DATACMNS-1498 - Improved attribute lookup on RepositoryConfigurationSource.

src/main/java/org/springframework/data/repository/config/AnnotationRepositoryConfigurationSource.java

@@ -328,9 +328,35 @@ public class AnnotationRepositoryConfigurationSource extends RepositoryConfigura
 	 */
 	@Override
 	public Optional<String> getAttribute(String name) {
+		return getAttribute(name, String.class);
+	}
 
-		String attribute = attributes.getString(name);
-		return StringUtils.hasText(attribute) ? Optional.of(attribute) : Optional.empty();
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.repository.config.RepositoryConfigurationSource#getAttribute(java.lang.String, java.lang.Class)
+	 */
+	@Override
+	public <T> Optional<T> getAttribute(String name, Class<T> type) {
+
+		if (!attributes.containsKey(name)) {
+			throw new IllegalArgumentException(String.format("No attribute named %s found!", name));
+		}
+
+		Object value = attributes.get(name);
+
+		if (value == null) {
+			return Optional.empty();
+		}
+
+		Assert.isInstanceOf(type, value,
+				() -> String.format("Attribute value for %s is of type %s but was expected to be of type %s!", name,
+						value.getClass(), type));
+
+		Object result = String.class.isInstance(value) //
+				? StringUtils.hasText((String) value) ? value : null //
+				: value;
+
+		return Optional.ofNullable(type.cast(result));
 	}
 
 	/*
@@ -342,7 +368,7 @@ public class AnnotationRepositoryConfigurationSource extends RepositoryConfigura
 		return hasExplicitFilters;
 	}
 
-	/* 
+	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.repository.config.RepositoryConfigurationSource#getBootstrapMode()
 	 */

src/main/java/org/springframework/data/repository/config/RepositoryConfigurationSource.java

@@ -24,6 +24,7 @@ import org.springframework.core.type.filter.TypeFilter;
 import org.springframework.data.repository.query.QueryLookupStrategy;
 import org.springframework.data.util.Streamable;
 import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 
 /**
  * Interface containing the configurable options for the Spring Data repository subsystem.
@@ -103,6 +104,31 @@ public interface RepositoryConfigurationSource {
 	 */
 	Optional<String> getAttribute(String name);
 
+	/**
+	 * Returns the value for the attribute with the given name and type. The name is expected to be handed in camel-case.
+	 *
+	 * @param name must not be {@literal null} or empty.
+	 * @param type the type of the attribute to look up.
+	 * @return the attribute with the given name or {@link Optional#empty()} if not configured or empty.
+	 * @since 2.2
+	 */
+	<T> Optional<T> getAttribute(String name, Class<T> type);
+
+	/**
+	 * Returns the attribute value for the attribute of the given name.
+	 *
+	 * @param name must not be {@literal null} or empty.
+	 * @return the attribute with the given name and type.
+	 * @since 2.2
+	 */
+	default <T> T getRequiredAttribute(String name, Class<T> type) {
+
+		Assert.hasText(name, "Attribute name must not be null or empty!");
+
+		return getAttribute(name, type)
+				.orElseThrow(() -> new IllegalArgumentException(String.format("No attribute named %s found!", name)));
+	}
+
 	/**
 	 * Returns whether the configuration uses explicit filtering to scan for repository types.
 	 *
@@ -131,7 +157,7 @@ public interface RepositoryConfigurationSource {
 	/**
 	 * Returns the {@link ImplementationDetectionConfiguration} to be used to scan for custom implementations of the
 	 * repository instances to be created from this {@link RepositoryConfigurationSource}.
-	 * 
+	 *
 	 * @param factory
 	 * @return will never be {@literal null}.
 	 * @since 2.1
@@ -140,7 +166,7 @@ public interface RepositoryConfigurationSource {
 
 	/**
 	 * Defines the repository {@link BootstrapMode} to be used.
-	 * 
+	 *
 	 * @return
 	 * @since 2.1
 	 */

src/main/java/org/springframework/data/repository/config/XmlRepositoryConfigurationSource.java

@@ -188,7 +188,6 @@ public class XmlRepositoryConfigurationSource extends RepositoryConfigurationSou
 	 */
 	@Override
 	public boolean shouldConsiderNestedRepositories() {
-
 		return getNullDefaultedAttribute(element, CONSIDER_NESTED_REPOSITORIES).map(Boolean::parseBoolean).orElse(false);
 	}
 
