Merge pull request #44305 from nosan

* pr/44305:
  Polish "Use ArgFile for classpath argument on Windows"
  Use ArgFile for classpath argument on Windows

Closes gh-44305

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/main/java/org/springframework/boot/maven/AbstractAotMojo.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2023 the original author or authors.
+ * Copyright 2012-2025 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.
@@ -46,8 +46,6 @@ import org.apache.maven.plugins.annotations.Parameter;
 import org.apache.maven.shared.artifact.filter.collection.ArtifactsFilter;
 import org.apache.maven.toolchain.ToolchainManager;
 
-import org.springframework.boot.maven.CommandLineBuilder.ClasspathBuilder;
-
 /**
  * Abstract base class for AOT processing MOJOs.
  *
@@ -149,7 +147,7 @@ public abstract class AbstractAotMojo extends AbstractDependencyFilterMojo {
 			JavaCompilerPluginConfiguration compilerConfiguration = new JavaCompilerPluginConfiguration(this.project);
 			List<String> options = new ArrayList<>();
 			options.add("-cp");
-			options.add(ClasspathBuilder.build(Arrays.asList(classPath)));
+			options.add(ClasspathBuilder.forURLs(classPath).build().argument());
 			options.add("-d");
 			options.add(outputDirectory.toPath().toAbsolutePath().toString());
 			String releaseVersion = compilerConfiguration.getReleaseVersion();

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/main/java/org/springframework/boot/maven/AbstractRunMojo.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2024 the original author or authors.
+ * Copyright 2012-2025 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.
@@ -20,15 +20,10 @@ import java.io.File;
 import java.io.IOException;
 import java.net.MalformedURLException;
 import java.net.URL;
-import java.nio.charset.Charset;
-import java.nio.charset.UnsupportedCharsetException;
-import java.nio.file.Files;
-import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
-import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
 import java.util.stream.Collectors;
@@ -44,9 +39,9 @@ import org.apache.maven.project.MavenProject;
 import org.apache.maven.toolchain.ToolchainManager;
 
 import org.springframework.boot.loader.tools.FileUtils;
+import org.springframework.boot.maven.ClasspathBuilder.Classpath;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
-import org.springframework.util.StringUtils;
 
 /**
  * Base class to run a Spring Boot application.
@@ -351,45 +346,19 @@ public abstract class AbstractRunMojo extends AbstractDependencyFilterMojo {
 
 	private void addClasspath(List<String> args) throws MojoExecutionException {
 		try {
-			StringBuilder classpath = new StringBuilder();
-			for (URL ele : getClassPathUrls()) {
-				if (!classpath.isEmpty()) {
-					classpath.append(File.pathSeparator);
-				}
-				classpath.append(new File(ele.toURI()));
-			}
+			Classpath classpath = ClasspathBuilder.forURLs(getClassPathUrls()).build();
 			if (getLog().isDebugEnabled()) {
-				getLog().debug("Classpath for forked process: " + classpath);
+				getLog().debug("Classpath for forked process: "
+						+ classpath.elements().map(Object::toString).collect(Collectors.joining(File.separator)));
 			}
 			args.add("-cp");
-			if (needsClasspathArgFile()) {
-				args.add("@" + ArgFile.create(classpath).path());
-			}
-			else {
-				args.add(classpath.toString());
-			}
+			args.add(classpath.argument());
 		}
 		catch (Exception ex) {
 			throw new MojoExecutionException("Could not build classpath", ex);
 		}
 	}
 
-	private boolean needsClasspathArgFile() {
-		// Windows limits the maximum command length, so we use an argfile there
-		return runsOnWindows();
-	}
-
-	private boolean runsOnWindows() {
-		String os = System.getProperty("os.name");
-		if (!StringUtils.hasLength(os)) {
-			if (getLog().isWarnEnabled()) {
-				getLog().warn("System property os.name is not set");
-			}
-			return false;
-		}
-		return os.toLowerCase(Locale.ROOT).contains("win");
-	}
-
 	protected URL[] getClassPathUrls() throws MojoExecutionException {
 		try {
 			List<URL> urls = new ArrayList<>();
@@ -468,37 +437,4 @@ public abstract class AbstractRunMojo extends AbstractDependencyFilterMojo {
 
