perf: eliminate intermediate byte[] copies in StreamMessageConsume

- Add MessageJsonHandler.serialize(Message, OutputStream, Charset)
- Serialize into ByteArrayOutputStream and write via writeTo(output)
- Remove String.getBytes(...) and toByteArray() clone
- Cache Charset instead of using encoding String

No breaking changes: existing constructors retained; new overloads are
additive.

Author: sebthom

org.eclipse.lsp4j.jsonrpc/src/main/java/org/eclipse/lsp4j/jsonrpc/json/MessageJsonHandler.java

@@ -12,10 +12,13 @@
 package org.eclipse.lsp4j.jsonrpc.json;
 
 import java.io.IOException;
+import java.io.OutputStream;
+import java.io.OutputStreamWriter;
 import java.io.Reader;
 import java.io.StringReader;
 import java.io.StringWriter;
 import java.io.Writer;
+import java.nio.charset.Charset;
 import java.util.Collections;
 import java.util.Map;
 import java.util.function.Consumer;
@@ -149,6 +152,16 @@ public void serialize(Message message, Writer output) throws JsonIOException {
 		gson.toJson(message, Message.class, output);
 	}
 
+	public void serialize(Message message, OutputStream out, Charset charset) throws JsonIOException {
+		try {
+			final var writer = new OutputStreamWriter(out, charset);
+			serialize(message, writer);
+			writer.flush();
+		} catch (IOException e) {
+			throw new JsonIOException(e);
+		}
+	}
+
 	/**
 	 * Perform JSON serialization of the given object using the configuration of JSON-RPC messages
 	 * enhanced with the pretty printing option.

org.eclipse.lsp4j.jsonrpc/src/main/java/org/eclipse/lsp4j/jsonrpc/json/StreamMessageConsumer.java

@@ -11,8 +11,10 @@
  ******************************************************************************/
 package org.eclipse.lsp4j.jsonrpc.json;
 
+import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
+import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
 
 import org.eclipse.lsp4j.jsonrpc.JsonRpcException;
@@ -24,22 +26,26 @@
  */
 public class StreamMessageConsumer implements MessageConsumer, MessageConstants {
 
-	private final String encoding;
+	private final Charset encoding;
 	private final MessageJsonHandler jsonHandler;
 
 	private final Object outputLock = new Object();
 
 	private OutputStream output;
 
 	public StreamMessageConsumer(MessageJsonHandler jsonHandler) {
-		this(null, StandardCharsets.UTF_8.name(), jsonHandler);
+		this(null, StandardCharsets.UTF_8, jsonHandler);
 	}
 
 	public StreamMessageConsumer(OutputStream output, MessageJsonHandler jsonHandler) {
-		this(output, StandardCharsets.UTF_8.name(), jsonHandler);
+		this(output, StandardCharsets.UTF_8, jsonHandler);
 	}
 
 	public StreamMessageConsumer(OutputStream output, String encoding, MessageJsonHandler jsonHandler) {
+		this(output, Charset.forName(encoding), jsonHandler);
+	}
+
+	public StreamMessageConsumer(OutputStream output, Charset encoding, MessageJsonHandler jsonHandler) {
 		this.output = output;
 		this.encoding = encoding;
 		this.jsonHandler = jsonHandler;
@@ -56,16 +62,16 @@ public void setOutput(OutputStream output) {
 	@Override
 	public void consume(Message message) {
 		try {
-			String content = jsonHandler.serialize(message);
-			byte[] contentBytes = content.getBytes(encoding);
-			int contentLength = contentBytes.length;
+			final var content = new ByteArrayOutputStream(256);
+			jsonHandler.serialize(message, content, encoding);
+			int contentLength = content.size();
 
 			String header = getHeader(contentLength);
 			byte[] headerBytes = header.getBytes(StandardCharsets.US_ASCII);
 
 			synchronized (outputLock) {
 				output.write(headerBytes);
-				output.write(contentBytes);
+				content.writeTo(output);
 				output.flush();
 			}
 		} catch (IOException exception) {
@@ -80,9 +86,9 @@ public void consume(Message message) {
 	protected String getHeader(int contentLength) {
 		final var headerBuilder = new StringBuilder();
 		appendHeader(headerBuilder, CONTENT_LENGTH_HEADER, contentLength).append(CRLF);
-		if (!StandardCharsets.UTF_8.name().equals(encoding)) {
+		if (!StandardCharsets.UTF_8.equals(encoding)) {
 			appendHeader(headerBuilder, CONTENT_TYPE_HEADER, JSON_MIME_TYPE);
-			headerBuilder.append("; charset=").append(encoding).append(CRLF);
+			headerBuilder.append("; charset=").append(encoding.name()).append(CRLF);
 		}
 		headerBuilder.append(CRLF);
 		return headerBuilder.toString();