Delphi XE DataSnap实现REST服务器：架构与实战指南

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本文档《REST服务器在Delphi XE中使用DataSnap.pdf》由Marco Cantù撰写，发表于2010年12月，主要介绍了如何在Delphi XE环境下利用DataSnap技术实现REST（Representational State Transfer，表述性状态转移）服务器。REST作为一种新兴的网络服务架构，由于其轻量级、简单易用的特点，正在对行业产生深远影响，尤其被大型科技公司如Google、Yahoo、Amazon（包括微软）广泛采用，用于整合和共享来自多个源的信息。 Delphi作为一款历史悠久的开发工具，自Delphi 2010版本起，就加强了对REST的支持，通过DataSnap框架实现了这一技术的集成。DataSnap是Embarcadero Technologies提供的强大工具集，它简化了与Web服务的交互，使得Delphi开发者能够轻松构建RESTful API（应用程序编程接口）。在Delphi XE中，DataSnap进一步增强了REST服务器的功能。它支持WebBroker集成，这是一种通信机制，允许Delphi应用与浏览器或其他非Delphi客户端无缝通信。此外，DataSnap还提供了JavaScript代理（JavaScript proxies），这使得在客户端和服务器之间建立低延迟、高效的数据交换成为可能，同时保持了代码的简洁性和可维护性。文档详细讲解了如何设置和配置REST服务器，包括定义资源（Resources）、处理HTTP请求（如GET、POST、PUT、DELETE等）、以及如何通过DataSnap组件如TDSRESTServer或TDSRESTClient来实现RESTful服务的创建和调用。此外，还包括了示例代码和最佳实践，帮助读者理解和掌握如何在Delphi XE的开发环境中利用DataSnap实现REST服务器，以适应现代Web服务的快速发展。本文档为Delphi开发者提供了一套完整的指南，帮助他们在Delphi XE平台上构建高效、灵活的RESTful服务，以适应快速变化的IT行业需求。通过学习和应用这些技术，开发者可以更好地与现代Web服务生态进行交互，提升应用的可扩展性和用户体验。

REST Servers in Delphi XE Using DataSnap

Embarcadero Technologies - 10 -

Don’t worry if you don’t enable authentication now, as you can easily add it to the project

later on. On the other hand, it is generally a good idea to add a server class with some

sample methods the first time you use this wizard. The server class is the class exposing its

methods as REST service requests, and you can add one (or more than one) later in the

project.

Next, if you select a sample server class, the Wizard will ask you which base class to use.

The available options are a plain TComponent, a TDataModule container (in which you can

easily add non-visual components such as data access components), and a DataSnap

server module. This last option makes little sense for a DataSnap REST application, but it is

an interesting option for other types of DataSnap servers:

For this first project, I’ve chosen TComponent as the base class. In the last page of the

wizard, you can select the base folder for the project. While you are prompted to enter the

path of a folder, the folder name (the last element of the path you provide) will also double

as project name. Since a project name must also be a valid identifier, the folder name

cannot contain spaces and cannot start with a number.

REST Servers in Delphi XE Using DataSnap

Embarcadero Technologies - 12 -

THE WEB DATA MODULE GENERATED BY THE WIZARD

Let’s now look at these web data module generated by the DataSnap REST Wizard in

detail, before we add some code to the program and test it. A web module is the core

element of the WebBroker architecture. It can define multiple actions tied to pathnames,

can intercept other pathnames with dispatcher components, and might also do pre-

processing and post-processing operations on any HTTP request.

Here is a table with a summary of the pathnames and extensions the server will handle, the

component or action managing them, and the source of the information:

Path or Extension Component or Action Target

/ DefaultAction WebModuleDefaultAction method

/ServerFunctionInvoker ServerFunctionInvokerAction ServerFunctionInvoker page producer

/ReverseString ReverseStringAction ReverseString page producer

/datasnap*

DSHTTPWebDispatcher1 DataSnap processing

/datasnap/rest

DSHTTPWebDispatcher1 DataSnap REST processing

*.css, *.js, *.png WebFileDispatcher1 Folders of the file system

The default action has a very limited role (it will redirect the request or return the output of

the ReverseString page producer). This producer, also tied to its own pathname and

action, returns a sample HTML page will look into later on.

In this web module, the core role is played by the DSHTTPWebDispatcher component,

which is the entry point of the DataSnap and REST requests. This component intercepts

any request with a URL starting with ‘datasnap’ (by default), which are passed to the

DataSnap server component (DSServer) also included in the web module. For requests

starting with ‘datasnap’ and indicating a ‘rest’ path (again a default), the processing will be

diverted to the built-in REST engine. In other words, the requests starting with a

‘datasnap/rest’ path are considered as REST requests.

The complete set of component that the Wizard adds to this web module is visible in the

image below, depicting this module at design time:

REST Servers in Delphi XE Using DataSnap

Embarcadero Technologies - 13 -

Here is a summary of the role of the various components:

 DSServer1 is the core DataSnap server component, gluing together all the various

components of this architecture. Despite the fact it has only a couple of properties,

its role is central.

 DSServerClass1 is the component that refers to the class exposing its methods as

REST services, creates and manages the lifetime of objects of this class. Its role

parallels that of a class factory in COM. The actual class this Server Class refers to is

returned in the OnGetClass event handler of the component, in a reference

parameter.

 DSHTTPWebDispatcher1 is the bridge between the WebBroker architecture and

the DataSnap server, as already described.

 WebFileDispather1 is a WebBroker component (new in Delphi XE) used to return

some of the support files (JavaScript files, images, Cascading Style Sheets)

generated by the Wizards, and others you can add. A pre-processing event handler

of this component will update the serverfunctions.js file every time you recompile

and re-execute the application. This JavaScript file contains the “proxy” interface to

the methods exposed by the REST server. The file is updated using the support

provided by the next two components.

 DSProxiGenerator1 is a new Delphi XE component that you can use to generate the

proxy interfaces for various programming languages (Delphi, C++, JavaScript).

These are helper classes you can use in those languages to invoke the methods of

the REST server easily, without having to manually create the calling URL. In this

case the Writer property of the component is set to ‘Java Script REST’. This

component works in conjunction with the next one.

 DSServermetaDataProvider1 offers to the DSProxiGenerator1 component the core

metadata of the server. This is a support component with basically no specific

settings.

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