 	}
 
-	record ArgFile(Path path) {
-
-		private void write(CharSequence content) throws IOException {
-			Files.writeString(this.path, "\"" + escape(content) + "\"", getCharset());
-		}
-
-		private Charset getCharset() {
-			String nativeEncoding = System.getProperty("native.encoding");
-			if (nativeEncoding == null) {
-				return Charset.defaultCharset();
-			}
-			try {
-				return Charset.forName(nativeEncoding);
-			}
-			catch (UnsupportedCharsetException ex) {
-				return Charset.defaultCharset();
-			}
-		}
-
-		private String escape(CharSequence content) {
-			return content.toString().replace("\\", "\\\\");
-		}
-
-		static ArgFile create(CharSequence content) throws IOException {
-			Path tempFile = Files.createTempFile("spring-boot-", ".argfile");
-			tempFile.toFile().deleteOnExit();
-			ArgFile argFile = new ArgFile(tempFile);
-			argFile.write(content);
-			return argFile;
-		}
-
-	}
-
 }

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/main/java/org/springframework/boot/maven/ClasspathBuilder.java

@@ -0,0 +1,177 @@
+/*
+ * Copyright 2012-2025 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.maven;
+
+import java.io.File;
+import java.io.IOException;
+import java.net.URISyntaxException;
+import java.net.URL;
+import java.nio.charset.Charset;
+import java.nio.charset.UnsupportedCharsetException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.Locale;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import org.springframework.util.ObjectUtils;
+import org.springframework.util.StringUtils;
+
+/**
+ * Helper class to build the -cp (classpath) argument of a java process.
+ *
+ * @author Stephane Nicoll
+ * @author Dmytro Nosan
+ */
+class ClasspathBuilder {
+
+	private final List<URL> urls;
+
+	protected ClasspathBuilder(List<URL> urls) {
+		this.urls = urls;
+	}
+
+	/**
+	 * Builds a classpath string or an argument file representing the classpath, depending
+	 * on the operating system.
+	 * @param urls an array of {@link URL} representing the elements of the classpath
+	 * @return the classpath; on Windows, the path to an argument file is returned,
+	 * prefixed with '@'
+	 */
+	static ClasspathBuilder forURLs(List<URL> urls) {
+		return new ClasspathBuilder(new ArrayList<>(urls));
+	}
+
+	/**
+	 * Builds a classpath string or an argument file representing the classpath, depending
+	 * on the operating system.
+	 * @param urls an array of {@link URL} representing the elements of the classpath
+	 * @return the classpath; on Windows, the path to an argument file is returned,
+	 * prefixed with '@'
+	 */
+	static ClasspathBuilder forURLs(URL... urls) {
+		return new ClasspathBuilder(Arrays.asList(urls));
+	}
+
+	Classpath build() {
+		if (ObjectUtils.isEmpty(this.urls)) {
+			return new Classpath("", Collections.emptyList());
+		}
+		if (this.urls.size() == 1) {
+			Path file = toFile(this.urls.get(0));
+			return new Classpath(file.toString(), List.of(file));
+		}
+		List<Path> files = this.urls.stream().map(ClasspathBuilder::toFile).toList();
+		String argument = files.stream().map(Object::toString).collect(Collectors.joining(File.pathSeparator));
+		if (needsClasspathArgFile()) {
+			argument = createArgFile(argument);
+		}
+		return new Classpath(argument, files);
+	}
+
+	protected boolean needsClasspathArgFile() {
+		String os = System.getProperty("os.name");
+		if (!StringUtils.hasText(os)) {
+			return false;
+		}
+		// Windows limits the maximum command length, so we use an argfile
+		return os.toLowerCase(Locale.ROOT).contains("win");
+	}
+
+	/**
+	 * Create a temporary file with the given {@code} classpath. Return a suitable
+	 * argument to load the file, that is the full path prefixed by {@code @}.
+	 * @param classpath the classpath to use
+	 * @return a suitable argument for the classpath using a file
+	 */
+	private String createArgFile(String classpath) {
+		try {
+			return "@" + writeClasspathToFile(classpath);
+		}
+		catch (IOException ex) {
+			return classpath;
+		}
+	}
+
+	private Path writeClasspathToFile(CharSequence classpath) throws IOException {
+		Path tempFile = Files.createTempFile("spring-boot-", ".argfile");
+		tempFile.toFile().deleteOnExit();
+		Files.writeString(tempFile, "\"" + escape(classpath) + "\"", getCharset());
+		return tempFile;
+	}
+
+	private static Charset getCharset() {
+		String nativeEncoding = System.getProperty("native.encoding");
+		if (nativeEncoding == null) {
+			return Charset.defaultCharset();
+		}
+		try {
+			return Charset.forName(nativeEncoding);
+		}
+		catch (UnsupportedCharsetException ex) {
+			return Charset.defaultCharset();
+		}
+	}
+
+	private static String escape(CharSequence content) {
+		return content.toString().replace("\\", "\\\\");
+	}
+
+	private static Path toFile(URL url) {
+		try {
+			return Paths.get(url.toURI());
+		}
+		catch (URISyntaxException ex) {
+			throw new IllegalArgumentException(ex);
+		}
+	}
+
+	static final class Classpath {
+
+		private final String argument;
+
+		private final List<Path> elements;
+
+		private Classpath(String argument, List<Path> elements) {
+			this.argument = argument;
+			this.elements = elements;
+		}
+
+		/**
+		 * Return the {@code -cp} argument value.
+		 * @return the argument to use
+		 */
+		String argument() {
+			return this.argument;
+		}
+
+		/**
+		 * Return the classpath elements.
+		 * @return the JAR files to use
+		 */
+		Stream<Path> elements() {
+			return this.elements.stream();
+		}
+
+	}
+
+}

