Since Ripple-lib-java Is Unmaintained, How Do You Manually Sign A Transaction?

Looking for a lightweight way to manually sign an OfferCreate ... it would be clumsy to start some JavaScript engine in order to get it done.

Hmm ... even though it hasn't been maintained for 4 years it looks like it still works.

Clone ripple-lib-java and do mvn install in ripple-bouncycastle & ripple-core

Then copy the built JARs into <YourProject>/libs

Add local dependencies in Gradle Kotlin DSL:

repositories {
    flatDir {
        >repositories {
    flatDir {
        dirs("libs")
    }
}

dependencies {
    implementation(":ripple-bouncycastle-0.0.1-SNAPSHOT")
    implementation(":ripple-core-0.0.1-SNAPSHOT")

    runtime("org.json:json:20190722") // No newskool kotlinx-serialization here :(
}

Create & sign OfferCreate:

val offerCreate = OfferCreate()
offerCreate.account(AccountID.fromString("r3jpWpUysF4SAkUNbG4WhDZ5mAJ7rGUDx6"))
offerCreate.expiration(UInt32(get2MinExpiration()))
offerCreate.fee(Amount(BigDecimal("0.00001")))
offerCreate.flags(UInt32(0))
offerCreate.sequence(UInt32(1))
val amountXRP = BigDecimal(200)
val amountBTC = convert(amountXRP, RIPPLE_XRP, BITCOIN)
offerCreate.takerGets(Amount(amountXRP))
offerCreate.takerPays(Amount(amountBTC, Currency.fromString(BITCOIN), AccountID.fromString(BITCOIN_TRUSTED_ISSUER)))
val signedTransaction = offerCreate.sign("[***Secret***]")
println(offerCreate.toJSON())
println(signedTransaction.tx_blob)

A bit annoying that you can't do a toJSON() on a SignedTransaction. It can t be a security thing, since sign() only adds public key fields: https://xrpl.org/transaction-common-fields.html#signers-field