Add layertools jarmode

Add a new `spring-boot-layertools` module which provides jarmode support
for working with layers. The module works with both classic fat jars,
as well as layered jars.

Closes gh-19849

Author: philwebb

eclipse/spring-boot-project.setup

@@ -127,7 +127,7 @@
         name="spring-boot-tools">
       <predicate
           xsi:type="predicates:NamePredicate"
-          pattern="spring-boot-(tools|antlib|configuration-.*|loader|.*-tools|.*-plugin|autoconfigure-processor|cloudnativebuildpack)"/>
+          pattern="spring-boot-(tools|antlib|configuration-.*|loader|.*-tools|*.layertools|.*-plugin|autoconfigure-processor|cloudnativebuildpack)"/>
     </workingSet>
     <workingSet
         name="spring-boot-starters">

settings.gradle

@@ -45,6 +45,7 @@ include 'spring-boot-project:spring-boot-tools:spring-boot-cloudnativebuildpack'
 include 'spring-boot-project:spring-boot-tools:spring-boot-configuration-metadata'
 include 'spring-boot-project:spring-boot-tools:spring-boot-configuration-processor'
 include 'spring-boot-project:spring-boot-tools:spring-boot-gradle-plugin'
+include 'spring-boot-project:spring-boot-tools:spring-boot-layertools'
 include 'spring-boot-project:spring-boot-tools:spring-boot-loader'
 include 'spring-boot-project:spring-boot-tools:spring-boot-loader-tools'
 include 'spring-boot-project:spring-boot-tools:spring-boot-maven-plugin'

spring-boot-project/spring-boot-dependencies/build.gradle

@@ -1425,6 +1425,7 @@ bom {
 				'spring-boot-configuration-metadata',
 				'spring-boot-configuration-processor',
 				'spring-boot-devtools',
+				'spring-boot-layertools',
 				'spring-boot-loader',
 				'spring-boot-loader-tools',
 				'spring-boot-properties-migrator',

spring-boot-project/spring-boot-tools/spring-boot-layertools/build.gradle

@@ -0,0 +1,21 @@
+plugins {
+	id 'java-library'
+	id 'org.springframework.boot.conventions'
+	id 'org.springframework.boot.deployed'
+	id 'org.springframework.boot.internal-dependency-management'
+}
+
+description = 'Spring Boot Layers Tools'
+
+dependencies {
+	api platform(project(':spring-boot-project:spring-boot-parent'))
+
+	implementation project(':spring-boot-project:spring-boot-tools:spring-boot-loader')
+	implementation project(':spring-boot-project:spring-boot')
+	implementation 'org.springframework:spring-core'
+
+	testImplementation "org.assertj:assertj-core"
+	testImplementation "org.junit.jupiter:junit-jupiter"
+	testImplementation "org.mockito:mockito-core"
+}
+

spring-boot-project/spring-boot-tools/spring-boot-layertools/src/main/java/org/springframework/boot/layertools/Command.java

