Add default-value getProperty convenience variants

Issue: SPR-8322

org.springframework.core/src/main/java/org/springframework/core/env/AbstractEnvironment.java

@@ -192,10 +192,18 @@ public abstract class AbstractEnvironment implements ConfigurableEnvironment {
 		return this.propertyResolver.getProperty(key);
 	}
 
+	public String getProperty(String key, String defaultValue) {
+		return this.propertyResolver.getProperty(key, defaultValue);
+	}
+
 	public <T> T getProperty(String key, Class<T> targetType) {
 		return this.propertyResolver.getProperty(key, targetType);
 	}
 
+	public <T> T getProperty(String key, Class<T> targetType, T defaultValue) {
+		return this.propertyResolver.getProperty(key, targetType, defaultValue);
+	};
+
 	public <T> Class<T> getPropertyAsClass(String key, Class<T> targetType) {
 		return this.propertyResolver.getPropertyAsClass(key, targetType);
 	}

org.springframework.core/src/main/java/org/springframework/core/env/PropertyResolver.java

@@ -30,17 +30,44 @@ public interface PropertyResolver {
 	boolean containsProperty(String key);
 
 	/**
-	 * Return the property value associated with the given key.
+	 * Return the property value associated with the given key, or {@code null}
+	 * if the key cannot be resolved.
+	 * @param key the property name to resolve
+	 * @see #getProperty(String, String)
 	 * @see #getProperty(String, Class)
+	 * @see #getRequiredProperty(String)
 	 */
 	String getProperty(String key);
 
+	/**
+	 * Return the property value associated with the given key, or
+	 * {@code defaultValue} if the key cannot be resolved.
+	 * @param key the property name to resolve
+	 * @param defaultValue the default value to return if no value is found
+	 * @see #getRequiredProperty(String)
+	 * @see #getProperty(String, Class)
+	 */
+	String getProperty(String key, String defaultValue);
+
 	/**
 	 * Return the property value associated with the given key, or {@code null}
 	 * if the key cannot be resolved.
+	 * @param key the property name to resolve
+	 * @param T the expected type of the property value
+	 * @see #getRequiredProperty(String, Class)
 	 */
 	<T> T getProperty(String key, Class<T> targetType);
 
+	/**
+	 * Return the property value associated with the given key, or
+	 * {@code defaultValue} if the key cannot be resolved.
+	 * @param key the property name to resolve
+	 * @param T the expected type of the property value
+	 * @param defaultValue the default value to return if no value is found
+	 * @see #getRequiredProperty(String, Class)
+	 */
+	<T> T getProperty(String string, Class<T> targetType, T defaultValue);
+
 	/**
 	 * Convert the property value associated with the given key to a {@code Class}
 	 * of type {@code T} or {@code null} if the key cannot be resolved.

org.springframework.core/src/main/java/org/springframework/core/env/PropertySourcesPropertyResolver.java

@@ -56,6 +56,11 @@ public class PropertySourcesPropertyResolver extends AbstractPropertyResolver {
 		return this.getProperty(key, String.class);
 	}
 
+	public String getProperty(String key, String defaultValue) {
+		String value = getProperty(key);
+		return value == null ? defaultValue : value;
+	}
+
 	public <T> T getProperty(String key, Class<T> targetValueType) {
 		boolean debugEnabled = logger.isDebugEnabled();
 		if (logger.isTraceEnabled()) {
@@ -89,6 +94,11 @@ public class PropertySourcesPropertyResolver extends AbstractPropertyResolver {
 		return null;
 	}
 
+	public <T> T getProperty(String key, Class<T> targetType, T defaultValue) {
+		T value = getProperty(key, targetType);
+		return value == null ? defaultValue : value;
+	};
+
 	public <T> Class<T> getPropertyAsClass(String key, Class<T> targetValueType) {
 		boolean debugEnabled = logger.isDebugEnabled();
 		if (logger.isTraceEnabled()) {

org.springframework.core/src/test/java/org/springframework/core/env/PropertySourcesPropertyResolverTests.java

@@ -65,6 +65,13 @@ public class PropertySourcesPropertyResolverTests {
 		assertThat(propertyResolver.getProperty("foo"), is("bar"));
 	}
 
+	@Test
+	public void getProperty_withDefaultValue() {
+		assertThat(propertyResolver.getProperty("foo", "myDefault"), is("myDefault"));
+		testProperties.put("foo", "bar");
+		assertThat(propertyResolver.getProperty("foo"), is("bar"));
+	}
+
 	@Test
 	public void getProperty_propertySourceSearchOrderIsFIFO() {
 		MutablePropertySources sources = new MutablePropertySources();
@@ -86,6 +93,13 @@ public class PropertySourcesPropertyResolverTests {
 		assertThat(propertyResolver.getProperty("foo"), nullValue());
 	}
 
+	@Test
+	public void getProperty_withTargetType_andDefaultValue() {
+		assertThat(propertyResolver.getProperty("foo", Integer.class, 42), equalTo(42));
+		testProperties.put("foo", 13);
+		assertThat(propertyResolver.getProperty("foo", Integer.class, 42), equalTo(13));
+	}
+
 	@Test
 	public void getProperty_withStringArrayConversion() {
 		testProperties.put("foo", "bar,baz");
@@ -197,7 +211,7 @@ public class PropertySourcesPropertyResolverTests {
 	}
 
 	@Test
-	public void resolvePlaceholders_withDefault() {
+	public void resolvePlaceholders_withDefaultValue() {
 		MutablePropertySources propertySources = new MutablePropertySources();
 		propertySources.addFirst(new MockPropertySource().withProperty("key", "value"));
 		PropertyResolver resolver = new PropertySourcesPropertyResolver(propertySources);
@@ -227,7 +241,7 @@ public class PropertySourcesPropertyResolverTests {
 	}
 
 	@Test
-	public void resolveRequiredPlaceholders_withDefault() {
+	public void resolveRequiredPlaceholders_withDefaultValue() {
 		MutablePropertySources propertySources = new MutablePropertySources();
 		propertySources.addFirst(new MockPropertySource().withProperty("key", "value"));
 		PropertyResolver resolver = new PropertySourcesPropertyResolver(propertySources);