Support []byte parameters and return type (#161)

Pass []byte directly instead of treating as a JSON array. The correct OpenAPI type for []byte is type "string" with format "byte". Signed-off-by: Mark S. Lewis <[email protected]>
hyperledger · Dec 23, 2024 · f5d39cc · f5d39cc
1 parent 20772f8
commit f5d39cc
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Showing 18 changed files with 147 additions and 85 deletions.
diff --git a/contractapi/contract_chaincode.go b/contractapi/contract_chaincode.go
@@ -156,40 +156,17 @@ func (cc *ContractChaincode) Init(stub shim.ChaincodeStubInterface) *peer.Respon
 // If no contract name is passed then the default contract is used.
 func (cc *ContractChaincode) Invoke(stub shim.ChaincodeStubInterface) *peer.Response {
 
-	nsFcn, params := stub.GetFunctionAndParameters()
+	ns, fn, params := cc.getNamespaceFunctionAndParams(stub)
 
-	li := strings.LastIndex(nsFcn, ":")
-
-	var ns string
-	var fn string
-
-	if li == -1 {
-		ns = cc.DefaultContract
-		fn = nsFcn
-	} else {
-		ns = nsFcn[:li]
-		fn = nsFcn[li+1:]
-	}
-
-	if _, ok := cc.contracts[ns]; !ok {
+	nsContract, ok := cc.contracts[ns]
+	if !ok {
 		return shim.Error(fmt.Sprintf("Contract not found with name %s", ns))
 	}
 
 	if fn == "" {
 		return shim.Error("Blank function name passed")
 	}
 
-	originalFn := fn
-
-	fnRune := []rune(fn)
-
-	if unicode.IsLower(fnRune[0]) {
-		fnRune[0] = unicode.ToUpper(fnRune[0])
-		fn = string(fnRune)
-	}
-
-	nsContract := cc.contracts[ns]
-
 	ctx := reflect.New(nsContract.transactionContextHandler)
 	ctxIface := ctx.Interface().(SettableTransactionContextInterface)
 	ctxIface.SetStub(stub)
@@ -213,10 +190,10 @@ func (cc *ContractChaincode) Invoke(stub shim.ChaincodeStubInterface) *peer.Resp
 
 	serializer := cc.TransactionSerializer
 
-	if _, ok := nsContract.functions[fn]; !ok {
+	if contractFn, ok := nsContract.functions[toFirstRuneUpperCase(fn)]; !ok {
 		unknownTransaction := nsContract.unknownTransaction
 		if unknownTransaction == nil {
-			return shim.Error(fmt.Sprintf("Function %s not found in contract %s", originalFn, ns))
+			return shim.Error(fmt.Sprintf("Function %s not found in contract %s", fn, ns))
 		}
 
 		successReturn, successIFace, errorReturn = unknownTransaction.Call(ctx, nil, serializer)
@@ -230,7 +207,7 @@ func (cc *ContractChaincode) Invoke(stub shim.ChaincodeStubInterface) *peer.Resp
 			}
 		}
 
-		successReturn, successIFace, errorReturn = nsContract.functions[fn].Call(ctx, transactionSchema, &cc.metadata.Components, serializer, params...)
+		successReturn, successIFace, errorReturn = contractFn.Call(ctx, transactionSchema, &cc.metadata.Components, serializer, params...)
 	}
 
 	if errorReturn != nil {
@@ -250,6 +227,18 @@ func (cc *ContractChaincode) Invoke(stub shim.ChaincodeStubInterface) *peer.Resp
 	return shim.Success([]byte(successReturn))
 }
 
+func (cc *ContractChaincode) getNamespaceFunctionAndParams(stub shim.ChaincodeStubInterface) (string, string, []string) {
+	nsFn, params := stub.GetFunctionAndParameters()
+
+	nsIndex := strings.LastIndex(nsFn, ":")
+
+	if nsIndex == -1 {
+		return cc.DefaultContract, nsFn, params
+	}
+
+	return nsFn[:nsIndex], nsFn[nsIndex+1:], params
+}
+
 func (cc *ContractChaincode) addContract(contract ContractInterface, excludeFuncs []string) error {
 	ns := contract.GetName()
 
