VMware VCLOUD API 1.0 - TECHNICAL NOTE, Руководство по программированию

Страница: 15 / 212

VMware, Inc. 15
Chapter 1 Introducing the VMware vCloud API
Virtual Systems and Media Images in a vCloud
Virtual systems and media images are stored in a vDC and can be included in a catalog. Media images are
stored in their native representation (ISO or floppy). Virtual systems are stored as templates, using an open
standard format (OVF 1.0). These templates can be retrieved from catalogs and transformed into virtual
systems, called vApps, through a process called instantiation, which binds a template’s abstract resource
requirements to resources available in a vDC. A vApp contains one or more individual virtual machines ( Vm
elements), along with parameters that define operational details such as:

How the contained virtual machines are connected to each other and to external networks.

The order in which individual virtual machines are powered on or off.

End ‐ user license agreement terms for each virtual machine.

Deployment lease terms (typically inherited from the containing organization) that constrain the vApp’s
consumption of vDC resources

Access control information specifying which users and groups can perform operations such as deploy,
power on, modify, and suspend on the vApp and the virtual machines it contains.
Objects, References, and Representations
The vCloud API represents objects in the vCloud as XML documents in which object properties are encoded
as elements and attributes with typed values and an explicit object hierarchy defined by an XML schema.
Every object in a vCloud is uniquely identified by a URL. This URL is constructed by the server and returned
in the value of the href attribute of the XML element that represents the object. It also appears in various
elements of LinkType and ReferenceType . This URL serves as a unique identifier that persists for the life of
the object and is never re ‐ used. Although URLs have a well ‐ known syntax and a well ‐ understood
interpretation, a client should treat each href as an opaque string. The rules that govern construction of href
strings by the server might change in future releases.
Object types, specified as MIME content types, are included in the XML representations of first ‐ class objects
such as the ones shown in Figure 1 ‐ 1 . For more information, see “Content Type” on page 142.
Links and Link Relations
The vCloud API makes extensive use of links (URLs) to provide references to objects and the actions that they
support. These links are the primary mechanism by which a server tells a client how to access and operate on
an object. Links are created by the server, and are read ‐ only at the client. (If a client request body includes a
link, the server ignores it.)
In the XML representation of a vCloud object, each link is defined in a Link element that has the following
form:
<Link rel=" relationship " type="application/vnd.vmware.vcloud.type+xml" href=" URL " name=" string "/>

The rel attribute value defines the relationship of the object whose XML representation contains the Link
to a target object. The relationship also indicates the HTTP request type to use when making a request
with the href attribute of the link, as shown in Table 1 ‐ 1 :
Table 1-1. Link Relationships and HTTP Request Types
rel Attribute Value Relation Description HTTP Request
add adds an item to this container POST
alternate a link to an alternate representation of this object GET
catalogItem a link to the catalogItem that contains a reference to this object. GET
controlAccess apply access controls POST
copy not supported in this release N/A
deploy deploy this object POST