Examples of javax.microedition.content.Registry

javax.microedition.content.Registry
The Registry provides method to invoke, register, unregister, and query information about content handlers. An application registers, for each content handler, zero or more content types, suffixes, and actions. Access to the registry is via the {@link #getRegistry getRegistry}method. The Registry class is thread safe. Applications are responsible for the thread safety of Invocation objects passed as arguments to Registry methods.
Multiple content handlers can be registered for each type, suffix, and action. The types, suffixes, and actions registered for a handler can be used to select a handler. The content handler ID is set during registration and is used to uniquely identify the content handler and to enforce access controls.
A content handler is any application that is registered to handle some content. It responds to requests and displays or acts on the content. Registration can occur dynamically or statically. Static registration occurs during the installation of the application package, while dynamic registration occurs via this API. A content handler may be a Java or a non-Java application. For example, MIDlet suites and Personal Basis Profile applications using the Xlet application model can be content handlers. Refer to the {@link ContentHandler ContentHandler}class for information on registering Java platform content handlers.

When a content handler is processing an invocation, it may be necessary to invoke another content handler before it is able to satisfy the first request. The invocation and chaining of content handlers is managed to maintain the context and sequence across application executions.

The term application is used more generally than the term content handler. The term application is used to refer to the common handling for making requests, handling responses, and querying the content handler registrations. The term content handler is used for an application that registers for types, suffixes, actions, etc. and processes the requests queued to it.

Content Types

A content handler can register a set of types that it can handle. Content types are simple opaque strings that are NOT case sensitive. Type strings are not case sensitive, types that differ only by case are treated as a single type.

Suffix Processing

A content handler can register a set of suffixes that identify from the syntax of a URL the content it can handle. Suffixes are NOT case sensitive.

Content Handler Actions

Each content handler may register a set of actions it supports. The set of actions is extensible but applications should choose from the actions defined in the {@link ContentHandler} class when they are appropriate. The predefined actions are: {@link ContentHandler#ACTION_OPEN open}, {@link ContentHandler#ACTION_EDIT edit}, {@link ContentHandler#ACTION_NEW new}, {@link ContentHandler#ACTION_SEND send}, {@link ContentHandler#ACTION_SAVE save}, {@link ContentHandler#ACTION_EXECUTE execute}, {@link ContentHandler#ACTION_SELECT select}, {@link ContentHandler#ACTION_INSTALL install}, {@link ContentHandler#ACTION_PRINT print}, and {@link ContentHandler#ACTION_STOP stop}.
Content Handler IDs

The content handler ID is a string chosen by the application vendor to identify the content handler. The ID registered by a content handler MUST be unique and MUST NOT match the prefix of any other registered content handler. IDs are case sensitive and are treated as opaque strings. They are compared for equality or as prefixes of IDs when used to locate an appropriate content handler.

Content handler IDs should follow the form of fully qualified Java class names or any naming syntax that provides a natural way to disambiguate between vendors. For example, IDs may be URLs including scheme, authority (server), and path information.

For example, if registered in the order below, the following content handler IDs would be valid or invalid as indicated because there is an ambiguity due to prefix comparisons.
1. com.sun.applications.calc - valid
2. com.sun.applications.trig - valid
3. com.sun.application - invalid, this is the prefix of the calc ID
4. com.sun.applications.calc.decimal - invalid, the calc ID is prefix of decimal
Java Application Class

The content handler to be launched is identified by the application class. The class MUST contain entry point(s) and be packaged according to the Java runtime environment. For MIDP, the application class MUST extend javax.microedition.midlet.MIDlet. The application class uniquely identifies a content handler within the application package, which is usually a JAR file. Each application class can only be registered to a single content handler. Registering a content handler for a class will replace any content handler previously registered to that class.
Content Handler Authentication
Applications and content handlers using the API may, for security purposes, need or want to authenticate the invoked content handler or the invoking application. The CHAPI implementation cooperates with the application management software to authenticate the applications (if possible) and pass the authentication information to the application. If the application can be authenticated, then the {@link ContentHandler#getAuthority ContentHandler.getAuthority}method will return the authority used in the authentication.
While processing an invocation request the content handler can use the {@link Invocation#getInvokingAuthority Invocation.getInvokingAuthority} method to verify the authenticity of the invoking application.