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/main/java/org/springframework/boot/maven/CommandLineBuilder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2024 the original author or authors.
+ * Copyright 2012-2025 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.
@@ -16,8 +16,6 @@
 
 package org.springframework.boot.maven;
 
-import java.io.File;
-import java.net.URISyntaxException;
 import java.net.URL;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -84,7 +82,7 @@ final class CommandLineBuilder {
 		}
 		if (!this.classpathElements.isEmpty()) {
 			commandLine.add("-cp");
-			commandLine.add(ClasspathBuilder.build(this.classpathElements));
+			commandLine.add(ClasspathBuilder.forURLs(this.classpathElements).build().argument());
 		}
 		commandLine.add(this.mainClass);
 		if (!this.arguments.isEmpty()) {
@@ -93,30 +91,6 @@ final class CommandLineBuilder {
 		return commandLine;
 	}
 
-	static class ClasspathBuilder {
-
-		static String build(List<URL> classpathElements) {
-			StringBuilder classpath = new StringBuilder();
-			for (URL element : classpathElements) {
-				if (!classpath.isEmpty()) {
-					classpath.append(File.pathSeparator);
-				}
-				classpath.append(toFile(element));
-			}
-			return classpath.toString();
-		}
-
-		private static File toFile(URL element) {
-			try {
-				return new File(element.toURI());
-			}
-			catch (URISyntaxException ex) {
-				throw new IllegalArgumentException(ex);
-			}
-		}
-
-	}
-
 	/**
 	 * Format System properties.
 	 */

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/test/java/org/springframework/boot/maven/AbstractRunMojoTests.java

@@ -1,41 +0,0 @@
-/*
- * Copyright 2012-2024 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.maven;
-
-import java.io.IOException;
-import java.nio.charset.StandardCharsets;
-
-import org.junit.jupiter.api.Test;
-
-import org.springframework.boot.maven.AbstractRunMojo.ArgFile;
-
-import static org.assertj.core.api.Assertions.assertThat;
-
-/**
- * Tests for {@link AbstractRunMojo}.
- *
- * @author Moritz Halbritter
- */
-class AbstractRunMojoTests {
-
-	@Test
-	void argfileEscapesContent() throws IOException {
-		ArgFile file = ArgFile.create("some \\ content");
-		assertThat(file.path()).content(StandardCharsets.UTF_8).isEqualTo("\"some \\\\ content\"");
-	}
-
-}

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/test/java/org/springframework/boot/maven/ClasspathBuilderTests.java

