A Container is an object that can execute requests received from a client, and return responses based on those requests. A Container may optionally support a pipeline of Valves that process the request in an order configured at runtime, by implementing the Pipeline interface as well. 
Containers will exist at several conceptual levels within Catalina. The following examples represent common cases: 
Engine - Representation of the entire Catalina servlet engine, most likely containing one or more subcontainers that are either Host or Context implementations, or other custom groups. 
Host - Representation of a virtual host containing a number of Contexts. 
Context - Representation of a single ServletContext, which will typically contain one or more Wrappers for the supported servlets. 
Wrapper - Representation of an individual servlet definition (which may support multiple servlet instances if the servlet itself implements SingleThreadModel). 
A given deployment of Catalina need not include Containers at all of the levels described above. For example, an administration application embedded within a network device (such as a router) might only contain a single Context and a few Wrappers, or even a single Wrapper if the application is relatively small. Therefore, Container implementations need to be designed so that they will operate correctly in the absence of parent Containers in a given deployment. 
A Container may also be associated with a number of support components that provide functionality which might be shared (by attaching it to a parent Container) or individually customized. The following support components are currently recognized: 
Loader - Class loader to use for integrating new Java classes for this Container into the JVM in which Catalina is running. 
Logger - Implementation of the log() method signatures of the ServletContext interface. 
Manager - Manager for the pool of Sessions associated with this Container. 
Realm - Read-only interface to a security domain, for authenticating user identities and their corresponding roles. 
Resources - JNDI directory context enabling access to static resources, enabling custom linkages to existing server components when Catalina is embedded in a larger server. 

生活中离不开杯子、碗、盆等容器


喝水需要杯子,装饭装肉用的碗,洗脸洗脚用的盆.

杯子、碗、洗脸盆都有自己的颜色、宽度、高度;这一切属性根据我们的需求到商店进行了购买.



在Flutter开发中接触到的Container(容器),它也有相关的属性供我们使用.

Container可以根据属性的设置来展现不同的布局大小和样式,还可以容纳其他Widget.

Container只所以可以是容器,因为它可以容纳其它的widget.

常用属性  width、height、color、alignment、padding

........




固定宽高




Center(
        child: Container(width: 100.0,height: 100.0,color: Colors.blue,),
      ),



Center(
        child: Container(width: 200.0,height: 100.0,color: Colors.red,),
      )

宽度和高度无穷大



Center(
        child: Container(
          width: double.infinity,
          height: double.infinity,
          //color: Colors.red,
          decoration: BoxDecoration(color: Colors.blue,),
        ),
      )

宽高>=-0.0 (宽高为正数和-0.0)

Center(
        child: Container(
          width: -100.0,
          height: -100.0,
          //color: Colors.red,
          decoration: BoxDecoration(color: Colors.blue,),
        ),
      ),

运行异常 





 Container宽高约束条件




子widget对其方式 


常见的对齐方式 

topLeft、topCenter、topRight、centerLeft、center、centerRight、bottomLeft、bottomCenter、bottomRight.

 对齐方式是以容器的中心点为基准 

Alignment center = Alignment(0.0, 0.0)



  

Container(
          width: 200.0,
          height: 200.0,
          color: Colors.red,
          alignment: Alignment.center,
          child: Text("xmiaoshen"),
        ),
      )

对齐方式以容器的最左边顶部为基准

Alignment topLeft = Alignment(-1.0, -1.0) 





Container(
          width: 200.0,
          height: 200.0,
          color: Colors.blue,
          alignment: Alignment.topLeft,
          child: Text("xmiaoshen",style: TextStyle(fontWeight: FontWeight.bold,fontSize: 18.0),),
        )

自定义对齐方式



 

Container(
          width: 200.0,
          height: 200.0,
          color: Colors.blue,
          alignment: Alignment(0.5,0.5),
          child: Text("xmiaoshen",style: TextStyle(fontWeight: FontWeight.bold,fontSize: 18.0),),
        ),


内边距 


内边距 (padding): Container 内部widget分别到四边距离.





