Provide more control over registration of GeneratedFiles

This commit provides an advanced handling of generated files that
provides more control over files registration. The callback provides
a FileHandler that can determine if the file already exists and its
content. The caller can then chose to override the content or leave it
as it is.

Closes gh-31331

spring-core/src/main/java/org/springframework/aot/generate/FileSystemGeneratedFiles.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -18,24 +18,29 @@
 
 import java.io.IOException;
 import java.io.InputStream;
+import java.nio.file.CopyOption;
 import java.nio.file.FileSystem;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
 import java.util.Arrays;
 import java.util.Objects;
 import java.util.function.Function;
 
+import org.springframework.core.io.FileSystemResource;
 import org.springframework.core.io.InputStreamSource;
 import org.springframework.util.Assert;
+import org.springframework.util.function.ThrowingConsumer;
 
 /**
  * {@link GeneratedFiles} implementation that stores generated files using a
  * {@link FileSystem}.
  *
  * @author Phillip Webb
+ * @author Stephane Nicoll
  * @since 6.0
  */
-public class FileSystemGeneratedFiles implements GeneratedFiles {
+public class FileSystemGeneratedFiles extends GeneratedFiles {
 
 	private final Function<Kind, Path> roots;
 
@@ -80,21 +85,54 @@ private static Function<Kind, Path> conventionRoots(Path root) {
 	}
 
 	@Override
-	public void addFile(Kind kind, String path, InputStreamSource content) {
+	public void handleFile(Kind kind, String path, ThrowingConsumer<FileHandler> handler) {
+		FileSystemFileHandler fileHandler = new FileSystemFileHandler(toPath(kind, path));
+		handler.accept(fileHandler);
+	}
+
+	private Path toPath(Kind kind, String path) {
 		Assert.notNull(kind, "'kind' must not be null");
 		Assert.hasLength(path, "'path' must not be empty");
-		Assert.notNull(content, "'content' must not be null");
 		Path root = this.roots.apply(kind).toAbsolutePath().normalize();
 		Path relativePath = root.resolve(path).toAbsolutePath().normalize();
 		Assert.isTrue(relativePath.startsWith(root), "'path' must be relative");
-		try {
-			try (InputStream inputStream = content.getInputStream()) {
-				Files.createDirectories(relativePath.getParent());
-				Files.copy(inputStream, relativePath);
+		return relativePath;
+	}
+
+	static final class FileSystemFileHandler extends FileHandler {
+
+		private final Path path;
+
+		FileSystemFileHandler(Path path) {
+			super(Files.exists(path), () -> new FileSystemResource(path));
+			this.path = path;
+		}
+
+		@Override
+		protected void copy(InputStreamSource content, boolean override) {
+			if (override) {
+				copy(content, StandardCopyOption.REPLACE_EXISTING);
+			}
+			else {
+				copy(content);
 			}
 		}
-		catch (IOException ex) {
-			throw new IllegalStateException(ex);
+
+		private void copy(InputStreamSource content, CopyOption... copyOptions) {
+			try {
+				try (InputStream inputStream = content.getInputStream()) {
+					Files.createDirectories(this.path.getParent());
+					Files.copy(inputStream, this.path, copyOptions);
+				}
+			}
+			catch (IOException ex) {
+				throw new IllegalStateException(ex);
+			}
+		}
+
+		@Override
+		public String toString() {
+			return this.path.toString();
 		}
 	}
 

spring-core/src/main/java/org/springframework/aot/generate/GeneratedFiles.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -16,8 +16,11 @@
 
 package org.springframework.aot.generate;
 
+import java.util.function.Supplier;
+
 import org.springframework.core.io.InputStreamSource;
 import org.springframework.javapoet.JavaFile;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.StringUtils;
@@ -36,14 +39,14 @@
  * @see InMemoryGeneratedFiles
  * @see FileSystemGeneratedFiles
  */
-public interface GeneratedFiles {
+public abstract class GeneratedFiles {
 
 	/**
 	 * Add a generated {@link Kind#SOURCE source file} with content from the
 	 * given {@link JavaFile}.
 	 * @param javaFile the java file to add
 	 */
-	default void addSourceFile(JavaFile javaFile) {
+	public void addSourceFile(JavaFile javaFile) {
 		validatePackage(javaFile.packageName, javaFile.typeSpec.name);
 		String className = javaFile.packageName + "." + javaFile.typeSpec.name;
 		addSourceFile(className, javaFile::writeTo);
@@ -56,7 +59,7 @@ default void addSourceFile(JavaFile javaFile) {
 	 * of the file
 	 * @param content the contents of the file
 	 */
-	default void addSourceFile(String className, CharSequence content) {
+	public void addSourceFile(String className, CharSequence content) {
 		addSourceFile(className, appendable -> appendable.append(content));
 	}
 
