Getting Started

Prerequisites

pom.xml

<dependencies>
	<dependency>
		<groupId>one.microstream</groupId>
		<artifactId>microstream-storage-embedded</artifactId>
		<version>08.01.02-MS-GA</version>
	</dependency>
</dependencies>

Hello World

// Initialize a storage manager ("the database") with purely defaults.
final EmbeddedStorageManager storageManager = EmbeddedStorage.start();

// print the last loaded root instance,
// replace it with a current version and store it
System.out.println(storageManager.root());
storageManager.setRoot("Hello World! @ " + new Date());
storageManager.storeRoot();

// shutdown storage
storageManager.shutdown();

This simplest example will create a new storage if no existing storage is found, if a existing storage is found it will be loaded (this is all done at line 2 in the example above).

In line 6 the current storage’s content is printed.

Line 7 assigns some data to the storage, replacing existing data if there is some.

In line 8 everything gets stored.

The Root Instance

When using MicroStream, your entire database is accessed starting at a root instance. This instance is the root object of an object graph that gets persisted by the MicroStream storage logic. While the root instance can be of any type (for example just a collection or an array), it is a good idea to define an explicit root type specific for the application. In this simple example, it is a class called DataRoot, which wraps a single String.

public class DataRoot
{
	private String content;

	public DataRoot()
	{
		super();
	}

	public String getContent()
	{
		return this.content;
	}

	public void setContent(final String content)
	{
		this.content = content;
	}

	@Override
	public String toString()
	{
		return "Root: " + this.content;
	}
}

For further information, see root instances.

Creating a Database

The following code is all that is required to setup a an application backed by a MicroStream database. The application’s convenience root instance is defined and an EmbeddedStorageManager instance, linked to the root, is created (and its database managing threads are started). This is a fully operational Java database application.

// Application-specific root instance
final DataRoot root = new DataRoot();

// Initialize a storage manager ("the database") with the given directory.
final EmbeddedStorageManager storageManager = EmbeddedStorage.start(
	root,             // root object
	Paths.get("data") // storage directory
);

Storing Data

// Set content data to the root element, including the time to visualize
// changes on the next execution.
root.setContent("Hello World! @ " + new Date());

// Store the modified root and its content.
storageManager.storeRoot();

This call is all that is necessary to store data in the simplest case.

storageManager.storeRoot() is a special case method that always stores the root object. If you want to store any other object than the root itself, just call storageManager.store(modifiedObject)

Subsequent calls to storageManager.storeRoot() may not update the whole object graph! storageManager.storeRoot() uses the default lazy storing behavior.

Stopping a Live Database

Best practice is to safely shutdown the storage manager by simply calling:

storageManager.shutdown();

The full code for the Hello World example is on GitHub.