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Java > Open Source Codes > org > apache > turbine > services > assemblerbroker > util > python > PythonBaseFactory


1 package org.apache.turbine.services.assemblerbroker.util.python;
2
3 /*
4  * Copyright 2001-2004 The Apache Software Foundation.
5  *
6  * Licensed under the Apache License, Version 2.0 (the "License")
7  * you may not use this file except in compliance with the License.
8  * You may obtain a copy of the License at
9  *
10  * http://www.apache.org/licenses/LICENSE-2.0
11  *
12  * Unless required by applicable law or agreed to in writing, software
13  * distributed under the License is distributed on an "AS IS" BASIS,
14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15  * See the License for the specific language governing permissions and
16  * limitations under the License.
17  */
18
19 import java.io.File JavaDoc;
20
21 import org.apache.commons.configuration.Configuration;
22
23 import org.apache.commons.lang.StringUtils;
24
25 import org.apache.commons.logging.Log;
26 import org.apache.commons.logging.LogFactory;
27
28 import org.apache.turbine.modules.Assembler;
29 import org.apache.turbine.services.assemblerbroker.TurbineAssemblerBroker;
30 import org.apache.turbine.services.assemblerbroker.util.AssemblerFactory;
31
32 import org.python.core.Py;
33 import org.python.util.PythonInterpreter;
34
35 /**
36  * A factory that attempts to load a python class in the
37  * JPython interpreter and execute it as a Turbine screen.
38  * The JPython script should inherit from Turbine Screen or one
39  * of its subclasses.
40  *
41  * @author <a HREF="mailto:leon@opticode.co.za">Leon Messerschmidt</a>
42  * @author <a HREF="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a>
43  * @version $Id: PythonBaseFactory.java,v 1.8.2.2 2004/05/20 03:05:17 seade Exp $
44  */
45 public abstract class PythonBaseFactory
46         implements AssemblerFactory
47 {
48     /** Key for the python path */
49     public static final String JavaDoc PYTHON_PATH = "python.path";
50
51     /** Global config file. This is executed before every screen */
52     public static final String JavaDoc PYTHON_CONFIG_FILE = "conf.py";
53
54     /** Logging */
55     private static Log log = LogFactory.getLog(PythonBaseFactory.class);
56
57     /** Our configuration */
58     private Configuration conf =
59         TurbineAssemblerBroker.getService().getConfiguration();
60
61     /**
62      * Get an Assembler.
63      *
64      * @param subDirectory subdirectory within python.path
65      * @param name name of the requested Assembler
66      * @return an Assembler
67      * @throws Exception generic exception
68      */
69     public Assembler getAssembler(String JavaDoc subDirectory, String JavaDoc name)
70             throws Exception JavaDoc
71     {
72         String JavaDoc path = conf.getString(PYTHON_PATH);
73
74         if (StringUtils.isEmpty(path))
75         {
76             throw new Exception JavaDoc(
77                 "Python path not found - check your Properties");
78         }
79             
80         log.debug("Screen name for JPython: " + name);
81
82         Assembler assembler = null;
83
84         String JavaDoc confName = path + "/" + PYTHON_CONFIG_FILE;
85
86         // The filename of the Python script
87 StringBuffer JavaDoc fName = new StringBuffer JavaDoc();
88
89         fName.append(path);
90         fName.append("/");
91         fName.append(subDirectory);
92         fName.append("/");
93         fName.append(name.toLowerCase());
94         fName.append(".py");
95
96         File JavaDoc f = new File JavaDoc(fName.toString());
97
98         if (f.exists())
99         {
100             try
101             {
102                 // We try to open the Py Interpreter
103 PythonInterpreter interp = new PythonInterpreter();
104
105                 // Make sure the Py Interpreter use the right classloader
106 // This is necessary for servlet engines generally has
107 // their own classloader implementations and servlets aren't
108 // loaded in the system classloader. The python script will
109 // load java package
110 // org.apache.turbine.services.assemblerbroker.util.python;
111 // the new classes to it as well.
112 Py.getSystemState().setClassLoader(
113                         this.getClass().getClassLoader());
114
115                 // We import the Python SYS module. Now we don't need to do this
116 // explicitely in the script. We always use the sys module to
117 // do stuff like loading java package
118 // org.apache.turbine.services.assemblerbroker.util.python;
119 interp.exec("import sys");
120
121                 // Now we try to load the script file
122 interp.execfile(confName);
123                 interp.execfile(fName.toString());
124
125                 try
126                 {
127                     // We create an instance of the screen class from the
128 // python script
129 interp.exec("scr = " + name + "()");
130                 }
131                 catch (Throwable JavaDoc e)
132                 {
133                     throw new Exception JavaDoc(
134                         "\nCannot create an instance of the python class.\n"
135                         + "You probably gave your class the wrong name.\n"
136                         + "Your class should have the same name as your "
137                         + "filename.\nFilenames should be all lowercase and "
138                         + "classnames should start with a capital.\n"
139                         + "Expected class name: " + name + "\n");
140                 }
141
142                 // Here we convert the python sceen instance to a java instance.
143 assembler = (Assembler) interp.get("scr", Assembler.class);
144             }
145             catch (Exception JavaDoc e)
146             {
147                 // We log the error here because this code is not widely tested
148 // yet. After we tested the code on a range of platforms this
149 // won't be usefull anymore.
150 log.error("PYTHON SCRIPT SCREEN LOADER ERROR:", e);
151                 throw e;
152             }
153         }
154         return assembler;
155     }
156 }
157
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