@@ -0,0 +1,157 @@
+/*
+ * Copyright 2012-2025 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.maven;
+
+import java.io.File;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.ArrayList;
+import java.util.List;
+
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.condition.DisabledOnOs;
+import org.junit.jupiter.api.condition.EnabledOnOs;
+import org.junit.jupiter.api.condition.OS;
+import org.junit.jupiter.api.io.TempDir;
+
+import org.springframework.boot.maven.ClasspathBuilder.Classpath;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link ClasspathBuilder}.
+ *
+ * @author Dmytro Nosan
+ * @author Stephane Nicoll
+ */
+class ClasspathBuilderTests {
+
+	@Test
+	@DisabledOnOs(OS.WINDOWS)
+	void buildWithMultipleClassPathURLs(@TempDir Path tempDir) throws Exception {
+		Path file = tempDir.resolve("test.jar");
+		Path file1 = tempDir.resolve("test1.jar");
+		assertThat(ClasspathBuilder.forURLs(file.toUri().toURL(), file1.toUri().toURL()).build().argument())
+			.isEqualTo(file + File.pathSeparator + file1);
+	}
+
+	@Test
+	@EnabledOnOs(OS.WINDOWS)
+	void buildWithMultipleClassPathURLsOnWindows(@TempDir Path tempDir) throws Exception {
+		Path file = tempDir.resolve("test.jar");
+		Path file1 = tempDir.resolve("test1.jar");
+		String classpath = ClasspathBuilder.forURLs(file.toUri().toURL(), file1.toUri().toURL()).build().argument();
+		assertThat(classpath).startsWith("@");
+		assertThat(Paths.get(classpath.substring(1)))
+			.hasContent("\"" + (file + File.pathSeparator + file1).replace("\\", "\\\\") + "\"");
+	}
+
+	@Nested
+	class WindowsTests {
+
+		@Test
+		void buildWithEmptyClassPath() throws MalformedURLException {
+			Classpath classpath = classPathBuilder().build();
+			assertThat(classpath.argument()).isEmpty();
+			assertThat(classpath.elements()).isEmpty();
+		}
+
+		@Test
+		void buildWithSingleClassPathURL(@TempDir Path tempDir) throws Exception {
+			Path file = tempDir.resolve("test.jar");
+			Classpath classpath = classPathBuilder(file).build();
+			assertThat(classpath.argument()).isEqualTo(file.toString());
+			assertThat(classpath.elements()).singleElement().isEqualTo(file);
+		}
+
+		@Test
+		void buildWithMultipleClassPathURLs(@TempDir Path tempDir) throws Exception {
+			Path file = tempDir.resolve("test.jar");
+			Path file2 = tempDir.resolve("test2.jar");
+			Classpath classpath = classPathBuilder(file, file2).build();
+			assertThat(classpath.argument()).startsWith("@");
+			assertThat(Paths.get(classpath.argument().substring(1)))
+				.hasContent("\"" + (file + File.pathSeparator + file2).replace("\\", "\\\\") + "\"");
+		}
+
+		private ClasspathBuilder classPathBuilder(Path... files) throws MalformedURLException {
+			return new TestClasspathBuilder(true, files);
+		}
+
+	}
+
+	@Nested
+	class UnixTests {
+
+		@Test
+		void buildWithEmptyClassPath() throws MalformedURLException {
+			Classpath classpath = classPathBuilder().build();
+			assertThat(classpath.argument()).isEmpty();
+			assertThat(classpath.elements()).isEmpty();
+		}
+
+		@Test
+		void buildWithSingleClassPathURL(@TempDir Path tempDir) throws Exception {
+			Path file = tempDir.resolve("test.jar");
+			Classpath classpath = classPathBuilder(file).build();
+			assertThat(classpath.argument()).isEqualTo(file.toString());
+			assertThat(classpath.elements()).singleElement().isEqualTo(file);
+		}
+
+		@Test
+		void buildWithMultipleClassPathURLs(@TempDir Path tempDir) throws Exception {
+			Path file = tempDir.resolve("test.jar");
+			Path file2 = tempDir.resolve("test2.jar");
+			Classpath classpath = classPathBuilder(file, file2).build();
+			assertThat(classpath.argument()).doesNotStartWith("@")
+				.isEqualTo((file + File.pathSeparator + file2).replace("\\", "\\\\"));
+		}
+
+		private ClasspathBuilder classPathBuilder(Path... files) throws MalformedURLException {
+			return new TestClasspathBuilder(false, files);
+		}
+
+	}
+
+	private static class TestClasspathBuilder extends ClasspathBuilder {
+
+		private final boolean needsClasspathArgFile;
+
+		protected TestClasspathBuilder(boolean needsClasspathArgFile, Path... files) throws MalformedURLException {
+			super(toURLs(files));
+			this.needsClasspathArgFile = needsClasspathArgFile;
+		}
+
+		private static List<URL> toURLs(Path... files) throws MalformedURLException {
+			List<URL> urls = new ArrayList<>();
+			for (Path file : files) {
+				urls.add(file.toUri().toURL());
+			}
+			return urls;
+		}
+
+		@Override
+		protected boolean needsClasspathArgFile() {
+			return this.needsClasspathArgFile;
+		}
+
+	}
+
+}

