# Nitrite Database

Nitrite database is a serverless, embedded, and self-contained Java NoSQL database. It is an open-source project that provides a simple API for persistent data storage. Nitrite database is designed to be lightweight, fast, and easy to use.

# Creating a Database

Nitrite database can be created in-memory or on-disk. By default, Nitrite database is created in-memory. To create a database on-disk, you need to add a storage module dependency to your project. More details about storage modules can be found here.

To create a database, you need to use NitriteBuilder class. To get an instance of NitriteBuilder, you need to call builder() method on Nitrite class.

NitriteBuilder builder = Nitrite.builder();

# In-memory Database

If you don't load any on-disk storage module, then Nitrite will create an in-memory database. The below code snippet shows how to create a database in-memory.

Nitrite db = Nitrite.builder()
    .openOrCreate();

# On-disk Database

The below code snippet shows how to create a database on-disk.

# MVStore Backed Database

MVStoreModule storeModule = MVStoreModule.withConfig()
    .filePath("/path/to/my.db")
    .build();

Nitrite db = Nitrite.builder()
    .loadModule(storeModule)
    .openOrCreate();

More details about MVStore configuration can be found here.

# RocksDB Backed Database

RocksDBModule storeModule = RocksDBModule.withConfig()
    .filePath("/path/to/my.db")
    .build();

Nitrite db = Nitrite.builder()
    .loadModule(storeModule)
    .openOrCreate();

More details about RocksDB configuration can be found here.

# NitriteBuilder

NitriteBuilder provides a fluent API to configure and create a Nitrite database instance.

# Open or Create a Database

To open or create a database, you need to call openOrCreate() method on NitriteBuilder instance. This method returns a Nitrite instance.

If no StoreModule is configured, then Nitrite will create an in-memory database. If a StoreModule is configured, then Nitrite will create a file-based database. If the database file does not exist, then Nitrite will create a new database file. If the database file already exists, then Nitrite will open the existing database file.

Nitrite db = Nitrite.builder()
    .loadModule(storeModule)
    .openOrCreate();

# Securing a Database

To secure a database, you need to call openOrCreate() method with username and password on NitriteBuilder instance. This method returns a Nitrite instance with the given username and password.

Nitrite db = Nitrite.builder()
    .loadModule(storeModule)
    .openOrCreate("user", "password");

# Registering an EntityConverter

Nitrite database uses a mapper to map Java entities to Nitrite documents and vice-versa. By default, Nitrite uses SimpleNitriteMapper as its mapper. This mapper uses EntityConverters to map Java entities to Nitrite documents and vice-versa. To register an EntityConverter, you need to call registerEntityConverter() method on NitriteBuilder instance. This method returns the same NitriteBuilder instance.

Nitrite db = Nitrite.builder()
    .loadModule(storeModule)
    .registerEntityConverter(new ProductConverter())
    .registerEntityConverter(new ProductIdConverter())
    .registerEntityConverter(new ManufacturerConverter())
    .openOrCreate();

More on EntityConverter can be found here.

# Loading a Module

Nitrite database is modular in nature. It provides various modules to extend its functionality. To load a module, you need to call loadModule() method on NitriteBuilder instance. This method returns the same NitriteBuilder instance.

# Loading a Storage Module

Nitrite db = Nitrite.builder()
    .loadModule(storeModule)
    .openOrCreate();

# Loading a Jackson Based Mapper Module

Nitrite db = Nitrite.builder()
    .loadModule(new JacksonMapperModule())
    .openOrCreate();

More on the Nitrite's module system can be found here.

# Adding Migration Steps

Nitrite database supports schema migration. To configure a migration step, you need to call addMigrations() method on NitriteBuilder instance. This method returns the same NitriteBuilder instance.

Migration migration = new Migration(Constants.INITIAL_SCHEMA_VERSION, 2) {
    @Override
    public void migrate(InstructionSet instruction) {
        instruction.forDatabase()
            .addUser("test-user", "test-password");

        instruction.forRepository(OldClass.class, "demo1")
            .renameRepository("new", null)
            .changeDataType("empId", (TypeConverter<String, Long>) Long::parseLong)
            .changeIdField(Fields.withNames("uuid"), Fields.withNames("empId"))
            .deleteField("uuid")
            .renameField("lastName", "familyName")
            .addField("fullName", document -> document.get("firstName", String.class) + " "
                + document.get("familyName", String.class))
            .dropIndex("firstName")
            .dropIndex("literature.text")
            .changeDataType("literature.ratings", (TypeConverter<Float, Integer>) Math::round);
    }
};

Nitrite db = Nitrite.builder()
    .loadModule(storeModule)
    .addMigrations(migration)
    .openOrCreate();

More on the schema migration can be found here.

# Current Schema Version

To configure the current schema version, you need to call schemaVersion() method on NitriteBuilder instance. This method returns the same NitriteBuilder instance.

Nitrite db = Nitrite.builder()
    .loadModule(storeModule)
    .schemaVersion(2)
    .openOrCreate();

# Field Separator Character

To configure the field separator character, you need to call fieldSeparator() method on NitriteBuilder instance. This method returns the same NitriteBuilder instance.

It is used to separate field names in a nested document. For example, if a document has a field address which is a nested document, then the field street of the nested document can be accessed using address.street syntax.

Nitrite db = Nitrite.builder()
    .loadModule(storeModule)
    .fieldSeparator('.')
    .openOrCreate();