jena-tdb/src-examples/tdb/examples/ExTDB_Txn2.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package tdb.examples;

import org.apache.jena.atlas.lib.StrUtils;
import org.apache.jena.query.Dataset;
import org.apache.jena.system.Txn;
import org.apache.jena.tdb.TDBFactory;
import org.apache.jena.update.UpdateExecutionFactory;
import org.apache.jena.update.UpdateFactory;
import org.apache.jena.update.UpdateProcessor;
import org.apache.jena.update.UpdateRequest;

/**
 * Example of a WRITE transaction. 
 * See {@link Txn#executeRead}.
 */
public class ExTDB_Txn2 {
    public static void main(String...argv) {
        String directory = "MyDatabases/DB1";
        Dataset dataset = TDBFactory.createDataset(directory);

        // Start WRITE transaction.
        // It's possible to read from the dataset inside the write transaction.

        // An application can have other Datasets, in the same JVM,
        // tied to the same TDB database performing read
        // transactions concurrently. If another write transaction
        // starts, the call of dataset.begin(WRITE) blocks until
        // existing writer finishes.
        
        // A WRITE transaction is
        // dataset.begin(ReadWrite.READ);
        // try {
        // ...
        // ... dataset.abort() or dataset.commit()
        // } finally { dataset.end();}
        //

        Txn.executeWrite(dataset, ()->{
            // Do a SPARQL Update.
            String sparqlUpdateString = StrUtils.strjoinNL
                ("PREFIX . <http://example/>"
                ,"INSERT { :s :p ?now } WHERE { BIND(now() AS ?now) }"
                );

            execUpdate(sparqlUpdateString, dataset);
        });
    }

    public static void execUpdate(String sparqlUpdateString, Dataset dataset) {
        UpdateRequest request = UpdateFactory.create(sparqlUpdateString);
        UpdateProcessor proc = UpdateExecutionFactory.create(request, dataset);
        proc.execute();
    }

}