RespCommand的使用方法
本篇内容主要讲解"RespCommand的使用方法"，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习"RespCommand的使用方法"吧!
序
本文主要研究一下RespCommand
RespCommand
resp-server-0.16.0/src/main/java/com/github/tonivade/resp/command/RespCommand.java
@FunctionalInterfacepublic interface RespCommand { RedisToken execute(Request request);}RespCommand定义了execute方法，接收Request参数，返回RedisToken
Request
resp-server-0.16.0/src/main/java/com/github/tonivade/resp/command/Request.java
public interface Request { String getCommand(); ImmutableArray getParams(); SafeString getParam(int i); Option getOptionalParam(int i); int getLength(); boolean isEmpty(); Session getSession(); ServerContext getServerContext(); boolean isExit();} Request接口定义了getCommand、getParams、getParam、getOptionalParam、getLength、isEmpty、getSession、getServerContext、isExit方法
DefaultRequest
resp-server-0.16.0/src/main/java/com/github/tonivade/resp/command/DefaultRequest.java
public class DefaultRequest implements Request { private final SafeString command; private final ImmutableArray params; private final Session session; private final ServerContext server; public DefaultRequest(ServerContext server, Session session, SafeString command, ImmutableArray params) { this.server = server; this.session = session; this.command = requireNonNull(command); this.params = requireNonNull(params); } @Override public String getCommand() { return command.toString(); } @Override public ImmutableArray getParams() { return params; } @Override public SafeString getParam(int i) { if (i < params.size()) { return params.get(i); } return null; } @Override public Option getOptionalParam(int i) { return Option.of(() -> getParam(i)); } @Override public int getLength() { return params.size(); } @Override public boolean isEmpty() { return params.isEmpty(); } @Override public boolean isExit() { return command.toString().equalsIgnoreCase("quit"); } @Override public Session getSession() { return session; } @Override public ServerContext getServerContext() { return server; } @Override public String toString() { return command + "[" + params.size() + "]: " + params; }} DefaultRequest实现了Request接口，它定义了command、params、session、server属性，均在构造器中传入
CommandSuite
resp-server-0.16.0/src/main/java/com/github/tonivade/resp/command/CommandSuite.java
public class CommandSuite { private static final Logger LOGGER = LoggerFactory.getLogger(CommandSuite.class); private final Map> metadata = new HashMap<>(); private final Map commands = new HashMap<>(); private final NullCommand nullCommand = new NullCommand(); private final CommandWrapperFactory factory; public CommandSuite() { this(new DefaultCommandWrapperFactory()); } public CommandSuite(CommandWrapperFactory factory) { this.factory = factory; addCommand(PingCommand.class); addCommand(EchoCommand.class); addCommand(QuitCommand.class); addCommand(TimeCommand.class); } public RespCommand getCommand(String name) { return commands.getOrDefault(name.toLowerCase(), nullCommand); } public boolean isPresent(String name, Class annotationClass) { return getMetadata(name).isAnnotationPresent(annotationClass); } public boolean contains(String name) { return commands.get(name) != null; } protected void addCommand(Class clazz) { Try.of(clazz::newInstance) .onSuccess(this::processCommand) .onFailure(e -> LOGGER.error("error loading command: " + clazz.getName(), e)); } protected void addCommand(String name, RespCommand command) { commands.put(name.toLowerCase(), factory.wrap(command)); } private void processCommand(Object command) { Class clazz = command.getClass(); Command annotation = clazz.getAnnotation(Command.class); if (annotation != null) { commands.put(annotation.value(), factory.wrap(command)); metadata.put(annotation.value(), clazz); } else { LOGGER.warn("annotation not present at {}", clazz.getName()); } } private Class getMetadata(String name) { return metadata.getOrDefault(name.toLowerCase(), Void.class); }} CommandSuite的构造器添加了PingCommand、EchoCommand、QuitCommand、TimeCommand四个command；addCommand方法将factory.wrap(command)的命令放入commands中
CommandWrapperFactory
resp-server-0.16.0/src/main/java/com/github/tonivade/resp/command/CommandWrapperFactory.java
public interface CommandWrapperFactory { RespCommand wrap(Object command);}CommandWrapperFactory定义了wrap方法，将command包装为RespCommand
DefaultCommandWrapperFactory
resp-server-0.16.0/src/main/java/com/github/tonivade/resp/command/DefaultCommandWrapperFactory.java
public class DefaultCommandWrapperFactory implements CommandWrapperFactory { @Override public RespCommand wrap(Object command) { if (command instanceof RespCommand) { return new CommandWrapper((RespCommand) command); } throw new IllegalArgumentException("must implements command interface"); }}DefaultCommandWrapperFactory实现了CommandWrapperFactory接口，其wrap方法使用CommandWrapper包装RespCommand
CommandWrapper
resp-server-0.16.0/src/main/java/com/github/tonivade/resp/command/CommandWrapper.java
public class CommandWrapper implements RespCommand { private int params; private final RespCommand command; public CommandWrapper(RespCommand command) { this.command = command; ParamLength length = command.getClass().getAnnotation(ParamLength.class); if (length != null) { this.params = length.value(); } } @Override public RedisToken execute(Request request) { if (request.getLength() < params) { return error("ERR wrong number of arguments for '" + request.getCommand() + "' command"); } return command.execute(request); }}CommandWrapper会读取ParamLength注解，若读的到则将注解的value值赋值给params，用于execute方法对request的参数长度进行校验
小结
RespCommand定义了execute方法，接收Request参数，返回RedisToken；CommandSuite的构造器添加了PingCommand、EchoCommand、QuitCommand、TimeCommand四个command；addCommand方法将factory.wrap(command)的命令放入commands中；DefaultCommandWrapperFactory实现了CommandWrapperFactory接口，其wrap方法使用CommandWrapper包装RespCommand；CommandWrapper会读取ParamLength注解，若读的到则将注解的value值赋值给params，用于execute方法对request的参数长度进行校验
到此，相信大家对"RespCommand的使用方法"有了更深的了解，不妨来实际操作一番吧！这里是网站，更多相关内容可以进入相关频道进行查询，关注我们，继续学习！
