or zwei Tagen habe ich in meinem Praktikum angefangen, Cassandra zu lernen, sie gaben mir einen Einblick in Cassandra und ich fand einige Codes aus dem Netz. Es gibt keine Fehler im Code, aber wenn ich den Code ausführe, erhalte ich Fehler wie:

InvalidRequestException (warum: Keyspace-Blog ist in diesem Schema nicht vorhanden.) Bei org.apache.cassandra.thrift.Cassandra $ remove_result.read (Cassandra.java:14354) bei org.apache.cassandra.thrift.Cassandra $ Client.recv_remove (Cassandra.java:755) bei org.apache.cassandra.thrift.Cassandra $ Client.remove (Cassandra.java:729) bei Authors.removeAuthor (Authors.java:141) bei Authors.main (Authors.java:59)

Ich führe Cassandra auch über die Konsole mit dem Befehl ./cassandra -f aus. Ich denke, ich muss zuerst eine Cassandra-Datenbank aufbauen, aber ich konnte wirklich nicht herausfinden, wie ich das mit Java machen kann. Bitte helfen Sie mir zu diesem Thema. Vielen Dank

wenn es hilfreich sein wird, ist der Code, den ich versuche, hier.

/**
 * Sample code for the blog posting:
 * 
 * Installing and using Apache Cassandra With Java Part 4 (Thrift Client)
 * http://www.sodeso.nl/?p=251
 * 
 * Please report any discrepancies that you may find,
 * if you have any requests for examples not mentioned here
 * but are within the scope of the blog posting then also
 * please let me know so i can add them..
 */


import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.cassandra.thrift.Cassandra;
import org.apache.cassandra.thrift.Column;
import org.apache.cassandra.thrift.ColumnOrSuperColumn;
import org.apache.cassandra.thrift.ColumnParent;
import org.apache.cassandra.thrift.ColumnPath;
import org.apache.cassandra.thrift.ConsistencyLevel;
import org.apache.cassandra.thrift.Deletion;
import org.apache.cassandra.thrift.InvalidRequestException;
import org.apache.cassandra.thrift.KeyRange;
import org.apache.cassandra.thrift.KeySlice;
import org.apache.cassandra.thrift.Mutation;
import org.apache.cassandra.thrift.NotFoundException;
import org.apache.cassandra.thrift.SlicePredicate;
import org.apache.cassandra.thrift.SliceRange;
import org.apache.cassandra.thrift.TimedOutException;
import org.apache.cassandra.thrift.UnavailableException;
import org.apache.thrift.TException;
import org.apache.thrift.protocol.TBinaryProtocol;
import org.apache.thrift.protocol.TProtocol;
import org.apache.thrift.transport.TSocket;
import org.apache.thrift.transport.TTransport;
import org.apache.thrift.transport.TTransportException;

/**
 * @author Ronald Mathies
 */
public class Authors {

    private static final String KEYSPACE = "Blog";
    private static final String COLUMN_FAMILY = "Authors";

    public static final String ENCODING = "utf-8";

    private static TTransport tr = null;

    public static void main(String[] args) throws TException, InvalidRequestException, UnavailableException, UnsupportedEncodingException, NotFoundException, TimedOutException {
        Cassandra.Client client = setupConnection();

        System.out.println("Remove all the authors we might have created before.\n");
        removeAuthor(client, "Eric Long");
        removeAuthor(client, "Ronald Mathies");
        removeAuthor(client, "John Steward");

        System.out.println("Create the authors.\n");
        createAuthor(client, "Eric Long", "eric (at) long.com", "United Kingdom", "01/01/2002");
        createAuthor(client, "Ronald Mathies", "ronald (at) sodeso.nl", "Netherlands, The", "01/01/2010");
        createAuthor(client, "John Steward", "john.steward (at) somedomain.com", "Australia", "01/01/2009");

        System.out.println("Select Eric Long.\n");
        selectSingleAuthorWithAllColumns(client, "Eric Long");

        System.out.println("Select Ronald Mathies.\n");
        selectSingleAuthorWithAllColumns(client, "Ronald Mathies");

        System.out.println("Select John Steward.\n");
        selectSingleAuthorWithAllColumns(client, "John Steward");

        System.out.println("Select all authors with all columns.\n");
        selectAllAuthorsWithAllColumns(client);

        System.out.println("Select all authors with only the email column.\n");
        selectAllAuthorsWithOnlyTheEmailColumn(client);

        System.out.println("Update John Steward.\n");
        updateJohnStewardAuthor(client);

        System.out.println("Select John Steward.\n");
        selectSingleAuthorWithAllColumns(client, "John Steward");

        System.out.println("Remove email address and birthday from John Steward.\n");
        deleteEmailAndBirthdayFromJohnSteward(client);

