背景
在Fabric链码中,我们可以使用PutState方法对一个key的值进行覆盖,当我们再使用GetState查询时是最新的值。如果我们希望找到这个key的修改记录,我们可以使用溯源方法GetHistoryForKey
。完整源码链接:https://github.com/hyperledger/fabric-samples/blob/main/asset-transfer-ledger-queries/chaincode-go/asset_transfer_ledger_chaincode.go
代码
go
// HistoryQueryResult structure used for returning result of history query
type HistoryQueryResult struct {
Record *Asset `json:"record"`
TxId string `json:"txId"`
Timestamp time.Time `json:"timestamp"`
IsDelete bool `json:"isDelete"`
}
// GetAssetHistory returns the chain of custody for an asset since issuance.
func (t *SimpleChaincode) GetAssetHistory(ctx contractapi.TransactionContextInterface, assetID string) ([]HistoryQueryResult, error) {
log.Printf("GetAssetHistory: ID %v", assetID)
resultsIterator, err := ctx.GetStub().GetHistoryForKey(assetID)
if err != nil {
return nil, err
}
defer resultsIterator.Close()
var records []HistoryQueryResult
for resultsIterator.HasNext() {
response, err := resultsIterator.Next()
if err != nil {
return nil, err
}
var asset Asset
if len(response.Value) > 0 {
err = json.Unmarshal(response.Value, &asset)
if err != nil {
return nil, err
}
} else {
asset = Asset{
ID: assetID,
}
}
timestamp, err := ptypes.Timestamp(response.Timestamp)
if err != nil {
return nil, err
}
record := HistoryQueryResult{
TxId: response.TxId,
Timestamp: timestamp,
Record: &asset,
IsDelete: response.IsDelete,
}
records = append(records, record)
}
return records, nil
}