Presentation and Deployment

## Deploying and Presenting JavaHelp Helpsets

The JavaHelp system is designed to be deployed in a number of different types of applications and in a variety of different network environments. The following scenarios illustrate some of the different ways that the JavaHelp system can be used to present and deploy information.

### Standalone Application

A standalone Java application runs independently of a web browser. In this scenario the Java application runs locally and accesses help data installed on the same machine.

The application:

1. Requests the creation of a `JavaHelp` instance.
2. Loads the help data in that instance.
3. Presents the requested help topic.

### Network Application

The JavaHelp system enables an application to transparently load help data from networks (intranet and Internet). When the help data is accessed across a network, the scenario is essentially the same as in the standalone scenario - the location of the data is transparent to the application.

The application:

1. Requests the creation of a `JavaHelp` instance
2. Loads the help data from the network
3. Presents the requested help topic

### Embedded Help

Both navigational and content information can be embedded directly in application windows. Embedding is accomplished by adding the JFC components that implement JavaHelp system components directly into the application frame.

In this illustration, the content viewer is embedded along the bottom of the application window, and the navigation viewer is embedded in a different portion of the window.

The application can directly control the contents of the content viewer by programmatic means. Likewise, JavaHelp system navigators can be used to control information displays other than the JavaHelp system content viewer.

### Component Help

Many modern applications are composed of a collection of interacting components. Examples range from large applications like Netscape NavigatorTM (with plugins), to applications where JavaBeans components are connected together using JavaScriptTM or Visual BasicTM.

In the case of JavaBeans, each component can be shipped with its own help data. The following illustrates such a case.

In this case, the help information from the red JavaBean (Bean1) and from the green JavaBean (Bean2) is merged in the help viewer table of contents. The merge operation can be performed by the developer ahead of time, or completed when the application or JavaBeans component is installed by the user.

In version 1 of the JavaHelp software, merging is accomplished by appending TOC and index information and searching merged full-text search databases.

### Help Server

In some environments, it is useful to separate the process that presents the help information from the application. For example:

- Applications that are written in a language other than the Java language (for example, C, C++, Visual Basic) can use the JavaHelp system to display online help when deployed on diverse computing platforms.
- A suite of applications might be installed together or separately. In this case the help server can be used to display help for the entire suite, rather than each of the constituent applications providing their own help system.

In the following scenario, applications not written in the Java language make requests to a JavaHelp system process (help server) through an RPC mechanism (the RPC might be wrapped in a library and be invisible to the application developer).

### Browser-Based Applications (Applets)

Applications that run in browsers have a number of unique deployment issues that the JavaHelp system addresses. The following three scenarios illustrate how the JavaHelp system can be used in three of the most common cases. In the following scenarios an applet or some other triggering entity on an HTML page requests the JavaHelp system to display help information.

#### Applet(1)

In the first scenario, the browser contains a customized implementation of the JavaHelp system and an appropriate version of the JRE (Java Runtime Environment). This JRE might have been delivered with the browser, or it might have been downloaded by the client into the `CLASSPATH`. The implementation can use the JavaHelp system content pane, or it can use the HTML viewer that is part of the web browser.

1. The HTML page that contains the applet tag is loaded into the browser.
2. The applet is downloaded from the server and executed.
3. The user requests help.
4. The applet forwards the request to the JavaHelp system.
5. Help data is downloaded from the server and displayed in the JavaHelp system viewer (or browser window).

#### Applet(2)

In the second scenario, the JavaHelp system classes are downloaded along with the applet. Because the JavaHelp system is an optional package of the Java release, it is possible that a fully compliant JavaTM 2 SDK browser might not have the the JavaHelp system classes in its `CLASSPATH`. In this case the JavaHelp system classes must be downloaded from the server. Since the JavaHelp system is quite small, this approach is often practical. Browsers might provide additional means for installing extensions downloaded through this mechanism.

1. The HTML page that contains the applet tag is loaded into the browser.
2. The applet is downloaded from the server and executed.
3. JavaHelp system classes are downloaded from the server.
4. The user requests help.
5. The applet forwards the request to the JavaHelp system.
6. Help data is downloaded from the server and displayed in the JavaHelp system viewer (or browser window).

#### Applet(3)

The third scenario describes the case in which the applet is downloaded to a browser environment that has neither the appropriate JRE nor the Javahelp system installed.

In this case, the JavaTM Plug-in can be used to download the required JRE and the JavaHelp system standard extension classes. The Java Plug-in allows developers to specify a specific JRE on the HTML page that is required to run their applet. If the correct JRE is not present on the user's system, the Java Plug-in software downloads the correct JRE and installs it on the user's system. The new JRE is subsequently available to any applet that requires it. Because the JavaHelp system is a standard extension to the Java platform, the JavaHelp system classes can be downloaded along with the JRE.

1. The HTML page that contains the applet tag is loaded into the browser
2. The Java Plug-in is downloaded. It prompts user to download appropriate JRE and JavaHelp system classes.
3. JRE and JavaHelp system classes are downloaded from the server.
4. Java Plug-in starts the JRE.
5. The applet is downloaded from the server and executed.
6. The user requests help.
7. The applet forwards the request to the JavaHelp system.
8. Help data is downloaded from the server and displayed in the JavaHelp system viewer (or browser window).

## Server-based JavaHelp Helpsets

By combining the JavaHelp software API with new JavaHelp JSP tag libraries, web developers are now able to provide help for server-based applications that provide HTML pages to a browser. The diagram below illustrates the architecture.

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A browser initiates a JSP request. Examples of a JSP request are displaying the help content in the helpset, the navigators, or the data for a given navigator. Typically, the JSP request contains JavaBeansTM components as well as JSP tag extensions. The JavaTM server turns the request into a Java Servlet. The servlet access the appropriate information from the helpset by using the classes in the JavaHelp library (`jh.jar`) and the JavaHelp tag library (`jhtags.jar`) and returns HTML and possibly JavaScript or dynamic HTML (DHTML) to the browser.

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