1 This file contains some information on the essential concepts and principles
2 involved in the use of this software.
3
4 Installation
5 ------------
6
7 Usually, I issue this command first:
8
9 python setup.py build
10
11 The following should, in any case, be sufficient:
12
13 python setup.py install
14
15 I don't think distutils supports uninstall, but the installation just adds the
16 java and javaclass packages to your site-packages directory and the
17 runclass.py program to the same bin directory that python resides in.
18
19 Testing
20 -------
21
22 It should be possible to just run the test.py program and see the results:
23
24 python test.py
25
26 Class Search Paths
27 ------------------
28
29 Java classes belonging to packages are located using sys.path or PYTHONPATH
30 in the same way that they would be located using the Java classpath (or
31 CLASSPATH environment variable). Thus, the rules for locating package
32 classes are as follows:
33
34 * Classes residing within plain directories which represent a package
35 hierarchy can be accessed by putting the parent directory of the top of
36 the package hierarchy on the PYTHONPATH (or sys.path). For example, a
37 package called mypackage, represented by a directory of the same name at
38 /home/java/classes/mypackage, would be made accessible by adding the
39 /home/java/classes directory to the PYTHONPATH.
40
41 * Classes residing within .jar files can be accessed by putting the path to
42 each .jar file on the PYTHONPATH. For example, a package called
43 mypackage, represented by a file located at /home/java/lib/mypackage.jar,
44 would be made accessible by adding the /home/java/lib/mypackage.jar file
45 to the PYTHONPATH.
46
47 Note that classes not belonging to a package cannot be accessed via such
48 search paths and are made available using a special module (see "Non-package
49 Classes" below).
50
51 Importing Classes
52 -----------------
53
54 In Python, the following statement should be enough to enable Java class
55 import:
56
57 import javaclass.classhook
58
59 (Other modules reside in the javaclass package, so it is possible to access
60 them without changing Python's import mechanisms, should such modification be
61 undesirable or unnecessary.)
62
63 Importing Non-package Classes
64 -----------------------------
65
66 Classes which do not belong to a package are only accessible when residing
67 in the current working directory of any program attempting to use them. Such
68 classes will not be made available automatically, but must be imported from
69 a special module called __this__.
70
71 * Usage of the "import __this__" statement will cause all classes in the
72 current directory to be made available within the __this__ module.
73
74 * Usage of the "from __this__ import" construct will cause all classes in
75 the current directory to be processsed, but only named classes will be
76 made available in the global namespace unless "*" was specified (which
77 will, as usual, result in all such classes being made available).
78
79 Running Java Classes
80 --------------------
81
82 Java classes with a public, static main method can be run directly using the
83 runclass.py program.
84
85 * Free-standing classes (ie. not belonging to packages) can be run from
86 the directory in which they reside. For example, suitable classes in the
87 tests directory would be run as follows:
88
89 cd tests
90 runclass.py MainTest hello world
91
92 * Classes residing in packages can be run by ensuring that the packages
93 are registered on the PYTHONPATH (see "Class Search Paths" above). Then,
94 the testpackage.MainTest class (for example) would be run as follows:
95
96 runclass.py testpackage.MainTest hello world
97
98 Accessing Python Libraries from Java
99 ------------------------------------
100
101 To wrap Python libraries for use with Java, skeleton classes need to be
102 compiled corresponding to each of the wrapped classes. Each of the methods
103 in the skeleton classes can be empty (or return any permissible value) since
104 the only purpose they serve is to provide the Java compiler with information
105 about the Python libraries.
106
107 1. Compile the skeleton classes:
108
109 javac examples/Tkinter/tkjava/*.java
110
111 2. Compile the Java classes which use the wrapped Python libraries:
112
113 javac -classpath examples/Tkinter examples/Tkinter/Application.java
114
115 3. Run the wrap.py tool on the directory where the skeleton class files
116 reside, providing the name of the Python package or module being
117 wrapped. This converts the directory into a Python package:
118
119 python tools/wrap.py examples/Tkinter/tkjava Tkinter
120
121 Since the Java class files, if left in the processed directory, would be
122 detected and imported using the special import hook, and since this would
123 result in two conflicting implementations being imported (with possibly the
124 non-functional Java classes being made available instead of the generated
125 wrapper classes), the wrap.py tool removes all processed class files,
126 leaving only Python source files in the processed directory.
127
128 4. The Java classes which use the wrapped Python libraries can now be
129 imported and used as described above. The wrapper package (tkjava in
130 the above example) needs to reside in sys.path or PYTHONPATH, as must
131 the wrapped library (Tkinter in the above example).
132
133 cd examples/Tkinter
134 runclass.py Application
135
136 Issues
137 ------
138
139 Investigate better exception raising. Currently, exceptions have to be
140 derived from object so that object.__new__ can be used upon them. However,
141 this seems to prevent them from being raised, and they need to be wrapped
142 within Exception so that the information can be transmitted to the
143 exception's handler.
144
145 Consider nicer ways of writing the method names in Python, perhaps using a
146 function which takes the individual parameter types as arguments.
147
148 Release Procedures
149 ------------------
150
151 Update the javaclass/__init__.py __version__ attribute.
152 Update the release notes (see above).
153 Check the setup.py file and ensure that all package directories are mentioned.
154 Tag, export.
155 Rename ClassFile to javaclass (and add the release to the directory name).
156 Archive, upload.
