Fix NPE when OnExpressionCondition is invoked with a null BeanFactory

Closes gh-13249

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

@@ -29,6 +29,7 @@ import org.springframework.core.type.AnnotatedTypeMetadata;
  * A Condition that evaluates a SpEL expression.
  *
  * @author Dave Syer
+ * @author Stephane Nicoll
  * @see ConditionalOnExpression
  */
 @Order(Ordered.LOWEST_PRECEDENCE - 20)
@@ -43,18 +44,28 @@ class OnExpressionCondition extends SpringBootCondition {
 		expression = wrapIfNecessary(expression);
 		String rawExpression = expression;
 		expression = context.getEnvironment().resolvePlaceholders(expression);
+		ConditionMessage.Builder messageBuilder = ConditionMessage
+				.forCondition(ConditionalOnExpression.class, "(" + rawExpression + ")");
 		ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
-		BeanExpressionResolver resolver = (beanFactory != null
-				? beanFactory.getBeanExpressionResolver() : null);
-		BeanExpressionContext expressionContext = (beanFactory != null
-				? new BeanExpressionContext(beanFactory, null) : null);
+		if (beanFactory != null) {
+			boolean result = evaluateExpression(beanFactory, expression);
+			return new ConditionOutcome(result, messageBuilder.resultedIn(result));
+		}
+		else {
+			return ConditionOutcome
+					.noMatch(messageBuilder.because("no BeanFactory available."));
+		}
+	}
+
+	private Boolean evaluateExpression(ConfigurableListableBeanFactory beanFactory,
+			String expression) {
+		BeanExpressionResolver resolver = beanFactory.getBeanExpressionResolver();
 		if (resolver == null) {
 			resolver = new StandardBeanExpressionResolver();
 		}
-		boolean result = (Boolean) resolver.evaluate(expression, expressionContext);
-		return new ConditionOutcome(result, ConditionMessage
-				.forCondition(ConditionalOnExpression.class, "(" + rawExpression + ")")
-				.resultedIn(result));
+		BeanExpressionContext expressionContext = new BeanExpressionContext(beanFactory,
+				null);
+		return (Boolean) resolver.evaluate(expression, expressionContext);
 	}
 
 	/**

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2016 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -16,25 +16,34 @@
 
 package org.springframework.boot.autoconfigure.condition;
 
+import java.util.HashMap;
+import java.util.Map;
+
 import org.junit.Test;
 
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ConditionContext;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.core.type.AnnotatedTypeMetadata;
+import org.springframework.mock.env.MockEnvironment;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.BDDMockito.given;
+import static org.mockito.Mockito.mock;
 
 /**
  * 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 expressionEvaluatesToTrueRegisterBean() {
 		this.context.register(BasicConfiguration.class);
 		this.context.refresh();
 		assertThat(this.context.containsBean("foo")).isTrue();
@@ -42,12 +51,34 @@ public class ConditionalOnExpressionTests {
 	}
 
 	@Test
-	public void testResourceNotExists() {
+	public void expressionEvaluatesToFalseDoesNotRegisterBean() {
 		this.context.register(MissingConfiguration.class);
 		this.context.refresh();
 		assertThat(this.context.containsBean("foo")).isFalse();
 	}
 
+	@Test
+	public void expressionEvaluationWithNoBeanFactoryDoesNotMatch() {
+		OnExpressionCondition condition = new OnExpressionCondition();
+		MockEnvironment environment = new MockEnvironment();
+		ConditionContext conditionContext = mock(ConditionContext.class);
+		given(conditionContext.getEnvironment()).willReturn(environment);
+		ConditionOutcome outcome = condition.getMatchOutcome(conditionContext,
+				mockMetaData("invalid-spel"));
+		assertThat(outcome.isMatch()).isFalse();
+		assertThat(outcome.getMessage()).contains("invalid-spel")
+				.contains("no BeanFactory available");
+	}
+
+	private AnnotatedTypeMetadata mockMetaData(String value) {
+		AnnotatedTypeMetadata metadata = mock(AnnotatedTypeMetadata.class);
+		Map<String, Object> attributes = new HashMap<String, Object>();
+		attributes.put("value", value);
+		given(metadata.getAnnotationAttributes(ConditionalOnExpression.class.getName()))
+				.willReturn(attributes);
+		return metadata;
+	}
+
 	@Configuration
 	@ConditionalOnExpression("false")
 	protected static class MissingConfiguration {