Cassandra--Java API

2017-11-16

Cassandra

Java API
直接看代码吧

　　前面已经说了一种访问Cassandra的一种方式CQL，本篇博客还讲解一下其他的方式访问，主要是以Java API的方式，当然它是支持很多语言的，看看下图就知道了：

Java API

Cassandra 的Java API官网给出了如下几种，都是一些公司写的开源客户端，我们这里主要看一下datastax的

直接看代码吧

访问前修改一下cassandra.yaml配置文件

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start_rpc: true
rpc_address: 0.0.0.0
broadcast_rpc_address: 1.2.3.4

下面的代码来源于：https://github.com/jbisso/cassandra-samples

import com.datastax.driver.core.Cluster;
import com.datastax.driver.core.Metadata;
import com.datastax.driver.core.ResultSet;
import com.datastax.driver.core.Row;
import com.datastax.driver.core.Session;

/**
 * A simple client application that illustrates connecting to
 * a Cassandra cluster. retrieving metadata, creating a schema,
 * loading data into it, and then querying it.
 */
public class SimpleClient {
    private Session session;

    public SimpleClient() {
    }

    /**
     * Connects to the specified node.
     * @param node a host name or IP address of the node in the cluster
     */
    public void connect(String node) {
        Cluster cluster = Cluster.builder()
                .addContactPoint(node)
//                .withCredentials("xiaoxiaomo", "blog")
                .build();
        Metadata metadata = cluster.getMetadata();
        System.out.printf("Connected to cluster: %s\n",
                metadata.getClusterName());
        session = cluster.connect();
    }


    public void connect(String[] nodes,int port) {
        Cluster cluster = Cluster.builder()
                .addContactPoints(nodes)
                .withPort(port)
                .withCredentials("xiaoxiaomo", "blog")
                .build();

        Metadata metadata = cluster.getMetadata();
        System.out.printf("Connected to cluster: %s\n",
                metadata.getClusterName());
        session = cluster.connect();
    }


   
    /**
     * Creates the simplex keyspace and two tables, songs and playlists.
     */
    public void createSchema() {
        session.execute(
                "CREATE KEYSPACE IF NOT EXISTS simplex  WITH replication " +
                        "= {'class':'SimpleStrategy', 'replication_factor':3};");
        // create songs and playlist tables
        session.execute(
                "CREATE TABLE IF NOT EXISTS simplex.songs (" +
                        "id uuid PRIMARY KEY," +
                        "title text," +
                        "album text," +
                        "artist text," +
                        "tags set<text>," +
                        "data blob" +
                        ");");
        session.execute(
                "CREATE TABLE IF NOT EXISTS  simplex.playlists (" +
                        "id uuid," +
                        "title text," +
                        "album text, " +
                        "artist text," +
                        "song_id uuid," +
                        "PRIMARY KEY (id, title, album, artist)" +
                        ");");
        System.out.println("Simplex keyspace and schema created.");
    }
   
