Fix ordering problem in PropertySourcesPropertyValues

This affected @ConfigurationProperties binding whenever there
were multiple PropertySources (from any source) in the
Environment and mor ethan one carried a value for a particular
key. The rules for override are clear in Environment.getProperty()
but they were being violated by the PropertySourcesPropertyValues.

Fixes gh-916

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

@@ -88,8 +88,10 @@ public class PropertySourcesPropertyValues implements PropertyValues {
 						catch (RuntimeException ex) {
 							// Probably could not resolve placeholders, ignore it here
 						}
-						this.propertyValues.put(propertyName, new PropertyValue(
-								propertyName, value));
+						if (!this.propertyValues.containsKey(propertyName)) {
+							this.propertyValues.put(propertyName, new PropertyValue(
+									propertyName, value));
+						}
 					}
 				}
 			}
@@ -99,13 +101,13 @@ public class PropertySourcesPropertyValues implements PropertyValues {
 				for (String propertyName : exacts) {
 					Object value;
 					value = source.getProperty(propertyName);
-					if (value != null) {
+					if (value != null && !this.propertyValues.containsKey(propertyName)) {
 						this.propertyValues.put(propertyName, new PropertyValue(
 								propertyName, value));
 						continue;
 					}
 					value = source.getProperty(propertyName.toUpperCase());
-					if (value != null) {
+					if (value != null && !this.propertyValues.containsKey(propertyName)) {
 						this.propertyValues.put(propertyName, new PropertyValue(
 								propertyName, value));
 						continue;

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

@@ -0,0 +1,72 @@
+package org.springframework.boot.bind;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.boot.bind.PropertySourcesBindingTests.TestConfig;
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.boot.context.properties.EnableConfigurationProperties;
+import org.springframework.boot.test.IntegrationTest;
+import org.springframework.boot.test.SpringApplicationConfiguration;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
+import org.springframework.context.annotation.PropertySource;
+import org.springframework.context.annotation.PropertySources;
+import org.springframework.context.support.PropertySourcesPlaceholderConfigurer;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+
+import static org.hamcrest.Matchers.is;
+import static org.junit.Assert.assertThat;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@SpringApplicationConfiguration(classes = TestConfig.class)
+@IntegrationTest
+public class PropertySourcesBindingTests {
+
+	@Value("${foo:}")
+	private String foo;
+
+	@Autowired
+	private Wrapper properties;
+
+	@Test
+	public void overridingOfPropertiesWorksAsExpected() {
+		assertThat(this.foo, is(this.properties.getFoo()));
+	}
+
+	@Import({ SomeConfig.class })
+	@PropertySources({ @PropertySource("classpath:/override.properties"),
+			@PropertySource("classpath:/some.properties") })
+	@Configuration
+	@EnableConfigurationProperties(Wrapper.class)
+	public static class TestConfig {
+
+		@Bean
+		public static PropertySourcesPlaceholderConfigurer propertySourcesPlaceholderConfigurer() {
+			return new PropertySourcesPlaceholderConfigurer();
+		}
+
+	}
+
+	@Configuration
+	@PropertySources({ @PropertySource("classpath:/override.properties"),
+			@PropertySource("classpath:/some.properties") })
+	public static class SomeConfig {
+	}
+
+	@ConfigurationProperties
+	public static class Wrapper {
+		private String foo;
+
+		public String getFoo() {
+			return this.foo;
+		}
+
+		public void setFoo(String foo) {
+			this.foo = foo;
+		}
+	}
+
+}

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

@@ -0,0 +1,64 @@
+package org.springframework.boot.bind;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.boot.bind.SimplerPropertySourcesBindingTests.TestConfig;
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.boot.context.properties.EnableConfigurationProperties;
+import org.springframework.boot.test.IntegrationTest;
+import org.springframework.boot.test.SpringApplicationConfiguration;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.PropertySource;
+import org.springframework.context.annotation.PropertySources;
+import org.springframework.context.support.PropertySourcesPlaceholderConfigurer;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+
+import static org.hamcrest.Matchers.is;
+import static org.junit.Assert.assertThat;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@SpringApplicationConfiguration(classes = TestConfig.class)
+@IntegrationTest
+public class SimplerPropertySourcesBindingTests {
+
+	@Value("${foo:}")
+	private String foo;
+
+	@Autowired
+	private Wrapper properties;
+
+	@Test
+	public void overridingOfPropertiesWorksAsExpected() {
+		assertThat(this.foo, is(this.properties.getFoo()));
+	}
+
+	@PropertySources({ @PropertySource("classpath:/override.properties"),
+			@PropertySource("classpath:/some.properties") })
+	@Configuration
+	@EnableConfigurationProperties(Wrapper.class)
+	public static class TestConfig {
+
+		@Bean
+		public static PropertySourcesPlaceholderConfigurer propertySourcesPlaceholderConfigurer() {
+			return new PropertySourcesPlaceholderConfigurer();
+		}
+
+	}
+
+	@ConfigurationProperties
+	public static class Wrapper {
+		private String foo;
+
+		public String getFoo() {
+			return this.foo;
+		}
+
+		public void setFoo(String foo) {
+			this.foo = foo;
+		}
+	}
+
+}

spring-boot/src/test/resources/override.properties

@@ -0,0 +1 @@
+foo=bar

spring-boot/src/test/resources/some.properties

@@ -0,0 +1 @@
+foo=spam