CachedIntrospectionResults uses SoftReference instead of WeakReference for non-cache-safe entries

Issue: SPR-11867
(cherry picked from commit f27b949)

Author: jhoeller

spring-beans/src/main/java/org/springframework/beans/CachedIntrospectionResults.java

@@ -21,7 +21,7 @@
 import java.beans.Introspector;
 import java.beans.PropertyDescriptor;
 import java.lang.ref.Reference;
-import java.lang.ref.WeakReference;
+import java.lang.ref.SoftReference;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.LinkedHashMap;
@@ -194,7 +194,7 @@ static CachedIntrospectionResults forClass(Class<?> beanClass) throws BeansExcep
 				}
 				results = new CachedIntrospectionResults(beanClass);
 				synchronized (classCache) {
-					classCache.put(beanClass, new WeakReference<CachedIntrospectionResults>(results));
+					classCache.put(beanClass, new SoftReference<CachedIntrospectionResults>(results));
 				}
 			}
 		}