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1
52
53 package freemarker.cache;
54
55 import java.lang.ref.Reference  ;
56 import java.lang.ref.ReferenceQueue ;
57 import java.lang.ref.SoftReference ;
58 import java.util.HashMap ;
59 import java.util.Map ;
60
61
75 public class SoftCacheStorage implements CacheStorage
76 {
77 private final ReferenceQueue queue = new ReferenceQueue ();
78 private final Map map;
79
80 public SoftCacheStorage()
81 {
82 this(new HashMap ());
83 }
84
85 public SoftCacheStorage(Map backingMap)
86 {
87 this.map = backingMap;
88 }
89
90 public Object get(Object key)
91 {
92 processQueue();
93 Reference ref = (Reference )map.get(key);
94 return ref == null ? null : ref.get();
95 }
96
97 public void put(Object key, Object value)
98 {
99 processQueue();
100 map.put(key, new SoftValueReference(key, value, queue));
101 }
102
103 public void remove(Object key)
104 {
105 processQueue();
106 map.remove(key);
107 }
108
109 public void clear()
110 {
111 map.clear();
112 processQueue();
113 }
114
115 private void processQueue()
116 {
117 for(;;)
118 {
119 SoftValueReference ref = (SoftValueReference)queue.poll();
120 if(ref == null)
121 {
122 return;
123 }
124 Object key = ref.getKey();
125 if(map.get(key) == ref)
128 {
129 map.remove(key);
130 }
131 }
132 }
133
134 private static final class SoftValueReference
135 extends
136 SoftReference
137 {
138 private final Object key;
139
140 SoftValueReference(Object key, Object value, ReferenceQueue queue)
141 {
142 super(value, queue);
143 this.key = key;
144 }
145
146 Object getKey()
147 {
148 return key;
149 }
150 }
151 }
152 |
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