Content Handler Access Control
The visibility and accessibility of a content handler can be controlled by the content handler itself either through dynamic or static registration. To restrict access and visibility, the content handler MUST provide the IDs of the content handlers that MUST be allowed access. If any of the allowed IDs match the beginning of the ID of the content handler requesting access, then the application will be granted visibility and access to the content handler. The comparison is performed as if the java.lang.string.startsWith method was used. The access controls are only visible to the content handler itself using the method {@link ContentHandlerServer#getAccessAllowed ContentHandlerServer.getAccessAllowed}. By default, access is allowed to all applications and content handlers. Access restrictions are established when the content handler is registered with the {@link #register register} method.
Dynamic Registration

Dynamic registration is performed by initializing the classname, types, suffixes, actions, action names, ID, and access restrictions, and passing them to the {@link #register register} method.The {@link #unregister unregister} method removesa registered content handler.
The current registrations can be examined by using various methods to get the {@link #getTypes types}, {@link #getIDs IDs}, {@link #getSuffixes suffixes}, {@link #getActions actions}, or to find a content handler by content handler {@link #getServer classname}, or to get all of the matching content handlers by {@link #forID ID}, by {@link #forType content type}, by {@link #forSuffix suffix}, or by {@link #forAction action}. Only content handlers that are accessible and visible to the application will be returned.
Invoking a Content Handler

To invoke a content handler, an application initializes an Invocation instance with the information needed to identify the content and/or the content handler. Typically this could include the URL, type, action, and content handler ID. The application may also supply arguments and data, and set whether a response is required. The application may request information about the content and the content handler that will process it before invocation. Calling the {@link Registry#invoke Registry.invoke} methodstarts the request.
When invoked, the ID, type, URL, and action are used to identify a target content handler. If multiple content handlers are registered for the ID, type, suffixes or action, the implementation can decide which to use to satisfy the request. If the application needs to select which handler to use, the {@link Registry#findHandler findHandler} method willreturn the set of matching ContentHandlers. The application can choose from the content handlers returned and use {@link Invocation#setID Invocation.setID}to select a specific handler.
In a runtime environment in which only a single application can run at a time, the invoking application must exit before the content handler can be started to handle the request. Invocation requests are queued so that the invoking application and the content handler can be run sequentially in resource-constrained environments. The return value of {@link Registry#invoke invoke}is true to indicate that the application must exit. This allows the invoking application to save the users context and leave the user interface, if any, with some visual that the user will see until the content handler is ready.

Invocation processing involves the invoking application, the invoked content handler, and the application management software (AMS). The implementation of the API and the AMS MUST implement the queuing of invocations to the appropriate content handler and the necessary interactions with the lifecycle to start and restart applications and content handlers.
The {@link Registry#invoke invoke} methods initiate the request.The URL, type, action, and ID, as described above, are used to dispatch the request to an appropriate content handler. If the content handler is not running, it MUST be started to process the request. If the content handler is already running, then the new request MUST be queued to the content handler. Only a single instance of each content handler application can be active at a time. The {@link ContentHandlerServer} class is used to dequeue and processrequests.

        final String[] actionNames = { "Send to demo app" };
        final ActionNameMap[] actionNameMaps =
                { new ActionNameMap(actions, actionNames, "en") };


        // Get access to the registry
        final Registry registry = Registry.getRegistry(CLASSNAME);


        try {
            // Register as a content handler
            registry.register(CLASSNAME, types, suffixes, actions,
                    actionNameMaps, ID, null);
        } catch (final ContentHandlerException che) {
            System.out.println("Registry#register() threw " + che.toString());
        } catch (final ClassNotFoundException cnfe) {
            System.out.println("Registry#register() threw " + cnfe.toString());

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            final String[] accessAllowed, String handlerName,
            final RequestListener requestListener)
            throws ContentHandlerException, ClassNotFoundException {


        // Get access to the registry and register as a content handler
        final Registry registry = Registry.getRegistry(classname);


        registry.register(classname, types, suffixes, actions, null, id, null);


        // When this content handler gets requests,
        // invocationRequestNotify() will be called
        final ContentHandlerServer contentHandlerServer =
                Registry.getServer(classname);

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        final ContentHandlerServer contentHandlerServer =
                Registry.getServer(classname);
        contentHandlerServer.setListener(null);


        final Registry registry = Registry.getRegistry(classname);
        registry.unregister(classname);
    }

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        }


        int invocationStatus = invoc.getStatus();


        try {
            final Registry registry =
                    Registry.getRegistry(getClass().getName());
            final DefaultContentHandlerRegistry defaultRegistry =
                    DefaultContentHandlerRegistry
                            .getDefaultContentHandlerRegistry(registry);
            final ApplicationDescriptor descriptor =

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Examples of javax.microedition.content.Registry

Content Types

Suffix Processing

Content Handler Actions

Content Handler IDs

Java Application Class

Content Handler Authentication

Content Handler Access Control

Dynamic Registration

Invoking a Content Handler

Related Classes of javax.microedition.content.Registry