Ensure Java 8 ByteBufferAPI usage.

[resolves #690]

Author: mp911de

src/main/java/io/r2dbc/postgresql/codec/Json.java

@@ -21,6 +21,7 @@
 import io.netty.buffer.ByteBufUtil;
 import io.netty.buffer.Unpooled;
 import io.r2dbc.postgresql.util.Assert;
+import io.r2dbc.postgresql.util.ByteBufferUtils;
 import org.jspecify.annotations.Nullable;
 
 import java.io.ByteArrayInputStream;
@@ -372,9 +373,7 @@ void assertNotReleased() {
         public <T> T mapBuffer(Function<ByteBuffer, ? extends T> mappingFunction) {
             assertNotReleased();
 
-            ByteBuffer buffer = ByteBuffer.allocate(this.buffer.readableBytes());
-            this.buffer.readBytes(buffer);
-            buffer.flip();
+            ByteBuffer buffer = ByteBufferUtils.toByteBuffer(this.buffer);
             release();
 
             return mappingFunction.apply(buffer);

src/main/java/io/r2dbc/postgresql/codec/JsonByteBufferCodec.java

@@ -21,6 +21,7 @@
 import io.r2dbc.postgresql.client.EncodedParameter;
 import io.r2dbc.postgresql.message.Format;
 import io.r2dbc.postgresql.util.Assert;
+import io.r2dbc.postgresql.util.ByteBufferUtils;
 
 import java.nio.ByteBuffer;
 
@@ -37,12 +38,7 @@ final class JsonByteBufferCodec extends AbstractJsonCodec<ByteBuffer> {
 
     @Override
     ByteBuffer doDecode(ByteBuf buffer, PostgresTypeIdentifier dataType, Format format, Class<? extends ByteBuffer> type) {
-
-        ByteBuffer result = ByteBuffer.allocate(buffer.readableBytes());
-        buffer.readBytes(result);
-        result.flip();
-
-        return result;
+        return ByteBufferUtils.toByteBuffer(buffer);
     }
 
     @Override

src/main/java/io/r2dbc/postgresql/message/frontend/GSSResponse.java

@@ -46,7 +46,6 @@ public final class GSSResponse implements FrontendMessage {
      */
     public GSSResponse(ByteBuffer data) {
         Assert.requireNonNull(data, "data must not be null");
-        data.flip();
         this.data = data;
     }
 

src/main/java/io/r2dbc/postgresql/message/frontend/SASLInitialResponse.java

@@ -38,7 +38,7 @@
  */
 public final class SASLInitialResponse implements FrontendMessage {
 
-    private final ByteBuffer initialResponse;
+    private final @Nullable ByteBuffer initialResponse;
 
     private final String name;
 
@@ -50,12 +50,7 @@ public final class SASLInitialResponse implements FrontendMessage {
      * @throws IllegalArgumentException if {@code name} is {@code null}
      */
     public SASLInitialResponse(@Nullable ByteBuffer initialResponse, String name) {
-        if (initialResponse == null) {
-            this.initialResponse = null;
-        } else {
-            initialResponse.flip();
-            this.initialResponse = initialResponse;
-        }
+        this.initialResponse = initialResponse;
         this.name = Assert.requireNonNull(name, "name must not be null");
     }
 

src/main/java/io/r2dbc/postgresql/message/frontend/SASLResponse.java

@@ -46,7 +46,6 @@ public final class SASLResponse implements FrontendMessage {
      */
     public SASLResponse(ByteBuffer data) {
         Assert.requireNonNull(data, "data must not be null");
-        data.flip();
         this.data = data;
     }
 

src/main/java/io/r2dbc/postgresql/util/ByteBufferUtils.java

@@ -18,6 +18,7 @@
 
 import io.netty.buffer.ByteBuf;
 
+import java.nio.Buffer;
 import java.nio.ByteBuffer;
 import java.nio.charset.StandardCharsets;
 
@@ -54,6 +55,7 @@ public static ByteBuffer encode(CharSequence s) {
 
         ByteBuffer buffer = StandardCharsets.UTF_8.encode(s.toString());
         buffer.position(buffer.limit());
+        ((Buffer) buffer).flip();
         return buffer;
     }
 
@@ -68,7 +70,7 @@ public static ByteBuffer toByteBuffer(ByteBuf source) {
 
         ByteBuffer out = ByteBuffer.allocate(source.readableBytes());
         source.readBytes(out);
-        out.flip();
+        ((Buffer) out).flip();
         return out;
     }
 

src/test/java/io/r2dbc/postgresql/message/frontend/GSSResponseUnitTests.java

@@ -36,7 +36,7 @@ void constructorNoData() {
 
     @Test
     void encode() {
-        assertThat(new GSSResponse(ByteBuffer.allocate(4).putInt(100))).encoded()
+        assertThat(new GSSResponse(ByteBuffer.allocate(4).putInt(100).flip())).encoded()
             .isDeferred()
             .isEncodedAs(buffer -> buffer
                 .writeByte('p')

src/test/java/io/r2dbc/postgresql/message/frontend/SASLInitialResponseUnitTests.java

@@ -37,7 +37,7 @@ void constructorNoName() {
 
     @Test
     void encode() {
-        assertThat(new SASLInitialResponse(ByteBuffer.allocate(4).putInt(100), "test-name")).encoded()
+        assertThat(new SASLInitialResponse(ByteBuffer.allocate(4).putInt(100).flip(), "test-name")).encoded()
             .isDeferred()
             .isEncodedAs(buffer -> {
                 buffer

src/test/java/io/r2dbc/postgresql/message/frontend/SASLResponseUnitTests.java

@@ -36,7 +36,7 @@ void constructorNoData() {
 
     @Test
     void encode() {
-        assertThat(new SASLResponse(ByteBuffer.allocate(4).putInt(100))).encoded()
+        assertThat(new SASLResponse(ByteBuffer.allocate(4).putInt(100).flip())).encoded()
             .isDeferred()
             .isEncodedAs(buffer -> buffer
                 .writeByte('p')