具有如下结构层次结构：type DomainStore struct { Domains []*Domain Users []*User}type Domain struct { Name string Records []*Record Owner *User}type User struct { Name string Email string Domains []*Domain}type Record struct { Name string Host string}使用具有域和用户列表的单个 DomainStore，以及域和用户之间的指针。我正在寻找一种对文件进行序列化/反序列化的方法。我一直在尝试使用 gob，但指针没有（按设计）序列化正确（扁平化）。考虑给每个对象一个唯一的 id 并制作一个函数来序列化/反序列化每种类型，但这似乎需要很多工作/样板。对策略有什么建议吗？我想将整个 DomainStore 保存在内存中，并根据用户请求序列化为文件。主要问题：如何序列化/反序列化并保持指针指向同一个对象而不是同一个对象的不同副本gob 和 json 似乎都“只是”复制对象的值并进行反序列化，我最终得到了多个独立的对象副本。使用 gob ang json 会发生以下情况：之前，A & C 都指向 B：A -> B <- C使用 json/gob 反序列化后：A -> B1 , C -> B2A & C 指向不同的对象，具有相同的值。但是，如果我更改 B1，它不会在 B2 中更改。- - 更新 - -编组时我可以获得对象的内存位置并将其用作 ID：func (u *User) MarshalJSON() ([]byte, error) { return json.Marshal(&JsonUser{ ID: fmt.Sprintf("%p", u), Name: u.Name, Email: u.Email, })}在编组域时，我可以替换func (d *Domain) MarshalJSON() ([]byte, error) { return json.Marshal(&struct { ID string `json:"id"` Name string `json:"name"` User string `json:"user"` }{ ID: fmt.Sprintf("%p", d), Name: d.Name, User: fmt.Sprintf("%p", d.User), })}现在我只需要能够解组这个，这给我带来了一个问题，UnmarshalJSON 需要访问 id 及其各自对象的映射。func (u *User) UnmarshalJSON(data []byte) error { // need acces to a map shared by all UnmarshalJSON functions}
2 回答
慕森卡
TA贡献1806条经验 获得超8个赞
可以使用以下方法完成：
所有对象都放置在地图中的状态对象中。
当 State 对象中的对象被编组时，所有使用指针引用的对象都将替换为该对象的内存位置。
当使用先前读取的对象的全局列表恢复未编组的指针时。
代码将运行，只是为了说明方法，我是 Go 的新手，所以请耐心等待。
package main
import (
"encoding/json"
"errors"
"fmt"
"log"
"strings"
)
type User struct {
Name string
Email string
}
type JsonUser struct {
ID string `json:"id"`
Name string `json:"name"`
Email string `json:"email"`
}
func (u *User) Print(level int) {
ident := strings.Repeat("-", level)
log.Println(ident, "Username:", u.Name, u.Email)
}
func (u *User) Id() string {
return fmt.Sprintf("%p", u)
}
func (u *User) MarshalJSON() ([]byte, error) {
return json.Marshal(&JsonUser{
ID: u.Id(),
Name: u.Name,
Email: u.Email,
})
}
func (u *User) UnmarshalJSON(data []byte) error {
aux := &JsonUser{}
if err := json.Unmarshal(data, &aux); err != nil {
return err
}
u.Name = aux.Name
u.Email = aux.Email
load_helper[aux.ID] = u
log.Println("Added user with id ", aux.ID, u.Name)
return nil
}
type Record struct {
Type string // MX / A / CNAME / TXT / REDIR / SVR
Name string // @ / www
Host string // IP / address
Priority int // Used for MX
Port int // Used for SVR
}
type JsonRecord struct {
ID string
Type string
Name string
Host string
Priority int
Port int
}
func (r *Record) Print(level int) {
ident := strings.Repeat("-", level)
log.Println(ident, "", r.Type, r.Name, r.Host)
}
func (r *Record) Id() string {
return fmt.Sprintf("%p", r)
}
func (r *Record) MarshalJSON() ([]byte, error) {
return json.Marshal(&JsonRecord{
ID: r.Id(),
Name: r.Name,
Type: r.Type,
Host: r.Host,
Priority: r.Priority,
Port: r.Port,
})
}
func (r *Record) UnmarshalJSON(data []byte) error {
aux := &JsonRecord{}
if err := json.Unmarshal(data, &aux); err != nil {
return err
}
r.Name = aux.Name
r.Type = aux.Type
r.Host = aux.Host
r.Priority = aux.Priority
r.Port = aux.Port
load_helper[aux.ID] = r
log.Println("Added record with id ", aux.ID, r.Name)
return nil
}
type Domain struct {
Name string
User *User // User ID
Records []*Record // Record ID's
}
type JsonDomain struct {
ID string `json:"id"`
Name string `json:"name"`
User string `json:"user"`
Records []string `json:"records"`
}
func (d *Domain) Print(level int) {
