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java - 是否可以检索 RDF4J 事务的更新语句？

问题描述

我正在尝试使用 RDF4J 支持 SPARQL 更新查询的“试运行”功能。我想通知用户将插入/删除的语句，最好是通过从当前事务中获取语句。我在想类似的事情：

conn.begin();
Update query = conn.prepareUpdate(queryString);
query.execute();
// Print statements in the transaction
System.out.println("Dry run completed.");
conn.rollback();
System.out.println("Dry run rolled back.");

有没有办法用 RDF4J 做到这一点？

标签： javasparqlrdfrdf4j

解决方案

（从https://github.com/eclipse/rdf4j/discussions/3163复制）

您可以使用SailConnectionListener. 不过，访问它的方式有点笨拙。这是一个例子：

Repository rep = new SailRepository(new MemoryStore());
try (SailRepositoryConnection conn = (SailRepositoryConnection) rep.getConnection()) {
    NotifyingSailConnection sailConn = (NotifyingSailConnection) conn.getSailConnection();
    sailConn.addConnectionListener(new SailConnectionListener() {

        @Override
        public void statementRemoved(Statement removed) {
            System.out.println("removed: " + removed);
        }

        @Override
        public void statementAdded(Statement added) {
            System.out.println("added: " + added);
        }
    });

    conn.begin();
    conn.add(FOAF.PERSON, RDF.TYPE, RDFS.CLASS);
    String update = "DELETE { ?p a rdfs:Class } INSERT { ?p rdfs:label \"Person\" } WHERE { ?p a rdfs:Class }";
    conn.prepareUpdate(update).execute();
    System.out.println("executed");
    conn.rollback();
    System.out.println("transaction aborted");
}

如您所见，我们需要将RepositoryConnection转换为特定类型以检索底层SailConnection，然后我们还需要将其SailConnection转换为 aNotifyingSailConnection以便能够SailConnectionListener在其上注册 a 。此侦听器将接收各个语句的预提交添加和删除事件。运行上述代码将产生以下控制台输出：

added: (http://xmlns.com/foaf/0.1/Person, http://www.w3.org/1999/02/22-rdf-syntax-ns#type, http://www.w3.org/2000/01/rdf-schema#Class)
removed: (http://xmlns.com/foaf/0.1/Person, http://www.w3.org/1999/02/22-rdf-syntax-ns#type, http://www.w3.org/2000/01/rdf-schema#Class) [null]
added: (http://xmlns.com/foaf/0.1/Person, http://www.w3.org/2000/01/rdf-schema#label, "Person")
executed
transaction aborted

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