How to create custom schema with Corda Vault Extension

问题

From Corda documents, it says we can have custom schema in Vault Extension.

However there is not much clarity for Vault Extension which should have ability to create/manage custom database schema pertaining to node vault database.

Are we going to publish API in feature release of Corda

回答1:

Inside flows, the node exposes a JDBC connection that allows you to write native custom SQL queries (as a vault extension). You can access this JDBC connection using serviceHub.jdbcSession().

If your question is about how to write a custom schema then please see the existing Corda Persistence API docs.

You can then query that custom schema using the new Vault Query API - please see the existing [Corda Vault Query API][3] docs.

回答2:

Just to add an example to the above, here's a custom schema for the Yo! CorDapp. See YoSchemaV1 below:

// State.
data class State(val origin: Party,
                 val target: Party,
                 val yo: String = "Yo!") : ContractState, QueryableState {
    override val participants get() = listOf(target)
    override val contract get() = Yo()
    override fun toString() = "${origin.name}: $yo"
    override fun supportedSchemas() = listOf(YoSchemaV1)
    override fun generateMappedObject(schema: MappedSchema) = YoSchemaV1.YoEntity(this)

    object YoSchemaV1 : MappedSchema(Yo.State::class.java, 1, listOf(YoEntity::class.java)) {
        @Entity @Table(name = "yos")
        class YoEntity(yo: State) : PersistentState() {
            @Column var origin: String = yo.origin.name.toString()
            @Column var target: String = yo.target.name.toString()
            @Column var yo: String = yo.yo
        }
    }
}

In short, your state object needs to implement QueryableState, as above.

The full CorDapp is available here: https://github.com/roger3cev/yo-cordapp

Cheers

来源：https://stackoverflow.com/questions/45083270/how-to-create-custom-schema-with-corda-vault-extension

标签

database-schema

corda