Java tutorial
/* * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.github.pgasync.impl.netty; import com.github.pgasync.impl.io.*; import com.github.pgasync.impl.message.Message; import io.netty.buffer.ByteBuf; import io.netty.channel.ChannelHandlerContext; import io.netty.handler.codec.MessageToByteEncoder; import java.nio.BufferOverflowException; import java.nio.ByteBuffer; import java.util.HashMap; import java.util.Map; /** * Encodes PostgreSQL protocol V3 messages to bytes. * * @author Antti Laisi */ public class ByteBufMessageEncoder extends MessageToByteEncoder<Message> { static final Map<Class<?>, Encoder<?>> ENCODERS = new HashMap<>(); static { for (Encoder<?> encoder : new Encoder<?>[] { new SSLHandshakeEncoder(), new StartupMessageEncoder(), new PasswordMessageEncoder(), new QueryEncoder(), new ParseEncoder(), new BindEncoder(), new ExtendedQueryEncoder(), new TerminateEncoder() }) { ENCODERS.put(encoder.getMessageType(), encoder); } } final ByteBuffer buffer = ByteBuffer.allocate(4096); @Override @SuppressWarnings("unchecked") protected void encode(ChannelHandlerContext ctx, Message msg, ByteBuf out) throws Exception { Encoder<Message> encoder = (Encoder<Message>) ENCODERS.get(msg.getClass()); buffer.clear(); ByteBuffer msgbuf = buffer; try { while (true) { try { encoder.write(msg, msgbuf); break; } catch (BufferOverflowException overflow) { // large clob/blob, resize buffer aggressively msgbuf = ByteBuffer.allocate(msgbuf.capacity() * 4); } } msgbuf.flip(); out.writeBytes(msgbuf); } catch (Throwable t) { // broad catch as otherwise the exception is silently dropped ctx.fireExceptionCaught(t); } } }