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-Version 0.5 (2000/04/20)
-This document specifies the behavior of Ant. At this time, this is a - working document with no implementation. It is hoped that this specification - will lead to a simplier and more consistent implementation of Ant.
-This document is not intended to be used as an end user manual or user - guide to Ant. To adequatly explain the concepts herein in a way appropriate to - such a use would potentially complicate this document.
-The following are the overall design goals of Ant:
-Ant must be simple to use. Of course, as the definition of simple varies - according to the audience of the program. For Ant, since it is a build tool - aimed at programmers, the goal is to be simple to use for a competent - programmer.
-Ant must be clearly understandible for a first time as well as a veteran - user. This means that a new user should be able to use Ant comfortably the - first time and understand how to modify a build file by looking at it. And it - should not require much experience with Ant to understand how it works and how - to configure it for particular situtations.
-Ant must be easy to extend. The API used to extend Ant must be easy to - use and the way in which these extensions are located and used by the core - runtime should be clear.
-This is a conceptual overview of the components used by Ant. Full APIs - will be defined later.
-The base unit of work in Ant is the Project. A Project
- is defined by an editable text file and is represented by an object of type
- org.apache.ant.Project
at runtime.
A Project is a collection of Properties and - Targets.
-Properties are mutable name-value pairs that are scoped to the Project
- and held in a table. Only one pair is allowed per name. It is anticipated that
- this data structure would be of type java.util.Properties
or a type that has approximatly
- the same contract.
Properties can be defined in a hierarchical manner. The order of - precidence in this hiearchy is:
-user.home
directoryNote: The current version of Ant allows the System property list to be
- consulted for a return value if the property list doesn't satisfy the requested
- property name. As all Java code has access to the system property list via the
- java.lang.System
class, this functionality is considered to be confusing and to be
- removed.
Note: The current version of Ant allows property substitution to be - performed in the project file. This functionality is being removed.
-Targets are ordered collections of Tasks, units of work - to be performed if a Target is executed.
-Targets can define dependancies on other Targets within the Project. If - a Target is deemed to be executed, either directly on the command line, or via - a dependancy from some other Target, then all of its dependencies must first be - executed. Circular depenancies are resolved by examination of the dependancy - stack when a Target is evaluated. If a dependancy is already on the stack of - targets to be executed, then the dependancy is considered to have been - satisfied.
-After all dependancies of a Target have been satisfied, all of the Tasks - contained by the target are configured and executed in sequential order.
-A Task is a unit of work. When a Task is to be executed, an instance of
- the class that defines the behavior of the particular task specified is
- instantiated and then configured. This class implements the org.apache.ant.Task
interface.
- It is then executed so that it may be able to perform its function. It is
- important to note that this configuration occurs just before execution of the
- task, and after execution of any previous tasks, so that configuration
- information that was modified by any other Task can be properly set.
When a Task is executed, it is provided access to the object - representing the Project it is running in allowing it to examine the Property - list of the project and access to various methods needed to operate.
-Tasks are defined within Java Archive files. The name of the JAR
- determines the name under which the task is known by in the system. For
- example, if a Task JAR is named mvdir.jar, the task is known to the system as
- "mvdir"
.
Question: Should we say that tasks belong in a JAR file with the - .tsk extension?
-The class within the Jar file that implements the org.apache.ant.Task
interface is
- specified by a manifest attribute named Ant-Task-Class
in the Jar manifest. An example
- manifest would look like:
Manifest-Version: 1.0 - Ant-Task-Class: org.apache.ant.task.javac.JavacTask-
When the task is used by Ant, a class loader is created that reads - classes from the JAR file. This ensures that there is no chance of namespace - collision in the classes of various task JAR files.
-When Ant is installed on a user system, it installs a directory - structure with the following form:
-<installdir>/ant (unix shell script) - /ant.bat - /ant.jar - /ant.properties - /tasks/[task jar files] - /docs/[documentation] - /README-
Note: Current Jakarta practice is to name the Unix shell script with a - .sh extension. This goes against Unix conventions and is unecessary. Testing - has shown that the leaving the extension off on Unix will not interfere with - the working of the Windows batch file.
-Note: The ant.jar file has been moved from the lib/ directory and placed - alongside the shell startup scripts (which have also been moved out of the bin/ - directory). This is because on windows platforms, the .jar file is an - executable file of sorts.