@@ -68,7 +71,7 @@ default void addSourceFile(String className, CharSequence content) {
 	 * @param content a {@link ThrowingConsumer} that accepts an
 	 * {@link Appendable} which will receive the file contents
 	 */
-	default void addSourceFile(String className, ThrowingConsumer<Appendable> content) {
+	public void addSourceFile(String className, ThrowingConsumer<Appendable> content) {
 		addFile(Kind.SOURCE, getClassNamePath(className), content);
 	}
 
@@ -80,7 +83,7 @@ default void addSourceFile(String className, ThrowingConsumer<Appendable> conten
 	 * @param content an {@link InputStreamSource} that will provide an input
 	 * stream containing the file contents
 	 */
-	default void addSourceFile(String className, InputStreamSource content) {
+	public void addSourceFile(String className, InputStreamSource content) {
 		addFile(Kind.SOURCE, getClassNamePath(className), content);
 	}
 
@@ -90,7 +93,7 @@ default void addSourceFile(String className, InputStreamSource content) {
 	 * @param path the relative path of the file
 	 * @param content the contents of the file
 	 */
-	default void addResourceFile(String path, CharSequence content) {
+	public void addResourceFile(String path, CharSequence content) {
 		addResourceFile(path, appendable -> appendable.append(content));
 	}
 
@@ -101,7 +104,7 @@ default void addResourceFile(String path, CharSequence content) {
 	 * @param content a {@link ThrowingConsumer} that accepts an
 	 * {@link Appendable} which will receive the file contents
 	 */
-	default void addResourceFile(String path, ThrowingConsumer<Appendable> content) {
+	public void addResourceFile(String path, ThrowingConsumer<Appendable> content) {
 		addFile(Kind.RESOURCE, path, content);
 	}
 
@@ -112,7 +115,7 @@ default void addResourceFile(String path, ThrowingConsumer<Appendable> content)
 	 * @param content an {@link InputStreamSource} that will provide an input
 	 * stream containing the file contents
 	 */
-	default void addResourceFile(String path, InputStreamSource content) {
+	public void addResourceFile(String path, InputStreamSource content) {
 		addFile(Kind.RESOURCE, path, content);
 	}
 
@@ -123,7 +126,7 @@ default void addResourceFile(String path, InputStreamSource content) {
 	 * @param content an {@link InputStreamSource} that will provide an input
 	 * stream containing the file contents
 	 */
-	default void addClassFile(String path, InputStreamSource content) {
+	public void addClassFile(String path, InputStreamSource content) {
 		addFile(Kind.CLASS, path, content);
 	}
 
@@ -134,7 +137,7 @@ default void addClassFile(String path, InputStreamSource content) {
 	 * @param path the relative path of the file
 	 * @param content the contents of the file
 	 */
-	default void addFile(Kind kind, String path, CharSequence content) {
+	public void addFile(Kind kind, String path, CharSequence content) {
 		addFile(kind, path, appendable -> appendable.append(content));
 	}
 
@@ -146,7 +149,7 @@ default void addFile(Kind kind, String path, CharSequence content) {
 	 * @param content a {@link ThrowingConsumer} that accepts an
 	 * {@link Appendable} which will receive the file contents
 	 */
-	default void addFile(Kind kind, String path, ThrowingConsumer<Appendable> content) {
+	public void addFile(Kind kind, String path, ThrowingConsumer<Appendable> content) {
 		Assert.notNull(content, "'content' must not be null");
 		addFile(kind, path, new AppendableConsumerInputStreamSource(content));
 	}
@@ -159,7 +162,21 @@ default void addFile(Kind kind, String path, ThrowingConsumer<Appendable> conten
 	 * @param content an {@link InputStreamSource} that will provide an input
 	 * stream containing the file contents
 	 */
-	void addFile(Kind kind, String path, InputStreamSource content);
+	public void addFile(Kind kind, String path, InputStreamSource content) {
+		Assert.notNull(kind, "'kind' must not be null");
+		Assert.hasLength(path, "'path' must not be empty");
+		Assert.notNull(content, "'content' must not be null");
+		handleFile(kind, path, handler -> handler.create(content));
+	}
+
+	/**
+	 * Add a generated file of the specified {@link Kind} with the given
+	 * {@linkplain FileHandler handler}.
+	 * @param kind the kind of file being written
+	 * @param path the relative path of the file
+	 * @param handler a consumer of a {@link FileHandler} for the file
+	 */
+	public abstract void handleFile(Kind kind, String path, ThrowingConsumer<FileHandler> handler);
 
 	private static String getClassNamePath(String className) {
 		Assert.hasLength(className, "'className' must not be empty");
@@ -194,7 +211,7 @@ private static boolean isJavaIdentifier(String className) {
 	/**
 	 * The various kinds of generated files that are supported.
 	 */
-	enum Kind {
+	public enum Kind {
 
