Java example source code file (SmtpResponseDecoder.java)

This example Java source code file (SmtpResponseDecoder.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

arraylist, bytebuf, charsequence, decoderexception, defaultsmtpresponse, linebasedframedecoder, list, override, received, smtpresponsedecoder, unstableapi, util

The SmtpResponseDecoder.java Java example source code

/*
 * Copyright 2016 The Netty Project
 *
 * The Netty Project licenses this file to you 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 io.netty.handler.codec.smtp;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.DecoderException;
import io.netty.handler.codec.LineBasedFrameDecoder;
import io.netty.util.CharsetUtil;
import io.netty.util.internal.UnstableApi;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * Decoder for SMTP responses.
 */
@UnstableApi
public final class SmtpResponseDecoder extends LineBasedFrameDecoder {

    private List<CharSequence> details;

    /**
     * Creates a new instance that enforces the given {@code maxLineLength}.
     */
    public SmtpResponseDecoder(int maxLineLength) {
        super(maxLineLength);
    }

    @Override
    protected SmtpResponse decode(ChannelHandlerContext ctx, ByteBuf buffer) throws Exception {
        ByteBuf frame = (ByteBuf) super.decode(ctx, buffer);
        if (frame == null) {
            // No full line received yet.
            return null;
        }
        try {
            final int readable = frame.readableBytes();
            final int readerIndex = frame.readerIndex();
            if (readable < 3) {
                throw newDecoderException(buffer, readerIndex, readable);
            }
            final int code = parseCode(frame);
            final int separator = frame.readByte();
            final CharSequence detail = frame.isReadable() ? frame.toString(CharsetUtil.US_ASCII) : null;

            List<CharSequence> details = this.details;

            switch (separator) {
            case ' ':
                // Marks the end of a response.
                this.details = null;
                if (details != null) {
                    if (detail != null) {
                        details.add(detail);
                    }
                } else {
                    details = Collections.singletonList(detail);
                }
                return new DefaultSmtpResponse(code, details);
            case '-':
                // Multi-line response.
                if (detail != null) {
                    if (details == null) {
                        // Using initial capacity as it is very unlikely that we will receive a multi-line response
                        // with more then 3 lines.
                        this.details = details = new ArrayList<CharSequence>(4);
                    }
                    details.add(detail);
                }
                break;
            default:
                throw newDecoderException(buffer, readerIndex, readable);
            }
        } finally {
            frame.release();
        }
        return null;
    }

    private static DecoderException newDecoderException(ByteBuf buffer, int readerIndex, int readable) {
        return new DecoderException(
                "Received invalid line: '" + buffer.toString(readerIndex, readable, CharsetUtil.US_ASCII) + '\'');
    }

    /**
     * Parses the io.netty.handler.codec.smtp code without any allocation, which is three digits.
     */
    private static int parseCode(ByteBuf buffer) {
        final int first = parseNumber(buffer.readByte()) * 100;
        final int second = parseNumber(buffer.readByte()) * 10;
        final int third = parseNumber(buffer.readByte());
        return first + second + third;
    }

    private static int parseNumber(byte b) {
        return Character.digit((char) b, 10);
    }
}