4.1.2 Java and NDB Cluster

A NDB Cluster is defined as one or more MySQL Servers providing access to an NDBCLUSTER storage engine—that is, to a set of NDB Cluster data nodes (ndbd processes). There are four main access paths from Java to NDBCLUSTER, listed here:

These paths are shown in the following API stack diagram:

Java access paths to NDB

JDBC and mysqld.  Connector/J provides standard access through the MySQL JDBC driver. Using Connector/J, JDBC applications can be written to work with a MySQL server acting as an NDB Cluster SQL node in much the same way that other Connector/J applications work with any other MySQL Server instance.

For more information, see Section 4.2.4, “Using Connector/J with NDB Cluster”.

ClusterJ.  ClusterJ is a native Java Connector for NDBCLUSTER (or NDB), the storage engine for NDB Cluster, in the style of Hibernate, JPA, and JDO. Like other persistence frameworks, ClusterJ uses the Data Mapper pattern, in which data is represented as domain objects, separate from business logic, mapping Java classes to database tables stored in the NDBCLUSTER storage engine.


The NDBCLUSTER storage engine is often referred to (in MySQL documentation and elsewhere) simply as NDB. The terms NDB and NDBCLUSTER are synonymous, and you can use either ENGINE=NDB or ENGINE=NDBCLUSTER in a CREATE TABLE statement to create a clustered table.

ClusterJ does not need to connect to a mysqld process, having direct access to NDBCLUSTER using a JNI bridge that is included in the dynamic library libnbdclient. However, unlike JDBC, ClusterJ does not support table creation and other data definition operations; these must be performed by some other means, such as JDBC or the mysql client.

OpenJPA (ClusterJPA).  ClusterJPA is an adapter for OpenJPA that can also bypass JDBC and MySQL Server, using ClusterJ for fast-track access to the cluster. However, for complex queries (not primary key lookups) ClusterJPA uses JDBC.

OpenJPA is an implementation of the JPA (Java Persistence API) specification, which provides an object-relational persistence framework with relationships, inheritance, and persistent classes. See openjpa.apache.org, for more information about OpenJPA.

ClusterJ is independent of ClusterJPA as well as JDBC. However, ClusterJ can be used together with these APIs. Because ClusterJ is limited to queries on single tables, and does not support relations or inheritance, you should use JPA if you need support for these features in your applications.

For more information, see Section 4.2.3, “Using JPA with NDB Cluster”.

Differences Between ClusterJPA and ClusterJ.  While ClusterJPA and ClusterJ are similar in many ways, there are importance differences between the two, highlighted in the following list.