Building Wikipedia query forms in java using jena
#!/usr/local/bin/python
import sys
sys.path.append(开发者_Python百科'/usr/home/bobd/lib/python/') # needed for hosted version
from SPARQLWrapper import SPARQLWrapper, JSON
import string
import urllib
import cgi
def main():
form = cgi.FieldStorage()
dir1name = form.getvalue('dir1')
dir2name = form.getvalue('dir2')
sparql = SPARQLWrapper("http://data.linkedmdb.org/sparql")
queryString = """
PREFIX m: <http://data.linkedmdb.org/resource/movie/>
SELECT DISTINCT ?actorName WHERE {
?dir1 m:director_name "DIR1-NAME".
?dir2 m:director_name "DIR2-NAME".
?dir1film m:director ?dir1;
m:actor ?actor.
?dir2film m:director ?dir2;
m:actor ?actor.
?actor m:actor_name ?actorName.
}
"""
queryString = queryString.replace("DIR1-NAME",dir1name)
queryString = queryString.replace("DIR2-NAME",dir2name)
sparql.setQuery(queryString)
sparql.setReturnFormat(JSON)
try:
ret = sparql.query()
results = ret.convert()
requestGood = True
except Exception, e:
results = str(e)
requestGood = False
print """Content-type: text/html
<html>
<head>
<title>results</title>
<link href="simple.css" type="text/css" rel="stylesheet" />
</head>
<body>
"""
if requestGood == False:
print "<h1>Problem communicating with the server</h1>"
print "<p>" + results + "</p>"
elif (len(results["results"]["bindings"]) == 0):
print "<p>No results found.</p>"
else:
for result in results["results"]["bindings"]:
print "<p>" + result["actorName"]["value"] + "</p>"
print "</body></html>"
main()
i got the above code from http://www.ibm.com/developerworks/xml/library/x-wikiquery/#download
Now,i want to do the same thing in java with servlets instead of cgi script.
so,how do i pass the query from servlet to http://data.linkedmdb.org/sparql endpoint using jena ?
and how should i get the result back and display it in a html form ?
PLease,HELP
Here's some example code. Note that I wouldn't actually do it this way for real: the presentation code and the back-end query handling are all mixed up in one class. Real apps don't do this! The example is faithful to your sample, except that rather than string-bash the query, I use Jena's facility to pre-bind some of the query variables (so DIR1-NAME becomes ?dir-1-name). I think this is much cleaner, and gives you more flexibility as to which of the query parameters are passed in from the client.
package example;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.*;
import com.hp.hpl.jena.query.*;
import com.hp.hpl.jena.rdf.model.*;
public class ServletExample
extends HttpServlet
{
/***********************************/
/* Constants */
/***********************************/
private static final long serialVersionUID = 1L;
public static final String SPARQL_ENDPOINT = "http://data.linkedmdb.org/sparql";
public static final String QUERY = "PREFIX m: <http://data.linkedmdb.org/resource/movie/>\n" +
"SELECT DISTINCT ?actorName WHERE {\n" +
" ?dir1 m:director_name %dir_name_1%.\n" +
" ?dir2 m:director_name %dir_name_2%.\n" +
" ?dir1film m:director ?dir1;\n" +
" m:actor ?actor.\n" +
" ?dir2film m:director ?dir2;\n" +
" m:actor ?actor.\n" +
" ?actor m:actor_name ?actorName.\n" +
"}\n" +
"";
private static final String HEADER = "<html>\n" +
" <head>\n" +
" <title>results</title>\n" +
" <link href=\"simple.css\" type=\"text/css\" rel=\"stylesheet\" />\n" +
" </head>\n" +
" <body>\n" +
"";
private static final String FOOTER = "</body></html>";
/**
* Respond to HTTP GET request. Will need to be mounted against some URL
* pattern in web.xml
*/
@Override
protected void doGet( HttpServletRequest req, HttpServletResponse resp )
throws ServletException, IOException
{
String dir1 = req.getParameter( "dir1" );
String dir2 = req.getParameter( "dir2" );
if (dir1 == null || dir2 == null || dir1.isEmpty() || dir2.isEmpty()) {
noInput( resp );
}
else {
runQuery( resp, dir1, dir2 );
}
}
protected void noInput( HttpServletResponse resp )
throws IOException
{
header( resp );
resp.getWriter().println( "<p>Please select director names as query params <code>dir1</code> and <code>dir2</code></p>" );
footer( resp );
}
protected void footer( HttpServletResponse resp ) throws IOException {
resp.getWriter().println( FOOTER );
}
protected void header( HttpServletResponse resp ) throws IOException {
resp.getWriter().println( HEADER );
}
protected void runQuery( HttpServletResponse resp, String dir1, String dir2 )
throws IOException
{
PrintWriter out = resp.getWriter();
// Set up the query
String q = QUERY.replace( "%dir_name_1%", "\"" + dir1 + "\"" )
.replace( "%dir_name_2%", "\"" + dir2 + "\"" );
Query query = QueryFactory.create( q ) ;
QueryExecution qexec = QueryExecutionFactory.sparqlService( SPARQL_ENDPOINT, query );
// perform the query
ResultSet results = qexec.execSelect();
// generate the output
header( resp );
if (!results.hasNext()) {
out.println( "<p>No results, sorry.</p>" );
}
else {
out.println( "<h1>Results</h1>" );
while (results.hasNext()) {
QuerySolution qs = results.next();
String actorName = qs.getLiteral( "actorName" ).getLexicalForm();
out.println( String.format( "<div>Actor named: %s</div>", actorName ) );
}
}
footer( resp );
}
}
This code works as far as I can tell, but I don't know which queries you're using that should return some results.
加载中,请稍侯......
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