1 package org.apache.turbine.services.assemblerbroker.util.java;
2
3
4 /*
5 * Licensed to the Apache Software Foundation (ASF) under one
6 * or more contributor license agreements. See the NOTICE file
7 * distributed with this work for additional information
8 * regarding copyright ownership. The ASF licenses this file
9 * to you under the Apache License, Version 2.0 (the
10 * "License"); you may not use this file except in compliance
11 * with the License. You may obtain a copy of the License at
12 *
13 * http://www.apache.org/licenses/LICENSE-2.0
14 *
15 * Unless required by applicable law or agreed to in writing,
16 * software distributed under the License is distributed on an
17 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
18 * KIND, either express or implied. See the License for the
19 * specific language governing permissions and limitations
20 * under the License.
21 */
22
23 import java.util.List;
24 import java.util.concurrent.ConcurrentHashMap;
25
26 import org.apache.commons.lang3.StringUtils;
27 import org.apache.logging.log4j.LogManager;
28 import org.apache.logging.log4j.Logger;
29 import org.apache.turbine.modules.Assembler;
30 import org.apache.turbine.modules.GenericLoader;
31 import org.apache.turbine.modules.Loader;
32 import org.apache.turbine.services.assemblerbroker.util.AssemblerFactory;
33
34 /**
35 * A screen factory that attempts to load a java class from
36 * the module packages defined in the TurbineResource.properties.
37 *
38 * @author <a href="mailto:leon@opticode.co.za">Leon Messerschmidt</a>
39 * @author <a href="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a>
40 * @param <T> the specialized assembler type
41 */
42 public abstract class JavaBaseFactory<T extends Assembler>
43 implements AssemblerFactory<T>
44 {
45 /** A vector of packages. */
46 private static List<String> packages = GenericLoader.getPackages();
47
48 /** Logging */
49 protected Logger log = LogManager.getLogger(this.getClass());
50
51 /**
52 * A cache for previously obtained Class instances, which we keep in order
53 * to reduce the Class.forName() overhead (which can be sizable).
54 */
55 private final ConcurrentHashMap<String, Class<T>> classCache = new ConcurrentHashMap<>();
56
57 /**
58 * Get an Assembler.
59 *
60 * @param packageName java package name
61 * @param name name of the requested Assembler
62 * @return an Assembler
63 */
64 @SuppressWarnings("unchecked")
65 public T getAssembler(String packageName, String name)
66 {
67 T assembler = null;
68
69 log.debug("Class Fragment is {}", name);
70
71 if (StringUtils.isNotEmpty(name))
72 {
73 for (String p : packages)
74 {
75 StringBuilder sb = new StringBuilder();
76
77 sb.append(p).append('.').append(packageName).append('.').append(name);
78 String className = sb.toString();
79
80 log.debug("Trying {}", className);
81
82 try
83 {
84 Class<T> servClass = classCache.get(className);
85 if (servClass == null)
86 {
87 servClass = (Class<T>) Class.forName(className);
88 Class<T> _servClass = classCache.putIfAbsent(className, servClass);
89 if (_servClass != null)
90 {
91 servClass = _servClass;
92 }
93 }
94 assembler = servClass.newInstance();
95 break; // for()
96 }
97 catch (ClassNotFoundException cnfe)
98 {
99 // Do this so we loop through all the packages.
100 log.debug("{}: Not found", className);
101 }
102 catch (NoClassDefFoundError ncdfe)
103 {
104 // Do this so we loop through all the packages.
105 log.debug("{}: No Class Definition found", className);
106 }
107 // With ClassCastException, InstantiationException we hit big problems
108 catch (ClassCastException | InstantiationException | IllegalAccessException e)
109 {
110 // This means trouble!
111 // Alternatively we can throw this exception so
112 // that it will appear on the client browser
113 log.error("Could not load {}", className, e);
114 break; // for()
115 }
116 }
117 }
118
119 log.debug("Returning: {}", assembler);
120
121 return assembler;
122 }
123
124 /**
125 * Get the loader for this type of assembler
126 *
127 * @return a Loader
128 */
129 @Override
130 public abstract Loader<T> getLoader();
131
132 /**
133 * Get the size of a possibly configured cache
134 *
135 * @return the size of the cache in bytes
136 */
137 @Override
138 public int getCacheSize()
139 {
140 return getLoader().getCacheSize();
141 }
142 }