@@ -0,0 +1,335 @@
+/*
+ * Copyright 2012-2020 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
+ *
+ *      https://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.layertools;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Deque;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Stream;
+
+/**
+ * A command that can be launched from the layertools jarmode.
+ *
+ * @author Phillip Webb
+ */
+abstract class Command {
+
+	private final String name;
+
+	private final String description;
+
+	private final Options options;
+
+	private final Parameters parameters;
+
+	/**
+	 * Create a new {@link Command} instance.
+	 * @param name the name of the command
+	 * @param description a description of the command
+	 * @param options the command options
+	 * @param parameters the command parameters
+	 */
+	Command(String name, String description, Options options, Parameters parameters) {
+		this.name = name;
+		this.description = description;
+		this.options = options;
+		this.parameters = parameters;
+	}
+
+	/**
+	 * Return the name of this command.
+	 * @return the command name
+	 */
+	String getName() {
+		return this.name;
+	}
+
+	/**
+	 * Return the description of this command.
+	 * @return the command description
+	 */
+	String getDescription() {
+		return this.description;
+	}
+
+	/**
+	 * Return options that this command accepts.
+	 * @return the command options
+	 */
+	Options getOptions() {
+		return this.options;
+	}
+
+	/**
+	 * Return parameters that this command accepts.
+	 * @return the command parameters
+	 */
+	Parameters getParameters() {
+		return this.parameters;
+	}
+
+	/**
+	 * Run the command by processing the remaining arguments.
+	 * @param args a mutable deque of the remaining arguments
+	 */
+	final void run(Deque<String> args) {
+		List<String> parameters = new ArrayList<>();
+		Map<Option, String> options = new HashMap<>();
+		while (!args.isEmpty()) {
+			String arg = args.removeFirst();
+			Option option = this.options.find(arg);
+			if (option != null) {
+				options.put(option, option.claimArg(args));
+			}
+			else {
+				parameters.add(arg);
+			}
+		}
+		run(options, parameters);
+	}
+
+	/**
+	 * Run the actual command.
+	 * @param options any options extracted from the arguments
+	 * @param parameters any parameters extracted from the arguements
+	 */
+	protected abstract void run(Map<Option, String> options, List<String> parameters);
+
+	/**
+	 * Static method that can be used to find a single command from a collection.
+	 * @param commands the commands to search
+	 * @param name the name of the command to find
+	 * @return a {@link Command} instance or {@code null}.
+	 */
+	static Command find(Collection<? extends Command> commands, String name) {
+		for (Command command : commands) {
+			if (command.getName().equals(name)) {
+				return command;
+			}
+		}
+		return null;
+	}
+
+	/**
+	 * Parameters that the command accepts.
+	 */
+	protected static final class Parameters {
+
+		private final List<String> descriptions;
+
+		private Parameters(String[] descriptions) {
+			this.descriptions = Collections.unmodifiableList(Arrays.asList(descriptions));
+		}
+
+		/**
+		 * Return the parameter descriptions.
+		 * @return the descriptions
+		 */
+		List<String> getDescriptions() {
+			return this.descriptions;
+		}
+
+		@Override
+		public String toString() {
+			return this.descriptions.toString();
+		}
+
+		/**
+		 * Factory method used if there are no expected parameters.
+		 * @return a new {@link Parameters} instance
+		 */
+		protected static Parameters none() {
+			return of();
+		}
+
+		/**
+		 * Factory method used to create a new {@link Parameters} instance with specific
+		 * descriptions.
+		 * @param descriptions the parameter descriptions
+		 * @return a new {@link Parameters} instance with the given descriptions
+		 */
+		protected static Parameters of(String... descriptions) {
+			return new Parameters(descriptions);
+		}
+
+	}
+
+	/**
+	 * Options that the command accepts.
+	 */
+	protected static final class Options {
+
+		private final Option[] values;
+
+		private Options(Option[] values) {
+			this.values = values;
+		}
+
+		private Option find(String arg) {
+			if (arg.startsWith("--")) {
+				String name = arg.substring(2);
+				for (Option candidate : this.values) {
+					if (candidate.getName().equals(name)) {
+						return candidate;
+					}
+				}
+			}
+			return null;
+		}
+
+		/**
+		 * Return if this options collection is empty.
+		 * @return if there are no options
+		 */
+		boolean isEmpty() {
+			return this.values.length == 0;
+		}
+
+		/**
+		 * Return a stream of each option.
+		 * @return a stream of the options
+		 */
+		Stream<Option> stream() {
+			return Arrays.stream(this.values);
+		}
+
+		/**
+		 * Factory method used if there are no expected options.
+		 * @return a new {@link Options} instance
+		 */
+		protected static Options none() {
+			return of();
+		}
+
+		/**
+		 * Factory method used to create a new {@link Options} instance with specific
+		 * values.
+		 * @param values the option values
+		 * @return a new {@link Options} instance with the given values
+		 */
+		protected static Options of(Option... values) {
+			return new Options(values);
+		}
+
+	}
+
+	/**
+	 * An individual option that the command can accepts. Can either be an option with a
+	 * value (e.g. {@literal --log debug}) or a flag (e.g. {@literal
+	 * --verbose}).
+	 */
+	protected static final class Option {
+
+		private final String name;
+
+		private final String valueDescription;
+
+		private final String description;
+
+		private Option(String name, String valueDescription, String description) {
+			this.name = name;
+			this.description = description;
+			this.valueDescription = valueDescription;
+		}
+
+		/**
+		 * Return the name of the option.
+		 * @return the options name
+		 */
+		String getName() {
+			return this.name;
+		}
+
+		/**
+		 * Return the description of the expected argument value or {@code null} if this
+		 * option is a flag/switch.
+		 * @return the option value description
+		 */
+		String getValueDescription() {
+			return this.valueDescription;
+		}
+
+		/**
+		 * Return the name and the value description combined.
+		 * @return the name and value description
+		 */
+		String getNameAndValueDescription() {
+			return this.name + ((this.valueDescription != null) ? " " + this.valueDescription : "");
+		}
+
+		/**
+		 * Return a description of the option.
+		 * @return the option description
+		 */
+		String getDescription() {
+			return this.description;
+		}
+
+		private String claimArg(Deque<String> args) {
+			return (this.valueDescription != null) ? args.removeFirst() : null;
+		}
+
+		@Override
+		public boolean equals(Object obj) {
+			if (this == obj) {
+				return true;
+			}
+			if (obj == null || getClass() != obj.getClass()) {
+				return false;
+			}
+			return this.name.equals(((Option) obj).name);
+		}
+
+		@Override
+		public int hashCode() {
+			return this.name.hashCode();
+		}
+
+		@Override
+		public String toString() {
+			return this.name;
+		}
+
+		/**
+		 * Factory method to create a flag/switch option.
+		 * @param name the name of the option
+		 * @param description a description of the option
+		 * @return a new {@link Option} instance
+		 */
+		protected static Option flag(String name, String description) {
+			return new Option(name, null, description);
+		}
+
+		/**
+		 * Factory method to create value option.
+		 * @param name the name of the option
+		 * @param valueDescription a description of the expected value
+		 * @param description a description of the option
+		 * @return a new {@link Option} instance
+		 */
+		protected static Option of(String name, String valueDescription, String description) {
+			return new Option(name, valueDescription, description);
+		}
+
+	}
+
+}