Source Code Cross Referenced for InvokeNoArgMethod.java in  » Development » jga-Generic-Algorithms » net » sf » jga » fn » property » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Development » jga Generic Algorithms » net.sf.jga.fn.property 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        // ============================================================================
002:        // $Id: InvokeNoArgMethod.java,v 1.9 2006/04/26 03:40:37 davidahall Exp $
003:        // Copyright (c) 2003-2005  David A. Hall
004:        // ============================================================================
005:        // The contents of this file are subject to the Common Development and
006:        // Distribution License (CDDL), Version 1.0 (the License); you may not use this 
007:        // file except in compliance with the License.  You should have received a copy
008:        // of the the License along with this file: if not, a copy of the License is 
009:        // available from Sun Microsystems, Inc.
010:        //
011:        // http://www.sun.com/cddl/cddl.html
012:        //
013:        // From time to time, the license steward (initially Sun Microsystems, Inc.) may
014:        // publish revised and/or new versions of the License.  You may not use,  
015:        // distribute, or otherwise make this file available under subsequent versions 
016:        // of the License.
017:        // 
018:        // Alternatively, the contents of this file may be used under the terms of the 
019:        // GNU Lesser General Public License Version 2.1 or later (the "LGPL"), in which
020:        // case the provisions of the LGPL are applicable instead of those above. If you 
021:        // wish to allow use of your version of this file only under the terms of the 
022:        // LGPL, and not to allow others to use your version of this file under the 
023:        // terms of the CDDL, indicate your decision by deleting the provisions above 
024:        // and replace them with the notice and other provisions required by the LGPL. 
025:        // If you do not delete the provisions above, a recipient may use your version 
026:        // of this file under the terms of either the CDDL or the LGPL.
027:        // 
028:        // This library is distributed in the hope that it will be useful,
029:        // but WITHOUT ANY WARRANTY; without even the implied warranty of
030:        // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 
031:        // ============================================================================
032:
033:        package net.sf.jga.fn.property;
034:
035:        import java.lang.reflect.InvocationTargetException;
036:        import java.lang.reflect.Method;
037:        import java.text.MessageFormat;
038:        import net.sf.jga.fn.BinaryFunctor;
039:        import net.sf.jga.fn.EvaluationException;
040:        import net.sf.jga.fn.UnaryFunctor;
041:        import net.sf.jga.fn.adaptor.ChainBinary;
042:        import net.sf.jga.fn.adaptor.ChainUnary;
043:
044:        /**
045:         * Functor that invokes a no-arg method named at construction and returns the
046:         * result or null if the result is void.
047:         * <p>
048:         * Note that declaring the return type incorrectly can result in
049:         * ClassCastExceptions being thrown when the functor is invoked: the compiler
050:         * cannot check the return type of a reflectively loaded method.
051:         * <p>
052:         * Copyright &copy; 2003-2005  David A. Hall
053:         *
054:         * @author <a href="mailto:davidahall@users.sourceforge.net">David A. Hall</a>
055:         **/
056:
057:        public class InvokeNoArgMethod<T, R> extends UnaryFunctor<T, R> {
058:
059:            static final long serialVersionUID = -2651164047444243205L;
060:
061:            // The name of the method
062:            private String _methName;
063:
064:            // The class on which the method is defined
065:            private Class<T> _objclass;
066:
067:            // The method being called (lazily populated after deserialization)
068:            private transient Method _meth;
069:
070:            /**
071:             * Builds a InvokeMethod for the given method, which takes no arguments.
072:             * @throws IllegalArgumentException if the method name is null or empty
073:             */
074:
075:            public InvokeNoArgMethod(Class<T> objclass, String methName) {
076:                if (methName == null || methName.length() == 0) {
077:                    String msg = "Must supply method name";
078:                    throw new IllegalArgumentException(msg);
079:                }
080:
081:                if (objclass == null) {
082:                    String msg = "Must supply object class";
083:                    throw new IllegalArgumentException(msg);
084:                }
085:
086:                _methName = methName;
087:                _objclass = objclass;
088:
089:                try {
090:                    _meth = objclass.getMethod(_methName, new Class[0]);
091:                } catch (NoSuchMethodException x) {
092:                    String msg = "No such method: " + x.getMessage();
093:                    IllegalArgumentException iax = new IllegalArgumentException(
094:                            msg);
095:                    iax.initCause(x);
096:                    throw iax;
097:                }
098:            }
099:
100:            /**
101:             * Builds a InvokeMethod for the given method, which takes no arguments.
