我现在正在做一个学习项目，我需要一些帮助。
基本上，我需要将以下 RDF 转换为 Java 类的表示。我将 RDF 读入一个模型，然后我就卡住了。
StringReader in = new StringReader(resultTemp);
Model model = ModelFactory.createDefaultModel();
model.read(in, null, "TURTLE");
我尝试使用函数 listSubjectsWithProperty(Property arg0, RDFNode arg1) 和 StmtIterator，但我就是想不通。 如果能提供一些帮助，我将不胜感激。
RDF:
@prefix d: <http://www.w3.org/2001/XMLSchema#> .
@prefix p: <http://parking.kmi.open.ac.uk/ontologies/parking#> .
@prefix s: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix g: <http://www.w3.org/2003/01/geo/wgs84_pos#> .
@prefix o: <http://linkedgeodata.org/ontology/> .
<http://parking.kmi.open.ac.uk/data/parks/4751.3> a o:Parking ;
g:lat "50.8509406"^^d:double ;
g:long "-0.983707"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/4934.6> a o:Parking ;
g:lat "50.8737457"^^d:double ;
g:long "-0.9731118"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/4934.8> a o:Parking ;
g:lat "50.873617"^^d:double ;
g:long "-0.9722267"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/4934.3> a o:Parking ;
g:lat "50.8696495"^^d:double ;
g:long "-0.9767757"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/4934.2> a o:Parking ;
g:lat "50.8698594"^^d:double ;
g:long "-0.9775482"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/4934.1> a o:Parking ;
g:lat "50.8704349"^^d:double ;
g:long "-0.9774731"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/4934.7> a o:Parking ;
g:lat "50.8732887"^^d:double ;
g:long "-0.9725968"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/28356.7> a o:Parking ;
g:lat "50.997992"^^d:double ;
g:long "-0.926222"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/40865.5> a o:Parking ;
g:lat "50.995467"^^d:double ;
g:long "-1.036603"^^d:double ;
s:label "Workhouse Lane" ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/7185.1> a o:Parking ;
g:lat "50.9885711"^^d:double ;
g:long "-1.0811721"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/33791.10> a o:Parking ;
g:lat "50.887628"^^d:double ;
g:long "-0.929626"^^d:double ;
s:label "Locked at 17:30" ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/20810.1> a o:Parking ;
g:lat "50.891515"^^d:double ;
g:long "-0.964029"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/33791.11> a o:Parking ;
g:lat "50.894162"^^d:double ;
g:long "-0.927854"^^d:double ;
s:label "Locked at 17:30" ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/41308.7> a o:Parking ;
g:lat "50.848336"^^d:double ;
g:long "-0.937472"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/41308.6> a o:Parking ;
g:lat "50.849124"^^d:double ;
g:long "-0.937969"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/38470.10> a o:Parking ;
g:lat "50.849454"^^d:double ;
g:long "-0.939969"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/33030.4> a o:Parking ;
g:lat "50.850708"^^d:double ;
g:long "-0.913150"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/33030.3> a o:Parking ;
g:lat "50.850421"^^d:double ;
g:long "-0.914416"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/41378.7> a o:Parking ;
g:lat "50.851734"^^d:double ;
g:long "-0.949425"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/23937.9> a o:Parking ;
g:lat "50.854045"^^d:double ;
g:long "-0.979164"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/23834.6> a o:Parking ;
g:lat "50.849214"^^d:double ;
g:long "-0.987087"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/23937.8> a o:Parking ;
g:lat "50.847012"^^d:double ;
g:long "-0.986388"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/23937.7> a o:Parking ;
g:lat "50.845044"^^d:double ;
g:long "-0.989708"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/23937.12> a o:Parking ;
g:lat "50.844084"^^d:double ;
g:long "-1.008944"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/30510.6> a o:Parking ;
g:lat "50.821892"^^d:double ;
g:long "-0.983163"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/30554.10> a o:Parking ;
g:lat "50.822039"^^d:double ;
g:long "-0.982497"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/25125.2> a o:Parking ;
g:lat "50.825640"^^d:double ;
g:long "-1.078993"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/25125.1> a o:Parking ;
g:lat "50.824621"^^d:double ;
g:long "-1.082243"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/25125> a o:Parking ;
g:lat "50.824789"^^d:double ;
g:long "-1.083873"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/7345.6> a o:Parking ;
g:lat "50.8249235"^^d:double ;
g:long "-1.0734443"^^d:double ;
s:label "Cycle-World" ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/21282> a o:Parking ;
g:lat "50.836295"^^d:double ;
g:long "-1.071699"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/25113.1> a o:Parking ;
g:lat "50.829433"^^d:double ;
g:long "-1.065990"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/25125.5> a o:Parking ;
g:lat "50.834706"^^d:double ;
g:long "-1.074678"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/29282.1> a o:Parking ;
g:lat "50.836060"^^d:double ;
g:long "-1.075153"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
<http://parking.kmi.open.ac.uk/data/parks/41323.3> a o:Parking ;
g:lat "50.853264"^^d:double ;
g:long "-0.990290"^^d:double ;
p:binaryAvailability "true"^^d:boole...`
您好，我需要遍历这些 block 中的每一个:
<http://parking.kmi.open.ac.uk/data/parks/4751.3> a o:Parking ;
g:lat "50.8509406"^^d:double ;
g:long "-0.983707"^^d:double ;
p:binaryAvailability "true"^^d:boolean .
