[Java] Generate MessageHeader as composite rather than just encoded primitive types. Issue aeron-io#435.

Author: mjpt777

sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/java/JavaGenerator.java

@@ -136,26 +136,7 @@ private String implementsInterface(final String interfaceName)
 
  public void generateMessageHeaderStub() throws IOException
  {
- final List<Token> tokens = ir.headerStructure().tokens();
- final Token firstToken = tokens.get(0);
- try (Writer out = outputManager.createOutput(MESSAGE_HEADER_ENCODER_TYPE))
- {
- generateFixedFlyweightHeader(firstToken, MESSAGE_HEADER_ENCODER_TYPE, out, mutableBuffer, fqMutableBuffer);
- out.append(concatEncodingTokens(
- tokens,
- (token) -> generatePrimitiveEncoder(MESSAGE_HEADER_ENCODER_TYPE, token.name(), token, BASE_INDENT)));
- out.append("}\n");
- }
-
- try (Writer out = outputManager.createOutput(MESSAGE_HEADER_DECODER_TYPE))
- {
- generateFixedFlyweightHeader(
- firstToken, MESSAGE_HEADER_DECODER_TYPE, out, readOnlyBuffer, fqReadOnlyBuffer);
- out.append(concatEncodingTokens(
- tokens,
- (token) -> generatePrimitiveDecoder(true, token.name(), token, BASE_INDENT)));
- out.append("}\n");
- }
+ generateComposite(ir.headerStructure().tokens());
  }
 
  public void generateTypeStubs() throws IOException
@@ -183,8 +164,8 @@ public void generateTypeStubs() throws IOException
 
  public void generate() throws IOException
  {
- generateMessageHeaderStub();
  generateTypeStubs();
+ generateMessageHeaderStub();
 
  for (final List<Token> tokens : ir.messages())
  {