Cassandra Database Java interview

Cassandra 2.0 database for

Java local client visit Cassandra, first establish javaproject, use MAVEN to manage.

Introduce dependencies:

<dependency>    <groupId>com.datastax.cassandra</groupId>    <artifactId> Cassandra-driver-core</artifactid>    <version>2.1.0</version></dependency>

1. Like Elasticsearch, the client now constructs a cluster object:

Cluster Cluster = Cluster.builder ()                . Addcontactpoint ("Your IP")                . Build ();        Metadata Metadata = Cluster.getmetadata ();        System.out.printf ("Connected to cluster:%s\n",                metadata.getclustername ());        For (Host host:metadata.getAllHosts ()) {            System.out.printf ("Datatacenter:%s; Host:%s; Rack:%s\n ",                    host.getdatacenter (), host.getaddress (), Host.getrack ());        }

2. Pass a Session object. Realize the Cassandra of all the additions and deletions to change.

Session session = Cluster.connect ();

3. Implement all DML operations through the session object. (PS: Before you operate on Cassandra, it is recommended to understand the architecture of Cassandra and the organization of data)

A. We first create a schema:

<pre name= "code" class= "java" >resultset results = Session.execute ("SELECT * from simplex.playlists");        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 ();

Session.execute ("CREATE keyspace simplex with replication" + "= {' class ': ' Simplestrategy ', ' Replication_factor ': 3};");

B. Create a table:

Session.execute ("                CREATE TABLE simplex.songs (" + "                        ID uuid PRIMARY KEY," + "                        title text," +                        "album text," +                        "artist text," +                        "tags set<text>," +                        "data blob" +                        ");

c. Inserting data:

Session.execute (                "INSERT into Simplex.songs (ID, title, album, Artist, Tags)" + "                        VALUES (" +                        "756716f7-2e5 4-4715-9F00-91DCBEA6CF50, "+                        " ' La Petite tonkinoise ', "+                        " ' Bye Bye Blackbird ', "+                        " ' Joséphine Baker ', "+ "                        {' Jazz ', '} ')" +                        ";");

D. Querying data:

ResultSet results = Session.execute ("SELECT * from simplex.playlists");        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 ();

Cassandra Database Java interview