是否有一些迭代器或其他方法允许我这样做？
最佳答案
如果您确实想手动迭代您关心的数据并手动选择您想要的数据，那么您可以使用 Jena 模型 API 来实现。但是，我认为使用 SPARQL 查询选择数据然后迭代生成的结果集会更容易。此答案的其余部分展示了如何实现这些方法中的每一种。
使用 Jena 模型 API
如果你想手动执行此操作，你可以这样做(评论解释了发生了什么):
import java.io.IOException;
import java.io.InputStream;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.rdf.model.ModelFactory;
import com.hp.hpl.jena.rdf.model.Property;
import com.hp.hpl.jena.rdf.model.ResIterator;
import com.hp.hpl.jena.rdf.model.Resource;
import com.hp.hpl.jena.rdf.model.Statement;
import com.hp.hpl.jena.vocabulary.RDF;
import com.hp.hpl.jena.vocabulary.RDFS;
public class ParkingExample {
public static void main(String[] args) throws IOException {
// Read the model from whereever it comes from. For this example,
// I made a local copy in parking.ttl and so I'm loading it as a
// resource. You're already able to load the model, so this
// isn't so important.
Model model = ModelFactory.createDefaultModel();
try ( final InputStream in = ParkingExample.class.getResourceAsStream( "/parking.ttl" ) ) {
model.read( in, null, "TTL" );
}
// Create some properties in advance for convenience.
final Property g_lat = model.createProperty( "http://www.w3.org/2003/01/geo/wgs84_pos#lat" );
final Property g_long = model.createProperty( "http://www.w3.org/2003/01/geo/wgs84_pos#long" );
final Property p_binaryAvailability = model.createProperty( "http://parking.kmi.open.ac.uk/ontologies/parking#binaryAvailability" );
// In N3, Turtle, and SPARQL, `a` is a shorthand for rdf:type. That means
// that each of the triples of the form
//
// <http://parking.kmi.open.ac.uk/data/parks/4934.1> a o:Parking
//
// is saying that the subject has rdf:type o:Parking. That's how we'll retrieve
// these resources. We'll select subjects that have o_Parking as a value for
// rdf:type. We'll predefine o_Parking for convenience.
final Resource o_Parking = model.createResource( "http://linkedgeodata.org/ontology/Parking" );
// Now we get an iterator over the resources that have type o_Parking.
for ( final ResIterator res = model.listResourcesWithProperty( RDF.type, o_Parking ); res.hasNext(); ) {
final Resource r = res.next();
// For each one of them, it appears that they have a mandatory lat, lon, and binAvailability,
// so we can retrieve those values, assuming that they'll be there.
final float lat = r.getRequiredProperty( g_lat ).getObject().asLiteral().getFloat();
final float lon = r.getRequiredProperty( g_long ).getObject().asLiteral().getFloat();
final boolean binAvailibility = r.getRequiredProperty( p_binaryAvailability ).getObject().asLiteral().getBoolean();
// Some of the Parkings have an rdfs:label, but not all of them do. For this, we'll retrieve
// a statement, but since there might not be one, we have to check whether it's null. If it
// is, then we'll make the label null, but otherwise we'll get the string value out of it.
final Statement s = r.getProperty( RDFS.label );
final String label = s == null ? null : s.getObject().asLiteral().getString();
// Now you can do whatever you want with these values. You could create an instance of another
// class, for instance.. I'll just print the values out.
