Load auto-configurations from META-INF/spring-boot
Implements a new AutoConfigurationLoader, which loads auto-configurations from a file in META-INF/spring-boot. Adapts the AutoConfigurationImportSelector to use the new loader. Adapts the ImportAutoConfigurationImportSelector to use the new loader. Adapts the metadata plugin in the build to additionally load the auto-configurations from the new file. Updates the documentation for auto-configurations and test slices. Closes gh-29872pull/29911/head
Moritz Halbritter
3 years ago
parent
a55759d531
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/*
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* Copyright 2012-2022 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.boot.autoconfigure;
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import java.io.BufferedReader;
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import java.io.IOException;
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import java.io.InputStreamReader;
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import java.net.URL;
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import java.nio.charset.StandardCharsets;
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import java.util.ArrayList;
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import java.util.Enumeration;
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import java.util.List;
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import org.springframework.core.io.UrlResource;
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import org.springframework.core.io.support.SpringFactoriesLoader;
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import org.springframework.util.Assert;
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/**
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* Loads the names of annotated classes, usually @{@link AutoConfiguration}.
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*
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* The names of the classes are stored in files named META-INF/spring-boot/{full qualified
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* name of the annotation}. Every line contains the full qualified class name of the
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* annotated class. Comments are supported using the # character.
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*
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* @author Moritz Halbritter
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* @see AutoConfiguration
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* @see SpringFactoriesLoader
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*/
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class AutoConfigurationLoader {
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private static final String LOCATION = "META-INF/spring-boot/";
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private static final String COMMENT_START = "#";
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/**
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* Loads the names of annotated classes.
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* @param annotation annotation to load
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* @param classLoader class loader to use for loading
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* @return list of names of annotated classes
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*/
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List<String> loadNames(Class<?> annotation, ClassLoader classLoader) {
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Assert.notNull(annotation, "'annotation' must not be null");
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ClassLoader classLoaderToUse = decideClassloader(classLoader);
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String location = LOCATION + annotation.getName();
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Enumeration<URL> urls = findUrlsInClasspath(classLoaderToUse, location);
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List<String> autoConfigurations = new ArrayList<>();
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while (urls.hasMoreElements()) {
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URL url = urls.nextElement();
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autoConfigurations.addAll(readAutoConfigurations(url));
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}
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return autoConfigurations;
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}
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private ClassLoader decideClassloader(ClassLoader classLoader) {
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if (classLoader == null) {
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return AutoConfigurationLoader.class.getClassLoader();
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}
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return classLoader;
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}
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private Enumeration<URL> findUrlsInClasspath(ClassLoader classLoader, String location) {
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try {
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return classLoader.getResources(location);
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}
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catch (IOException ex) {
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throw new IllegalArgumentException("Failed to load autoconfigurations from location [" + location + "]",
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ex);
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}
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}
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private List<String> readAutoConfigurations(URL url) {
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try (BufferedReader reader = new BufferedReader(
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new InputStreamReader(new UrlResource(url).getInputStream(), StandardCharsets.UTF_8))) {
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List<String> autoConfigurations = new ArrayList<>();
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String line;
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while ((line = reader.readLine()) != null) {
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line = stripComment(line);
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line = line.trim();
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if (line.isEmpty()) {
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continue;
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}
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autoConfigurations.add(line);
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}
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return autoConfigurations;
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}
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catch (IOException ex) {
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throw new IllegalArgumentException("Unable to load autoconfigurations from location [" + url + "]", ex);
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}
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}
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private String stripComment(String line) {
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int commentStart = line.indexOf(COMMENT_START);
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if (commentStart == -1) {
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return line;
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}
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return line.substring(0, commentStart);
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}
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}
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@ -0,0 +1,53 @@
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/*
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* Copyright 2012-2022 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.boot.autoconfigure;
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import java.lang.annotation.ElementType;
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import java.lang.annotation.Retention;
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import java.lang.annotation.RetentionPolicy;
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import java.lang.annotation.Target;
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import java.util.List;
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import org.junit.jupiter.api.BeforeEach;
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import org.junit.jupiter.api.Test;
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import static org.assertj.core.api.Assertions.assertThat;
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class AutoConfigurationLoaderTests {
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private AutoConfigurationLoader sut;
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@BeforeEach
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void setUp() {
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this.sut = new AutoConfigurationLoader();
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}
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@Test
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void loadNames() {
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List<String> classNames = this.sut.loadNames(TestAutoConfiguration.class, null);
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assertThat(classNames).containsExactly("class1", "class2", "class3");
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}
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@AutoConfiguration
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@Target(ElementType.TYPE)
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@Retention(RetentionPolicy.RUNTIME)
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public @interface TestAutoConfiguration {
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}
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}
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@ -0,0 +1,6 @@
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# A comment spanning a complete line
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class1
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class2 # with comment at the end
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# Comment with some whitespace in front
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class3
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