Fix `spring.application.exclude` YAML property

`spring.application.exclude` is retrieved via the
`RelaxedPropertyResolver` API explicitly and it does not have any
standard API to retrieve a list of values. As a consequence that property
could only be specified as a comma-separated value.

This felt convoluted in YAML. `RelaxedPropertyResolver` has now a
`getProperties` method that works with both comma-separated value and
index elements (i.e. list).

Closes gh-4352

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

@@ -153,8 +153,12 @@ public class EnableAutoConfigurationImportSelector implements DeferredImportSele
 	private List<String> getExcludeAutoConfigurationsProperty() {
 		RelaxedPropertyResolver resolver = new RelaxedPropertyResolver(getEnvironment(),
 				"spring.autoconfigure.");
-		String[] exclude = resolver.getProperty("exclude", String[].class);
-		return (Arrays.asList(exclude == null ? new String[0] : exclude));
+		Collection<Object> raw = resolver.getProperties("exclude");
+		List<String> values = new ArrayList<String>();
+		for (Object r : raw) {
+			values.add(r.toString());
+		}
+		return values;
 	}
 
 	private List<String> sort(List<String> configurations) throws IOException {

spring-boot-autoconfigure/src/main/resources/META-INF/additional-spring-configuration-metadata.json

@@ -45,7 +45,7 @@
   },
   {
     "name": "spring.autoconfigure.exclude",
-    "type": "java.lang.Class[]",
+    "type": "java.util.List<java.lang.Class>",
     "description": "Auto-configuration classes to exclude."
   },
   {

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

@@ -134,6 +134,21 @@ public class EnableAutoConfigurationImportSelectorTests {
 						VelocityAutoConfiguration.class.getName()));
 	}
 
+	@Test
+	public void severalPropertyYamlExclusionsAreApplied() {
+		configureExclusions(new String[0], new String[0], new String[0]);
+		this.environment.setProperty("spring.autoconfigure.exclude[0]",
+				FreeMarkerAutoConfiguration.class.getName());
+		this.environment.setProperty("spring.autoconfigure.exclude[1]",
+				VelocityAutoConfiguration.class.getName());
+		String[] imports = this.importSelector.selectImports(this.annotationMetadata);
+		assertThat(imports.length,
+				is(equalTo(getAutoConfigurationClassNames().size() - 2)));
+		assertThat(ConditionEvaluationReport.get(this.beanFactory).getExclusions(),
+				containsInAnyOrder(FreeMarkerAutoConfiguration.class.getName(),
+						VelocityAutoConfiguration.class.getName()));
+	}
+
 	@Test
 	public void combinedExclusionsAreApplied() {
 		configureExclusions(new String[] { VelocityAutoConfiguration.class.getName() },

spring-boot/src/main/java/org/springframework/boot/bind/RelaxedPropertyResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2014 the original author or authors.
+ * Copyright 2012-2015 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.
@@ -16,6 +16,9 @@
 
 package org.springframework.boot.bind;
 
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
 import java.util.Map;
 
 import org.springframework.core.env.ConfigurableEnvironment;
@@ -128,6 +131,21 @@ public class RelaxedPropertyResolver implements PropertyResolver {
 				"Unable to resolve placeholders with relaxed properties");
 	}
 
+	/**
+	 * Return the property values associated with the given key, or an empty
+	 * list if the key cannot be resolved.
+	 * @param key the property name to resolve
+	 * @return the property values for that key
+	 */
+	public List<Object> getProperties(String key) {
+		Object[] singular = getProperty(key, Object[].class);
+		if (singular != null) {
+			return Arrays.asList(singular);
+		}
+		Map<String, Object> subProperties = getSubProperties(key);
+		return new ArrayList<Object>(subProperties.values());
+	}
+
 	/**
 	 * Return a Map of all values from all underlying properties that start with the
 	 * specified key. NOTE: this method can only be used if the underlying resolver is a

spring-boot/src/test/java/org/springframework/boot/bind/RelaxedPropertyResolverTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2013 the original author or authors.
+ * Copyright 2012-2015 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.
@@ -17,6 +17,7 @@
 package org.springframework.boot.bind;
 
 import java.util.LinkedHashMap;
+import java.util.List;
 import java.util.Map;
 import java.util.Properties;
 
@@ -30,6 +31,7 @@ import org.springframework.core.env.MutablePropertySources;
 import org.springframework.core.env.PropertiesPropertySource;
 import org.springframework.core.env.StandardEnvironment;
 
+import static org.hamcrest.Matchers.contains;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.nullValue;
 import static org.junit.Assert.assertEquals;
@@ -39,6 +41,7 @@ import static org.junit.Assert.assertThat;
  * Tests for {@link RelaxedPropertyResolver}.
  *
  * @author Phillip Webb
+ * @author Stephane Nicoll
  */
 public class RelaxedPropertyResolverTests {
 
@@ -166,6 +169,34 @@ public class RelaxedPropertyResolverTests {
 		assertThat(this.resolver.getProperty("foo-bar"), equalTo("spam"));
 	}
 
+	@Test
+	public void commaSeparatedProperties() throws Exception {
+		this.source.put("x.y.foo", "1,2");
+		this.resolver = new RelaxedPropertyResolver(this.environment, "x.y.");
+		List<Object> properties = this.resolver.getProperties("foo");
+		assertThat(properties.size(), equalTo(2));
+		assertThat(properties, contains((Object) "1", (Object) "2"));
+	}
+
+	@Test
+	public void commaSeparatedPropertiesSingleValue() throws Exception {
+		this.source.put("x.y.foo", "1");
+		this.resolver = new RelaxedPropertyResolver(this.environment, "x.y.");
+		List<Object> properties = this.resolver.getProperties("foo");
+		assertThat(properties.size(), equalTo(1));
+		assertThat(properties, contains((Object) "1"));
+	}
+
+	@Test
+	public void indexedProperties() throws Exception {
+		this.source.put("x.y.foo[0]", "1");
+		this.source.put("x.y.foo[1]", "2");
+		this.resolver = new RelaxedPropertyResolver(this.environment, "x.y.");
+		List<Object> properties = this.resolver.getProperties("foo");
+		assertThat(properties.size(), equalTo(2));
+		assertThat(properties, contains((Object) "1", (Object) "2"));
+	}
+
 	@Test
 	public void subProperties() throws Exception {
 		this.source.put("x.y.my-sub.a.b", "1");