        System.out.println("Select John Steward.\n");
        selectSingleAuthorWithAllColumns(client, "John Steward");

        closeConnection();
    }

    /**
     * Open up a new connection to the Cassandra Database.
     * 
     * @return the Cassandra Client
     */
    private static Cassandra.Client setupConnection() throws TTransportException {
        try {
            tr = new TSocket("localhost", 9160);
            TProtocol proto = new TBinaryProtocol(tr);
            Cassandra.Client client = new Cassandra.Client(proto);
            tr.open();

            return client;
        } catch (TTransportException exception) {
            exception.printStackTrace();
        }

        return null;
    }

    /**
     * Close the connection to the Cassandra Database.
     */
    private static void closeConnection() {
        try {
            tr.flush();
            tr.close();
        } catch (TTransportException exception) {
            exception.printStackTrace();
        }
    }

    /**
     * Removes an Author from the Authors ColumnFamily.
     * cccc
     * @param client the Corg.apache.thrift;

importassandra Client
     * @param authorKey The key of the Author
     */
    private static void removeAuthor(Cassandra.Client client, String authorKey) {
        try {
            ColumnPath columnPath = new ColumnPath(COLUMN_FAMILY);
            client.remove(KEYSPACE, authorKey, columnPath, System.currentTimeMillis(), ConsistencyLevel.ALL);
        } catch (Exception exception) {
            exception.printStackTrace();
        }
    }

    /**
     * Creates and stores an Author in the Cassandra Database.
     * 
     * @param client the Cassandra Client
     * @param authorKey The key of the Author
     * @param email the email address
     * @param country the country
     * @param registeredSince the registration date
     */
    private static void createAuthor(Cassandra.Client client, String authorKey, String email, String country, String registeredSince) {
        try {
            long timestamp = System.currentTimeMillis();
            Map<String, List<ColumnOrSuperColumn>> job = new HashMap<String, List<ColumnOrSuperColumn>>();

            List<ColumnOrSuperColumn> columns = new ArrayList<ColumnOrSuperColumn>();
            Column column = new Column("email".getBytes(ENCODING), email.getBytes(ENCODING), timestamp);
            ColumnOrSuperColumn columnOrSuperColumn = new ColumnOrSuperColumn();
            columnOrSuperColumn.setColumn(column);
            columns.add(columnOrSuperColumn);

            column = new Column("country".getBytes(ENCODING), country.getBytes(ENCODING), timestamp);
            columnOrSuperColumn = new ColumnOrSuperColumn();
            columnOrSuperColumn.setColumn(column);
            columns.add(columnOrSuperColumn);

            column = new Column("country".getBytes(ENCODING), country.getBytes(ENCODING), timestamp);
            columnOrSuperColumn = new ColumnOrSuperColumn();
            columnOrSuperColumn.setColumn(column);
            columns.add(columnOrSuperColumn);

            column = new Column("registeredSince".getBytes(ENCODING), registeredSince.getBytes(ENCODING), timestamp);
            columnOrSuperColumn = new ColumnOrSuperColumn();
            columnOrSuperColumn.setColumn(column);
            columns.add(columnOrSuperColumn);

            job.put(COLUMN_FAMILY, columns);

            client.batch_insert(KEYSPACE, authorKey, job, ConsistencyLevel.ALL);
        } catch (Exception exception) {
            exception.printStackTrace();
        }
    }

    /**
     * Selects a single author with all the columns from the Cassandra database
     * and display it in the console.
     * 
     * @param client the Cassandra client
     * @param authorKey The key of the Author
     */
    private static void selectSingleAuthorWithAllColumns(Cassandra.Client client, String authorKey) {
        try {
            SlicePredicate slicePredicate = new SlicePredicate();
            SliceRange sliceRange = new SliceRange();
            sliceRange.setStart(new byte[] {});
            sliceRange.setFinish(new byte[] {});
            slicePredicate.setSlice_range(sliceRange);

            ColumnParent columnParent = new ColumnParent(COLUMN_FAMILY);
            List<ColumnOrSuperColumn> result = client.get_slice(KEYSPACE, authorKey, columnParent, slicePredicate, ConsistencyLevel.ONE);

            printToConsole(authorKey, result);
        } catch (Exception exception) {
            exception.printStackTrace();
        }
    }

    /**
     * Selects all the authors with all the columns from the Cassandra database.
     * 
     * @param client the Cassandra client
     */
    private static void selectAllAuthorsWithAllColumns(Cassandra.Client client) {
        try {
            KeyRange keyRange = new KeyRange(3);
            keyRange.setStart_key("");
            keyRange.setEnd_key("");

            SliceRange sliceRange = new SliceRange();
            sliceRange.setStart(new byte[] {});
            sliceRange.setFinish(new byte[] {});

            SlicePredicate slicePredicate = new SlicePredicate();
            slicePredicate.setSlice_range(sliceRange);

            ColumnParent columnParent = new ColumnParent(COLUMN_FAMILY);
            List<KeySlice> keySlices = client.get_range_slices(KEYSPACE, columnParent, slicePredicate, keyRange, ConsistencyLevel.ONE);

            for (KeySlice keySlice : keySlices) {
                printToConsole(keySlice.getKey(), keySlice.getColumns());
            }