Container(
          width: 200.0,
          height: 200.0,
          color: Colors.blue,
          padding: EdgeInsets.only(top: 10.0,left: 10.0),
          alignment: Alignment.topLeft,
          child: Text("xmiaoshen",style: TextStyle(fontWeight: FontWeight.bold,fontSize: 18.0),),
        )

子widget宽高超过或者等于父容器时,内边距属性padding依然有效



Container(
          width: 200.0,
          height: 200.0,
          color: Colors.blue,
          padding: EdgeInsets.all(18.0),
          alignment: Alignment.topLeft,
          child: Container(width: 200.0,height: 200.0,color: Colors.black45,),
        )

Container(
          width: 200.0,
          height: 200.0,
          color: Colors.blue,
          padding: EdgeInsets.all(18.0),
          alignment: Alignment.topLeft,
          child: Container(width: 300.0,height: 300.0,color: Colors.black45,),
        )


外边距


外边距 (margin): Container 分别到父容器Container四边距离.



Container(
          width: 200.0,
          height: 200.0,
          color: Colors.blue,
          alignment: Alignment.topLeft,
          child: Container(
            width: 200.0,
            height: 200.0,
            color: Colors.black45,
            margin: EdgeInsets.all(20.0),
          ),
        )

container宽高超过或者等于父容器时,外边距属性margin依然有效



Container(
          width: 200.0,
          height: 200.0,
          color: Colors.blue,
          alignment: Alignment.topLeft,
          child: Container(
            width: 300.0,
            height: 300.0,
            color: Colors.black45,
            margin: EdgeInsets.all(20.0),
          ),
        )


添加约束


容器约束

当我们设置容器的 width 必须在 minWith 和 maxWith 之间.

当我们设置容器的 height 必须在 minHeight 和 maxHeight 之间.






美化Container


通过设置 Container 的属性 

decoration (装饰、装饰品)

Box (盒子)

设置边框



Container(
            width: 200.0,
            height: 200.0,
            //color: Colors.black45,
            decoration: BoxDecoration(
              color: Colors.blue,
              border: Border.all(color: Colors.purple,width: 6.0),
            ),
          )

边框变圆角



Container(
            width: 200.0,
            height: 200.0,
            //color: Colors.black45,
            decoration: BoxDecoration(
              color: Colors.blue,
              border: Border.all(color: Colors.purple,width: 6.0),
              borderRadius: BorderRadius.all(Radius.circular(20.0))
            ),
          )



Container(
            width: 200.0,
            height: 200.0,
            //color: Colors.black45,
            decoration: BoxDecoration(
              color: Colors.blue,
              border: Border.all(color: Colors.purple,width: 6.0),
              borderRadius: BorderRadius.only(
topLeft: Radius.circular(20.0),
bottomRight: Radius.circular(20.0))
            ),
          )

矩形变圆形



Container(
            width: 200.0,
            height: 200.0,
            //color: Colors.black45,
            decoration: BoxDecoration(
              color: Colors.blue,
              border: Border.all(color: Colors.purple,width: 6.0),
              shape: BoxShape.circle
            ),
          )

设置阴影

offset 阴影开始坐标(相对于手机屏幕原点偏移量) ,blurRadius 阴影模糊半径 ,spreadRadius 阴影扩散半径.




Container(
          width: 200.0,
          height: 200.0,
          //color: Colors.black45,
          decoration: BoxDecoration(
              color: Colors.blue,
              boxShadow: [
                BoxShadow(
                    color: Colors.purple,
                    offset: Offset(-6.0, 6.0),
                    blurRadius: 6.0,spreadRadius: 3.0)
              ],
              shape: BoxShape.rectangle),
        )



Container(
          width: 200.0,
          height: 200.0,
          //color: Colors.black45,
          decoration: BoxDecoration(
              color: Colors.blue,
              boxShadow: [
                BoxShadow(
                    color: Colors.purple,
                    offset: Offset(-6.0, 6.0),
                    blurRadius: 6.0,spreadRadius: 3.0)
              ],
              shape: BoxShape.circle),
        )

渐变背景



Container(
          width: 200.0,
          height: 200.0,
          //color: Colors.black45,
          decoration: BoxDecoration(
              color: Colors.blue,
              gradient: LinearGradient(colors: [
                Colors.blue.withOpacity(1.0),
                Colors.blue.withOpacity(0.9),
                Colors.blue.withOpacity(0.8),
                Colors.blue.withOpacity(0.7),
                Colors.blue.withOpacity(0.6),
                Colors.blue.withOpacity(0.5),
                Colors.blue.withOpacity(0.4),
                Colors.blue.withOpacity(0.3),
                Colors.blue.withOpacity(0.2),
                Colors.blue.withOpacity(0.1),
              ], begin: Alignment.topCenter, 
end: Alignment.bottomCenter)),
        )