102:             * @throws IllegalArgumentException if the method name is null or empty,
103:             * or if it is not defined for the given class, or if it takes arguments
104:             */
105:
106:            public InvokeNoArgMethod(Class<T> objClass, Method method) {
107:                if (method == null) {
108:                    String msg = "Must supply method";
109:                    throw new IllegalArgumentException(msg);
110:                }
111:
112:                if (objClass == null) {
113:                    String msg = "Must supply object class";
114:                    throw new IllegalArgumentException(msg);
115:                }
116:
117:                if (method.getParameterTypes().length != 0) {
118:                    String msg = "Method {0} takes arguments";
119:                    Object[] args = { method.getName() };
120:                    throw new IllegalArgumentException(MessageFormat.format(
121:                            msg, args));
122:                }
123:
124:                if (!method.getDeclaringClass().isAssignableFrom(objClass)) {
125:                    String msg = "Method {0} not defined for class {1}";
126:                    Object[] args = { method.getName(), objClass.getName() };
127:                    throw new IllegalArgumentException(MessageFormat.format(
128:                            msg, args));
129:                }
130:
131:                _objclass = objClass;
132:                _meth = method;
133:                _methName = method.getName();
134:            }
135:
136:            /**
137:             * Returns the name of the property that this functor retrieves.
138:             */
139:            public String getMethodName() {
140:                return _methName;
141:            }
142:
143:            /**
144:             * Returns the type of the method 
145:             */
146:            public Class<R> getReturnType() {
147:                return (Class<R>) _meth.getReturnType();
148:            }
149:
150:            /**
151:             * Lazy loads the method 
152:             */
153:            public synchronized Method getMethod() throws NoSuchMethodException {
154:                if (_meth == null)
155:                    _meth = _objclass.getMethod(_methName, new Class[0]);
156:
157:                return _meth;
158:            }
159:
160:            // Unary Functor interface
161:
162:            /**
163:             * Invokes the method on the given object, and returns the result.
164:             * @return the result of the designated method of the object
165:             * @throws EvaluationException if the argument does not have the designated
166:             *         public property, or if it is not of the correct type. 
167:             */
168:            public R fn(T obj) {
169:                try {
170:                    // @SuppressWarnings
171:                    // There's nothing we can do about this other than warn the users
172:                    // to make sure that they don't use an inappropriate return type
173:                    return (R) getMethod().invoke(obj, new Object[0]);
174:                } catch (NoSuchMethodException x) {
175:                    String msg = "No method {0} for class {1} that takes no arguments";
176:                    Object[] args = new Object[] { _methName,
177:                            _objclass.getName() };
178:                    throw new EvaluationException(MessageFormat.format(msg,
179:                            args), x);
180:                } catch (ClassCastException x) {
181:                    String msg = "ClassCastException: " + _objclass + "."
182:                            + _methName + "()";
183:                    throw new EvaluationException(msg, x);
184:                } catch (IllegalAccessException x) {
185:                    String msg = _objclass + "." + _methName
186:                            + " is not accessible";
187:                    throw new EvaluationException(msg, x);
188:                } catch (InvocationTargetException x) {
189:                    String xmsg = x.getMessage();
190:                    String msg = "InvocationException: " + _objclass + "."
191:                            + _methName + "()"
192:                            + (xmsg != null ? (":" + xmsg) : "");
193:                    throw new EvaluationException(msg, x);
194:                }
195:            }
196:
197:            /**
198:             * Calls the Visitor's <code>visit(InvokeMethod)</code> method, if it
199:             * implements the nested Visitor interface.
200:             */
201:            public void accept(net.sf.jga.fn.Visitor v) {
202:                if (v instanceof  InvokeNoArgMethod.Visitor)
203:                    ((InvokeNoArgMethod.Visitor) v).visit(this );
204:                else
205:                    v.visit(this );
206:            }
207:
208:            // Object overrides
209:
210:            public String toString() {
211:                return "InvokeNoArgMethod(" + _meth + ")";
212:            }
213:
214:            // AcyclicVisitor
215:
216:            /**
217:             * Interface for classes that may interpret a <b>InvokeMethod</b>
218:             * function.
219:             */
220:            public interface Visitor extends net.sf.jga.fn.Visitor {
221:                public void visit(InvokeNoArgMethod host);
222:            }
223:        }
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