问题描述
我正在尝试构建一个TCP服务器，该服务器从 CSV 文件加载数据集并提供查询数据集的接口。 TCP服务器将公开端口4040。CSV文件包含与日冕病毒案例相关的以下列：
- 累积测试阳性
- 进行的累积测试
- 日期
- 出院
- 已过期
- 已入学
- 地区
在基于Linux / Unix的系统上，用户应该能够使用 NetCat
nc localhost 4040命令连接到服务器。
连接到TCP后，用户应该能够通过发送JSON格式的查询来与应用程序进行通信。
{
"query": {
"region": "Sindh"
}
}
{
"query": {
"date": "2020-03-20"
}
}
我的server.go
package main
import (
"fmt"
"net"
"os"
"flag"
"log"
"encoding/csv"
"encoding/json"
"bufio"
"io"
"strings"
)
type CovidPatient struct {
Positive string `json:"Covid_Positive"`
Performed string `json:"Coivd_Performed"`
Date string `json:"Covid_Date"`
discharged string `json:"Covid_discharged"`
Expired string `json:"Covid_Expired"`
Region string `json:"Covid_Region"`
Admitted string `json:"Covid_Admitted"`
}
type DataRequest struct {
Get string `json:"get"`
}
type DataError struct {
Error string `json:"Covid_error"`
}
func Load(path string) []CovidPatient {
table := make([]CovidPatient,0)
var patient CovidPatient
file,err := os.Open(path)
if err != nil {
panic(err.Error())
}
defer file.Close()
reader := csv.NewReader(file)
csvData,err := reader.ReadAll()
if err != nil {
fmt.Println(err)
os.Exit(1)
}
for _,row := range csvData{
patient.Positive = row[0]
patient.Performed = row[1]
patient.Date = row[2]
patient.discharged = row[3]
patient.Expired = row[4]
patient.Region = row[5]
patient.Admitted = row[6]
table = append(table,patient)
}
return table
}
func Find(table []CovidPatient,filter string) []CovidPatient {
if filter == "" || filter == "*" {
return table
}
result := make([]CovidPatient,0)
filter = strings.toupper(filter)
for _,cp := range table {
if cp.Date == filter ||
cp.Region == filter ||
strings.Contains(strings.toupper(cp.Positive),filter) ||
strings.Contains(strings.toupper(cp.Performed),filter) ||
strings.Contains(strings.toupper(cp.Date),filter) ||
strings.Contains(strings.toupper(cp.discharged),filter) ||
strings.Contains(strings.toupper(cp.Expired),filter) ||
strings.Contains(strings.toupper(cp.Region),filter) ||
strings.Contains(strings.toupper(cp.Admitted),filter){
result = append(result,cp)
}
}
return result
}
var (
patientsDetail = Load("./covid_final_data.csv")
)
func main(){
var addr string
var network string
flag.StringVar(&addr,"e",":4040","service endpoint [ip addr or socket path]")
flag.StringVar(&network,"n","tcp","network protocol [tcp,unix]")
flag.Parse()
switch network {
case "tcp","tcp4","tcp6","unix":
default:
fmt.Println("unsupported network protocol")
os.Exit(1)
}
ln,err := net.Listen(network,addr)
if err != nil {
log.Println(err)
os.Exit(1)
}
defer ln.Close()
log.Println("Covid19 Condition in Pakistan")
log.Printf("Service started: (%s) %s\n",network,addr)
for {
conn,err := ln.Accept()
if err != nil {
log.Println(err)
conn.Close()
continue
}
log.Println("Connected to ",conn.RemoteAddr())
go handleConnection(conn)
}
}
func handleConnection(conn net.Conn) {
defer func() {
if err := conn.Close(); err != nil {
log.Println("error closing connection:",err)
}
}()
reader := bufio.NewReaderSize(conn,4)
for {
buf,err := reader.ReadSlice('}')
if err != nil {
if err != io.EOF {
log.Println("connection read error:",err)
return
}
}
reader.Reset(conn)
var req DataRequest
if err := json.Unmarshal(buf,&req); err != nil {
log.Println("Failed to unmarshal request:",err)
cerr,jerr := json.Marshal(DataError{Error: err.Error()})
if jerr != nil {
log.Println("Failed to marshal DataError:",jerr)
continue
}
if _,werr := conn.Write(cerr); werr != nil {
log.Println("Failed to write to DataError:",werr)
return
}
continue
}
result := Find(patientsDetail,req.Get)
rsp,err := json.Marshal(&result)
if err != nil {
log.Println("Failed to marshal data:",err)
if _,err := fmt.Fprintf(conn,`{"data_error":"internal error"}`); err != nil {
log.Printf("Failed to write to client: %v",err)
return
}
continue
}
if _,err := conn.Write(rsp); err != nil {
log.Println("Failed to write response:",err)
return
}
}
}
这可以正确加载csv并将其转换为JSON。但是，当我尝试使用NetCat命令运行查询时，它返回空的JSON元素。请指导我哪里出错了。
解决方法
猜你想要这个：
╭─root@DESKTOP-OCDRD7Q ~
╰─# nc localhost 4040
{"get": "Sindh"}
[{"Covid_Positive":"1","Coivd_Performed":"1","Covid_Date":"1","Covid_Discharged":"1","Covid_Expired":"1","Covid_Region":"Sindh","Covid_Admitted":"1"}]
您应该做的只是修改您的json请求。
package main
import (
"bufio"
"encoding/csv"
"encoding/json"
"flag"
"fmt"
"io"
"log"
"net"
"os"
)
type CovidPatient struct {
Positive string `json:"Covid_Positive"`
Performed string `json:"Coivd_Performed"`
Date string `json:"Covid_Date"`
Discharged string `json:"Covid_Discharged"`
Expired string `json:"Covid_Expired"`
Region string `json:"Covid_Region"`
Admitted string `json:"Covid_Admitted"`
