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发信人: oopilix (PADRAD), 信区: Visual
标 题: [zz][zl]delphi 中的多层(架构不是数据)连接方式
发信站: 荔园晨风BBS站 (Tue May 27 23:13:51 2003), 站内信件
面试题自csdn:
参考
COM/COM+
Advantages:
· Fastest DataSnap Protocol on Windows platform
· Can be used with other MS« and 3rd party COM applications
· Can be use as Transaction Server (MTS/COM+) objects
Disadvantages:
· Location Dependant
· DCOM has proven to be unstable
· Relies on Windows NT Domain
· Can be difficult to set up
· Cannot port to other environments, MS« only technology
When to use:
· Same machine application server and client application
· A department sized implementation of +- 30 connected clients
· When there is a need to integrate into other MS« or COM based
applications
· Closed NT domains (i.e. No WAN or internet access required)
· Pure speed is at a premium
· Reliability is not at a premium
COM/COM+
优点:
Windows平台上最快的DataSnap协议
可以和微软或第三方的COM应用程序一起使用
可以像MTS/COM+的事务服务对象一样使用
缺点:
位置依赖
DCOM被证明是不稳定的
依赖Windows NT域
安装困难
不能用于其它的环境下,只是微软的技术
什么时候用呢:
客户端和服务器使用相同的机器
大约30个客户端同时执行
需要整合到其它基于微软或者基于COM的应用中去
封闭的NT域(没有广域网或互联网的存取需要)
速度非常宝贵(速度要求非常高)
可靠性要求不是很高
CORBA (VisiBroker)
Advantages:
· Location Independent
· Automatic Fail-Over
· Automatic Load-Balancing, Scales easily
· Easy to set up
· Easily ported to other systems, CORBA is a standard
· Proven technology - reliable, robust
· Highly scalable
Disadvantages:
· Relies on TCP/IP Subnet
· Costly (?) (Outweighed by advantages!)
· Cannot "talk" to MS® software
When to use:
· Large implementations
· Reliability is at a premium
· Scalability (potential for growth) is required
· When implementation requires connectivity to:
o Non-Windows legacy systems
o state-of-the-art systems (EJB's and JSP's)
o heterogeneous external parties (clients and suppliers)
CORBA (VisiBroker)
优点:
位置无关
自动失败恢复
自动负载平衡,易扩展
易安装
易分发到其它系统,CORBA是一个标准
被证明是可靠的技术
高扩展性
缺点:
依靠TCP/IP子网
昂贵?(优点超过代价)
不能和微软的软件交互
什么时候用呢:
大型应用
对可靠性要求高
必须有一定扩展性
当应用需要和以下进行交互时:
非Windows系列系统
state-of-the-art systems (EJB's and JSP's)
异构的外部部分(客户或者提供者)
TCP/IP (Sockets)
Advantages:
· Uses COM, can be used as add-on to existing COM implementations
· Easy to connect to over remote connections or the internet
· Easy to configure
· Can be secured (with interceptor)
Disadvantages:
· Dependant on COM
· Single-point-of-entry, busy socket will bottleneck!
· Slow, single socket must marshal all incoming calls.
· Does not work on DCOM (no remote COM objects)
· Location dependant
When to use:
· Remote or dial-up access is required
· Tiny implementations were COM is to difficult to configure
TCP/IP (Sockets)
优点:
用COM,可以被当作插件添加到已有的COM应用中
方便的连接到远程连接或互联网中
配置容易
可以是安全的
缺点:
依靠COM
单点接入,繁忙的端口将是瓶颈
速度慢,单一的端口必须要分配给所有的进来的调用
不在DCOM上运行(没有远程的COM对象)
位置依赖
什么时候用呢:
需要远程或拨号存取数据
小型的很难配置COM的应用
HTTP (Web)
Advantages:
· Uses COM, can be used as add-on to existing COM implementations
· Very easy to connect to over the internet
· Easy to configure
· Very secure (with IE to IIS SSL)
Disadvantages:
· Dependant on COM
· Single-point-of-entry, busy web-server will bottleneck!
· Slow, web-server must marshal all incoming calls.
· Does not work on DCOM (no remote COM objects)
· Web-site dependant
When to use:
· Pure Internet connection is required
· Tiny implementations that use the Internet as backbone.
HTTP (Web)
优点:
用COM,可以被当作插件添加到已有的COM应用中
方便的连接到远程连接或互联网中
配置容易
非常安全(用IE连接到IIS SSL)
缺点:
依靠COM
单点接入,繁忙的WEB服务器将是瓶颈
速度慢,WEB服务器必须要分配给所有的进来的调用
不在DCOM上运行(没有远程的COM对象)
依靠网站
什么时候用呢:
纯互联网接入
小型的用互联网作为骨干的应用
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