API: Persistence

Corda offers developers the option to expose all or some part of a contract state to an Object Relational Mapping (ORM) tool to be persisted in a RDBMS. The purpose of this is to assist vault development by effectively indexing persisted contract states held in the vault for the purpose of running queries over them and to allow relational joins between Corda data and private data local to the organisation owning a node.

The ORM mapping is specified using the Java Persistence API (JPA) as annotations and is converted to database table rows by the node automatically every time a state is recorded in the node’s local vault as part of a transaction.


Every ContractState can implement the QueryableState interface if it wishes to be inserted into the node’s local database and accessible using SQL.

 * A contract state that may be mapped to database schemas configured for this node to support querying for,
 * or filtering of, states.
interface QueryableState : ContractState {
     * Enumerate the schemas this state can export representations of itself as.
    fun supportedSchemas(): Iterable<MappedSchema>

     * Export a representation for the given schema.
    fun generateMappedObject(schema: MappedSchema): PersistentState


The QueryableState interface requires the state to enumerate the different relational schemas it supports, for instance in cases where the schema has evolved, with each one being represented by a MappedSchema object return by the supportedSchemas() method. Once a schema is selected it must generate that representation when requested via the generateMappedObject() method which is then passed to the ORM.

Nodes have an internal SchemaService which decides what to persist and what not by selecting the MappedSchema to use.

 * A configuration and customisation point for Object Relational Mapping of contract state objects.
interface SchemaService {
     * Represents any options configured on the node for a schema.
    data class SchemaOptions(val databaseSchema: String? = null, val tablePrefix: String? = null)

     * Options configured for this node's schemas.  A missing entry for a schema implies all properties are null.
    val schemaOptions: Map<MappedSchema, SchemaOptions>

     * Given a state, select schemas to map it to that are supported by [generateMappedObject] and that are configured
     * for this node.
    fun selectSchemas(state: ContractState): Iterable<MappedSchema>

     * Map a state to a [PersistentState] for the given schema, either via direct support from the state
     * or via custom logic in this service.
    fun generateMappedObject(state: ContractState, schema: MappedSchema): PersistentState


 * A database schema that might be configured for this node.  As well as a name and version for identifying the schema,
 * also list the classes that may be used in the generated object graph in order to configure the ORM tool.
 * @param schemaFamily A class to fully qualify the name of a schema family (i.e. excludes version)
 * @param version The version number of this instance within the family.
 * @param mappedTypes The JPA entity classes that the ORM layer needs to be configure with for this schema.
open class MappedSchema(schemaFamily: Class<*>,
                        val version: Int,
                        val mappedTypes: Iterable<Class<*>>) {
    val name: String = schemaFamily.name
    override fun toString(): String = "${this.javaClass.simpleName}(name=$name, version=$version)"


The SchemaService can be configured by a node administrator to select the schemas used by each app. In this way the relational view of ledger states can evolve in a controlled fashion in lock-step with internal systems or other integration points and not necessarily with every upgrade to the contract code. It can select from the MappedSchema offered by a QueryableState, automatically upgrade to a later version of a schema or even provide a MappedSchema not originally offered by the QueryableState.

It is expected that multiple different contract state implementations might provide mappings to some common schema. For example an Interest Rate Swap contract and an Equity OTC Option contract might both provide a mapping to a common Derivative schema. The schemas should typically not be part of the contract itself and should exist independently of it to encourage re-use of a common set within a particular business area or Cordapp.

MappedSchema offer a family name that is disambiguated using Java package style name-spacing derived from the class name of a schema family class that is constant across versions, allowing the SchemaService to select a preferred version of a schema.

The SchemaService is also responsible for the SchemaOptions that can be configured for a particular MappedSchema which allow the configuration of a database schema or table name prefixes to avoid any clash with other MappedSchema.

Custom schema registration

Custom contract schemas are automatically registered at startup time for CorDapps. The node bootstrap process will scan for schemas (any class that extends the MappedSchema interface) in the plugins configuration directory in your CorDapp jar.

For testing purposes it is necessary to manually register the packages containing custom schemas as follows:

  • Tests using MockNetwork and MockNode must explicitly register packages using the cordappPackages parameter of MockNetwork
  • Tests using MockServices must explicitly register packages using the cordappPackages parameter of the MockServices makeTestDatabaseAndMockServices() helper method.

Object relational mapping

The persisted representation of a QueryableState should be an instance of a PersistentState subclass, constructed either by the state itself or a plugin to the SchemaService. This allows the ORM layer to always associate a StateRef with a persisted representation of a ContractState and allows joining with the set of unconsumed states in the vault.