ident := strings.Repeat("-", level)
log.Println(ident, "Domain:", d.Name)
d.User.Print(level + 1)
log.Println(ident, " Records:")
for _, r := range d.Records {
r.Print(level + 2)
}
}
func (d *Domain) Id() string {
return fmt.Sprintf("%p", d)
}
func (d *Domain) MarshalJSON() ([]byte, error) {
var record_ids []string
for _, r := range d.Records {
record_ids = append(record_ids, r.Id())
}
return json.Marshal(JsonDomain{
ID: d.Id(),
Name: d.Name,
User: d.User.Id(),
Records: record_ids,
})
}
func (d *Domain) UnmarshalJSON(data []byte) error {
log.Println("UnmarshalJSON domain")
aux := &JsonDomain{}
if err := json.Unmarshal(data, &aux); err != nil {
return err
}
d.Name = aux.Name
d.User = load_helper[aux.User].(*User) // restore pointer to domains user
for _, record_id := range aux.Records {
d.Records = append(d.Records, load_helper[record_id].(*Record))
}
return nil
}
type State struct {
Users map[string]*User
Records map[string]*Record
Domains map[string]*Domain
}
func NewState() *State {
s := &State{}
s.Users = make(map[string]*User)
s.Domains = make(map[string]*Domain)
s.Records = make(map[string]*Record)
return s
}
func (s *State) Print() {
log.Println("State:")
log.Println("Users:")
for _, u := range s.Users {
u.Print(1)
}
log.Println("Domains:")
for _, d := range s.Domains {
d.Print(1)
}
}
func (s *State) NewUser(name string, email string) *User {
u := &User{Name: name, Email: email}
id := fmt.Sprintf("%p", u)
s.Users[id] = u
return u
}
func (s *State) NewDomain(user *User, name string) *Domain {
d := &Domain{Name: name, User: user}
s.Domains[d.Id()] = d
return d
}
func (s *State) NewMxRecord(d *Domain, rtype string, name string, host string, priority int) *Record {
r := &Record{Type: rtype, Name: name, Host: host, Priority: priority}
d.Records = append(d.Records, r)
s.Records[r.Id()] = r
return r
}
func (s *State) FindDomain(name string) (*Domain, error) {
for _, v := range s.Domains {
if v.Name == name {
return v, nil
}
}
return nil, errors.New("Not found")
}
func Save(s *State) (string, error) {
b, err := json.MarshalIndent(s, "", " ")
if err == nil {
return string(b), nil
} else {
log.Println(err)
return "", err
}
}
var load_helper map[string]interface{}
func Load(s *State, blob string) {
load_helper = make(map[string]interface{})
if err := json.Unmarshal([]byte(blob), s); err != nil {
log.Println(err)
} else {
log.Println("OK")
}
}
func test_state() {
s := NewState()
u := s.NewUser("Ownername", "some@email.com")
d := s.NewDomain(u, "somedomain.com")
s.NewMxRecord(d, "MX", "@", "192.168.1.1", 10)
s.NewMxRecord(d, "A", "www", "192.168.1.1", 0)
s.Print()
x, _ := Save(s) // Saved to json string
log.Println("State saved, the json string is:")
log.Println(x)
s2 := NewState() // Create a new empty State
Load(s2, x)
s2.Print()
d, err := s2.FindDomain("somedomain.com")
if err == nil {
d.User.Name = "Changed"
} else {
log.Println("Error:", err)
}
s2.Print()
}
func main() {
test_state()
}
这是相当多的代码，对象和序列化之间有很多耦合。全局变量 load_helper 也不好。改进的想法将不胜感激。
另一种方法是使用反射来制作更通用的解决方案。以下是使用此方法的示例：
package main
import (
"encoding/json"
"fmt"
"log"
"strings"
"reflect"
)
func pprint(x interface{}) {
b, err := json.MarshalIndent(x, "", " ")
if err != nil {
fmt.Println("error:", err)
}
fmt.Println(string(b))
}
var typeRegistry = make(map[string]reflect.Type)
// Register a type to make it possible for the Save/Load functions
// to serialize it.
