命令模式和activiti中的命令模式应用

命令模式是将行为请求者和行为实现者解耦合的方式。对命令进行封装，将命令和执行命令分隔开。请求的一方发出命令，要求执行某些操作，接受一方收到命令，执行这些操作的真正实现。请求的一方不必知道接受方的接口，以及如何被操作。

命令模式：

命令接口

public interface Command {
	public void execute();
}

命令实现类

public class ConcreteCommand implements Command{
	private Receiver receiver=null;
	private String state;
	
	public ConcreteCommand(Receiver receiver){
		this.receiver=receiver;
	}
	
	@Override
	public void execute() {
		receiver.action();
	}

}

接受者

public class Receiver {
	public void action(){
		
	}
}

命令对象入口

public class Invoker {
	private Command command=null;
	
	public void setCommand(Command command){
		this.command=command;
	}
	
	public void runCommand(){
		command.execute();
	}
}

装配者

public class Client {
	public void assemble(){
		Receiver receiver=new Receiver();
		Command command=new ConcreteCommand(receiver);
		Invoker invoker=new Invoker();
		invoker.setCommand(command);
	}
}

activiti中也有命令模式的应用

命令实现类

import org.activiti.engine.impl.interceptor.Command;
import org.activiti.engine.impl.interceptor.CommandContext;
public class ApproveCommand implements Command<Void>, Serializable {
        //请求操作真正实现者，相当于接受者Receive
	ApproveService approveService;	

	public ApproveCommand(ApproveService approveService){
		this.approveService=approveService;
	}

	public Void execute(CommandContext commandContext) {
                 //其他操作
		approveService.approve();
                 //其他操作
	}
}

命令入口invoker

import org.activiti.engine.impl.cfg.ProcessEngineConfigurationImpl;
import org.activiti.engine.impl.ServiceImpl;
@Service
public class BpmsService extends ServiceImpl {
	private ProcessEngineConfigurationImpl config;
	
	@Autowired
	public void setConfig(ProcessEngineConfigurationImpl config){
		this.config = config;
                //commandExecutor相当于装配器
		this.commandExecutor = this.config.getCommandExecutorTxRequired();
	}


	public void approve(ApproveService approveService){
		this.commandExecutor.execute(new ApproveCommand(approveService));
	}
}

@Autowired
BpmsService bpmsService;
public void test(){
    ApproveService service=new ApproveService();
    bpmsService.approve(service);
}