@@ -507,3 +496,18 @@ func getBoolEnv(key string, defaultVal bool) bool {
 	}
 	return value
 }
+
+func toFirstRuneUpperCase(text string) string {
+	if len(text) == 0 {
+		return text
+	}
+
+	runes := []rune(text)
+
+	if unicode.IsUpper(runes[0]) {
+		return text
+	}
+
+	runes[0] = unicode.ToUpper(runes[0])
+	return string(runes)
+}
diff --git a/contractapi/contract_chaincode_test.go b/contractapi/contract_chaincode_test.go
@@ -11,14 +11,17 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/google/go-cmp/cmp"
 	"github.com/hyperledger/fabric-chaincode-go/v2/shim"
 	"github.com/hyperledger/fabric-contract-api-go/v2/internal"
 	"github.com/hyperledger/fabric-contract-api-go/v2/internal/utils"
 	"github.com/hyperledger/fabric-contract-api-go/v2/metadata"
 	"github.com/hyperledger/fabric-contract-api-go/v2/serializer"
 	"github.com/hyperledger/fabric-protos-go-apiv2/peer"
 	"github.com/stretchr/testify/require"
+	"google.golang.org/protobuf/encoding/prototext"
 	"google.golang.org/protobuf/proto"
+	"google.golang.org/protobuf/testing/protocmp"
 )
 
 // ================================
@@ -37,8 +40,36 @@ const (
 
 // AssertProtoEqual ensures an expected protobuf message matches an actual message
 func AssertProtoEqual(t *testing.T, expected proto.Message, actual proto.Message) {
-	t.Helper()
-	require.True(t, proto.Equal(expected, actual), "Expected %v, got %v", expected, actual)
+	if diff := cmp.Diff(expected, actual, protocmp.Transform()); diff != "" {
+		require.FailNow(t, fmt.Sprintf(
+			"Not equal:\nexpected: %s\nactual  : %s\n\nDiff:\n- Expected\n+ Actual\n\n%s",
+			formatProto(expected),
+			formatProto(actual),
+			diff,
+		))
+	}
+}
+
+func formatProto(message proto.Message) string {
+	if message == nil {
+		return fmt.Sprintf("%T", message)
+	}
+
+	marshal := prototext.MarshalOptions{
+		Multiline:    true,
+		Indent:       "\t",
+		AllowPartial: true,
+	}
+	formatted := strings.TrimSpace(marshal.Format(message))
+	return fmt.Sprintf("%s{\n%s\n}", protoMessageType(message), indent(formatted))
+}
+
+func protoMessageType(message proto.Message) string {
+	return string(message.ProtoReflect().Descriptor().Name())
+}
+
+func indent(text string) string {
+	return "\t" + strings.ReplaceAll(text, "\n", "\n\t")
 }
 
 type simpleStruct struct {
@@ -104,6 +135,14 @@ func (gc *goodContract) ReturnsError() error {
 
 func (gc *goodContract) ReturnsNothing() {}
 
+func (gc *goodContract) ReturnsBytes() []byte {
+	return []byte("Some bytes")
+}
+
+func (gc *goodContract) AcceptsBytes(arg []byte) []byte {
+	return arg
+}
+
 func (gc *goodContract) CheckContextStub(ctx *TransactionContext) (string, error) {
 	if ctx.GetStub().GetTxID() != standardTxID {
 		return "", fmt.Errorf("You used a non standard txID [%s]", ctx.GetStub().GetTxID())
@@ -267,6 +306,12 @@ func testCallingContractFunctions(t *testing.T, callType CallType) {
 	// should return success when function returns no error
 	callContractFunctionAndCheckSuccess(t, cc, []string{"goodContract:ReturnsString"}, callType, gc.ReturnsString())
 
+	// should return success when function returns slice of byte
+	callContractFunctionAndCheckSuccess(t, cc, []string{"goodContract:ReturnsBytes"}, callType, string(gc.ReturnsBytes()))
+
+	// should return success when function accepts slice of byte
+	callContractFunctionAndCheckSuccess(t, cc, []string{"goodContract:AcceptsBytes", "bytes message"}, callType, string("bytes message"))
+
 	// Should return error when function returns error
 	callContractFunctionAndCheckError(t, cc, []string{"goodContract:ReturnsError"}, callType, gc.ReturnsError().Error())
 

diff --git a/go.mod b/go.mod
@@ -5,11 +5,12 @@ go 1.21.0
 require (
 	github.com/cucumber/godog v0.15.0
 	github.com/go-openapi/spec v0.21.0
+	github.com/google/go-cmp v0.6.0
 	github.com/hyperledger/fabric-chaincode-go/v2 v2.0.0
 	github.com/hyperledger/fabric-protos-go-apiv2 v0.3.4
 	github.com/stretchr/testify v1.10.0
 	github.com/xeipuuv/gojsonschema v1.2.0
-	google.golang.org/protobuf v1.35.2
+	google.golang.org/protobuf v1.36.1
 )
 
