2

我正在尝试将OpenRDF Alibaba（与Sesame相关联）作为将 Java 对象映射到 RDF 三元组并再次映射回来的工具。目前，我正在研究它如何处理对象图。

我有两个对象，内部和外部。外部引用了内部。当我坚持一个外部实例时，似乎内部实例被表示为 b 节点，即使我之前已经用分配的 IRI 坚持了内部实例。

我必须做些什么才能自己成功分配内部实例的 IRI，而不是创建 b 节点？

额外的信用问题：我怎样才能使资源 IRI 成为 Java 对象的属性，而不是让它与它识别的对象平行但断开连接？

代码：

内：

package alibabaeval.domain;

import org.openrdf.annotations.Iri;

@Iri("http://example.com/innerType")
public class Inner {

    @Iri("http://example.com/innerType/data")
    private String data;

    public Inner(String data) {
        this.data = data;
    }


    // if this is missing, an unhelpful ClassCastException will be thrown on retrieval
    public Inner() {
    }

    public String getData() {
        return data;
    }

    public void setData(String data) {
        this.data = data;
    }
}

外：

package alibabaeval.domain;

import org.openrdf.annotations.Iri;

@Iri("http://example.com/outerType")
public class Outer {

    @Iri("http://example.com/outerType/data")
    private String outerData;

    @Iri("http://example.com/outerType/innerObject")
    private Inner innerObject;

    public Outer(String outerData) {
        this.outerData = outerData;
    }

    // if this is missing, an unhelpful ClassCastException will be thrown on retrieval
    public Outer() {
    }

    public String getOuterData() {
        return outerData;
    }

    public void setOuterData(String outerData) {
        this.outerData = outerData;
    }

    public Inner getInnerObject() {
        return innerObject;
    }

    public void setInnerObject(Inner innerObject) {
        this.innerObject = innerObject;
    }
}

测试程序：

package alibabaeval;

import org.junit.Test;
import org.openrdf.model.URI;
import org.openrdf.model.ValueFactory;
import org.openrdf.query.QueryLanguage;
import org.openrdf.repository.Repository;
import org.openrdf.repository.object.ObjectConnection;
import org.openrdf.repository.object.ObjectRepository;
import org.openrdf.repository.object.config.ObjectRepositoryFactory;
import org.openrdf.repository.sail.SailRepository;
import org.openrdf.rio.RDFFormat;
import org.openrdf.rio.RDFWriter;
import org.openrdf.rio.Rio;
import org.openrdf.sail.memory.MemoryStore;

import alibabaeval.domain.Inner;
import alibabaeval.domain.Outer;

public class AlibabaEval {

    public static void main(String[] args) throws Exception {
        Repository store = new SailRepository(new MemoryStore());
        store.initialize();

        // wrap in an object repository
        ObjectRepositoryFactory factory = new ObjectRepositoryFactory();
        ObjectRepository repository = factory.createRepository(store);

        // add a stuff to the repository
        ObjectConnection con = repository.getConnection();
        ValueFactory vf = con.getValueFactory();

        Inner inner = new Inner("some inner data");
        URI innerId = vf.createURI("http://example.com/inners/inner1");
        con.addObject(innerId, inner);

        URI outerId = vf.createURI("http://example.com/outers/outer1");
        Outer outer = new Outer("some outer data");
        outer.setInnerObject(inner);
        con.addObject(outerId, outer);

        // look at the triples that were created
        System.out.println("\n\n\nGenerated triples:");
        RDFWriter writer = Rio.createWriter(RDFFormat.NTRIPLES, System.out);
        con.prepareGraphQuery(QueryLanguage.SPARQL, "CONSTRUCT { ?s ?p ?o } WHERE {?s ?p ?o }").evaluate(writer);

        // close everything down
        con.close();
        repository.shutDown();
    }
}

输出：

我只创建了两个对象实例，并将它们分别持久化。阿里巴巴似乎忽略了这一点，并创建了 Inner-instance 的第二个副本作为 b 节点，以供 Outer-instance 引用。

SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/C:/Users/me/.gradle/caches/modules-2/files-2.1/org.slf4j/slf4j-jdk14/1.7.7/25d160723ea37a6cb84e87cd70773ff02997e857/slf4j-jdk14-1.7.7.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/C:/Users/me/.gradle/caches/modules-2/files-2.1/org.slf4j/slf4j-log4j12/1.7.12/485f77901840cf4e8bf852f2abb9b723eb8ec29/slf4j-log4j12-1.7.12.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.slf4j.impl.JDK14LoggerFactory]
Jan 08, 2016 6:00:21 PM org.openrdf.repository.object.managers.helpers.Scanner scan
INFO: Scanning C:\workspace\AlibabaTest\bin for concepts
Jan 08, 2016 6:00:22 PM org.openrdf.repository.object.ObjectRepository compileSchema
INFO: Compiling schema
Jan 08, 2016 6:00:22 PM org.openrdf.repository.object.composition.ClassResolver setBaseClassRoles
WARNING: Concept will only be mergable: class alibabaeval.domain.Inner
Jan 08, 2016 6:00:22 PM org.openrdf.repository.object.composition.ClassResolver setBaseClassRoles
WARNING: Concept will only be mergable: class alibabaeval.domain.Outer



Generated triples:
<http://example.com/inners/inner1> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://example.com/innerType> .
<http://example.com/inners/inner1> <http://example.com/innerType/data> "some inner data" .
<http://example.com/outers/outer1> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://example.com/outerType> .
_:node1a8hqu4aqx1 <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://example.com/innerType> .
_:node1a8hqu4aqx1 <http://example.com/innerType/data> "some inner data" .
<http://example.com/outers/outer1> <http://example.com/outerType/innerObject> _:node1a8hqu4aqx1 .
<http://example.com/outers/outer1> <http://example.com/outerType/data> "some outer data" .
4

2 回答 2

1

现在我对阿里巴巴稍微熟悉了一点，在再次阅读文档后，我看到了更好的答案。

阿里巴巴将在分离的对象上使用 RDFObject.getResource() 返回的值。这是执行此操作的内部实现：

package alibabaeval.domain;

import org.openrdf.annotations.Iri;
import org.openrdf.model.Resource;
import org.openrdf.model.impl.URIImpl;
import org.openrdf.repository.object.ObjectConnection;
import org.openrdf.repository.object.RDFObject;

@Iri("http://example.com/#innerType")
public class Inner implements RDFObject {

    @Iri("http://example.com/innerType/data")
    private String data;

    private Resource detachedId;

    public Inner() {

    }

    @Override
    public ObjectConnection getObjectConnection() {
        // don't really care about this one right now
        return null;
    }

    @Override
    public Resource getResource() {
        // only run on detached object, is hidden by a proxy on managed objects
        return detachedId;
    }

    public Resource getDetachedId() {
        return detachedId;
    }

    public void setDetachedId(Resource detachedId) {
        this.detachedId = detachedId;
    }

    public void setDetachedId(String detachedId) {
        this.detachedId = new URIImpl(detachedId);
    }

    public void setResource(Resource resource) {
        detachedId = resource;
    }

    public Inner(String data) {
        this.data = data;
    }

    public String getData() {
        return data;
    }

    public void setData(String data) {
        this.data = data;
    }
}

这使您可以这样做：

    Inner inner = new Inner("some inner data");
    inner.setDetachedId("http://example.com/inners/inner1");

    URI outerId = vf.createURI("http://example.com/outers/outer1");
    Outer outer = new Outer("some outer data");
    outer.setInnerObject(inner);
    con.addObject(outerId, outer);

并得到这些三元组：

<http://example.com/inners/inner1> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://example.com/#innerType> .
<http://example.com/inners/inner1> <http://example.com/innerType/data> "some inner data" .
<http://example.com/outers/outer1> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://example.com/#outerType> .
<http://example.com/outers/outer1> <http://example.com/outerType/data> "some outer data" .
<http://example.com/outers/outer1> <http://example.com/outerType/innerObject> <http://example.com/inners/inner1> .

该技术也适用于单参数ObjectConnection.addObject(Object instance)方法。

This also only works for detached objects. Instances managed by Alibaba will proxy the RDFObject.getResource() method, so you no longer have control over what it returns.

于 2016-01-13T23:19:06.910 回答
0

问题是 idInner被添加到存储中，但您的实际InnerPOJO 没有得到更新。要解决此问题，只需inner = con.getObject(Inner.class, innerId);在调用addObject.

FWIW 额外的往返惩罚并不像阿里巴巴做最近访问对象缓存那样特别严重 - 因此它不需要一直到持久层进行此查找。

至于如何从对象本身取回标识资源：如果你确定你的 POJO 实现了RDFObject接口，你可以调用getResource来检索关联的 id。顺便说一句，您的getResource方法实现可以简单地返回null，因为阿里巴巴将覆盖其生成对象中的实现。

于 2016-01-11T22:24:56.033 回答