System.out.println( r + ":" +
"\n\tlatitude: " + lat +
"\n\tlongitude: " + lon +
"\n\tavailibility: " + binAvailibility +
"\n\tlabel: " + label );
}
}
}
这会产生如下输出:
http://parking.kmi.open.ac.uk/data/parks/4751.3:
latitude: 50.85094
longitude: -0.983707
availibility: true
label: null
http://parking.kmi.open.ac.uk/data/parks/41378.7:
latitude: 50.851734
longitude: -0.949425
availibility: true
label: null
http://parking.kmi.open.ac.uk/data/parks/25125:
latitude: 50.824787
longitude: -1.083873
availibility: true
label: null
…
使用 SPARQL 查询
我认为使用 SPARQL 查询更容易做到这一点。 SPARQL 查询让您可以准确地写入您要查找的数据类型，包括可选值，并且您可以使用 ResultSet API 获取您想要返回的特定值。在这种情况下，您需要这样的查询:
prefix d: <http://www.w3.org/2001/XMLSchema#>
prefix p: <http://parking.kmi.open.ac.uk/ontologies/parking#>
prefix s: <http://www.w3.org/2000/01/rdf-schema#>
prefix g: <http://www.w3.org/2003/01/geo/wgs84_pos#>
prefix o: <http://linkedgeodata.org/ontology/>
select ?parking ?lat ?lon ?availability ?label where {
?parking a o:Parking ;
g:lat ?lat ;
g:long ?lon ;
p:binaryAvailability ?availability .
optional { ?parking s:label ?label }
}
下面是如何在代码中使用它:
import java.io.IOException;
import java.io.InputStream;
import com.hp.hpl.jena.query.QueryExecution;
import com.hp.hpl.jena.query.QueryExecutionFactory;
import com.hp.hpl.jena.query.QuerySolution;
import com.hp.hpl.jena.query.ResultSet;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.rdf.model.ModelFactory;
public class ParkingExample {
public static void main(String[] args) throws IOException {
final String query =
"prefix d: <http://www.w3.org/2001/XMLSchema#>\n" +
"prefix p: <http://parking.kmi.open.ac.uk/ontologies/parking#>\n" +
"prefix s: <http://www.w3.org/2000/01/rdf-schema#>\n" +
"prefix g: <http://www.w3.org/2003/01/geo/wgs84_pos#>\n" +
"prefix o: <http://linkedgeodata.org/ontology/>\n" +
"\n" +
"select ?parking ?lat ?lon ?availability ?label where {\n" +
" ?parking a o:Parking ;\n" +
" g:lat ?lat ;\n" +
" g:long ?lon ;\n" +
" p:binaryAvailability ?availability .\n" +
" optional { ?parking s:label ?label }\n" +
"}";
Model model = ModelFactory.createDefaultModel();
try ( final InputStream in = ParkingExample.class.getResourceAsStream( "/parking.ttl" ) ) {
model.read( in, null, "TTL" );
}
final QueryExecution exec = QueryExecutionFactory.create( query, model );
final ResultSet rs = exec.execSelect();
while ( rs.hasNext() ) {
final QuerySolution qs = rs.next();
System.out.println( qs.get( "parking" ) +
"\n\t" + qs.get( "lat" ) +
"\n\t" + qs.get( "lon" ) +
"\n\t" + qs.get( "availability" ) +
"\n\t" + qs.get( "label" ));
}
}
}
输出是:
http://parking.kmi.open.ac.uk/data/parks/38470.10
50.849454^^http://www.w3.org/2001/XMLSchema#double
-0.939969^^http://www.w3.org/2001/XMLSchema#double
true^^http://www.w3.org/2001/XMLSchema#boolean
null
http://parking.kmi.open.ac.uk/data/parks/28356.7
50.997992^^http://www.w3.org/2001/XMLSchema#double
-0.926222^^http://www.w3.org/2001/XMLSchema#double
true^^http://www.w3.org/2001/XMLSchema#boolean
null
http://parking.kmi.open.ac.uk/data/parks/33791.11
50.894162^^http://www.w3.org/2001/XMLSchema#double
-0.927854^^http://www.w3.org/2001/XMLSchema#double
true^^http://www.w3.org/2001/XMLSchema#boolean
Locked at 17:30
…
关于java - 使用 Jena 迭代 RDF，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/20453082/