Connect to and use LindormTable with the Cassandra CQL Java driver - Lindorm

Use the Cassandra CQL Java driver (3.x) to connect to LindormTable and run CQL statements for creating keyspaces, tables, and managing data.

Prerequisites

Before you begin, make sure that you have:

A Java environment with JDK 1.8 or later
The Cassandra CQL Java driver installed. See Install the Cassandra CQL driver
The client IP address added to the whitelist for your Lindorm instance. See Set a whitelist
The CQL Connection endpoint for LindormTable, obtained from the Lindorm console. See View Connection Addresses

Maven dependency

Add the DataStax Cassandra Java driver (V3.7 or later) to your Maven project:

<dependency>
    <groupId>com.datastax.cassandra</groupId>
    <artifactId>cassandra-driver-core</artifactId>
    <version>3.8.0</version>
</dependency>

This dependency introduces public libraries. To prevent dependency conflicts, test it in a new project first.

Complete example

The following example connects to LindormTable, creates a keyspace and table, inserts and queries data, then cleans up resources.

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

public class LindormCqlExample {
    public static void main(String[] args) {
        String[] contactPoints = new String[]{
            "<host>"
        };

        // Build the cluster and connect.
        Cluster cluster = Cluster.builder()
            .addContactPoints(contactPoints)
            .withAuthProvider(new PlainTextAuthProvider("<username>", "<password>"))
            .build();
        cluster.init();
        Session session = cluster.connect();

        try {
            // Create a keyspace.
            session.execute(
                "CREATE KEYSPACE IF NOT EXISTS testKeyspace WITH replication "
                    + "= {'class':'SimpleStrategy', 'replication_factor':1};");

            // Create a table.
            session.execute(
                "CREATE TABLE IF NOT EXISTS testKeyspace.testTable ("
                    + "id int PRIMARY KEY,"
                    + "name text,"
                    + "age int,"
                    + "address text"
                    + ");");

            // Insert data.
            session.execute(
                "INSERT INTO testKeyspace.testTable (id, name, age, address) "
                    + "VALUES ("
                    + "1,"
                    + "'testname',"
                    + "11,"
                    + "'hangzhou');");

            // Query all columns.
            ResultSet res = session.execute(
                "SELECT * FROM testKeyspace.testTable ;");

            // Retrieve values from each row.
            for (Row row : res) {
                int id = row.getInt("id");
                String name = row.getString("name");
                int age = row.getInt("age");
                String address = row.getString("address");
            }

            // Truncate the table.
            session.execute("TRUNCATE TABLE testKeyspace.testTable;");

            // Drop the table.
            session.execute("DROP TABLE testKeyspace.testTable ");
        } finally {
            // Close the session first, then shut down the cluster.
            session.close();
            cluster.close();
        }
    }
}

Connection parameters

Parameter	Description	How to obtain
`<host>`	The CQL Connection endpoint for LindormTable.	In the Lindorm console, go to the instance details page and find CQL Connection. Example: `ld-bp17j28j2y7pm****-proxy-lindorm.lindorm.rds.aliyuncs.com`
`<username>`	The username for the Lindorm instance. Default: `root`.	In the Lindorm console, view or create users in the Cluster Management System. See Manage users.
`<password>`	The password for the Lindorm instance username.	If you forget the password, reset it in the Cluster Management System of LindormTable. See Change a user password.

Connection sequence

The driver connects to LindormTable through the following steps:

Create a Cluster instance with Cluster.builder().
Add contact points with .addContactPoints().
Set authentication with .withAuthProvider(new PlainTextAuthProvider()).
Call .build() to finalize the cluster configuration.
Call cluster.init() to initialize the cluster.
Call cluster.connect() to open a session.

CQL operations reference

After connecting, run CQL statements through session.execute(). The following table summarizes the supported operations.

DDL operations

Operation	CQL statement	Example
Create a keyspace	`CREATE KEYSPACE IF NOT EXISTS <keyspace> WITH replication = {'class':'SimpleStrategy', 'replication_factor':1};`	Creates `testKeyspace` with `SimpleStrategy` and a replication factor of 1.
Create a table	`CREATE TABLE IF NOT EXISTS <keyspace>.<table> (<column definitions>);`	Creates `testKeyspace.testTable` with columns: `id` (int, PRIMARY KEY), `name` (text), `age` (int), `address` (text).
Truncate a table	`TRUNCATE TABLE <keyspace>.<table>;`	Removes all rows from `testKeyspace.testTable` without deleting the table.
Drop a table	`DROP TABLE <keyspace>.<table>`	Deletes `testKeyspace.testTable` and all its data.

DML operations

Operation	CQL statement	Example
Insert data	`INSERT INTO <keyspace>.<table> (<columns>) VALUES (<values>);`	Inserts `(1, 'testname', 11, 'hangzhou')` into `testKeyspace.testTable`.
Query data	`SELECT * FROM <keyspace>.<table>;`	Returns all columns from `testKeyspace.testTable`. Specify column names to return specific columns.
Retrieve column values	Use typed getter methods on `Row`: `row.getInt()`, `row.getString()`	Retrieves `id`, `name`, `age`, and `address` from each row in the result set.

Clean up resources

Always close the session before shutting down the cluster. Use a try-finally block to make sure resources are released even if an exception occurs.

session.close();
cluster.close();