简介

将“请求”封装成对象，以便使用不同的请求、队列或者日志来参数化其他对象。命令模式也支持可撤销的操作。(简化: 将请求封装成对象，将动作请求者和动作执行者解耦。)

实际应用场景

假设现在有电视、电脑、电灯等家电，现在需要你做个遥控器控制所有家电的开关，要求做到每个按钮对应的功能供用户个性化，对于新买入家电要有非常强的扩展性

UML

代码实现

/**
 * 命令执行器接口
 *
 * @author xiaoy
 * @since 2021-3-8 8:51
 */
public interface Command {

    void execute();
}

/**
 * @author xiaoy
 * @since 2021-3-8 8:52
 */
public class SqlCrud {

    public void query() {
        System.out.println("query...");
    }

    public void create() {
        System.out.println("create...");
    }

    public void delete() {
        System.out.println("delete...");
    }

    public void update() {
        System.out.println("update...");
    }
}

/**
 * @author xiaoy
 * @since 2021-3-8 8:55
 */
public class SqlCrudCreateCommand implements Command {

    private SqlCrud sqlCrud;

    public SqlCrudCreateCommand(SqlCrud sqlCrud) {
        this.sqlCrud = sqlCrud;
    }

    @Override
    public void execute() {
        sqlCrud.create();
    }
}

/**
 * @author xiaoy
 * @since 2021-3-8 8:55
 */
public class SqlCrudDeleteCommand implements Command {

    private SqlCrud sqlCrud;

    public SqlCrudDeleteCommand(SqlCrud sqlCrud) {
        this.sqlCrud = sqlCrud;
    }

    @Override
    public void execute() {
        sqlCrud.delete();
    }
}

/**
 * @author xiaoy
 * @since 2021-3-8 8:55
 */
public class SqlCrudQueryCommand implements Command {

    private SqlCrud sqlCrud;

    public SqlCrudQueryCommand(SqlCrud sqlCrud) {
        this.sqlCrud = sqlCrud;
    }

    @Override
    public void execute() {
        sqlCrud.query();
    }
}

/**
 * @author xiaoy
 * @since 2021-3-8 8:55
 */
public class SqlCrudUpdateCommand implements Command {

    private SqlCrud sqlCrud;

    public SqlCrudUpdateCommand(SqlCrud sqlCrud) {
        this.sqlCrud = sqlCrud;
    }

    @Override
    public void execute() {
        sqlCrud.update();
    }
}