Polishing external contribution

This commit makes several changes to PR #24651.

- Add byte[] getContentAsByteArray() on Resource.
- Remove getContentAsString() from Resource, as it relied on the default
charset which is not reliable.
- Add getContentAsString() to EncodedResource, as a charset is provided
through the constructor.

See gh-24651

Author: poutsma

spring-core/src/main/java/org/springframework/core/io/AbstractFileResolvingResource.java

@@ -26,10 +26,7 @@
 import java.net.URLConnection;
 import java.nio.channels.FileChannel;
 import java.nio.channels.ReadableByteChannel;
-import java.nio.charset.Charset;
-import java.nio.file.Files;
 import java.nio.file.NoSuchFileException;
-import java.nio.file.Paths;
 import java.nio.file.StandardOpenOption;
 import java.util.jar.JarEntry;
 
@@ -323,39 +320,6 @@ protected void customizeConnection(URLConnection con) throws IOException {
 	protected void customizeConnection(HttpURLConnection con) throws IOException {
 	}
 
-	/**
-	 * This implementation returns the contents of a file as a string using the
-	 * system default Charset. Provided the resource exists and the context has
-	 * access to it, the contents will be returned as a single string with line
-	 * feed characters retained.
-	 * @return the contents of the requested file as a {@code String}.
-	 * @throws FileNotFoundException in the event the file path is invalid.
-	 * @throws IOException if the file can not be read or cannot be serialzied.
-	 */
-	@Override
-	public String getContentAsString() throws IOException {
-
-		if( !exists() ) {
-			throw new FileNotFoundException(getDescription() + " cannot be found.");
-		}
-		if ( !isReadable() ) {
-			throw new IOException(getDescription() + " cannot be opened for reading.");
-		}
-		return new String(Files.readAllBytes(Paths.get(getFile().getAbsolutePath())), Charset.defaultCharset());
-	}
-
-	@Override
-	public String getContentAsString(Charset charset) throws IOException {
-
-		if( !exists() ) {
-			throw new FileNotFoundException(getDescription() + " cannot be found.");
-		}
-		if ( !isReadable() ) {
-			throw new IOException(getDescription() + " cannot be opened for reading.");
-		}
-		return new String(Files.readAllBytes(Paths.get(getFile().getAbsolutePath())), charset);
-
-	}
 
 	/**
 	 * Inner delegate class, avoiding a hard JBoss VFS API dependency at runtime.

spring-core/src/main/java/org/springframework/core/io/ByteArrayResource.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -19,6 +19,7 @@
 import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.io.InputStream;
+import java.nio.charset.Charset;
 import java.util.Arrays;
 
 import org.springframework.lang.Nullable;
@@ -100,6 +101,19 @@ public InputStream getInputStream() throws IOException {
 		return new ByteArrayInputStream(this.byteArray);
 	}
 
+	@Override
+	public byte[] getContentAsByteArray() throws IOException {
+		int length = this.byteArray.length;
+		byte[] result = new byte[length];
+		System.arraycopy(this.byteArray, 0, result, 0, length);
+		return result;
+	}
+
+	@Override
+	public String getContentAsString(Charset charset) throws IOException {
+		return new String(this.byteArray, charset);
+	}
+
 	/**
 	 * This implementation returns a description that includes the passed-in
 	 * {@code description}, if any.

spring-core/src/main/java/org/springframework/core/io/FileSystemResource.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -27,6 +27,7 @@
 import java.nio.channels.FileChannel;
 import java.nio.channels.ReadableByteChannel;
 import java.nio.channels.WritableByteChannel;
+import java.nio.charset.Charset;
 import java.nio.file.FileSystem;
 import java.nio.file.Files;
 import java.nio.file.NoSuchFileException;
@@ -196,6 +197,26 @@ public InputStream getInputStream() throws IOException {
 		}
 	}
 
+	@Override
+	public byte[] getContentAsByteArray() throws IOException {
+		try {
+			return Files.readAllBytes(this.filePath);
+		}
+		catch (NoSuchFileException ex) {
+			throw new FileNotFoundException(ex.getMessage());
+		}
+	}
+
+	@Override
+	public String getContentAsString(Charset charset) throws IOException {
+		try {
+			return Files.readString(this.filePath, charset);
+		}
+		catch (NoSuchFileException ex) {
+			throw new FileNotFoundException(ex.getMessage());
+		}
+	}
+
 	/**
 	 * This implementation checks whether the underlying file is marked as writable
 	 * (and corresponds to an actual file with content, not to a directory).

spring-core/src/main/java/org/springframework/core/io/PathResource.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -25,6 +25,7 @@
 import java.net.URL;
 import java.nio.channels.ReadableByteChannel;
 import java.nio.channels.WritableByteChannel;
+import java.nio.charset.Charset;
 import java.nio.file.Files;
 import java.nio.file.NoSuchFileException;
 import java.nio.file.OpenOption;
@@ -141,6 +142,26 @@ public InputStream getInputStream() throws IOException {
 		return Files.newInputStream(this.path);
 	}
 
