Allow use of underscores in @ConfigurationProperties prefix

Currently the PropertiesConfigurationFilter filters them out.
Thus when deploying to IAAS these environment variables are ignored.

Fixes gh-154

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

@@ -258,6 +258,7 @@ public class PropertiesConfigurationFactory<T> implements FactoryBean<T>,
 					names.add(name);
 					names.add(name + ".*");
 					names.add(name + "_*");
+					names.add("*_"+name);
 				}
 			}
 		}

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

@@ -68,6 +68,14 @@ public class PropertiesConfigurationFactoryTests {
 		assertEquals("blah", foo.name);
 	}
 
+	
+	@Test
+	public void testUnderscore() throws Exception {
+		Foo foo = createFoo("spring_foo_baz: blah\nname: blah");
+		assertEquals("blah", foo.spring_foo_baz);
+		assertEquals("blah", foo.name);
+	}
+	
 	@Test
 	public void testUnknownPropertyOkByDefault() throws Exception {
 		Foo foo = createFoo("hi: hello\nname: foo\nbar: blah");
@@ -130,6 +138,16 @@ public class PropertiesConfigurationFactoryTests {
 
 		private String bar;
 		
+		private String spring_foo_baz;
+
+		public String getSpringFooBaz() {
+			return spring_foo_baz;
+		}
+
+		public void setSpringFooBaz(String spring_foo_baz) {
+			this.spring_foo_baz = spring_foo_baz;
+		}
+
 		public String getName() {
 			return this.name;
 		}

spring-boot/src/test/java/org/springframework/boot/context/properties/EnableConfigurationPropertiesTests.java

@@ -109,6 +109,17 @@ public class EnableConfigurationPropertiesTests {
 		assertEquals("foo", this.context.getBean(TestProperties.class).name);
 	}
 
+	@Test
+	public void testPropertiesEmbeddedBinding() {
+		this.context.register(EmbeddedTestConfiguration.class);
+		TestUtils.addEnviroment(this.context, "spring_foo_name:foo");
+		this.context.refresh();
+		assertEquals(1,
+				this.context.getBeanNamesForType(EmbeddedTestProperties.class).length);
+		assertEquals("foo", this.context.getBean(TestProperties.class).name);
+	}
+	
+	
 	@Test
 	public void testIgnoreNestedPropertiesBinding() {
 		this.context.register(IgnoreNestedTestConfiguration.class);
@@ -287,6 +298,10 @@ public class EnableConfigurationPropertiesTests {
 	protected static class StrictTestConfiguration {
 	}
 	
+	@Configuration
+	@EnableConfigurationProperties(EmbeddedTestProperties.class)
+	protected static class EmbeddedTestConfiguration {
+	}
 	@Configuration
 	@EnableConfigurationProperties(IgnoreNestedTestProperties.class)
 	protected static class IgnoreNestedTestConfiguration {
@@ -410,6 +425,10 @@ public class EnableConfigurationPropertiesTests {
 	@ConfigurationProperties(ignoreUnknownFields = false)
 	protected static class StrictTestProperties extends TestProperties {
 
+	}
+	@ConfigurationProperties(name = "spring.foo")
+	protected static class EmbeddedTestProperties extends TestProperties {
+
 	}
 	
 	@ConfigurationProperties(ignoreUnknownFields = false, ignoreNestedProperties = true)

spring-boot/src/test/java/org/springframework/boot/context/test/EnableConfigurationPropertiesTests.java

@@ -48,8 +48,9 @@ public class EnableConfigurationPropertiesTests {
 				.getEnvironment()
 				.getPropertySources()
 				.addFirst(
-						new PropertiesPropertySource("props",
-								getProperties("external.name=foo\nanother.name=bar")));
+						new PropertiesPropertySource(
+								"props",
+								getProperties("external.name=foo\nanother.name=bar\nspring_test_external_val=baz")));
 	}
 
 	@After
@@ -59,6 +60,13 @@ public class EnableConfigurationPropertiesTests {
 		}
 	}
 
+	@Test
+	public void testUnderscoresInPrefix() throws Exception {
+		this.context.register(SystemExampleConfig.class);
+		this.context.refresh();
+		assertEquals("baz", this.context.getBean(SystemEnvVar.class).getVal());
+	}
+
 	@Test
 	public void testSimpleAutoConfig() throws Exception {
 		this.context.register(ExampleConfig.class);
@@ -105,6 +113,11 @@ public class EnableConfigurationPropertiesTests {
 	public static class FurtherExampleConfig {
 	}
 
+	@EnableConfigurationProperties({ SystemEnvVar.class })
+	@Configuration
+	public static class SystemExampleConfig {
+	}
+
 	@ConfigurationProperties(name = "external")
 	public static class External {
 
@@ -132,4 +145,18 @@ public class EnableConfigurationPropertiesTests {
 			this.name = name;
 		}
 	}
+
+	@ConfigurationProperties(name = "spring_test_external")
+	public static class SystemEnvVar {
+		public String getVal() {
+			return this.val;
+		}
+
+		public void setVal(String val) {
+			this.val = val;
+		}
+
+		private String val;
+
+	}
 }