Introduced "spring.beaninfo.ignore" system property for optimized Introspector usage

Issue: SPR-9014
(cherry picked from commit f88cbda)

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

@@ -52,6 +52,18 @@ import org.springframework.util.StringUtils;
  * implements the factory design pattern, using a private constructor and
  * a static {@link #forClass(Class)} factory method to obtain instances.
  *
+ * <p>Note that for caching to work effectively, some preconditions need to be met:
+ * Prefer an arrangement where the Spring jars live in the same ClassLoader as the
+ * application classes, which allows for clean caching along with the application's
+ * lifecycle in any case. For a web application, consider declaring a local
+ * {@link org.springframework.web.util.IntrospectorCleanupListener} in {@code web.xml}
+ * in case of a multi-ClassLoader layout, which will allow for effective caching as well.
+ *
+ * <p>In case of a non-clean ClassLoader arrangement without a cleanup listener having
+ * been set up, this class will fall back to a weak-reference-based caching model that
+ * recreates much-requested entries every time the garbage collector removed them. In
+ * such a scenario, consider the {@link #IGNORE_BEANINFO_PROPERTY_NAME} system property.
+ *
  * @author Rod Johnson
  * @author Juergen Hoeller
  * @since 05 May 2001
@@ -61,11 +73,33 @@ import org.springframework.util.StringUtils;
  */
 public class CachedIntrospectionResults {
 
+	/**
+	 * System property that instructs Spring to use the {@link Introspector#IGNORE_ALL_BEANINFO}
+	 * mode when calling the JavaBeans {@link Introspector}: "spring.beaninfo.ignore", with a
+	 * value of "true" skipping the search for {@code BeanInfo} classes (typically for scenarios
+	 * where no such classes are being defined for beans in the application in the first place).
+	 * <p>Default is "false", considering all {@code BeanInfo} metadata classes, like for
+	 * standard {@link Introspector#getBeanInfo(Class)} calls. Consider switching this flag to
+	 * "true" if you experience repeated ClassLoader access for non-existing {@code BeanInfo}
+	 * classes, in case such access is expensive on startup or on lazy loading.
+	 * <p>Note that such an effect may also indicate a scenario where caching doesn't work
+	 * effectively: Prefer an arrangement where the Spring jars live in the same ClassLoader
+	 * as the application classes, which allows for clean caching along with the application's
+	 * lifecycle in any case. For a web application, consider declaring a local
+	 * {@link org.springframework.web.util.IntrospectorCleanupListener} in {@code web.xml}
+	 * in case of a multi-ClassLoader layout, which will allow for effective caching as well.
+	 * @see Introspector#getBeanInfo(Class, int)
+	 */
+	public static final String IGNORE_BEANINFO_PROPERTY_NAME = "spring.beaninfo.ignore";
+
+
 	private static final Log logger = LogFactory.getLog(CachedIntrospectionResults.class);
 
+	private static final boolean shouldIntrospectorIgnoreBeaninfoClasses;
+
 	/** Stores the BeanInfoFactory instances */
-	private static List<BeanInfoFactory> beanInfoFactories =
-			SpringFactoriesLoader.loadFactories(BeanInfoFactory.class, CachedIntrospectionResults.class.getClassLoader());
+	private static List<BeanInfoFactory> beanInfoFactories = SpringFactoriesLoader.loadFactories(
+			BeanInfoFactory.class, CachedIntrospectionResults.class.getClassLoader());
 
 	/**
 	 * Set of ClassLoaders that this CachedIntrospectionResults class will always
@@ -81,6 +115,21 @@ public class CachedIntrospectionResults {
 	static final Map<Class<?>, Object> classCache = new WeakHashMap<Class<?>, Object>();
 
 
+	static {
+		boolean ignoreValue;
+		try {
+			ignoreValue = "true".equalsIgnoreCase(System.getProperty(IGNORE_BEANINFO_PROPERTY_NAME));
+		}
+		catch (Throwable ex) {
+			if (logger.isDebugEnabled()) {
+				logger.debug("Could not obtain system property '" + IGNORE_BEANINFO_PROPERTY_NAME + "': " + ex);
+			}
+			ignoreValue = false;
+		}
+		shouldIntrospectorIgnoreBeaninfoClasses = ignoreValue;
+	}
+
+
 	/**
 	 * Accept the given ClassLoader as cache-safe, even if its classes would
 	 * not qualify as cache-safe in this CachedIntrospectionResults class.
@@ -243,7 +292,9 @@ public class CachedIntrospectionResults {
 			}
 			if (beanInfo == null) {
 				// If none of the factories supported the class, fall back to the default
-				beanInfo = Introspector.getBeanInfo(beanClass);
+				beanInfo = (shouldIntrospectorIgnoreBeaninfoClasses ?
+						Introspector.getBeanInfo(beanClass, Introspector.IGNORE_ALL_BEANINFO) :
+						Introspector.getBeanInfo(beanClass));
 			}
 			this.beanInfo = beanInfo;