聊聊dubbo的CommandExecutor

序

本文主要研究一下 dubbo 的 CommandExecutor

CommandExecutor

dubbo-2.7.2/dubbo-plugin/dubbo-qos/src/main/java/org/apache/dubbo/qos/command/CommandExecutor.java

public interface CommandExecutor {
    /**
     * Execute one command and return the execution result
     *
     * @param commandContext command context
     * @return command execution result
     * @throws NoSuchCommandException
     */
    String execute(CommandContext commandContext) throws NoSuchCommandException;
}

• CommandExecutor 定义了 execute 方法，其方法传入 CommandContext 参数

CommandContext

dubbo-2.7.2/dubbo-plugin/dubbo-qos/src/main/java/org/apache/dubbo/qos/command/CommandContext.java

public class CommandContext {

    private String commandName;
    private String[] args;
    private Channel remote;
    private boolean isHttp;
    private Object originRequest;

    public CommandContext(String commandName) {this.commandName = commandName;}

    public CommandContext(String commandName, String[] args, boolean isHttp) {
        this.commandName = commandName;
        this.args = args;
        this.isHttp = isHttp;
    }

    public String getCommandName() {return commandName;}

    public void setCommandName(String commandName) {this.commandName = commandName;}

    public String[] getArgs() {return args;}

    public void setArgs(String[] args) {this.args = args;}

    public Channel getRemote() {return remote;}

    public void setRemote(Channel remote) {this.remote = remote;}

    public boolean isHttp() {return isHttp;}

    public void setHttp(boolean http) {isHttp = http;}

    public Object getOriginRequest() {return originRequest;}

    public void setOriginRequest(Object originRequest) {this.originRequest = originRequest;}
}

• CommandContext 定义了 commandName、args、remote、isHttp、originRequest 参数

DefaultCommandExecutor

dubbo-2.7.2/dubbo-plugin/dubbo-qos/src/main/java/org/apache/dubbo/qos/command/DefaultCommandExecutor.java

public class DefaultCommandExecutor implements CommandExecutor {
    @Override
    public String execute(CommandContext commandContext) throws NoSuchCommandException {
        BaseCommand command = null;
        try {command = ExtensionLoader.getExtensionLoader(BaseCommand.class).getExtension(commandContext.getCommandName());
        } catch (Throwable throwable) {//can't find command}
        if (command == null) {throw new NoSuchCommandException(commandContext.getCommandName());
        }
        return command.execute(commandContext, commandContext.getArgs());
    }
}

• DefaultCommandExecutor 实现了 CommandExecutor 接口，其 execute 方法会根据 commandName 通过 ExtensionLoader 来加载对应的 comamnd，然后执行 command 的 execute 方法

小结

CommandExecutor 定义了 execute 方法，其方法传入 CommandContext 参数；CommandContext 定义了 commandName、args、remote、isHttp、originRequest 参数；DefaultCommandExecutor 实现了 CommandExecutor 接口，其 execute 方法会根据 commandName 通过 ExtensionLoader 来加载对应的 comamnd，然后执行 command 的 execute 方法

doc

• CommandExecutor