Web3j v3 3 1 Error while generating compiled solidity smart contracts which returns array of struct

Question

I am returning an array of struct from solidity function as below.

pragma solidity ^0.4.21;

pragma experimental ABIEncoderV2;

function getPurchaseOrderForVendor(string vendorNameInput) constant returns (PurchaseOrderStruct[])

It is compiled to abi and bin files. The issue is with creating wrapper files for the contract using web3j(v3.3.1). Im getting the below errors.

Generating com.contract.InvoiceSettlement_sol_InvoiceSettlement ... 
Exception in thread "main" java.lang.UnsupportedOperationException: 
Unsupported type
encountered: tuple
    at org.web3j.abi.datatypes.generated.AbiTypes.getType(AbiTypes.java:221)

    at org.web3j.codegen.SolidityFunctionWrapper.buildTypeName(SolidityFunct
ionWrapper.java:851)
    at org.web3j.codegen.SolidityFunctionWrapper.buildTypeNames(SolidityFunc
tionWrapper.java:508)
    at org.web3j.codegen.SolidityFunctionWrapper.buildFunction(SolidityFunct
ionWrapper.java:523)
    at org.web3j.codegen.SolidityFunctionWrapper.buildFunctionDefinitions(So
lidityFunctionWrapper.java:216)
    at org.web3j.codegen.SolidityFunctionWrapper.generateJavaFiles(SolidityF
unctionWrapper.java:112)
    at org.web3j.codegen.SolidityFunctionWrapper.generateJavaFiles(SolidityF
unctionWrapper.java:94)
    at org.web3j.codegen.SolidityFunctionWrapperGenerator.generate(SolidityF
unctionWrapperGenerator.java:123)
    at org.web3j.codegen.SolidityFunctionWrapperGenerator.main(SolidityFunct
ionWrapperGenerator.java:87)
    at org.web3j.codegen.SolidityFunctionWrapperGenerator.run(SolidityFuncti
onWrapperGenerator.java:48)
    at org.web3j.console.Runner.main(Runner.java:38)

aryya · Answer 1 · Jun 19, 2018

Solidity does not support returning structs in external calls. It is only allowed in internal function calls. You need to decompose the struct and return the elements via a tuple.

Source: Solidity documentation