    /**
     * Loads some data into the schema so that we can query the tables.
     */
    public void loadData() {
        // insert data in the tables
        session.execute(
                "INSERT INTO simplex.songs (id, title, album, artist, tags) " +
                        "VALUES (" +
                        "756716f7-2e54-4715-9f00-91dcbea6cf50," +
                        "'La Petite Tonkinoise'," +
                        "'Bye Bye Blackbird'," +
                        "'Joséphine Baker'," +
                        "{'jazz', '2013'})" +
                        ";");
        session.execute(
                "INSERT INTO simplex.songs (id, title, album, artist, tags) " +
                        "VALUES (" +
                        "f6071e72-48ec-4fcb-bf3e-379c8a696488," +
                        "'Die Mösch'," +
                        "'In Gold'," +
                        "'Willi Ostermann'," +
                        "{'kölsch', '1996', 'birds'}" +
                        ");");
        session.execute(
                "INSERT INTO simplex.songs (id, title, album, artist, tags) " +
                        "VALUES (" +
                        "fbdf82ed-0063-4796-9c7c-a3d4f47b4b25," +
                        "'Memo From Turner'," +
                        "'Performance'," +
                        "'Mick Jager'," +
                        "{'soundtrack', '1991'}" +
                        ");");
        session.execute(
                "INSERT INTO simplex.playlists (id, song_id, title, album, artist) " +
                        "VALUES (" +
                        "2cc9ccb7-6221-4ccb-8387-f22b6a1b354d," +
                        "756716f7-2e54-4715-9f00-91dcbea6cf50," +
                        "'La Petite Tonkinoise'," +
                        "'Bye Bye Blackbird'," +
                        "'Joséphine Baker'" +
                        ");");
        session.execute(
                "INSERT INTO simplex.playlists (id, song_id, title, album, artist) " +
                        "VALUES (" +
                        "2cc9ccb7-6221-4ccb-8387-f22b6a1b354d," +
                        "f6071e72-48ec-4fcb-bf3e-379c8a696488," +
                        "'Die Mösch'," +
                        "'In Gold'," +
                        "'Willi Ostermann'" +
                        ");");
        session.execute(
                "INSERT INTO simplex.playlists (id, song_id, title, album, artist) " +
                        "VALUES (" +
                        "3fd2bedf-a8c8-455a-a462-0cd3a4353c54," +
                        "fbdf82ed-0063-4796-9c7c-a3d4f47b4b25," +
                        "'Memo From Turner'," +
                        "'Performance'," +
                        "'Mick Jager'" +
                        ");");
        System.out.println("Data loaded.");
    }
   
    /**
     * Queries the songs and playlists tables for data.
     */
    public void querySchema() {
        ResultSet results = session.execute(
                "SELECT * FROM simplex.playlists " +
                        "WHERE id = 2cc9ccb7-6221-4ccb-8387-f22b6a1b354d;");
        System.out.println(
                String.format("%-30s\t%-20s\t%-20s\n%s", "title", "album", "artist",
                "-------------+------------------+---------------"));
        for (Row row : results) {
            System.out.println(
                    String.format("%-30s\t%-20s\t%-20s", 
                    row.getString("title"),
                    row.getString("album"), 
                    row.getString("artist")));
        }
        System.out.println();
    }
   
    /**
     * Updates the songs table with a new song and then queries the table
     * to retrieve data.
     */
    public void updateSchema() {
        session.execute(
                "UPDATE simplex.songs " +
                        "SET tags = tags + { 'entre-deux-guerres' } " +
                        "WHERE id = 756716f7-2e54-4715-9f00-91dcbea6cf50;");
      
        ResultSet results = session.execute(
                "SELECT * FROM simplex.songs " +
                        "WHERE id = 756716f7-2e54-4715-9f00-91dcbea6cf50;");
      
        System.out.println(
                String.format("%-30s\t%-20s\t%-20s%-30s\n%s", 
                "title", "album", "artist", "tags", 
                "--------------------------+-----------------+-----------------+-------"));
        
        for (Row row : results) {
            System.out.println(
                    String.format("%-30s\t%-20s\t%-20s", 
                    row.getString("title"),
                    row.getString("album"), 
                    row.getString("artist"), 
                    row.getSet("tags", String.class)));
        }
    }

    /**
     * Drops the specified schema.
     * @param keyspace the keyspace to drop (and all of its data)
     */
    public void dropSchema(String keyspace) {
        getSession().execute("DROP KEYSPACE " + keyspace);
        System.out.println("Finished dropping " + keyspace + " keyspace.");
    }

    /**
     * Returns the current session.
     * @return the current session to execute statements on
     */
    public Session getSession() {
        return this.session;
    }
   
    // used by the workaround method in the BoundStatementsclient child class.
    void setSession(Session session) {
        this.session = session;
    }

    /**
     * Shuts down the session and its cluster.
     */
    public void close() {
        session.close();
        session.getCluster().close();
    }

    /**
     * Creates  simple client application that illustrates connecting to
     * a Cassandra cluster. retrieving metadata, creating a schema,
     * loading data into it, and then querying it.
     * @param args ignored
     */
    public static void main(String[] args) {
        SimpleClient client = new SimpleClient();
        client.connect("10.141.5.27");
        client.createSchema();
        client.loadData();
        client.querySchema();
        client.updateSchema();
        client.dropSchema("simplex");
        client.close();
    }
}

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