        } catch (Exception exception) {
            exception.printStackTrace();
        }
    }

    /**
     * Selects all the authors with only the email column from the Cassandra
     * database.
     * 
     * @param client the Cassandra client
     */
    private static void selectAllAuthorsWithOnlyTheEmailColumn(Cassandra.Client client) {
        try {
            KeyRange keyRange = new KeyRange(3);
            keyRange.setStart_key("");
            keyRange.setEnd_key("");

            List<byte[]> columns = new ArrayList<byte[]>();
            columns.add("email".getBytes(ENCODING));

            SlicePredicate slicePredicate = new SlicePredicate();
            slicePredicate.setColumn_names(columns);

            ColumnParent columnParent = new ColumnParent(COLUMN_FAMILY);
            List<KeySlice> keySlices = client.get_range_slices(KEYSPACE, columnParent, slicePredicate, keyRange, ConsistencyLevel.ONE);

            for (KeySlice keySlice : keySlices) {
                printToConsole(keySlice.getKey(), keySlice.getColumns());
            }

        } catch (Exception exception) {
            exception.printStackTrace();
        }
    }

    /**
     * Update the John Steward author with a new email address and a new field, the birthday.
     * 
     * @param client the Cassandra client
     */
    private static void updateJohnStewardAuthor(Cassandra.Client client) {
        try {
            long timestamp = System.currentTimeMillis();

            Map<String, Map<String, List<Mutation>>> job = new HashMap<String, Map<String, List<Mutation>>>();
            List<Mutation> mutations = new ArrayList<Mutation>();

            // Change the email address
            Column column = new Column("email".getBytes(ENCODING), "[email protected]".getBytes(ENCODING), timestamp);
            ColumnOrSuperColumn columnOrSuperColumn = new ColumnOrSuperColumn();
            columnOrSuperColumn.setColumn(column);

            Mutation mutation = new Mutation();
            mutation.setColumn_or_supercolumn(columnOrSuperColumn);
            mutations.add(mutation);

            // Add a new column
            column = new Column("birthday".getBytes(ENCODING), "05-04-1978".getBytes(ENCODING), timestamp);
            columnOrSuperColumn = new ColumnOrSuperColumn();
            columnOrSuperColumn.setColumn(column);

            mutation = new Mutation();
            mutation.setColumn_or_supercolumn(columnOrSuperColumn);
            mutations.add(mutation);

            Map<String, List<Mutation>> mutationsForColumnFamily = new HashMap<String, List<Mutation>>();
            mutationsForColumnFamily.put(COLUMN_FAMILY, mutations);

            job.put("John Steward", mutationsForColumnFamily);

            client.batch_mutate(KEYSPACE, job, ConsistencyLevel.ALL);
        } catch (Exception exception) {
            exception.printStackTrace();
        }
    }

    /**
     * Delete the email address and birthday from John Steward.
     * 
     * @param client the Cassandra client
     */
    private static void deleteEmailAndBirthdayFromJohnSteward(Cassandra.Client client) {
        try {
            long timestamp = System.currentTimeMillis();

            // The columns we want to remove
            List<byte[]> columns = new ArrayList<byte[]>();
            columns.add("email".getBytes(ENCODING));
            columns.add("birthday".getBytes(ENCODING));

            // Add the columns to a SlicePredicate
            SlicePredicate slicePredicate = new SlicePredicate();
            slicePredicate.setColumn_names(columns);

            Deletion deletion = new Deletion(timestamp);
            deletion.setPredicate(slicePredicate);

            Mutation mutation = new Mutation();
            mutation.setDeletion(deletion);

            List<Mutation> mutations = new ArrayList<Mutation>();
            mutations.add(mutation);

            Map<String, List<Mutation>> mutationsForColumnFamily = new HashMap<String, List<Mutation>>();
            mutationsForColumnFamily.put(COLUMN_FAMILY, mutations);

            Map<String, Map<String, List<Mutation>>> batch = new HashMap<String, Map<String, List<Mutation>>>();
            batch.put("John Steward", mutationsForColumnFamily);

            client.batch_mutate(KEYSPACE, batch, ConsistencyLevel.ALL);
        } catch (Exception exception) {
            exception.printStackTrace();
        }
    }

    /**
     * Prints out the information to the console.
     * 
     * @param key the key of the Author
     * @param result the result to print out
     */
    private static void printToConsole(String key, List<ColumnOrSuperColumn> result) {
        try {
            System.out.println("Key: '" + key + "'");
            for (ColumnOrSuperColumn c : result) {
                if (c.getColumn() != null) {
                    String name = new String(c.getColumn().getName(), ENCODING);
                    String value = new String(c.getColumn().getValue(), ENCODING);
                    long timestamp = c.getColumn().getTimestamp();
                    System.out.println("  name: '" + name + "', value: '" + value + "', timestamp: " + timestamp);
                } else {

                }
            }
        } catch (UnsupportedEncodingException exception) {
            exception.printStackTrace();
        }
    }

}