title: How to fix custom function class not registered in apache jena fuseki error?
body: <p>I need a custom filter function in apache-jena-fuseki. I tried adding custom function class name to config.ttl. I added function class files to class path. But it's always throwing error that function is not registered.</p>
  <p>Can anyone please share a detailed approach I can try or some documentation? Desperately need it.</p>
  <p>Added following line To Configuration File</p>
  <pre><code>[] ja:loadClass &quot;org.apache.jena.sparql.function.library.function&quot; .
  </code></pre>
  <p>Class file is in folder /home/user/custom_functions/</p>
  <p>Class file package name = org.apache.jena.sparql.function.library.</p>
  <p>Java command to launch fuseki server is</p>
  <pre><code>java -cp /home/user/custom_functions/function.class:/home/user/apache-jena-4.5.0/lib-src/*:/home/user/apache-jena-4.5.0/lib/* -jar fuseki-server.jar
  </code></pre>
  <p>Function takes one argument.
  When I run query, it gives me error log that function has not registered FunctionFactory.</p>
  <pre><code>PREFIX rdfs: &lt;http://www.w3.org/2000/01/rdf-schema#&gt;
  PREFIX java: &lt;http://www.w3.org/2007/uwa/context/java.owl#&gt;
  PREFIX f: &lt;java:org.apache.jena.sparql.function.library.&gt;
  SELECT ?s ?o { 
      ?s rdfs:label ?o . 
      FILTER (f:function(?o) ) .
  }
  </code></pre>