}
type DataRequest struct {
Get CovidPatient `json:"get"`
}
type DataError struct {
Error string `json:"Covid_error"`
}
func Load(path string) []CovidPatient {
table := make([]CovidPatient,0)
var patient CovidPatient
file,err := os.Open(path)
if err != nil {
panic(err.Error())
}
defer file.Close()
reader := csv.NewReader(file)
csvData,err := reader.ReadAll()
if err != nil {
fmt.Println(err)
os.Exit(1)
}
for _,row := range csvData {
patient.Positive = row[0]
patient.Performed = row[1]
patient.Date = row[2]
patient.Discharged = row[3]
patient.Expired = row[4]
patient.Region = row[5]
patient.Admitted = row[6]
table = append(table,patient)
}
return table
}
func Find(table []CovidPatient,filter CovidPatient) []CovidPatient {
result := make([]CovidPatient,0)
log.Println(filter,table)
for _,cp := range table {
if filter.Positive == "" {
} else if filter.Positive != cp.Positive {
continue
}
if filter.Performed == "" {
} else if filter.Performed != cp.Performed {
continue
}
if filter.Date == "" {
} else if filter.Date != cp.Date {
continue
}
if filter.Discharged == "" {
} else if filter.Discharged != cp.Discharged {
continue
}
if filter.Expired == "" {
} else if filter.Expired != cp.Expired {
continue
}
if filter.Region == "" {
} else if filter.Region != cp.Region {
continue
}
if filter.Admitted == "" {
} else if filter.Admitted != cp.Admitted {
continue
}
result = append(result,cp)
}
return result
}
var (
patientsDetail = Load("./covid_final_data.csv")
)
func main() {
log.SetFlags(log.Lshortfile | log.Ltime)
var addr string
var network string
flag.StringVar(&addr,"e",":4040","service endpoint [ip addr or socket path]")
flag.StringVar(&network,"n","tcp","network protocol [tcp,unix]")
flag.Parse()
switch network {
case "tcp","tcp4","tcp6","unix":
default:
fmt.Println("unsupported network protocol")
os.Exit(1)
}
ln,err := net.Listen(network,addr)
if err != nil {
log.Println(err)
os.Exit(1)
}
defer ln.Close()
log.Println("Covid19 Condition in Pakistan")
log.Printf("Service started: (%s) %s\n",network,addr)
for {
conn,err := ln.Accept()
if err != nil {
log.Println(err)
conn.Close()
continue
}
log.Println("Connected to ",conn.RemoteAddr())
go handleConnection(conn)
}
}
func handleConnection(conn net.Conn) {
defer func() {
if err := conn.Close(); err != nil {
log.Println("error closing connection:",err)
}
}()
reader := bufio.NewReaderSize(conn,100)
for {
buf,err := reader.ReadBytes('|')
if err != nil {
if err != io.EOF {
log.Println("connection read error:",err)
return
}
}
reader.Reset(conn)
var req DataRequest
if err := json.Unmarshal(buf[:len(buf)-1],&req); err != nil {
log.Println("failed to unmarshal request:",string(buf),err)
cerr,jerr := json.Marshal(DataError{Error: err.Error()})
if jerr != nil {
log.Println("failed to marshal DataError:",jerr)
continue
}
if _,werr := conn.Write(cerr); werr != nil {
log.Println("failed to write to DataError:",werr)
return
}
continue
}
result := Find(patientsDetail,req.Get)
rsp,err := json.Marshal(&result)
if err != nil {
log.Println("failed to marshal data:",err)
if _,err := fmt.Fprintf(conn,`{"data_error":"internal error"}`); err != nil {
log.Printf("failed to write to client: %v",err)
return
}
continue
}
if _,err := conn.Write(rsp); err != nil {
log.Println("failed to write response:",err)
return
}
}
}
查询是：
╭─root@DESKTOP-OCDRD7Q ~
╰─# nc localhost 4040 127 ↵
{
"get": {
"Covid_Region": "Sindh","Covid_Date": "2020-03-20"
}
}|
[{"Covid_Positive":"1","Covid_Date":"2020-03-20","Covid_Admitted":"1"}]
在函数handleConnection中，第一件事是“读取直到找到第一个}”，想象用户正在发送请求：
{ "get": { "Covid_Region": "Sindh","Covid_Date": "2020-03-20" } }
然后该步骤读取：
{ "get": { "Covid_Region": "Sindh","Covid_Date": "2020-03-20" }
请注意，结尾的}丢失了，然后json.Unmarshal试图取消对没有最后一个}（这是无效的json）的查询的封送。
此问题可以利用JSON流解码，换句话说，使用json.NewDecoder(r io.Reader)代替json.Unmarshal。让我复制并修改该函数的第一部分：
func handleConnection(conn net.Conn) {
defer func() {
if err := conn.Close(); err != nil {
log.Println("error closing connection:",err)
}
}()
jsonDecoder := json.NewDecoder(conn) // A json decoder read a stream to find a
// valid JSON and stop just the byte
// after the JSON ends. Process can be
// repeated.
for {
var req DataRequest
err := jsonDecoder.Decode(&req)
if err == io.EOF {
log.Println("finish")
return
}
if err != nil {
log.Println("unmarshal:",err)
return
}
result := Find(patientsDetail,req.Get) // Here query the system
// ...
现在可能可以了，但是您也可以利用json流在de for循环之前以jsonEncoder := json.NewEncoder(conn)的形式发送响应并发送请求，如下所示：
err := jsonEncoder.Encode(&result)
if err != nil {
log.Println("failed to marshal data:",err)
// ...
continue
}