@@ -205,6 +204,19 @@ public class XmlRepositoryConfigurationSource extends RepositoryConfigurationSou
 		return StringUtils.hasText(attribute) ? Optional.of(attribute) : Optional.empty();
 	}
 
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.repository.config.RepositoryConfigurationSource#getAttribute(java.lang.String, java.lang.Class)
+	 */
+	@SuppressWarnings("unchecked")
+	@Override
+	public <T> Optional<T> getAttribute(String name, Class<T> type) {
+
+		Assert.isAssignable(String.class, type, "Only String attribute lookups are allowed for XML namespaces!");
+
+		return (Optional<T>) getAttribute(name);
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.repository.config.RepositoryConfigurationSource#usesExplicitFilters()
@@ -214,7 +226,7 @@ public class XmlRepositoryConfigurationSource extends RepositoryConfigurationSou
 		return !(this.includeFilters.isEmpty() && this.excludeFilters.isEmpty());
 	}
 
-	/* 
+	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.repository.config.RepositoryConfigurationSource#getBootstrapMode()
 	 */

src/test/java/org/springframework/data/repository/config/AnnotationRepositoryConfigurationSourceUnitTests.java

@@ -33,6 +33,7 @@ import org.springframework.core.io.DefaultResourceLoader;
 import org.springframework.core.io.ResourceLoader;
 import org.springframework.core.type.AnnotationMetadata;
 import org.springframework.core.type.StandardAnnotationMetadata;
+import org.springframework.data.repository.PagingAndSortingRepository;
 import org.springframework.data.util.Streamable;
 
 /**
@@ -138,6 +139,34 @@ public class AnnotationRepositoryConfigurationSourceUnitTests {
 		assertThat(configurationSource.getRepositoryBaseClassName()).isNotPresent();
 	}
 
+	@Test // DATACMNS-1498
+	public void allowsLookupOfNonStringAttribute() {
+
+		RepositoryConfigurationSource source = getConfigSource(DefaultConfiguration.class);
+
+		assertThat(source.getAttribute("repositoryBaseClass", Class.class)).hasValue(PagingAndSortingRepository.class);
+		assertThat(source.getRequiredAttribute("repositoryBaseClass", Class.class))
+				.isEqualTo(PagingAndSortingRepository.class);
+	}
+
+	@Test // DATACMNS-1498
+	public void rejectsInvalidAttributeName() {
+
+		RepositoryConfigurationSource source = getConfigSource(DefaultConfiguration.class);
+
+		assertThatExceptionOfType(IllegalArgumentException.class).isThrownBy(() -> source.getAttribute("fooBar"));
+	}
+
+	@Test // DATACMNS-1498
+	public void lookupOfEmptyStringExposesAbsentValue() {
+
+		RepositoryConfigurationSource source = getConfigSource(DefaultConfiguration.class);
+
+		assertThat(source.getAttribute("namedQueriesLocation", String.class)).isEmpty();
+		assertThatExceptionOfType(IllegalArgumentException.class)
+				.isThrownBy(() -> source.getRequiredAttribute("namedQueriesLocation", String.class));
+	}
+
 	private AnnotationRepositoryConfigurationSource getConfigSource(Class<?> type) {
 
 		AnnotationMetadata metadata = new StandardAnnotationMetadata(type, true);

src/test/java/org/springframework/data/repository/config/XmlRepositoryConfigurationSourceUnitTests.java

@@ -16,6 +16,7 @@
 package org.springframework.data.repository.config;
 
 import static org.assertj.core.api.Assertions.*;
+import static org.mockito.ArgumentMatchers.*;
 import static org.mockito.Mockito.*;
 
 import org.junit.Test;
@@ -40,8 +41,8 @@ public class XmlRepositoryConfigurationSourceUnitTests {
 
 		RepositoryConfigurationSource source = mock(XmlRepositoryConfigurationSource.class);
 		ReflectionTestUtils.setField(source, "element", element);
-		when(source.getAttribute(anyString())).thenCallRealMethod();
 
+		when(source.getAttribute(anyString())).thenCallRealMethod();
 		when(element.getAttribute("some-xml-attribute")).thenReturn("value");
 
 		assertThat(source.getAttribute("someXmlAttribute")).hasValue("value");