 		/**
 		 * A source file containing Java code that should be compiled.
@@ -215,4 +232,62 @@ enum Kind {
 
 	}
 
+	/**
+	 * Provide access to a particular file and offer convenient method to save
+	 * or override its content.
+	 */
+	public abstract static class FileHandler {
+
+		private final boolean exists;
+
+		private final Supplier<InputStreamSource> existingContent;
+
+		protected FileHandler(boolean exists, Supplier<InputStreamSource> existingContent) {
+			this.exists = exists;
+			this.existingContent = existingContent;
+		}
+
+		/**
+		 * Specify whether the file already exists.
+		 * @return {@code true} if the file already exists
+		 */
+		public boolean exists() {
+			return this.exists;
+		}
+
+		/**
+		 * Return an {@link InputStreamSource} for the content of the file or
+		 * {@code null} if the file does not exist.
+		 */
+		@Nullable
+		public InputStreamSource getContent() {
+			return (exists() ? this.existingContent.get() : null);
+		}
+
+		/**
+		 * Create a file with the given {@linkplain InputStreamSource content}.
+		 * @throws IllegalStateException if the file already exists
+		 */
+		public void create(InputStreamSource content) {
+			Assert.notNull(content, "'content' must not be null");
+			if (exists()) {
+				throw new IllegalStateException("%s already exists".formatted(this));
+			}
+			copy(content, false);
+		}
+
+		/**
+		 * Override the content of the file handled by this instance using the
+		 * given {@linkplain InputStreamSource content}. If the file does not
+		 * exist, it is created.
+		 */
+		public void override(InputStreamSource content) {
+			Assert.notNull(content, "'content' must not be null");
+			copy(content, true);
+		}
+
+		protected abstract void copy(InputStreamSource content, boolean override);
+
+	}
+
 }

spring-core/src/main/java/org/springframework/aot/generate/InMemoryGeneratedFiles.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -26,27 +26,25 @@
 import org.springframework.core.io.InputStreamSource;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.function.ThrowingConsumer;
 
 /**
  * {@link GeneratedFiles} implementation that keeps generated files in-memory.
  *
  * @author Phillip Webb
+ * @author Stephane Nicoll
  * @since 6.0
  */
-public class InMemoryGeneratedFiles implements GeneratedFiles {
+public class InMemoryGeneratedFiles extends GeneratedFiles {
 
 	private final Map<Kind, Map<String, InputStreamSource>> files = new HashMap<>();
 
 
 	@Override
-	public void addFile(Kind kind, String path, InputStreamSource content) {
-		Assert.notNull(kind, "'kind' must not be null");
-		Assert.hasLength(path, "'path' must not be empty");
-		Assert.notNull(content, "'content' must not be null");
+	public void handleFile(Kind kind, String path, ThrowingConsumer<FileHandler> handler) {
 		Map<String, InputStreamSource> paths = this.files.computeIfAbsent(kind,
 				key -> new LinkedHashMap<>());
-		Assert.state(!paths.containsKey(path), () -> "Path '" + path + "' already in use");
-		paths.put(path, content);
+		handler.accept(new InMemoryFileHandler(paths, path));
 	}
 
 	/**
@@ -89,4 +87,27 @@ public InputStreamSource getGeneratedFile(Kind kind, String path) {
 		return (paths != null ? paths.get(path) : null);
 	}
 
+	private static class InMemoryFileHandler extends FileHandler {
+
+		private final Map<String, InputStreamSource> paths;
+
+		private final String key;
+
+		InMemoryFileHandler(Map<String, InputStreamSource> paths, String key) {
+			super(paths.containsKey(key), () -> paths.get(key));
+			this.paths = paths;
+			this.key = key;
+		}
+
+		@Override
+		protected void copy(InputStreamSource content, boolean override) {
+			this.paths.put(this.key, content);
+		}
+
+		@Override
+		public String toString() {
+			return this.key;
+		}
+	}
+
 }