How to get value from solidity contract using java?

0 votes

My solidity contract is this:

contract SimpleStorage {
uint storedData;

function set(uint x) {
    storedData = x;
}

function get() constant returns (uint retVal) {
    return storedData;
}}

and generate the abi is following:

[ { "constant": false, "inputs": [ { "name": "x", "type": "uint256" } ], "name": "set", "outputs": [], "type": "function" }, { "constant": true, "inputs": [], "name": "get", "outputs": [ { "name": "retVal", "type": "uint256", "value": "0" } ], "type": "function" } ]

and referenced by https://github.com/ethereum/wiki/wiki/JSON-RPC,

How to invoke get funtion and get the value by using java (not js)?

Sep 28, 2018 in Blockchain by digger
• 26,550 points
255 views

1 answer to this question.

0 votes

web3j caters for this very use case. It generates Smart Contract wrappers in Java from a Solidity compiled binary and ABI file.

Once you've generated the wrapper code with web3j, you will be able to deploy, then call the methods on the above contract example as follows:

SimpleStorage simpleStorage = SimpleStorage.deploy(
    <web3j>, <credentials>, GAS_PRICE, GAS_LIMIT,
    BigInteger.ZERO);  // ether value of contract

TransactionReceipt transactionReceipt = simpleStorage.set(
        new Uint256(BigInteger.valueOf(1000))),
        .get();

Uint256 result = simpleStorage.get()
        .get();

See the docs for further information.

answered Sep 28, 2018 by slayer
• 29,170 points

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