小太阳



Container(
          width: 200.0,
          height: 200.0,
          //color: Colors.black45,
          decoration: BoxDecoration(
              color: Colors.blue,
              gradient: RadialGradient(
                center: const Alignment(0.0, 0.0), // near the top right
                radius: 0.2,
                colors: [
                  const Color(0xFFFFFF00), // yellow sun
                  const Color(0xFF0099FF), // blue sky
                ],
                stops: [0.3, 1.0],
              )),
        )


参考


虚线容器插件

matrix4_transform

我是在guigu上学习的springboot的视频，有一些很难受的问题，这个问题已经让我难受一天多了，后来终于在一片文章中解决了，给大家分享一下：

docker 启动容器报错：Error response from daemon: oci runtime error: container_linux.go:247: starting container process caused "write parent: broken pipe"

其实原因还是，linux与docker版本的兼容性问题

第一步：通过uname -r命令查看你当前的内核版本

uname -r

第二步：使用 root 权限登录 Centos。确保 yum 包更新到最新。

sudo yum update

第三步：卸载旧版本(如果安装过旧版本的话)

sudo yum remove docker  docker-common docker-selinux dockesr-engine

第四步：安装需要的软件包， yum-util 提供yum-config-manager功能，另外两个是devicemapper驱动依赖的

sudo yum install -y yum-utils device-mapper-persistent-data lvm2

第五步：设置yum源

sudo yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo

第六步：可以查看所有仓库中所有docker版本，并选择特定版本安装

yum list docker-ce --showduplicates | sort -r

第七步：安装docker

sudo yum install docker-ce

第八步：启动并加入开机启动

sudo systemctl start docker
sudo systemctl enable docker

第九步：验证安装是否成功(有client和service两部分表示docker安装启动都成功了)

 docker version

完美解决，如果还没有解决请联系做作者下方评论！

转载请注明出处：http://blog.csdn.net/dongdong9223/article/details/52998375

本文出自【我是干勾鱼的博客】

1 启动docker服务
首先需要知道启动docker服务是：
service docker start

或者：
systemctl start docker

2 关闭docker服务
关闭docker服务是：
service docker stop

或者：
systemctl stop docker

3 启动docker某个image（镜像）的container（容器）
Docker的镜像称为image，容器称为container。
对于Docker来说，image是静态的，类似于操作系统快照，而container则是动态的，是image的运行实例。
比如，有一个image名称为ubuntu，那么比如现在我们启动这个image的container并且进入到这个container的bash命令行中：
docker run -t -i ubuntu /bin/bash

官网是这么说的：

docker run: runs a container.
ubuntu: is the image you would like to run.
-t: flag assigns a pseudo-tty or terminal inside the new container.
-i: flag allows you to make an interactive connection by grabbing the standard in (STDIN) of the container.
/bin/bash: launches a Bash shell inside our container.

理解很简单：


docker run：启动container


ubuntu：你想要启动的image


-t：进入终端


-i：获得一个交互式的连接，通过获取container的输入


/bin/bash：在container中启动一个bash shell


这样就进入container的内部了：
root@af8bae53bdd3:/#

如果有运行中的container，可以在container所在的外部操作系统中运行：
docker ps

查看到这个container。
如果想看到所有的container，包括运行中的，以及未运行的或者说是沉睡镜像，则运行：
docker ps -a

如果要退出就：
Ctrl-D
或：
root@af8bae53bdd3:/# exit

如果想再次打开这个container，运行：
docker start goofy_almeida

其中“goofy_almeida”是容器的名称。
4 进入container（容器）
4.1 使用“docker attach”命令进入
这个时候container运行在后台，如果想进入它的终端，则：
docker attach goofy_almeida

就可以了。
4.2 使用“docker exec -it”命令进入
使用“docker attach”命令进入container（容器）有一个缺点，那就是每次从container中退出到前台时，container也跟着退出了。
要想退出container时，让container仍然在后台运行着，可以使用“docker exec -it”命令。每次使用这个命令进入container，当退出container后，container仍然在后台运行，命令使用方法如下：
docker exec -it goofy_almeida /bin/bash



goofy_almeida：要启动的container的名称


/bin/bash：在container中启动一个bash shell


这样输入“exit”或者按键“Ctrl + C”退出container时，这个container仍然在后台运行，通过：
docker ps

就可以查找到。
5 退出container
输入：
exit

或者按键：
Ctrl + D