StandardServletEnvironment supports "spring.jndi.ignore" flag for efficient property lookups

Issue: SPR-14026

spring-context/src/main/java/org/springframework/jndi/JndiLocatorDelegate.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2016 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,6 +19,8 @@ package org.springframework.jndi;
 import javax.naming.InitialContext;
 import javax.naming.NamingException;
 
+import org.springframework.core.SpringProperties;
+
 /**
  * {@link JndiLocatorSupport} subclass with public lookup methods,
  * for convenient use as a delegate.
@@ -28,6 +30,29 @@ import javax.naming.NamingException;
  */
 public class JndiLocatorDelegate extends JndiLocatorSupport {
 
+	/**
+	 * System property that instructs Spring to ignore a default JNDI environment, i.e.
+	 * to always return {@code false} from {@link #isDefaultJndiEnvironmentAvailable()}.
+	 * <p>The default is "false", allowing for regular default JNDI access e.g. in
+	 * {@link JndiPropertySource}. Switching this flag to {@code true} is an optimization
+	 * for scenarios where nothing is ever to be found for such JNDI fallback searches
+	 * to begin with, avoiding the repeated JNDI lookup overhead.
+	 * <p>Note that this flag just affects JNDI fallback searches, not explicitly configured
+	 * JNDI lookups such as for a {@code DataSource} or some other environment resource.
+	 * The flag literally just affects code which attempts JNDI searches based on the
+	 * {@code JndiLocatorDelegate.isDefaultJndiEnvironmentAvailable()} check: in particular,
+	 * {@code StandardServletEnvironment} and {@code StandardPortletEnvironment}.
+	 * @since 4.3
+	 * @see #isDefaultJndiEnvironmentAvailable()
+	 * @see JndiPropertySource
+	 */
+	public static final String IGNORE_JNDI_PROPERTY_NAME = "spring.jndi.ignore";
+
+
+	private static final boolean shouldIgnoreDefaultJndiEnvironment =
+			SpringProperties.getFlag(IGNORE_JNDI_PROPERTY_NAME);
+
+
 	@Override
 	public Object lookup(String jndiName) throws NamingException {
 		return super.lookup(jndiName);
@@ -57,6 +82,9 @@ public class JndiLocatorDelegate extends JndiLocatorSupport {
 	 * {@code false} if not
 	 */
 	public static boolean isDefaultJndiEnvironmentAvailable() {
+		if (shouldIgnoreDefaultJndiEnvironment) {
+			return false;
+		}
 		try {
 			new InitialContext().getEnvironment();
 			return true;