Defining interfaces graphically  Importing interfaces from registered ActiveX components

Chapter 5: Defining Component Interfaces

Importing interfaces from compiled Java files

EAServer Manager provides a Java import feature that creates a component definition by reading method definitions from a compiled Java class or interface file (to import a JavaBeans component, you must specify the class that implements the JavaBeans component). The import process creates a corresponding IDL interface in the EAServer interface repository. This feature is primarily used to adapt existing Java classes to be run as Java components within EAServer. However, you can import a Java interface to define a component of any type.


Coding classes, interfaces, and JavaBeans for import

Before using the importer for the first time, you should read this section to understand how Java methods are mapped to EAServer component methods.

Determining eligible methods

Each method in a class or interface (including those inherited from a base class or interface) is inspected to see if they use allowable parameter and return types. Suitable methods are added to the component’s IDL interface. EAServer Manager displays warning dialog boxes describing any methods that are not imported. The importer accepts methods that use the following datatypes:

The method can throw any exception, but only exceptions that extend org.omg.CORBA.UserException are added to the IDL method’s raises clause.

Holders for user-defined classes and arrays For an inout parameter declared as a user-defined class or a single-dimension array, the Java method definition must use a holder class that you have created. For a user-defined class, the template for the holder class is as follows:

package comp-package;
class TypeHolder {
    Type value;
    // Default constructor:
    TypeHolder(); 
    // Initial-value constructor:
    TypeHolder(Type value); 
}

where

For an array, the template for the holder class is as follows:

package comp-package;
class TypenameHolder {
    BaseType value;
    // Default constructor:
    TypenameHolder(); 
    // Initial-value constructor:
    TypnameHolder(BaseType[] value); 
}

where:

Importing Java interfaces

Methods to be imported from a Java interface must adhere to the restrictions described in “Determining eligible methods”. In addition, the interface cannot contain any fields.

You must specify a class that implements the interface before you can run the component. Specify the implementation class name in the Component Properties window (see “Component properties: General”). Make sure that the class has a default constructor (that is, a constructor with no arguments). EAServer calls the default constructor to create new component instances.

Importing Java classes

Methods to be imported from a Java class must adhere to the restrictions described in “Determining eligible methods”. In addition, the class must have a constructor method with zero parameters. Other constructors are not called by EAServer.

NoteClasses that implement the ServerBean interface can be imported. The ServerBean methods are not added to the component’s IDL interface.

Importing JavaBeans components

To import method definitions from a JavaBeans component, you choose the Java Class option on the import screen, then specify the name of the class that implements the component.

Methods to be imported from a JavaBeans component must adhere to the restrictions described in “Determining eligible methods”. In addition, the class must have a constructor method with zero parameters. Other constructors are not imported.

The add and remove methods for the JavaBeans event listeners are not imported.


Importing a Java class or interface in EAServer Manager

StepsImporting a Java class or interface in EAServer Manager

  1. If necessary, create the EAServer package that will contain the component. See “Creating a new package” for details.

  2. Specify the package to install the component in as follows:

    1. Double-click the Packages folder to expand it.

    2. Highlight the package to which the component will be added.

  3. Choose File | New Component from the menu.

  4. In the Component Wizard dialog box, select Import from Java File, and click Next.

  5. Verify that the displayed importer CLASSPATH contains the JAR files and directories required to instantiate the bean’s classes, specifically:

    If necessary, use the Add, Modify, Delete, Move Up, and Move Down buttons in the Component Wizard to modify the CLASSPATH. The displayed CLASSPATH affects only this importer session, not the EAServer process.

  6. Enter the component name in the Import Java Class File dialog box.

  7. Choose the type of file to be imported:

  8. If importing a Java interface, choose the type of component to be defined in the drop-down list.

  9. Browse for the Java class file that contains the class or interface that is being imported.

The importer will read the specified file, define an IDL interface as described below, and define a component that implements the IDL interface.





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