How to get hash of transaction **before** it has been mined in web3j?

I have been working on my project where I use web3j. I work with ledger over contract wrappers where the actual call to the ledger is encapsulated over variety of layers.

The issue is I need to get a hash of tx when it has been put into the pool, not after it has been mined.

Current implementation of the contract wrappers gives me txReceipt only after it has been mined. I have not found yet any way to get it before it has been mined.

Do you know a solution?

A wider context is after the call to the chain from a mobile client, I need to verify does tx succeed or not. I plan to do it via call web3.ethGetTransactionByHash(txHash).