+	@Override
+	public byte[] getContentAsByteArray() throws IOException {
+		try {
+			return Files.readAllBytes(this.path);
+		}
+		catch (NoSuchFileException ex) {
+			throw new FileNotFoundException(ex.getMessage());
+		}
+	}
+
+	@Override
+	public String getContentAsString(Charset charset) throws IOException {
+		try {
+			return Files.readString(this.path, charset);
+		}
+		catch (NoSuchFileException ex) {
+			throw new FileNotFoundException(ex.getMessage());
+		}
+	}
+
 	/**
 	 * This implementation checks whether the underlying file is marked as writable
 	 * (and corresponds to an actual file with content, not to a directory).

spring-core/src/main/java/org/springframework/core/io/Resource.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -17,16 +17,17 @@
 package org.springframework.core.io;
 
 import java.io.File;
-import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
+import java.io.InputStreamReader;
 import java.net.URI;
 import java.net.URL;
 import java.nio.channels.Channels;
 import java.nio.channels.ReadableByteChannel;
 import java.nio.charset.Charset;
 
 import org.springframework.lang.Nullable;
+import org.springframework.util.FileCopyUtils;
 
 /**
  * Interface for a resource descriptor that abstracts from the actual
@@ -179,40 +180,29 @@ default ReadableByteChannel readableChannel() throws IOException {
 	String getDescription();
 
 	/**
-	 * Return a {@link ReadableByteChannel}.
-	 * <p>It is expected that each call creates a <i>fresh</i> channel.
-	 * <p>The default implementation returns {@link Channels#newChannel(InputStream)}
-	 * with the result of {@link #getInputStream()}.
-	 * @return the byte channel for the underlying resource (must not be {@code null})
-	 * @throws java.io.FileNotFoundException if the underlying resource doesn't exist
-	 * @throws IOException if the content channel could not be opened
-	 * @since 5.0
-	 * @see #getInputStream()
-	 */
-
-	/**
-	 * Returns the contents of a file as a string using the system default Charset.
-	 * <p>The default implementation returns a {@link Object#toString()} representation of the resource.
-	 * @return the contents of the requested file as a {@code String}.
-	 * @throws FileNotFoundException in the event the file path is invalid.
-	 * @throws IOException if the file can not be read or cannot be accessed.
-	 * @since 5.2.5
+	 * Return the contents of this resource as a byte array.
+	 * @return the contents of this resource as byte array
+	 * @throws java.io.FileNotFoundException if the resource cannot be resolved as
+	 * absolute file path, i.e. if the resource is not available in a file system
+	 * @throws IOException in case of general resolution/reading failures
+	 * @since 6.0.5
 	 */
-	default String getContentAsString() throws IOException{
-		return toString();
+	default byte[] getContentAsByteArray() throws IOException {
+		return FileCopyUtils.copyToByteArray(getInputStream());
 	}
 
 	/**
-	 * Returns the contents of a file as a string using the specified Charset.
-	 * <p>The default implementation returns a {@link Object#toString()} representation of the resource.
-	 * @param charset the {@code Charset} to use to deserialize the content. Defaults to system default.
-	 * @return the contents of the requested file as a {@code String}.
-	 * @throws FileNotFoundException in the event the file path is invalid.
-	 * @throws IOException if the file can not be read or cannot be accessed.
-	 * @since 5.2.5
+	 * Returns the contents of this resource as a string, using the specified
+	 * charset.
+	 * @param charset the charset to use for decoding
+	 * @return the contents of this resource as a {@code String}
+	 * @throws java.io.FileNotFoundException if the resource cannot be resolved as
+	 * absolute file path, i.e. if the resource is not available in a file system
+	 * @throws IOException in case of general resolution/reading failures
+	 * @since 6.0.5
 	 */
-	default String getContentAsString(Charset charset) throws IOException{
-		return toString();
+	default String getContentAsString(Charset charset) throws IOException {
+		return FileCopyUtils.copyToString(new InputStreamReader(getInputStream(), charset));
 	}
 
 }

spring-core/src/main/java/org/springframework/core/io/support/EncodedResource.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -159,6 +159,27 @@ public InputStream getInputStream() throws IOException {
 		return this.resource.getInputStream();
 	}
 
+	/**
+	 * Returns the contents of the specified resource as a string, using the specified
+	 * {@link #getCharset() Charset} or {@linkplain #getEncoding() encoding}
+	 * (if any).
+	 * @throws IOException if opening the resource failed
+	 * @since 6.0.5
+	 */
+	public String getContentAsString() throws IOException {
+		Charset charset;
+		if (this.charset != null) {
+			charset = this.charset;
+		}
+		else if (this.encoding != null) {
+			charset = Charset.forName(this.encoding);
+		}
+		else {
+			charset = Charset.defaultCharset();
+		}
+		return this.resource.getContentAsString(charset);
+	}
+
 
 	@Override
 	public boolean equals(@Nullable Object other) {