Oh yes indeed:
http://plantuml.com/server section "Proxy service"
With the proxy service, the source description of the diagram can be fetched by the PlantUML Server from a remote document.
The proxy service uses the following URL scheme: /plantuml/proxy?src=RESOURCE&idx=INDEX&fmt=FORMAT
- RESOURCE is the complete URL of the document which contains the diagram description (with the @startxxx and @endxxx tags), it could be a .html or a .txt file.
- INDEX is optional, it specifies the occurrence (starting at 0) of the diagram description that will be parsed when there are more than one diagram descriptions in the remote document. It defaults to zero.
- FORMAT is optional, it specifies the format to return. Supported values are: png, svg, eps, epstext and txt. Default is png,
For example, try this link: http://www.plantuml.com/plantuml/proxy?src=https://raw.github.com/plantuml/plantuml-server/master/src/main/webapp/resource/test2diagrams.txt
Note that the address of the remote document is specified as a parameter, so it is not necessary to URL encode the URL.