SPARQL is a query language and a remote access protocol. The remote access protocol runs over HTTP.
See Fuseki for an implementation of the SPARQL protocol over HTTP. Fuseki uses ARQ to provide SPARQL query access to Jena models, including Jena persistent models.
ARQ includes a query engine capable of using the HTTP version.
From your application
The QueryExecutionHTTP has methods for creating a
QueryExecution object for remote use. There are various
HTTP specific settings; the default should work in most cases.
The remote request is made when the execSelect, execConstruct,
execDescribe or execAsk method is called.
The results are held locally after remote execution and can be processed as usual.
From the command line
The arq.rsparql command can issue remote
query requests using the --service argument:
java -cp ... arq.rsparql --service 'http://host/service' --query 'SELECT ?s WHERE {?s [] []}'
Or: rsparql –service ‘http://host/service’ –query ‘SELECT ?s WHERE {?s [] []}’
This takes a URL that is the service location.
The query given is parsed locally to check for syntax errors before sending.
Authentication
ARQ provides a flexible API for authenticating against remote services, see the HTTP Authentication documentation for more details.
Firewalls and Proxies
Don’t forget to set the proxy for Java if you are accessing a public server from behind a blocking firewall. Most home firewalls do not block outgoing requests; many corporate firewalls do block outgoing requests.
If, to use your web browser, you need to set a proxy, you need to do so for a Java program.
Simple examples include:
-DsocksProxyHost=YourSocksServer
-DsocksProxyHost=YourSocksServer -DsocksProxyPort=port
-Dhttp.proxyHost=WebProxy -Dhttp.proxyPort=Port
This can be done in the application if it is done before any network connection are made:
System.setProperty("socksProxyHost", "socks.corp.com");
Consult the Java documentation for more details. Searching the web is also very helpful.