Merge pull request #8128 from tinexw:master

* pr/8128:
  Polish "Handle null value in OnExpressionCondition"
  Handle null value in OnExpressionCondition

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/OnExpressionCondition.java

 /*
- * Copyright 2012-2016 the original author or authors.
+ * Copyright 2012-2017 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.
@@ -51,8 +51,9 @@ class OnExpressionCondition extends SpringBootCondition {
 		if (resolver == null) {
 			resolver = new StandardBeanExpressionResolver();
 		}
-		boolean result = (Boolean) resolver.evaluate(expression, expressionContext);
-		return new ConditionOutcome(result, ConditionMessage
+		Object result = resolver.evaluate(expression, expressionContext);
+		boolean match = result != null && (boolean) result;
+		return new ConditionOutcome(match, ConditionMessage
 				.forCondition(ConditionalOnExpression.class, "(" + rawExpression + ")")
 				.resultedIn(result));
 	}

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/condition/ConditionalOnExpressionTests.java

 /*
- * Copyright 2012-2016 the original author or authors.
+ * Copyright 2012-2017 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.
@@ -28,13 +28,14 @@ import static org.assertj.core.api.Assertions.assertThat;
  * Tests for {@link ConditionalOnExpression}.
  *
  * @author Dave Syer
+ * @author Stephane Nicoll
  */
 public class ConditionalOnExpressionTests {
 
 	private final AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
 
 	@Test
-	public void testResourceExists() {
+	public void expressionIsTrue() {
 		this.context.register(BasicConfiguration.class);
 		this.context.refresh();
 		assertThat(this.context.containsBean("foo")).isTrue();
@@ -42,12 +43,19 @@ public class ConditionalOnExpressionTests {
 	}
 
 	@Test
-	public void testResourceNotExists() {
+	public void expressionIsFalse() {
 		this.context.register(MissingConfiguration.class);
 		this.context.refresh();
 		assertThat(this.context.containsBean("foo")).isFalse();
 	}
 
+	@Test
+	public void expressionIsNull() {
+		this.context.register(NullConfiguration.class);
+		this.context.refresh();
+		assertThat(this.context.containsBean("foo")).isFalse();
+	}
+
 	@Configuration
 	@ConditionalOnExpression("false")
 	protected static class MissingConfiguration {
@@ -70,4 +78,15 @@ public class ConditionalOnExpressionTests {
 
 	}
 
+	@Configuration
+	@ConditionalOnExpression("true ? null : false")
+	protected static class NullConfiguration {
+
+		@Bean
+		public String foo() {
+			return "foo";
+		}
+
+	}
+
 }