 require (

diff --git a/go.sum b/go.sum
@@ -88,8 +88,8 @@ google.golang.org/genproto/googleapis/rpc v0.0.0-20240814211410-ddb44dafa142 h1:
 google.golang.org/genproto/googleapis/rpc v0.0.0-20240814211410-ddb44dafa142/go.mod h1:UqMtugtsSgubUsoxbuAoiCXvqvErP7Gf0so0mK9tHxU=
 google.golang.org/grpc v1.67.0 h1:IdH9y6PF5MPSdAntIcpjQ+tXO41pcQsfZV2RxtQgVcw=
 google.golang.org/grpc v1.67.0/go.mod h1:1gLDyUQU7CTLJI90u3nXZ9ekeghjeM7pTDZlqFNg2AA=
-google.golang.org/protobuf v1.35.2 h1:8Ar7bF+apOIoThw1EdZl0p1oWvMqTHmpA2fRTyZO8io=
-google.golang.org/protobuf v1.35.2/go.mod h1:9fA7Ob0pmnwhb644+1+CVWFRbNajQ6iRojtC/QF5bRE=
+google.golang.org/protobuf v1.36.1 h1:yBPeRvTftaleIgM3PZ/WBIZ7XM/eEYAaEyCwvyjq/gk=
+google.golang.org/protobuf v1.36.1/go.mod h1:9fA7Ob0pmnwhb644+1+CVWFRbNajQ6iRojtC/QF5bRE=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=

diff --git a/integrationtest/chaincode/advancedtypes/go.mod b/integrationtest/chaincode/advancedtypes/go.mod
@@ -21,7 +21,7 @@ require (
 	golang.org/x/text v0.17.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20240814211410-ddb44dafa142 // indirect
 	google.golang.org/grpc v1.67.0 // indirect
-	google.golang.org/protobuf v1.35.2 // indirect
+	google.golang.org/protobuf v1.36.1 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
 

diff --git a/integrationtest/chaincode/advancedtypes/go.sum b/integrationtest/chaincode/advancedtypes/go.sum
@@ -50,8 +50,8 @@ google.golang.org/genproto/googleapis/rpc v0.0.0-20240814211410-ddb44dafa142 h1:
 google.golang.org/genproto/googleapis/rpc v0.0.0-20240814211410-ddb44dafa142/go.mod h1:UqMtugtsSgubUsoxbuAoiCXvqvErP7Gf0so0mK9tHxU=
 google.golang.org/grpc v1.67.0 h1:IdH9y6PF5MPSdAntIcpjQ+tXO41pcQsfZV2RxtQgVcw=
 google.golang.org/grpc v1.67.0/go.mod h1:1gLDyUQU7CTLJI90u3nXZ9ekeghjeM7pTDZlqFNg2AA=
-google.golang.org/protobuf v1.35.2 h1:8Ar7bF+apOIoThw1EdZl0p1oWvMqTHmpA2fRTyZO8io=
-google.golang.org/protobuf v1.35.2/go.mod h1:9fA7Ob0pmnwhb644+1+CVWFRbNajQ6iRojtC/QF5bRE=
+google.golang.org/protobuf v1.36.1 h1:yBPeRvTftaleIgM3PZ/WBIZ7XM/eEYAaEyCwvyjq/gk=
+google.golang.org/protobuf v1.36.1/go.mod h1:9fA7Ob0pmnwhb644+1+CVWFRbNajQ6iRojtC/QF5bRE=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=

diff --git a/integrationtest/chaincode/private/go.mod b/integrationtest/chaincode/private/go.mod
@@ -21,7 +21,7 @@ require (
 	golang.org/x/text v0.17.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20240814211410-ddb44dafa142 // indirect
 	google.golang.org/grpc v1.67.0 // indirect
-	google.golang.org/protobuf v1.35.2 // indirect
+	google.golang.org/protobuf v1.36.1 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
 