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/test/java/org/springframework/boot/maven/CommandLineBuilderTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2023 the original author or authors.
+ * Copyright 2012-2025 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.
@@ -16,10 +16,25 @@
 
 package org.springframework.boot.maven;
 
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
+import java.lang.management.ManagementFactory;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Arrays;
+import java.util.List;
 import java.util.Map;
 
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.condition.DisabledOnOs;
+import org.junit.jupiter.api.condition.EnabledOnOs;
+import org.junit.jupiter.api.condition.OS;
+import org.junit.jupiter.api.io.TempDir;
 
+import org.springframework.boot.loader.tools.JavaExecutable;
 import org.springframework.boot.maven.sample.ClassWithMainMethod;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -76,4 +91,55 @@ class CommandLineBuilderTests {
 			.containsExactly(CLASS_NAME, "--test", "--another");
 	}
 
+	@Test
+	@DisabledOnOs(OS.WINDOWS)
+	void buildWithClassPath(@TempDir Path tempDir) throws Exception {
+		Path file = tempDir.resolve("test.jar");
+		Path file1 = tempDir.resolve("test1.jar");
+		assertThat(CommandLineBuilder.forMainClass(CLASS_NAME)
+			.withClasspath(file.toUri().toURL(), file1.toUri().toURL())
+			.build()).containsExactly("-cp", file + File.pathSeparator + file1, CLASS_NAME);
+	}
+
+	@Test
+	@EnabledOnOs(OS.WINDOWS)
+	void buildWithClassPathOnWindows(@TempDir Path tempDir) throws Exception {
+		Path file = tempDir.resolve("test.jar");
+		Path file1 = tempDir.resolve("test1.jar");
+		List<String> args = CommandLineBuilder.forMainClass(CLASS_NAME)
+			.withClasspath(file.toUri().toURL(), file1.toUri().toURL())
+			.build();
+		assertThat(args).hasSize(3);
+		assertThat(args.get(0)).isEqualTo("-cp");
+		assertThat(args.get(1)).startsWith("@");
+		assertThat(args.get(2)).isEqualTo(CLASS_NAME);
+		assertThat(Paths.get(args.get(1).substring(1)))
+			.hasContent("\"" + (file + File.pathSeparator + file1).replace("\\", "\\\\") + "\"");
+	}
+
+	@Test
+	void buildAndRunWithLongClassPath() throws IOException, InterruptedException {
+		URL[] urls = Arrays.stream(ManagementFactory.getRuntimeMXBean().getClassPath().split(File.pathSeparator))
+			.map(this::toURL)
+			.toArray(URL[]::new);
+		List<String> command = CommandLineBuilder.forMainClass(ClassWithMainMethod.class.getName())
+			.withClasspath(urls)
+			.build();
+		ProcessBuilder pb = new JavaExecutable().processBuilder(command.toArray(new String[0]));
+		Process process = pb.start();
+		assertThat(process.waitFor()).isEqualTo(0);
+		try (InputStream inputStream = process.getInputStream()) {
+			assertThat(inputStream).hasContent("Hello World");
+		}
+	}
+
+	private URL toURL(String path) {
+		try {
+			return Paths.get(path).toUri().toURL();
+		}
+		catch (MalformedURLException ex) {
+			throw new RuntimeException(ex);
+		}
+	}
+
 }