-The ant.properties
file contains a list of all the properties that should be
- set by default when ant is run. In addition there are a few special properties
- that are used directly by ant. An example of these properties in use is:
system.taskdir=tasks/ - user.taskdir=anttasks/-
The system.taskdir
property sets where the system looks for Java ARchive files
- containing tasks. If this property defines a relative path, then the path is
- taken as relative from the installation directory.
The user.taskdir
property defines where users can locate Java Archive files
- containing tasks. If this property defines a realtive path, then the path is
- taken as relative from the users home directory (as defined by the user.home
- system property). Task JAR files in this directory take precendence of those in
- the system directory.
Note: It has been suggested to add a properties file hook to the - command line to roll in props. Pending investigation.
-In addition to the Ant installation directory, an ant.properties
file can be
- located in the user's home directory (as found by the system property user.home
)
- which can define user preferences such as the location of a user tasks
- directory. Properties defined in this file take precidence over those set in
- the installation's ant.properties
file. Such a file could look like:
user.taskdir=anttasks/ - javac.debug=off-
Properties starting with "system."
in the user's ant.properties
file are not
- allowed and must cause a warning to be thrown.
Ant's Project text file is structured using XML and reflects the - structure of the various components described in the Conceptual Overview.
-A sample Project file:
-<project name="projectname" defaulttarget="main" taskdir="tasks/"> - <property name="javac.debug" value="on"/> - <target name="main"> - <taskimpl ...> - ... - </taskimpl> - </target> -</project>-
The project
element has the following required attributes:
defaulttarget
defining the default target to be executed if no other target
- is specified when Ant is runIt also has the following optional allowed attributes:
-name
defining a name for this projecttaskdir
defining a directory in which project specific tasks can be
- located. Tasks in this directory take precedence over those in the either the
- user taskdir or the installation taskdir.The following elements are allowed as children of the project - element:
-property
defining a property scoped to the projecttarget
defining a targetasdf
-asfd
-The Task section of the configuration file is structured as such:
-<[taskname] [attname=value] [attname=value]...]> - [<[elementname] [attname=value] ...> ... </[elementname]>] - </[taskname]>-
The taskname is used to find the class of the Task. Once the class has - been located and an instance of it created, all of the attributes of the Task - are reflected into the task instance using bean patterns. For example, if a - Task contains an attribute named "directory", the method named - setDirectory would be called with the attribute value cast to the appropriate - type desired by the method. (What to do if the type isn't a file or a - simple type, look for the class and see if it has a setString method?)
- -Text blocks contained by the element are added to task using an addText - method. Place an example...
-For each element contained in the Task definition, an addElementname - method is found on the task. The parameter type of the method defines an object - that will be loaded and instantiated. The attributes of the element are - reflected into the object using bean methods. Any text is set using the addText - method. Any elements are recursed in the same fashion.
-Search order of tasks.... project/user/system
-The command line utility provided with Ant must support the following - allowable syntax:
-ant projectfile [prop=value [prop=value...]] [target]
Internally, the command line shell scripts should call the org.apache.ant.Main
class
- with the following arguments:
java -Dant.home=installdir org.apache.ant.Main $*-
or its equivalent on the host platform. Note that the ant installation - directory is a System property. The above syntax results in ant.home being - placed in the System property list.
-Note: On unix, finding the directory of the script that was launched - is relatively easy. However on Windows, I'm not sure the best way of handling - this.
-File naming in a cross platform tool is tricky. For maximum portability - and understandiblity it is recommended that project files use the following - conventions:
-However, to allow for maximum flexibility and to allow project authors - to use conventions that make sense on their native platform, Ant allows for a - representation of file names which has the following rules:
-Absolute paths are not recommended for build files as they reduce the - ability to share a project between u sers or machines.
-In situtations where a set of filenames need to be specified, such as - defining a classpath, both the colon (':') andsemicolon (';') are allowable - characters to seperate each filename. The only case that has to be - disambiguated is if a user specifies paths that contain windows style absolute - paths. In this case, the colon is not treated as a path seperator if the - following rules are met:
-Sam, I'm leaving this to you.
-The following requirements are system requirements that Ant should have - in order to run correctly. We should not bundle in any of these into the - distribution of ant.
-Note: When running on JDK 1.2 or greater, the tools.jar isn't on the - classpath by default. There's a few different ways we can take care of this. - One is to put it on the classpath in the execute script (I don't like this - one). Another is to find the location of tools.jar at runtime and put it on the - classpath of class loaders that load in task.jars so that, at least in the - scope of the Tasks, the relevant classes are there.
- - -