func Register(v interface{}) {
t := reflect.TypeOf(v)
n := t.Name()
fmt.Println("Register type",n)
typeRegistry[n] = reflect.TypeOf(v)
}
// Make an instance of a type from the string name of the type.
func makeInstance(name string) reflect.Value {
v := reflect.New(typeRegistry[name]).Elem()
return v
}
// Translate a string type name tpo a real type.
func getTypeFromString(name string) reflect.Type {
return typeRegistry[name]
}
// Serializeable interface must be supported by all objects passed to the Load / Save functions.
type Serializeable interface {
Id() string
}
// GenericSave saves the object d
func GenericSave(d interface{}) (string, error) {
r := make(map[string]interface{})
v := reflect.ValueOf(d)
t := reflect.TypeOf(d)
if t.Kind()==reflect.Ptr {
t=t.Elem()
v=v.Elem()
}
r["_TYPE"]=t.Name()
r["_ID"]=fmt.Sprintf("%p", d)
for i := 0; i < t.NumField(); i++ {
f := t.Field(i)
name := f.Name
vf := v.FieldByName(name)
// fmt.Println("Field", i+1, "name is", name, "type is", f.Type.Name(), "and kind is", f.Type.Kind())
// fmt.Println("V:", vf)
if f.Tag != "" {
store:=strings.Split(f.Tag.Get("store"),",")
switch store[1] {
case "v":
switch t.Field(i).Type.Name() {
case "string":
r[store[0]]=vf.String()
case "int":
r[store[0]]=vf.Int()
}
case "p":
vals:=vf.MethodByName("Id").Call([]reflect.Value{})
r[store[0]]=vals[0].String()
case "lp":
tr:=[]string{}
for j := 0; j < vf.Len(); j++ {
vals:=vf.Index(j).MethodByName("Id").Call([]reflect.Value{})
tr=append(tr,vals[0].String())
}
r[store[0]]=tr
}
}
}
m,_:=json.Marshal(r)
return string(m),nil
}
// Save saves the list of objects.
func Save(objects []Serializeable) []byte {
lst:=[]string{}
for _,o := range(objects) {
os,_:= GenericSave(o) // o.Save()
lst=append(lst,os)
}
m,_:=json.Marshal(lst)
return m
}
func toStructPtr(obj interface{}) interface{} {
vp := reflect.New(reflect.TypeOf(obj))
vp.Elem().Set(reflect.ValueOf(obj))
return vp.Interface()
}
// Load creates a list of serializeable objects from json blob
func Load(blob []byte) []Serializeable {
objects := []Serializeable{}
loadHelper := make(map[string]interface{})
var olist []interface{}
if err := json.Unmarshal(blob, &olist); err != nil {
log.Println(err)
} else {
for _,o := range(olist) {
var omap map[string]interface{}
json.Unmarshal([]byte(o.(string)), &omap)
t:= getTypeFromString(omap["_TYPE"].(string))
obj := reflect.New(t).Elem()
for i := 0; i < t.NumField(); i++ {
// n:=t.Field(i).Name
// fmt.Println(i,n,t.Field(i).Type.Name())
if t.Field(i).Tag != "" {
store:=strings.Split(t.Field(i).Tag.Get("store"),",")
// fmt.Println(store)
switch store[1] {
case "v":
switch t.Field(i).Type.Name() {
case "string":
obj.FieldByIndex([]int{i}).SetString(omap[store[0]].(string))
case "int":
obj.FieldByIndex([]int{i}).SetInt(int64(omap[store[0]].(float64)))
}
case "p":
nObj:=loadHelper[omap[store[0]].(string)]
obj.FieldByIndex([]int{i}).Set(reflect.ValueOf(nObj.(*User)))
case "lp":
ptrItemType:=t.Field(i).Type.Elem()
