The Product Tree
The product tree is a set of objects used to describe a specific product. This product description consists of content as well as behavior. The product tree is responsible for the installation and removal of software. The product tree is tied in to the wizard through the use of a ProductTask Task object that is added to the install Sequence.A product is a set of components. For example, a simple product may have two components: Software and Documentation. The Software component might consist of one or more files (ignoring for the moment the install mechanism for the content of the component) that comprise the portion of the product that the user would execute. The Documentation component might consist of one or more files that comprise the information describing the product and its operation. It is conceivable that the user of this installer might want the Software and Documentation components installed, only the Software component installed, or only the Documentation component installed.
The product tree for this simple product must be able to express the arrangement of the files comprising the Software component as a single element of install. The leaves of the product tree are responsible for software installation and removal. The nodes (non-leaf objects) within the tree provide a structure to the product tree that describes the components within the product.
A product tree that describes the simple product example outlined above could be constructed in the following way:
The leaves of the product tree are responsible for installing and removing files. The objects representing the leaves of the product trees are called Units. The specific Unit class used must correspond to the install mechanism that will be used to lay down the bits.
For example, the correct mechanism to install bits on the Solaris operating system is the command pkgadd. Within the com.sun.install.products package, there is a PkgUnit class that performs a pkgadd command to install software from an SVR4 package, and performs a pkgrm command to remove the software at uninstall time.
On operating systems that do not use SVR4 packages (for example, Microsoft Windows), files are simply moved onto the file system and registered in the Registry. FileUnit is the class that handles this sort of installation.
Dependencies Within the Product Tree
As described in the previous section, nodes within the product tree are used to group Unit objects into components. Nodes can also be used to omit product components from the installation.A product that supports more than one platform may have components or files within a specific component that should not be installed on all platforms. For example, a product supporting the Solaris operating system both for the Sparc and Intel platforms should not install the Sparc-specific files or components if the installer is running on an Intel platform. This is an example of a dependency within the product tree. Parts of this example product tree depend on the platform on which the installer is executed.
PlatformDependency is a subclass of InstallNode that only allows its child components or leaves to be installed if a platform condition is met. This platform condition is specified within the wizard builder that creates the install archive.
The simple example presented earlier will be expanded on to demonstrate the use of the PlatformDependency class. The product being installed works on both Solaris Sparc and Solaris Intel platforms. This dual platform support is achieved through a duplication of binary files. One set of binary files works on Solaris Sparc; the other set works on Solaris Intel. There are two ways in which this dependency could be expressed within the product tree.
The first expression of the platform dependency example assumes that the binaries that are platform-specific comprise the set of files within the Software component. In this case, we might create two components which install the Software binaries, as shown in the following diagram:
The second expression of the platform dependency example considers that there may be some unneccessary duplication between the Software component for Solaris-Sparc and the Software component for Solaris-Intel. This duplication may include configuration files, images, audio clips, or other files that work on both platforms. The executables and shared libraries are the parts of the Software component that the dependency should affect. This will result in only one Software component that consists of leaves for the specific platforms, and a common unit with contents that work on both platforms. Following is a diagram that demonstrates this strategy.
The platform dependency is only one example in which sections of the product tree should be omitted. Other dependencies are possible. Dependency classes can be created to key off almost any attribute of the runtime environment by subclassing InstallNode and overriding the updateDependency method.
Install Client Tree
The install client tree defines the set of panels the user experiences during a product installation. Though the developer of an install wizard is free to define any client tree with the Web Start SDK, developers are encouraged to use the client tree designed with the SDK.The install client tree described in this section is the one demonstrated in the SampleBuilder. This client tree makes installation easier by not requiring the user to enter any information if the default settings are acceptable. This suits the needs of novice users, by not requiring them to manipulate (or even see) every setting in order to install the software. For the advanced user, the install client tree presents additional panels to allow the user more control over the installation.
The install client tree consists of an ordered arrangement of nodes and panels that are designed to guide the user through a product installation.
The following diagram depicts the install client tree:
