Add AutoConfigurationMetadata abstraction

Add AutoConfigurationMetadata interface and a an internal loader that
allows easy access to data written by `spring-boot-configure-processor`.

See gh-7573

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

@@ -0,0 +1,88 @@
+/*
+ * Copyright 2012-2017 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.autoconfigure;
+
+import java.util.Set;
+
+/**
+ * Provides access to meta-data written by the auto-configure annotation processor.
+ *
+ * @author Phillip Webb
+ * @since 1.5.0
+ */
+public interface AutoConfigurationMetadata {
+
+	/**
+	 * Return {@code true} if the specified class name was processed by the annotation
+	 * processor.
+	 * @param className the source class
+	 * @return if the class was processed
+	 */
+	boolean wasProcessed(String className);
+
+	/**
+	 * Get an {@link Integer} value from the meta-data.
+	 * @param className the source class
+	 * @param key the meta-data key
+	 * @return the meta-data value or {@code null}
+	 */
+	Integer getInteger(String className, String key);
+
+	/**
+	 * Get an {@link Integer} value from the meta-data.
+	 * @param className the source class
+	 * @param key the meta-data key
+	 * @param defaultValue the default value
+	 * @return the meta-data value or {@code defaultValue}
+	 */
+	Integer getInteger(String className, String key, Integer defaultValue);
+
+	/**
+	 * Get a {@link Set} value from the meta-data.
+	 * @param className the source class
+	 * @param key the meta-data key
+	 * @return the meta-data value or {@code null}
+	 */
+	Set<String> getSet(String className, String key);
+
+	/**
+	 * Get a {@link Set} value from the meta-data.
+	 * @param className the source class
+	 * @param key the meta-data key
+	 * @param defaultValue the default value
+	 * @return the meta-data value or {@code defaultValue}
+	 */
+	Set<String> getSet(String className, String key, Set<String> defaultValue);
+
+	/**
+	 * Get an {@link String} value from the meta-data.
+	 * @param className the source class
+	 * @param key the meta-data key
+	 * @return the meta-data value or {@code null}
+	 */
+	String get(String className, String key);
+
+	/**
+	 * Get an {@link String} value from the meta-data.
+	 * @param className the source class
+	 * @param key the meta-data key
+	 * @param defaultValue the default value
+	 * @return the meta-data value or {@code defaultValue}
+	 */
+	String get(String className, String key, String defaultValue);
+
+}

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

@@ -0,0 +1,121 @@
+/*
+ * Copyright 2012-2017 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.autoconfigure;
+
+import java.io.IOException;
+import java.net.URL;
+import java.util.Enumeration;
+import java.util.Properties;
+import java.util.Set;
+
+import org.springframework.core.io.UrlResource;
+import org.springframework.core.io.support.PropertiesLoaderUtils;
+import org.springframework.util.StringUtils;
+
+/**
+ * Internal utility used to load {@link AutoConfigurationMetadata}.
+ *
+ * @author Phillip Webb
+ */
+final class AutoConfigurationMetadataLoader {
+
+	protected static final String PATH = "META-INF/"
+			+ "spring-autoconfigure-metadata.properties";
+
+	private AutoConfigurationMetadataLoader() {
+	}
+
+	public static AutoConfigurationMetadata loadMetadata(ClassLoader classLoader) {
+		return loadMetadata(classLoader, PATH);
+	}
+
+	static AutoConfigurationMetadata loadMetadata(ClassLoader classLoader, String path) {
+		try {
+			Enumeration<URL> urls = (classLoader != null ? classLoader.getResources(path)
+					: ClassLoader.getSystemResources(path));
+			Properties properties = new Properties();
+			while (urls.hasMoreElements()) {
+				properties.putAll(PropertiesLoaderUtils
+						.loadProperties(new UrlResource(urls.nextElement())));
+			}
+			return loadMetadata(properties);
+		}
+		catch (IOException ex) {
+			throw new IllegalArgumentException(
+					"Unable to load @ConditionalOnClass location [" + path + "]", ex);
+		}
+	}
+
+	static AutoConfigurationMetadata loadMetadata(Properties properties) {
+		return new PropertiesAutoConfigurationMetadata(properties);
+	}
+
+	/**
+	 * {@link AutoConfigurationMetadata} implementation backed by a properties file.
+	 */
+	private static class PropertiesAutoConfigurationMetadata
+			implements AutoConfigurationMetadata {
+
+		private final Properties properties;
+
+		PropertiesAutoConfigurationMetadata(Properties properties) {
+			this.properties = properties;
+		}
+
+		@Override
+		public boolean wasProcessed(String className) {
+			return this.properties.containsKey(className);
+		}
+
+		@Override
+		public Integer getInteger(String className, String key) {
+			return getInteger(className, key, null);
+		}
+
+		@Override
+		public Integer getInteger(String className, String key, Integer defaultValue) {
+			String value = get(className, key);
+			return (value != null ? Integer.valueOf(value) : defaultValue);
+		}
+
+		@Override
+		public Set<String> getSet(String className, String key) {
+			return getSet(className, key, null);
+		}
+
+		@Override
+		public Set<String> getSet(String className, String key,
+				Set<String> defaultValue) {
+			String value = get(className, key);
+			return (value != null ? StringUtils.commaDelimitedListToSet(value)
+					: defaultValue);
+		}
+
+		@Override
+		public String get(String className, String key) {
+			return get(className, key, null);
+		}
+
+		@Override
+		public String get(String className, String key, String defaultValue) {
+			String value = this.properties.getProperty(className + "." + key);
+			return (value != null ? value : defaultValue);
+		}
+
+	}
+
+}

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

@@ -0,0 +1,98 @@
+/*
+ * Copyright 2012-2017 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.autoconfigure;
+
+import java.util.Collections;
+
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Test for {@link AutoConfigurationMetadataLoader}.
+ *
+ * @author Phillip Webb
+ */
+public class AutoConfigurationMetadataLoaderTests {
+
+	@Test
+	public void loadShouldLoadProperties() throws Exception {
+		assertThat(load()).isNotNull();
+	}
+
+	@Test
+	public void wasProcessedWhenProcessedShouldReturnTrue() throws Exception {
+		assertThat(load().wasProcessed("test")).isTrue();
+	}
+
+	@Test
+	public void wasProcessedWhenNotProcessedShouldReturnFalse() throws Exception {
+		assertThat(load().wasProcessed("testx")).isFalse();
+	}
+
+	@Test
+	public void getIntegerShouldReturnValue() throws Exception {
+		assertThat(load().getInteger("test", "int")).isEqualTo(123);
+	}
+
+	@Test
+	public void getIntegerWhenMissingShouldReturnNull() throws Exception {
+		assertThat(load().getInteger("test", "intx")).isNull();
+	}
+
+	@Test
+	public void getIntegerWithDefaultWhenMissingShouldReturnDefault() throws Exception {
+		assertThat(load().getInteger("test", "intx", 345)).isEqualTo(345);
+	}
+
+	@Test
+	public void getSetShouldReturnValue() throws Exception {
+		assertThat(load().getSet("test", "set")).containsExactly("a", "b", "c");
+	}
+
+	@Test
+	public void getSetWhenMissingShouldReturnNull() throws Exception {
+		assertThat(load().getSet("test", "setx")).isNull();
+	}
+
+	@Test
+	public void getSetWithDefaultWhenMissingShouldReturnDefault() throws Exception {
+		assertThat(load().getSet("test", "setx", Collections.singleton("x")))
+				.containsExactly("x");
+	}
+
+	@Test
+	public void getShouldReturnValue() throws Exception {
+		assertThat(load().get("test", "string")).isEqualTo("abc");
+	}
+
+	@Test
+	public void getWhenMissingShouldReturnNull() throws Exception {
+		assertThat(load().get("test", "stringx")).isNull();
+	}
+
+	@Test
+	public void getWithDefaultWhenMissingShouldReturnDefault() throws Exception {
+		assertThat(load().get("test", "stringx", "xyz")).isEqualTo("xyz");
+	}
+
+	private AutoConfigurationMetadata load() {
+		return AutoConfigurationMetadataLoader.loadMetadata(null,
+				"META-INF/AutoConfigurationMetadataLoaderTests.properties");
+	}
+
+}

spring-boot-autoconfigure/src/test/resources/META-INF/AutoConfigurationMetadataLoaderTests.properties

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+test=
+test.string=abc
+test.int=123
+test.set=a,b,b,c