For an example of finding objects by external link, see JAXRSearchByExternalLink.java in the directory INSTALL/registry-samples/search-external-link/src, which searches for objects that have a specified external link. The http.proxyHost and http.proxyPort properties are specified in the run target in the build.xml file. Make sure you have set these properties as described in To Edit the build.properties File.
To obtain results from this example, first run the publish-object example described in Adding Classifications: Example.