自己动手写一个Redis客户端

作者: 我是杨正 | 来源:发表于2018-12-28 10:17 被阅读1次

原文链接：https://www.dubby.cn/detail.html?id=9121

使用JavaFX，不依赖任何其他依赖，实现的一个简单的Redis客户端，编写的初衷是觉得Redis Desktop Manager太难用，并且Redis的RESP比较简单，所以这里就尝试着写了下

RESP

REdis Serialization Protocol，这里给出官方的文档链接。为啥Redis要自己搞一套序列化协议，因为他们希望有这么一个协议：

实现起来很简单
转换起来很快
人类容易阅读的

一句话概括——简单。

RESP主要有这么几种类型：

简单字符串，开头是 "+"
错误信息，开头是 "-"
数字，开头是 ":"
大字符串（一般是二进制），开头是 "$"
数组，开头是 "*"

实现Redis客户端

把command解析成Redis认识的byte[]：

public class RedisCommandParser {

    private static final Charset charset = Charset.forName("UTF-8");

    public static byte[] parse(String inputCommand) throws IOException {
        if (StringUtil.isEmpty(inputCommand)) {
            inputCommand = RedisCommandConstant.PING;
        }

        inputCommand = inputCommand.trim();

        ByteArrayOutputStream stream = new ByteArrayOutputStream();
        stream.write(RESPConstant.ASTERISK_BYTE);

        String[] cmdSplit = inputCommand.split(" ");
        int length = 0;
        for (String str : cmdSplit) {
            if (!StringUtil.isEmpty(str)) {
                length++;
            }
        }
        stream.write(intToByte(length));
        stream.write('\r');
        stream.write('\n');

        for (String str : cmdSplit) {
            if (StringUtil.isEmpty(str)) {
                continue;
            }
            stream.write(RESPConstant.DOLLAR_BYTE);
            stream.write(intToByte(str.getBytes(charset).length));
            stream.write('\r');
            stream.write('\n');
            stream.write(str.getBytes(charset));
            stream.write('\r');
            stream.write('\n');
        }

        return stream.toByteArray();
    }


    private final static byte[] Digit = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9'};


    private static byte[] intToByte(int i) {
        if (i <= 0) {
            return new byte[0];
        }
        if (i < 10) {
            byte[] bytes = new byte[1];
            bytes[0] = Digit[i];
            return bytes;
        }
        if (i < 100) {
            byte[] bytes = new byte[2];
            bytes[0] = Digit[i / 10];
            bytes[1] = Digit[i % 10];
            return bytes;
        }
        throw new InvalidParameterException("redis command too long");
    }

}

发送逻辑：

Socket socket = new Socket();
socket.setReuseAddress(true);
socket.setKeepAlive(true);
socket.setTcpNoDelay(true);
socket.setSoLinger(true, 0);
socket.connect(new InetSocketAddress(host, port), 10 * 1000);
socket.setSoTimeout(10 * 1000);
OutputStream outputStream = socket.getOutputStream();
InputStream inputStream = socket.getInputStream();
//AUTH password
String authCmd = "AUTH " + password;
byte[] authCmdBytes = RedisCommandParser.parse(authCmd);
outputStream.write(authCmdBytes);
outputStream.flush();
byte[] bytes = new byte[102400];
int length = inputStream.read(bytes);
String authResult = new String(bytes, 0, length, charset);
logger.info(authResult);
//SELECT dbIndex
String selectCmd = "SELECT " + dbIndex;
byte[] selectCmdBytes = RedisCommandParser.parse(selectCmd);
outputStream.write(selectCmdBytes);
outputStream.flush();
bytes = new byte[102400];
length = inputStream.read(bytes);
String selectResult = new String(bytes, 0, length, charset);
logger.info(selectResult);
//COMMAND
byte[] commandBytes = RedisCommandParser.parse(command);
outputStream.write(commandBytes);
outputStream.flush();
bytes = new byte[102400];
length = inputStream.read(bytes);
String result = new String(bytes, 0, length, charset);
logger.info(String.format("\ncommand:\n%s\nresult:\n%s", new String(commandBytes, charset), result));