java—是否可以检索rdf4j事务的更新语句？

xu3bshqb 于 2021-08-20 发布在 Java

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我正在尝试使用rdf4j在sparql更新查询上支持“干运行”功能。我想通知用户将插入/删除的语句，最好是从当前事务中获取语句。我的想法是：

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？

Java rdf sparql rdf4j

来源：https://stackoverflow.com/questions/68306956/is-it-possible-to-retrieve-the-update-statements-of-an-rdf4j-transaction

1条答案

按热度按时间

tcbh2hod1#

（抄袭自https://github.com/eclipse/rdf4j/discussions/3163 )
你可以用一个 SailConnectionListener . 但是访问这个的方法有点笨拙。下面是一个例子：

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");
}

正如你所看到的，我们需要 RepositoryConnection 到特定类型以检索基础 SailConnection ，然后我们需要更进一步地 SailConnection 到 NotifyingSailConnection 能够注册 SailConnectionListener 在上面。此侦听器将接收单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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java—是否可以检索rdf4j事务的更新语句？

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