ChaincodeRichQueryWithPagination.go

package main

import (
	"encoding/json"
	"strconv"

	"github.com/hyperledger/fabric/core/chaincode/shim"
	"github.com/hyperledger/fabric/protos/peer"
)


// GetStudents : Get student by page
func (cc *SmartContract) GetStudents(stub shim.ChaincodeStubInterface, args []string) peer.Response {
	if len(args) < 1 {
		return shim.Error("{\"status\":false,\"error\":\"Invalid number of arguments. Expecting 1 argument\"}")
	}

	page, err := strconv.Atoi(args[0])
	if err != nil {
		return shim.Error("{\"status\":false,\"error\":\"" + err.Error() + "\"}")
	}
	if page < 1 {
		return shim.Error("{\"status\":false,\"error\":\"Page number must be > 0\"}")
	}

	queryString := "{\"selector\":{\"doc_type\":\"student\"},\"sort\":[\"student_id\"]}"
	var pageSize int32 = 15
	bookmark := ""

	pageCount := 0
	recordCount := 0

	var resultsIterator shim.StateQueryIteratorInterface
	var responseMetadata *peer.QueryResponseMetadata

	responseJSON := "{\"status\":true,\"message\":\"Success get students\",\"data\":["
	for true {
		resultsIterator, responseMetadata, err = stub.GetQueryResultWithPagination(queryString, pageSize, bookmark)
		if err != nil {
			return shim.Error(err.Error())
		}

		if bookmark == responseMetadata.Bookmark {
			break
		}
		pageCount++
		if page == pageCount {
			for resultsIterator.HasNext() {
				resultKV, err := resultsIterator.Next()
				if err != nil {
					return shim.Error(err.Error())
				}
				bytes := resultKV.GetValue()
				var student Student
				err = json.Unmarshal(bytes, &student)
				if err != nil {
					return shim.Error(err.Error())
				}
				if recordCount != 0 {
					responseJSON += ","
				}
				responseJSON += GetStudentJSON(student)
				recordCount++
			}
			responseJSON += "],\"paging\":{\"page\":" + strconv.Itoa(page) + ",\"count\":" + strconv.Itoa(recordCount)
		}
		// responseMetadata will be "nil" if the record is 0 at first page
		bookmark = responseMetadata.Bookmark
		if responseMetadata.Bookmark == "nil" {
			break
		}
		resultsIterator.Close()
	}
	responseJSON += ",\"total_page\":" + strconv.Itoa(pageCount) + "}}"
	if page > pageCount {
		return shim.Error("{\"status\":false,\"error\":\"Invalid page number, only " + strconv.Itoa(pageCount) + " page(s) available.\"}")
	}

	return shim.Success([]byte(responseJSON))
}