The PersistentState subclass should be marked up as a JPA 2.1 Entity with a defined table name and having properties (in Kotlin, getters/setters in Java) annotated to map to the appropriate columns and SQL types. Additional entities can be included to model these properties where they are more complex, for example collections, so the mapping does not have to be flat. The MappedSchema must provide a list of all of the JPA entity classes for that schema in order to initialise the ORM layer.

Several examples of entities and mappings are provided in the codebase, including Cash.State and CommercialPaper.State. For example, here’s the first version of the cash schema.

package net.corda.finance.schemas

import net.corda.core.identity.AbstractParty
import net.corda.core.schemas.MappedSchema
import net.corda.core.schemas.PersistentState
import net.corda.core.serialization.CordaSerializable
import net.corda.core.utilities.MAX_HASH_HEX_SIZE
import net.corda.core.contracts.MAX_ISSUER_REF_SIZE
import org.hibernate.annotations.Type
import javax.persistence.*

 * An object used to fully qualify the [CashSchema] family name (i.e. independent of version).
object CashSchema

 * First version of a cash contract ORM schema that maps all fields of the [Cash] contract state as it stood
 * at the time of writing.
object CashSchemaV1 : MappedSchema(schemaFamily = CashSchema.javaClass, version = 1, mappedTypes = listOf(PersistentCashState::class.java)) {
    @Table(name = "contract_cash_states",
            indexes = arrayOf(Index(name = "ccy_code_idx", columnList = "ccy_code"),
                    Index(name = "pennies_idx", columnList = "pennies")))
    class PersistentCashState(
            /** X500Name of owner party **/
            @Column(name = "owner_name")
            var owner: AbstractParty,

            @Column(name = "pennies")
            var pennies: Long,

            @Column(name = "ccy_code", length = 3)
            var currency: String,

            @Column(name = "issuer_key_hash", length = MAX_HASH_HEX_SIZE)
            var issuerPartyHash: String,

            @Column(name = "issuer_ref", length = MAX_ISSUER_REF_SIZE)
            @Type(type = "corda-wrapper-binary")
            var issuerRef: ByteArray
    ) : PersistentState()


Identity mapping

Schema entity attributes defined by identity types (AbstractParty, Party, AnonymousParty) are automatically processed to ensure only the X500Name of the identity is persisted where an identity is well known, otherwise a null value is stored in the associated column. To preserve privacy, identity keys are never persisted. Developers should use the IdentityService to resolve keys from well know X500 identity names.

JDBC session

Apps may also interact directly with the underlying Node’s database by using a standard JDBC connection (session) as described by the Java SQL Connection API

Use the ServiceHub jdbcSession function to obtain a JDBC connection as illustrated in the following example:

JDBC session’s can be used in Flows and Service Plugins (see “ Writing flows”)

The following example illustrates the creation of a custom corda service using a jdbcSession:

object CustomVaultQuery {

    class Service(val services: AppServiceHub) : SingletonSerializeAsToken() {
        private companion object {
            private val log = contextLogger()

        fun rebalanceCurrencyReserves(): List<Amount<Currency>> {
            val nativeQuery = """
                    vault_states vaultschema
                    contract_cash_states cashschema
                    and vaultschema.transaction_id=cashschema.transaction_id
                    and vaultschema.state_status=0
                group by
                order by
                    sum(cashschema.pennies) desc
            log.info("SQL to execute: $nativeQuery")
            val session = services.jdbcSession()
            return session.prepareStatement(nativeQuery).use { prepStatement ->
                prepStatement.executeQuery().use { rs ->
                    val topUpLimits: MutableList<Amount<Currency>> = mutableListOf()
                    while (rs.next()) {
                        val currencyStr = rs.getString(1)
                        val amount = rs.getLong(2)
                        log.info("$currencyStr : $amount")
                        topUpLimits.add(Amount(amount, Currency.getInstance(currencyStr)))


which is then referenced within a custom flow:

        override fun call(): List<SignedTransaction> {
            progressTracker.currentStep = AWAITING_REQUEST
            val topupRequest = otherPartySession.receive<TopupRequest>().unwrap {

            val customVaultQueryService = serviceHub.cordaService(CustomVaultQuery.Service::class.java)
            val reserveLimits = customVaultQueryService.rebalanceCurrencyReserves()

            val txns: List<SignedTransaction> = reserveLimits.map { amount ->
                // request asset issue
                logger.info("Requesting currency issue $amount")
                val txn = issueCashTo(amount, topupRequest.issueToParty, topupRequest.issuerPartyRef)
                progressTracker.currentStep = SENDING_TOP_UP_ISSUE_REQUEST
                return@map txn.stx

            return txns


For examples on testing @CordaService implementations, see the oracle example here