diff --git a/integrationtest/chaincode/private/go.sum b/integrationtest/chaincode/private/go.sum
@@ -50,8 +50,8 @@ google.golang.org/genproto/googleapis/rpc v0.0.0-20240814211410-ddb44dafa142 h1:
 google.golang.org/genproto/googleapis/rpc v0.0.0-20240814211410-ddb44dafa142/go.mod h1:UqMtugtsSgubUsoxbuAoiCXvqvErP7Gf0so0mK9tHxU=
 google.golang.org/grpc v1.67.0 h1:IdH9y6PF5MPSdAntIcpjQ+tXO41pcQsfZV2RxtQgVcw=
 google.golang.org/grpc v1.67.0/go.mod h1:1gLDyUQU7CTLJI90u3nXZ9ekeghjeM7pTDZlqFNg2AA=
-google.golang.org/protobuf v1.35.2 h1:8Ar7bF+apOIoThw1EdZl0p1oWvMqTHmpA2fRTyZO8io=
-google.golang.org/protobuf v1.35.2/go.mod h1:9fA7Ob0pmnwhb644+1+CVWFRbNajQ6iRojtC/QF5bRE=
+google.golang.org/protobuf v1.36.1 h1:yBPeRvTftaleIgM3PZ/WBIZ7XM/eEYAaEyCwvyjq/gk=
+google.golang.org/protobuf v1.36.1/go.mod h1:9fA7Ob0pmnwhb644+1+CVWFRbNajQ6iRojtC/QF5bRE=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=

diff --git a/integrationtest/chaincode/simple/go.mod b/integrationtest/chaincode/simple/go.mod
@@ -21,7 +21,7 @@ require (
 	golang.org/x/text v0.17.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20240814211410-ddb44dafa142 // indirect
 	google.golang.org/grpc v1.67.0 // indirect
-	google.golang.org/protobuf v1.35.2 // indirect
+	google.golang.org/protobuf v1.36.1 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
 

diff --git a/integrationtest/chaincode/simple/go.sum b/integrationtest/chaincode/simple/go.sum
@@ -50,8 +50,8 @@ google.golang.org/genproto/googleapis/rpc v0.0.0-20240814211410-ddb44dafa142 h1:
 google.golang.org/genproto/googleapis/rpc v0.0.0-20240814211410-ddb44dafa142/go.mod h1:UqMtugtsSgubUsoxbuAoiCXvqvErP7Gf0so0mK9tHxU=
 google.golang.org/grpc v1.67.0 h1:IdH9y6PF5MPSdAntIcpjQ+tXO41pcQsfZV2RxtQgVcw=
 google.golang.org/grpc v1.67.0/go.mod h1:1gLDyUQU7CTLJI90u3nXZ9ekeghjeM7pTDZlqFNg2AA=
-google.golang.org/protobuf v1.35.2 h1:8Ar7bF+apOIoThw1EdZl0p1oWvMqTHmpA2fRTyZO8io=
-google.golang.org/protobuf v1.35.2/go.mod h1:9fA7Ob0pmnwhb644+1+CVWFRbNajQ6iRojtC/QF5bRE=
+google.golang.org/protobuf v1.36.1 h1:yBPeRvTftaleIgM3PZ/WBIZ7XM/eEYAaEyCwvyjq/gk=
+google.golang.org/protobuf v1.36.1/go.mod h1:9fA7Ob0pmnwhb644+1+CVWFRbNajQ6iRojtC/QF5bRE=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=

diff --git a/integrationtest/chaincode/transactionhooks/go.mod b/integrationtest/chaincode/transactionhooks/go.mod
@@ -21,7 +21,7 @@ require (
 	golang.org/x/text v0.17.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20240814211410-ddb44dafa142 // indirect
 	google.golang.org/grpc v1.67.0 // indirect
-	google.golang.org/protobuf v1.35.2 // indirect
+	google.golang.org/protobuf v1.36.1 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
 

diff --git a/integrationtest/chaincode/transactionhooks/go.sum b/integrationtest/chaincode/transactionhooks/go.sum
@@ -50,8 +50,8 @@ google.golang.org/genproto/googleapis/rpc v0.0.0-20240814211410-ddb44dafa142 h1:
 google.golang.org/genproto/googleapis/rpc v0.0.0-20240814211410-ddb44dafa142/go.mod h1:UqMtugtsSgubUsoxbuAoiCXvqvErP7Gf0so0mK9tHxU=
 google.golang.org/grpc v1.67.0 h1:IdH9y6PF5MPSdAntIcpjQ+tXO41pcQsfZV2RxtQgVcw=
 google.golang.org/grpc v1.67.0/go.mod h1:1gLDyUQU7CTLJI90u3nXZ9ekeghjeM7pTDZlqFNg2AA=
-google.golang.org/protobuf v1.35.2 h1:8Ar7bF+apOIoThw1EdZl0p1oWvMqTHmpA2fRTyZO8io=
-google.golang.org/protobuf v1.35.2/go.mod h1:9fA7Ob0pmnwhb644+1+CVWFRbNajQ6iRojtC/QF5bRE=
+google.golang.org/protobuf v1.36.1 h1:yBPeRvTftaleIgM3PZ/WBIZ7XM/eEYAaEyCwvyjq/gk=
+google.golang.org/protobuf v1.36.1/go.mod h1:9fA7Ob0pmnwhb644+1+CVWFRbNajQ6iRojtC/QF5bRE=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=

diff --git a/internal/contract_function.go b/internal/contract_function.go
@@ -140,7 +140,10 @@ func (cf *ContractFunction) formatArgs(ctx reflect.Value, supplementaryMetadata
 		}
 
 		c := make(chan formatArgResult)
-		go cf.formatArg(params[i], fieldType, paramMetadata, components, serializer, c)
+		go func(i int) {
+			defer close(c)
+			c <- cf.formatArg(params[i], fieldType, paramMetadata, components, serializer)
+		}(i)
 		channels = append(channels, c)
 	}
 
