not, then your IDL file will be looking for a Widgets package rather than a com.abc.Widgets package.

If you have a number of these packages that require prefixes, it might be easier to place them into the idl.config file described above. Each package prefix line should be of the form:

PkgPrefix.<type>=<prefix>

So the line for the above example would be:

PkgPrefix.Widgets=com.abc

The use of this option does not affect the Repository ID.

Defining Symbols Before Compilation¶

You may need to define a symbol for compilation that is not defined within the IDL file, perhaps to include debugging code in the bindings. The command

idlj -d MYDEF My.idl

is the equivalent of putting the line #define MYDEF inside My.idl.

Preserving Pre-Existing Bindings¶

If the Java binding files already exist, the -keep flag will keep the compiler from overwriting them. The default is to generate all files without considering if they already exist. If you've customized those files (which you should not do unless you are very comfortable with their contents), then the -keep option is very useful. The command

idlj -keep My.idl

emits all client-side bindings that do not already exist.

Viewing Progress of Compilation¶

The IDL-to-Java compiler will generate status messages as it progresses through its phases of execution. Use the -v option to activate this "verbose" mode:

idlj -v My.idl

By default the compiler does not operate in verbose mode.

Displaying Version Information¶

To display the build version of the IDL-to-Java compiler, specify the -version option on the command-line:

idlj -version

Version information also appears within the bindings generated by the compiler. Any additional options appearing on the command-line are ignored.