vberetti / cassandra-metamodel

Cassandra Metamodel

Cassandra Metamodel

Cassandra Metamodel is a thin and non-intrusive layer on top of Datastax Java Driver to provides typed queries and result sets.

Benefits

• Discovers problems at compilation time instead of runtime
• Improves refactoring on columns name/type changes

Requirements

• Java 1.7+
• Cassandra 2.0+
• Datastax Java Driver 2.0.1+

Quick Start

Generate metamodel

Cassandra metamodel maven plugin

Goals

• generate: generates the metamodel for the provided cql files. Bound on generate-sources.

Plugin definition example

<plugin>
	<groupId>fr.vberetti.cassandra.metamodel</groupId>
	<artifactId>cassandra-metamodel-maven-plugin</artifactId>
	<version>XXXXX</version>
	<configuration>
		<cqlFiles>
			<cqlFile>src/main/cql/file.cql</cqlFile>
		</cqlFiles>
		<keyspace>DEFAULT_KSP</keyspace>
		<basePackage>fr.vberetti.cassandra.sample</basePackage>
	</configuration>
	<executions>
		<execution>
			<id>generate</id>
			<goals>
				<goal>generate</goal>
			</goals>
		</execution>
	</executions>
</plugin>

Manually

Cassandra metamodel maven plugin is optional. Be free to define the metamodel manually.

How to use

Query Creation

com.datastax.driver.core.querybuilder.TypedQueryBuilder

Before

QueryBuilder.select("name")
			.from("sample")
			.where(QueryBuilder.eq("id", "2"))

Now

TypedQueryBuilder.select(Sample_.name)
			.from(Sample_.TABLE_NAME)
			.where(TypedQueryBuilder.eq(Sample_.id, "2"))

ResultSet

fr.vberetti.cassandra.metamodel.rs.RowData

Before

ResultSet rs = session.execute(...);
Row one = rs.one();
String name = one.getString("name");

Now

ResultSet rs = session.execute(...);
Row one = rs.one();
String name = RowData.getString(row, Sample_.name);

How does it work ?

Project configuration

3 modules :

• maven-plugin : provides the ability to generate metamodel from maven.
• core : contains the API to be used in queries and resultSet as well as the generator used by maven plugin.
• integration-tests : validates core and maven plugin. Can be used as a sample project.

Generator

Steps

• starts an embedded Cassandra instance
• loads CQL files into embedded instance
• browses the keyspace metadata and generate one class per table

Fields naming

Every table/column names are converted into camel case format for classes and fields names.

Maven Plugin

The Maven plugin simply wraps the generator into a maven plugin structure.