@@ -158,23 +161,20 @@ func (cf *ContractFunction) formatArgs(ctx reflect.Value, supplementaryMetadata
 	return values, nil
 }
 
-func (cf *ContractFunction) formatArg(param string, fieldType reflect.Type, parameterMetadata *metadata.ParameterMetadata, components *metadata.ComponentMetadata, serializer serializer.TransactionSerializer, c chan formatArgResult) {
-	defer close(c)
-
+func (cf *ContractFunction) formatArg(param string, fieldType reflect.Type, parameterMetadata *metadata.ParameterMetadata, components *metadata.ComponentMetadata, serializer serializer.TransactionSerializer) formatArgResult {
 	converted, err := serializer.FromString(param, fieldType, parameterMetadata, components)
 
-	paramName := ""
+	var paramName string
 
 	if parameterMetadata != nil {
 		paramName = " " + parameterMetadata.Name
 	}
 
-	res := new(formatArgResult)
-	res.paramName = paramName
-	res.converted = converted
-	res.err = err
-
-	c <- *res
+	return formatArgResult{
+		paramName: paramName,
+		converted: converted,
+		err:       err,
+	}
 }
 
 func (cf *ContractFunction) handleResponse(response []reflect.Value, returnsMetadata *metadata.ReturnMetadata, components *metadata.ComponentMetadata, serializer serializer.TransactionSerializer) (string, interface{}, error) {

diff --git a/internal/functionaltests/contracts/simplecontract/simplecontract.go b/internal/functionaltests/contracts/simplecontract/simplecontract.go
@@ -37,7 +37,7 @@ func (sc *SimpleContract) Create(ctx contractapi.TransactionContextInterface, ke
 }
 
 // Update - Updates a key with given ID in the world state
-func (sc *SimpleContract) Update(ctx contractapi.TransactionContextInterface, key string, value string) error {
+func (sc *SimpleContract) Update(ctx contractapi.TransactionContextInterface, key string, value []byte) error {
 	existing, err := ctx.GetStub().GetState(key)
 
 	if err != nil {
@@ -48,7 +48,7 @@ func (sc *SimpleContract) Update(ctx contractapi.TransactionContextInterface, ke
 		return fmt.Errorf("cannot update key. Key with id %s does not exist", key)
 	}
 
-	err = ctx.GetStub().PutState(key, []byte(value))
+	err = ctx.GetStub().PutState(key, value)
 
 	if err != nil {
 		return errors.New("unable to interact with world state")
@@ -58,16 +58,16 @@ func (sc *SimpleContract) Update(ctx contractapi.TransactionContextInterface, ke
 }
 
 // Read - Returns value of a key with given ID from world state as string
-func (sc *SimpleContract) Read(ctx contractapi.TransactionContextInterface, key string) (string, error) {
+func (sc *SimpleContract) Read(ctx contractapi.TransactionContextInterface, key string) ([]byte, error) {
 	existing, err := ctx.GetStub().GetState(key)
 
 	if err != nil {
-		return "", errors.New("unable to interact with world state")
+		return nil, errors.New("unable to interact with world state")
 	}
 
 	if existing == nil {
-		return "", fmt.Errorf("cannot read key. Key with id %s does not exist", key)
+		return nil, fmt.Errorf("cannot read key. Key with id %s does not exist", key)
 	}
 
-	return string(existing), nil
+	return existing, nil
 }
diff --git a/internal/types/types.go b/internal/types/types.go
@@ -355,6 +355,10 @@ var BasicTypes = map[reflect.Kind]basicType{
 	reflect.Interface: new(interfaceType),
 }
 
+func IsBytes(t reflect.Type) bool {
+	return (t.Kind() == reflect.Array || t.Kind() == reflect.Slice) && t.Elem().Kind() == reflect.Uint8
+}
+
 // ErrorType reflect type for errors
 var ErrorType = reflect.TypeOf((*error)(nil)).Elem()