build(www): 添加 Drone CI 流水线配置
- 新增 .drone.yml 文件用于定义 CI/CD 流程 - 配置了基于 Docker 的部署步骤 - 设置了工作区和卷映射以支持持久化数据 - 添加了构建准备阶段和 Docker 部署阶段 - 定义了环境变量和代理设置 - 配置了 artifacts 目录的处理逻辑 - 添加了 timezone 映射以确保时间同步 - 设置了 docker.sock 映射以支持 Docker in Docker
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blogs/database/redis/redis.md
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178
blogs/database/redis/redis.md
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---
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title: 使用Java实现Redis客户端
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date: 2022-11-11
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sidebar: 'auto'
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tags:
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- Redis
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categories:
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- NoSQL
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- Java
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---
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## Redis通信协议-RESP协议
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Redis是一个CS架构的软件，通信一般分两步（不包括pipeline和PubSub）：
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客户端（client）向服务端（server）发送一条命令
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服务端解析并执行命令，返回响应结果给客户端
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因此客户端发送命令的格式、服务端响应结果的格式必须有一个规范，这个规范就是通信协议。
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而在Redis中采用的是RESP（Redis Serialization Protocol）协议：
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- Redis 1.2版本引入了RESP协议
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- Redis 2.0版本中成为与Redis服务端通信的标准，称为RESP2
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- Redis 6.0版本中，从RESP2升级到了RESP3协议，增加了更多数据类型并且支持6.0的新特性--客户端缓存
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但目前，默认使用的依然是RESP2协议，也是我们要学习的协议版本（以下简称RESP）。
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在RESP中，通过首字节的字符来区分不同数据类型，常用的数据类型包括5种：
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- 单行字符串：首字节是 ‘+’ ，后面跟上单行字符串，以CRLF（ "\r\n" ）结尾。例如返回"OK"： "+OK\r\n"
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- 错误（Errors）：首字节是 ‘-’ ，与单行字符串格式一样，只是字符串是异常信息，例如："-Error message\r\n"
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- 数值：首字节是 ‘:’ ，后面跟上数字格式的字符串，以CRLF结尾。例如：":10\r\n"
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- 多行字符串：首字节是 ‘$’ ，表示二进制安全的字符串，最大支持512MB：
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- 如果大小为0，则代表空字符串："$0\r\n\r\n"
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- 如果大小为-1，则代表不存在："$-1\r\n"
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- 数组：首字节是 ‘*’，后面跟上数组元素个数，再跟上元素，元素数据类型不限
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Redis支持TCP通信，因此我们可以使用Socket来模拟客户端，与Redis服务端建立连接：
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```java
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public class RedisClient {
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/** Redis中 RESP 协议头 */
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private final static char SIMPLE_STRING = '+';
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private final static char ERRORS = '-';
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private final static char NUMBER = ':';
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private final static char MULTI_STRING = '$';
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private final static char ARRAY = '*';
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private final static String NEW_LINEAR = "\r\n";
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/** Redis服务端连接信息 */
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private final static String CONN_HOST = "localhost";
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private final static Integer CONN_PORT = 6379;
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private Socket socket;
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private InputStream is;
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private OutputStream os;
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public RedisClient() {
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try {
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// 使用Socket进行远程连接
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socket = new Socket(CONN_HOST, CONN_PORT);
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is = socket.getInputStream();
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os = socket.getOutputStream();
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} catch (IOException e) {
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e.printStackTrace();
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close();
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}
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}
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public void sendRequest(String msg) throws IOException {
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// 解析命令
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String[] commands = parseCommand(msg);
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// 进行命令的拼接写出
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StringBuilder sb = new StringBuilder();
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// *3\r\n 命令数组头
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sb.append(ARRAY).append(commands.length).append(NEW_LINEAR);
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for (String command : commands) {
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// $4\r\nname\r\n
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sb.append(MULTI_STRING).append(command.length()).append(NEW_LINEAR).append(command).append(NEW_LINEAR);
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}
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os.write(sb.toString().getBytes(StandardCharsets.UTF_8));
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os.flush();
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}
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private String[] parseCommand(String commandStr) {
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return commandStr.split(" ");
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}
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public Object handlerResponse() throws IOException {
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int read = is.read();
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switch (read) {
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case SIMPLE_STRING:
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case ERRORS:
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return new BufferedReader(new InputStreamReader(is)).readLine();
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case NUMBER:
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return readNumber();
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case MULTI_STRING:
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return readMulti();
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case ARRAY:
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return readArrays();
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default:
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throw new RuntimeException("结果有误");
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}
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}
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private Object readMulti() throws IOException {
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int count = readNumber().intValue();
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if (count == -1) {
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return null;
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}
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if (count == 0) {
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return "";
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}
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return readLine(count);
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}
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private Long readNumber() throws IOException {
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byte[] bytes = new byte[1024];
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int temp;
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int count = 0;
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while ((temp = is.read()) != '\n') {
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if (temp != '\r') {
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bytes[count++] = (byte) temp;
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}
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}
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return Long.parseLong(new String(bytes, 0, count));
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}
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private Object readArrays() throws IOException {
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int count = readNumber().intValue();
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List<Object> data = new ArrayList<>(count);
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for (int i = 0; i < count; i++) {
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data.add(handlerResponse());
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}
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return data;
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}
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private String readLine(int count) throws IOException {
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byte[] bytes = new byte[1024];
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for (int i = 0; i < count + NEW_LINEAR.length(); i++) {
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int temp = is.read();
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if (temp != '\r' && temp != '\n') {
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bytes[i] = (byte) temp;
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}
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}
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return new String(bytes, 0, count, StandardCharsets.UTF_8);
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}
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public void close() {
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try {
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if (socket != null) {
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socket.close();
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}
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if (is != null) {
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is.close();
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}
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if (os != null) {
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os.close();
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}
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} catch (IOException e) {
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e.printStackTrace();
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}
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}
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public static void main(String[] args) throws IOException {
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RedisClient redisClient = new RedisClient();
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BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
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while (true) {
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System.out.print("[INFO] 请输入redis命令>>> ");
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String command = reader.readLine();
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if (command.equalsIgnoreCase("exit")) {
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redisClient.close();
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break;
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}
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redisClient.sendRequest(command);
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System.out.println(redisClient.handlerResponse());
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}
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}
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}
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```
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