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sql server 2000,±¾Ìå³Ö¾Ã»¯£ºException in thread "main" com.hp.hpl.jena.db.RDFRDBException: Failed to lock database after 5 attempts. Êý¾Ý¿âÊÇÁ¬ÉÏÈ¥ÁË£¬³öÏÖÁËÏÂÃæµÄ´íÎó£¬Íû¸ßÊִͽ̣¬²»Ê¤¸Ð¼¤£º exception in thread "main" com.hp.hpl.jena.db.RDFRDBException: Failed to lock database after 5 attempts. Try later or else call DriverRDB.unlockDB() after ensuring that no other Jena applications are using the database.  at com.hp.hpl.jena.db.impl.DriverRDB.lockDB(DriverRDB.java:925)  at com.hp.hpl.jena.db.impl.DriverRDB.getSystemSpecializedGraph(DriverRDB.java:296)  at com.hp.hpl.jena.db.DBConnection.containsModel(DBConnection.java:227)  at com.hp.hpl.jena.db.impl.GraphRDBMaker.hasGraph(GraphRDBMaker.java:144)  at com.hp.hpl.jena.db.impl.GraphRDBMaker.createGraph(GraphRDBMaker.java:106)  at com.hp.hpl.jena.rdf.model.impl.ModelMakerImpl.createModel(ModelMakerImpl.java:46)  at jena.examples.ontology.persistentOntology.PersistentOntology.listClasses(PersistentOntology.java:79)  at jena.examples.ontology.persistentOntology.Main.main(Main.java:128)    Êղؠ  ·ÖÏí   ¶¥(0)

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Q: Why am I getting an exception on failure to lock or unlock the database? A: The Jena2 storage subsystem uses a lock internally to implement a critical section for operations that modify the database structure (create/delete tables). The lock is implemented as a database table, i.e., if the table exists in the database, the lock is held. Normally, this lock should be transparent to applications. But if an application has an exception while in a critical section, the database may remain locked for subsequent applications. In this case, a user must manually unlock the database either by calling DriverRDB.unlockDB() or by deleting the table (Jena_Mutex) from the database.

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Last but not the least, please allow me to avail myself of this opportunity to extend to you my heartfelt gratitude for your care and support. Thank you.

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Ôõôcalling DriverRDB.unlockDB()

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public ModelMaker getRDBMaker(String dbURL, String dbUser, String dbPw,    String dbType, boolean cleanDB) {   try {    // Create database connection    IDBConnection conn = new DBConnection(dbURL, dbUser, dbPw, dbType);    // do we need to clean the database?    if (cleanDB) {     conn.cleanDB();    }    // Create a model maker object    return ModelFactory.createModelRDBMaker(conn);   } catch (Exception e) {    e.printStackTrace();    System.exit(1);   }   return null;  } ÎÒµ÷ÊÔµÄÊÇjena×Ô´øµÄÒ»¸öÀý×Ó£¨PersistentOntology£©,Âé·³ÁË£¡

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