2010 年就快結束了，12 月到目前為止只寫了一篇，不及格。這原因又是說來話長，還是不說了，藉口講太多 Teddy 都有點心虛了。聽說一般的公司年底都有所謂的『作帳行情』，就算是業績不好看也要想辦法在帳面上動點手腳，粉飾一下太平。以上所說，正是 Teddy 接下來要做的事情。
前一陣子 Teddy 和指導教授寫了一篇關於持續整合的論文，想想 Teddy 也有好一陣子沒談這個主題了，所以就拿點論文中的內容來充數一下，讓本月篇數帳面上不要太難看。這篇論文的題目叫做：
Emerging Patterns of Continuous Integration for Cross-Platform Software Development
這篇論文一共提到 11 個關於跨平台軟體開發的持續整合樣式，其中有兩個樣式有列出詳細的內容，其餘的以 problem-solution 的簡短形式呈現。今天先看兩個詳細樣式中的第一個：Installation Project.
Installation Project
Context: Traditionally, the deployment of a software product is considered at the very late stage of the software development, usually before release. For a project that applies incremental and iterative processes as well as continues integration, working software is expected to be ready at the end of iteration. The working software may be deployed internally for testing and for demonstration. It may also be deployed on the customer site for trial use. Since multiple target platforms are involved in a cross-platform software product, the deployment task is made much more difficult.
Problem: How to provide an easy-to-use and robust method for users to deploy a cross-platform software product?
Forces:
- A software product can fail to attract users if it cannot be easily installed.
- Different operating systems have their own flavors in installation modes, ranging from text-based to GUI-based modes and using different formats such as the Microsoft MSI and the RedHat RPM.
- You want to simplify the installation procedures and minimize possible deployment problems.
Solution: At an early stage of software development, create an installation project to produce an installer for the cross-platform application under development. Add the project to your CI system. When the CI system builds the installation project either automatically or by request, an installer is produced. Release software at the end of iteration has become a norm for projects applying incremental and iterative development. Thus, it is reasonable to consider the installation problem at the early stage of a product development so that running software can be provided via the installer. Once the installation project can produce an installer, find a way to automate the testing of the installer on all supported operating systems.
Many commercial and open source tools are available for creating installation programs. Some of them support the creation of cross-platform installers while the others are platform-specific. An example of the former category is InstallAnywhere. By using InstallAnywhere, an Installation Project can produce multiple installers for multiple platforms. For example, InstallAnywhere can produce .exe installers for Windows platforms and .bin installers for Linux-based platforms. The installers can be configured in a way that they run in the GUI mode on Windows platforms and in the text mode on Linux-based platforms. InstallAnywhere also supports a silent installation mode. When an installer is run in the silent mode, users need not (and cannot) to interact with the installer to modify the default behavior of the installer (e.g., to change the installation folder). Instead, the installer accepts a pre-defined configuration file that contains all necessary settings to guide the installer.
Developers can also use platform-specific tools to produce platform-specific installers. For example, InstallShield is a popular tool that prodcues .msi installers for the Windows platforms. For Linux-based systems such as RedHat and Ubuntu, tools to package .rpm and .deb modules are used.
It is also possible to package a cross-platform product as the so-called green software, portable applications, or portable software if the product does not contain low-level native drivers which must be installed in a specific location and does not require the systems to reboot. Green software does not require a sophisticated installation procedure. To use the software, merely copy the software (usually an executable file or a folder) or unzip it to a hard disk or flash disk.
Resulting Context: Using sophisticated tools like InstallAnywhere is very convenient to produce cross-platform installers. However, such a tool is usually very expensive. Also, the produced installers may be larger in size than those produced by platform-specific installation tools. Sophisticated installation tools that support complicated scripts and customization functions produce flexible installers, but can lead developers to experience a sharp learning curve and consequently put off the creation of an Installation Project.
Installation Projects produce installers to deploy a software product from scratch. To install a new version of the software with the installers, the old one usually needs to be uninstalled first and then the new one can be installed. If only a minor part of the product is revised, using Installation Projects to produce an installer to upgrade the software may be taxing. In this situation, use a Patch Project instead.
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友藏內心獨白：為什麼領錢的都是學弟而寫 paper 的都是『老』學長和老師？
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