Support override enable auto-configuration

Provide a way for full auto-configuration to be disabled
programmatically. Primarily added to allow special test annotations to
take over partial auto-configuration but still load
@SpringBootApplication classes.

See gh-4901

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/EnableAutoConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2015 the original author or authors.
+ * Copyright 2012-2016 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.
@@ -75,6 +75,8 @@ import org.springframework.core.io.support.SpringFactoriesLoader;
 @Import(EnableAutoConfigurationImportSelector.class)
 public @interface EnableAutoConfiguration {
 
+	String ENABLED_OVERRIDE_PROPERTY = "spring.boot.enableautoconfiguration";
+
 	/**
 	 * Exclude specific auto-configuration classes such that they will never be applied.
 	 * @return the classes to exclude

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/EnableAutoConfigurationImportSelector.java

@@ -64,6 +64,8 @@ public class EnableAutoConfigurationImportSelector
 		implements DeferredImportSelector, BeanClassLoaderAware, ResourceLoaderAware,
 		BeanFactoryAware, EnvironmentAware, Ordered {
 
+	private static final String[] NO_IMPORTS = {};
+
 	private ConfigurableListableBeanFactory beanFactory;
 
 	private Environment environment;
@@ -74,6 +76,9 @@ public class EnableAutoConfigurationImportSelector
 
 	@Override
 	public String[] selectImports(AnnotationMetadata metadata) {
+		if (!isEnabled(metadata)) {
+			return NO_IMPORTS;
+		}
 		try {
 			AnnotationAttributes attributes = getAttributes(metadata);
 			List<String> configurations = getCandidateConfigurations(metadata,
@@ -90,6 +95,15 @@ public class EnableAutoConfigurationImportSelector
 		}
 	}
 
+	protected boolean isEnabled(AnnotationMetadata metadata) {
+		if (getClass().equals(EnableAutoConfigurationImportSelector.class)) {
+			return this.environment.getProperty(
+					EnableAutoConfiguration.ENABLED_OVERRIDE_PROPERTY, Boolean.class,
+					true);
+		}
+		return true;
+	}
+
 	/**
 	 * Return the appropriate {@link AnnotationAttributes} from the
 	 * {@link AnnotationMetadata}. By default this method will return attributes for

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/EnableAutoConfigurationImportSelectorTests.java

@@ -150,11 +150,28 @@ public class EnableAutoConfigurationImportSelectorTests {
 						ThymeleafAutoConfiguration.class.getName());
 	}
 
+	@Test
+	public void propertyOverrideSetToTrue() throws Exception {
+		configureExclusions(new String[0], new String[0], new String[0]);
+		this.environment.setProperty(EnableAutoConfiguration.ENABLED_OVERRIDE_PROPERTY, "true");
+		String[] imports = this.importSelector.selectImports(this.annotationMetadata);
+		assertThat(imports).isNotEmpty();
+	}
+
+	@Test
+	public void propertyOverrideSetToFalse() throws Exception {
+		configureExclusions(new String[0], new String[0], new String[0]);
+		this.environment.setProperty(EnableAutoConfiguration.ENABLED_OVERRIDE_PROPERTY, "false");
+		String[] imports = this.importSelector.selectImports(this.annotationMetadata);
+		assertThat(imports).isEmpty();
+	}
+
 	private void configureExclusions(String[] classExclusion, String[] nameExclusion,
 			String[] propertyExclusion) {
-		given(this.annotationMetadata
-				.getAnnotationAttributes(EnableAutoConfiguration.class.getName(), true))
-						.willReturn(this.annotationAttributes);
+		String annotationName = EnableAutoConfiguration.class.getName();
+		given(this.annotationMetadata.isAnnotated(annotationName)).willReturn(true);
+		given(this.annotationMetadata.getAnnotationAttributes(annotationName, true))
+				.willReturn(this.annotationAttributes);
 		given(this.annotationAttributes.getStringArray("exclude"))
 				.willReturn(classExclusion);
 		given(this.annotationAttributes.getStringArray("excludeName"))