1 /*
2  * Copyright (C) 2011 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package android.util;
17 
18 import java.lang.reflect.Field;
19 import java.lang.reflect.InvocationTargetException;
20 import java.lang.reflect.Method;
21 
22 /**
23  * Internal class to automatically generate a Property for a given class/name pair, given the
24  * specification of {@link Property#of(java.lang.Class, java.lang.Class, java.lang.String)}
25  */
26 class ReflectiveProperty<T, V> extends Property<T, V> {
27 
28     private static final String PREFIX_GET = "get";
29     private static final String PREFIX_IS = "is";
30     private static final String PREFIX_SET = "set";
31     private Method mSetter;
32     private Method mGetter;
33     private Field mField;
34 
35     /**
36      * For given property name 'name', look for getName/isName method or 'name' field.
37      * Also look for setName method (optional - could be readonly). Failing method getters and
38      * field results in throwing NoSuchPropertyException.
39      *
40      * @param propertyHolder The class on which the methods or field are found
41      * @param name The name of the property, where this name is capitalized and appended to
42      * "get" and "is to search for the appropriate methods. If the get/is methods are not found,
43      * the constructor will search for a field with that exact name.
44      */
ReflectiveProperty(Class<T> propertyHolder, Class<V> valueType, String name)45     public ReflectiveProperty(Class<T> propertyHolder, Class<V> valueType, String name) {
46          // TODO: cache reflection info for each new class/name pair
47         super(valueType, name);
48         char firstLetter = Character.toUpperCase(name.charAt(0));
49         String theRest = name.substring(1);
50         String capitalizedName = firstLetter + theRest;
51         String getterName = PREFIX_GET + capitalizedName;
52         try {
53             mGetter = propertyHolder.getMethod(getterName, (Class<?>[])null);
54         } catch (NoSuchMethodException e) {
55             // getName() not available - try isName() instead
56             getterName = PREFIX_IS + capitalizedName;
57             try {
58                 mGetter = propertyHolder.getMethod(getterName, (Class<?>[])null);
59             } catch (NoSuchMethodException e1) {
60                 // Try public field instead
61                 try {
62                     mField = propertyHolder.getField(name);
63                     Class fieldType = mField.getType();
64                     if (!typesMatch(valueType, fieldType)) {
65                         throw new NoSuchPropertyException("Underlying type (" + fieldType + ") " +
66                                 "does not match Property type (" + valueType + ")");
67                     }
68                     return;
69                 } catch (NoSuchFieldException e2) {
70                     // no way to access property - throw appropriate exception
71                     throw new NoSuchPropertyException("No accessor method or field found for"
72                             + " property with name " + name);
73                 }
74             }
75         }
76         Class getterType = mGetter.getReturnType();
77         // Check to make sure our getter type matches our valueType
78         if (!typesMatch(valueType, getterType)) {
79             throw new NoSuchPropertyException("Underlying type (" + getterType + ") " +
80                     "does not match Property type (" + valueType + ")");
81         }
82         String setterName = PREFIX_SET + capitalizedName;
83         try {
84             mSetter = propertyHolder.getMethod(setterName, getterType);
85         } catch (NoSuchMethodException ignored) {
86             // Okay to not have a setter - just a readonly property
87         }
88     }
89 
90     /**
91      * Utility method to check whether the type of the underlying field/method on the target
92      * object matches the type of the Property. The extra checks for primitive types are because
93      * generics will force the Property type to be a class, whereas the type of the underlying
94      * method/field will probably be a primitive type instead. Accept float as matching Float,
95      * etc.
96      */
typesMatch(Class<V> valueType, Class getterType)97     private boolean typesMatch(Class<V> valueType, Class getterType) {
98         if (getterType != valueType) {
99             if (getterType.isPrimitive()) {
100                 return (getterType == float.class && valueType == Float.class) ||
101                         (getterType == int.class && valueType == Integer.class) ||
102                         (getterType == boolean.class && valueType == Boolean.class) ||
103                         (getterType == long.class && valueType == Long.class) ||
104                         (getterType == double.class && valueType == Double.class) ||
105                         (getterType == short.class && valueType == Short.class) ||
106                         (getterType == byte.class && valueType == Byte.class) ||
107                         (getterType == char.class && valueType == Character.class);
108             }
109             return false;
110         }
111         return true;
112     }
113 
114     @Override
set(T object, V value)115     public void set(T object, V value) {
116         if (mSetter != null) {
117             try {
118                 mSetter.invoke(object, value);
119             } catch (IllegalAccessException e) {
120                 throw new AssertionError();
121             } catch (InvocationTargetException e) {
122                 throw new RuntimeException(e.getCause());
123             }
124         } else if (mField != null) {
125             try {
126                 mField.set(object, value);
127             } catch (IllegalAccessException e) {
128                 throw new AssertionError();
129             }
130         } else {
131             throw new UnsupportedOperationException("Property " + getName() +" is read-only");
132         }
133     }
134 
135     @Override
get(T object)136     public V get(T object) {
137         if (mGetter != null) {
138             try {
139                 return (V) mGetter.invoke(object, (Object[])null);
140             } catch (IllegalAccessException e) {
141                 throw new AssertionError();
142             } catch (InvocationTargetException e) {
143                 throw new RuntimeException(e.getCause());
144             }
145         } else if (mField != null) {
146             try {
147                 return (V) mField.get(object);
148             } catch (IllegalAccessException e) {
149                 throw new AssertionError();
150             }
151         }
152         // Should not get here: there should always be a non-null getter or field
153         throw new AssertionError();
154     }
155 
156     /**
157      * Returns false if there is no setter or public field underlying this Property.
158      */
159     @Override
isReadOnly()160     public boolean isReadOnly() {
161         return (mSetter == null && mField == null);
162     }
163 }
164