目标：用原生Java实现Redis连接、向Redis发送命令，解析回复等。
1、解析Redis命令
Redis协议参考：Redis Protocol specification
例如：
命令：set key1 value1
转换后：*3\r\n$3\r\nset\r\n$4\r\nkey1\r\n$6\r\nvalue1\r\n代码实现
//根据redis协议，构造命令的byte数组
private static byte[] cmd(String cmd){
if(StringUtils.isEmpty(cmd)){
return null;
}
StringBuilder sb = new StringBuilder();
String[] cmds = cmd.trim().split(" ");
sb.append("*" + cmds.length);
sb.append("\r\n");
int i = 0;
while(i < cmds.length){
String c = cmds[i++];
sb.append("$" + c.length());
sb.append("\r\n");
sb.append(c);
sb.append("\r\n");
}
return sb.toString().getBytes();
}
2、回复解析
从输入流读取第一个byte，判断是（+、-、*、$、:）中的哪一个，再根据不同情况处理之后的byte。
此处做简化处理，设置一个测试环境足够大的缓冲区，一次性读取回复并处理
//接收缓存
byte[] buff = new byte[256];
//读取redis回复
if(in.read(buff) > 0){
return handleReply(buff);
}回复解析的代码实现：
//处理redis回复
private static String handleReply(byte[] reply) {
if(reply == null || reply.length == 0){
return null;
}
//读取第一个byte
byte first = reply[0];
if(first == '+'){
//单行回复
int end = findRN(reply, 1);
return new String(reply, 1, end - 1);
}else if(first == '-'){
//错误消息
int end = findRN(reply, 1);
return new String(reply, 1, end - 1);
}else if(first == '*'){
//多个批量回复
int end = findRN(reply, 1);
int replyLength = getInt(reply, 1, end);
String[] rs = new String[replyLength];
for(int i = 0; i < replyLength; i++){
int dollar = findDollar(reply, end);
end = findRN(reply, dollar);
int length = getInt(reply, dollar + 1, end);
rs[i] = length == -1 ? "-1" : new String(reply, end + 2, length);
}
return Arrays.toString(rs);
}else if(first == '$'){
//批量回复
int end = findRN(reply, 1);
int length = getInt(reply, 1, end);
return length == -1 ? "-1" : new String(reply, end + 2, length);
}else if(first == ':'){
//整型数字
int end = findRN(reply, 1);
int rs = getInt(reply, 1, end);
return "(integer)" + rs;
}
return null;
}3、搭建Redis服务
参考：在windows上部署使用Redis
4、完整代码
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;
import java.util.Arrays;
import java.util.Scanner;
import org.apache.commons.lang.StringUtils;
public class MyRedisClient {
//redis ip
private final static String IP = "127.0.0.1";
//redis 端口
private final static int PORT = 6379;
//redis 接收数据缓冲区大小
private final static int REPLY_BUFF = 256;
//main方法，接收控制台的命令，发送给redis
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
while(in.hasNext()){
String cmd = in.nextLine();
if(StringUtils.isNotEmpty(cmd)){
//输入exit时退出
if("exit".equals(cmd)){
break;
}
String reply = sendCmdToRedis(cmd);
System.out.println(reply);
}
}
in.close();
}
//向redis发送命令
private static String sendCmdToRedis(String cmd){
if(StringUtils.isEmpty(cmd)){
return null;
}
Socket socket = null;
OutputStream out = null;
InputStream in = null;
try{
//根据redis协议，构造命令的byte数组
byte[] cmdBytes = cmd(cmd);
//socket连接
socket = new Socket(IP, PORT);
//获取socket输出流
out = socket.getOutputStream();
//获取socket输入流
in = socket.getInputStream();
//发送命令
out.write(cmdBytes);
//接收缓存
byte[] buff = new byte[REPLY_BUFF];
//读取redis回复
if(in.read(buff) > 0){
return handleReply(buff);
}
}catch(Exception e){
e.printStackTrace();
}finally{
if(socket != null){
try{
out.close();
in.close();
socket.close();
}catch(Exception e){}
}
}
return null;
}
//根据redis协议，构造命令的byte数组
private static byte[] cmd(String cmd){
if(StringUtils.isEmpty(cmd)){
return null;
}
StringBuilder sb = new StringBuilder();
String[] cmds = cmd.trim().split(" ");
sb.append("*" + cmds.length);
sb.append("\r\n");
int i = 0;
while(i < cmds.length){
String c = cmds[i++];
sb.append("$" + c.length());
sb.append("\r\n");
sb.append(c);
sb.append("\r\n");
}
return sb.toString().getBytes();
}
//处理redis回复
private static String handleReply(byte[] reply) {
if(reply == null || reply.length == 0){
return null;
}
//读取第一个byte
byte first = reply[0];
if(first == '+'){
//单行回复
int end = findRN(reply, 1);
return new String(reply, 1, end - 1);
}else if(first == '-'){
//错误消息
int end = findRN(reply, 1);
return new String(reply, 1, end - 1);
}else if(first == '*'){
//多个批量回复
int end = findRN(reply, 1);
int replyLength = getInt(reply, 1, end);
String[] rs = new String[replyLength];
for(int i = 0; i < replyLength; i++){
int dollar = findDollar(reply, end);
end = findRN(reply, dollar);
int length = getInt(reply, dollar + 1, end);
rs[i] = length == -1 ? "-1" : new String(reply, end + 2, length);
}
return Arrays.toString(rs);
}else if(first == '$'){
//批量回复
int end = findRN(reply, 1);
int length = getInt(reply, 1, end);
return length == -1 ? "-1" : new String(reply, end + 2, length);
}else if(first == ':'){
//整型数字
int end = findRN(reply, 1);
int rs = getInt(reply, 1, end);
return "(integer)" + rs;
}
return null;
}
//获取bytes指定区间的整数
private static int getInt(byte[] bytes, int start, int end) {
if(bytes == null || bytes.length == 0 || start > end || end >= bytes.length){
return -1;
}
int rs = 0;
boolean isNeg = false;
if(bytes[start] == '-'){
isNeg = true;
start++;
}
while(start < end){
rs = rs * 10 + bytes[start] - '0';
start++;
}
return isNeg ? -rs : rs;
}
//在byte数组中，从指定位置开始查找 \r\n 的位置
private static int findRN(byte[] bytes, int start){
if(bytes == null || bytes.length == 0 || start >= bytes.length){
return -1;
}
start = Math.max(start, 0);
boolean find = false;
while(start < bytes.length - 1){
if(bytes[start] == '\r'){
if(bytes[start + 1] != '\n'){
throw new RuntimeException("不合规的回复");
}
find = true;
break;
}
start++;
}
return find ? start : -1;
}
//在byte数组中，从指定位置开始查找 $ 的位置
private static int findDollar(byte[] bytes, int start){
if(bytes == null || bytes.length == 0 || start >= bytes.length){
return -1;
}
start = Math.max(start, 0);
boolean find = false;
while(start < bytes.length - 1){
if(bytes[start] == '$'){
find = true;
break;
}
start++;
}
return find ? start : -1;
}
}
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