Xodus-DNQ is a Kotlin library that contains the data definition language and queries for Xodus, a transactional schema-less embedded database. Xodus-DNQ provides the same support for Xodus that ORM frameworks provide for SQL databases. With Xodus-DNQ, you can define your persistent meta-model using Kotlin classes.
JetBrains team tools YouTrack and Hub use Xodus-DNQ for persistent layer definition.
More documentation https://jetbrains.github.io/xodus-dnq.
List of released versions is available at https://github.com/JetBrains/xodus-dnq/releases.
repositories {
mavenCentral()
}
compile 'org.jetbrains.xodus:dnq:${version}'<dependency>
<groupId>org.jetbrains.xodus</groupId>
<artifactId>dnq</artifactId>
<version>$version</version>
</dependency>// Define persistent class. It should extend XdEntity
class XdPost(entity: Entity) : XdEntity(entity) {
// and have component object of type XdEntityType
companion object : XdNaturalEntityType<XdPost>()
// Define persistent property of type org.joda.time.DateTime?
var publishedAt by xdDateTimeProp()
// Define required persistent property of type String
var text by xdRequiredStringProp()
}
class XdBlog(entity: Entity) : XdEntity(entity) {
companion object : XdNaturalEntityType<XdBlog>()
// Define multi-value link to XdPost
val posts by xdLink0_N(XdPost)
}
fun main(args: Array<String>) {
// Register persistent classes
XdModel.registerNodes(XdPost, XdBlog)
// Initialize Xodus persistent storage
val xodusStore = StaticStoreContainer.init(
dbFolder = File(System.getProperty("user.home"), ".xodus-dnq-blog-db"),
environmentName = "db"
)
// Initialize Xodus-DNQ metadata
initMetaData(XdModel.hierarchy, xodusStore)
// Do in transaction
val blog = xodusStore.transactional {
// Find an existing blog in database
XdBlog.all().firstOrNull()
// or create a new one if there are no blogs yet
?: XdBlog.new()
}
xodusStore.transactional {
// Create new post
val post = XdPost.new {
this.publishedAt = DateTime.now()
this.text = args.firstOrNull() ?: "Empty post"
}
// Add new post to blog
blog.posts.add(post)
}
// Do in read-only transaction
xodusStore.transactional(readonly = true) {
// Print all blog posts
for (post in blog.posts) {
println("${post.publishedAt}: ${post.text}")
}
}
}