slice := reflect.Zero(reflect.SliceOf( ptrItemType /* reflect.TypeOf( &Record{} ) */ ))//.Interface()
for _, pID := range(omap[store[0]].([]interface{})) {
nObj:=loadHelper[pID.(string)]
slice=reflect.Append(slice, reflect.ValueOf(nObj) )
}
obj.FieldByIndex([]int{i}).Set(slice)
}
}
}
oi:=toStructPtr(obj.Interface())
oip:=oi.(Serializeable)
objects=append(objects,oip)
loadHelper[omap["_ID"].(string)]=oip
}
}
return objects
}
/* Application data structures */
type User struct {
Name string `store:"name,v"`
Email string `store:"email,v"`
}
func (u *User) Id() string {
return fmt.Sprintf("%p", u)
}
func (u *User) Save() (string, error) {
return GenericSave(u)
}
func (u *User) Print() {
fmt.Println("User:",u.Name)
}
type Record struct {
Type string `store:"type,v"`// MX / A / CNAME / TXT / REDIR / SVR
Name string `store:"name,v"`// @ / www
Host string `store:"host,v"`// IP / address
Priority int `store:"priority,v"`// Used for MX
Port int `store:"port,v"`// Used for SVR
}
func (r *Record) Id() string {
return fmt.Sprintf("%p", r)
}
func (r *Record) Save() (string, error) {
return GenericSave(r)
}
func (r *Record) Print() {
fmt.Println("Record:",r.Type,r.Name,r.Host)
}
type Domain struct {
Name string `store:"name,v"`
User *User `store:"user,p"` // User ID
Records []*Record `store:"record,lp"` // Record ID's
}
func (d *Domain) Id() string {
return fmt.Sprintf("%p", d)
}
func (d *Domain) Save() (string, error) {
return GenericSave(d)
}
func (d *Domain) Print() {
fmt.Println("Domain:",d.Name)
d.User.Print()
fmt.Println("Records:")
for _, r := range d.Records {
r.Print()
}
}
type DBM struct {
Domains []*Domain
Users []*User
Records []*Record
}
func (dbm *DBM) AddDomain(d *Domain) {
dbm.Domains=append(dbm.Domains,d)
}
func (dbm *DBM) AddUser(u *User) {
dbm.Users=append(dbm.Users,u)
}
func (dbm *DBM) AddRecord(r *Record) {
dbm.Records=append(dbm.Records,r)
}
func (dbm *DBM) GetObjects() []Serializeable {
objects:=[]Serializeable{}
for _,r := range(dbm.Records) {
objects=append(objects, r)
}
for _,u := range(dbm.Users) {
objects=append(objects, u)
}
for _,d := range(dbm.Domains) {
objects=append(objects, d)
}
return objects
}
func (dbm *DBM) SetObjects(objects []Serializeable) {
for _,o := range(objects) {
switch o.(type) {
case *Record:
fmt.Println("record")
dbm.AddRecord(o.(*Record))
case *User:
fmt.Println("record")
dbm.AddUser(o.(*User))
case *Domain:
fmt.Println("record")
dbm.AddDomain(o.(*Domain))
}
}
}
func testState() {
Register(User{})
Register(Domain{})
Register(Record{})
dbm:=DBM{}
u := &User{Name: "Martin", Email: "some@email.com"}
dbm.AddUser(u)
r1 := &Record{Name: "@", Type: "MX", Host: "mail.ishost.dk"}
r2 := &Record{Name: "@", Type: "MX", Host: "mail.infoserv.dk"}
dbm.AddRecord(r1)
dbm.AddRecord(r2)
d := &Domain{User:u, Name: "Martin", Records: []*Record{r1, r2}}
dbm.AddDomain(d)
x:=Save(dbm.GetObjects())
fmt.Println("== Saved objects")
// fmt.Println(string(x))
fmt.Println("== Loading")
dbm2:=DBM{}
dbm2.SetObjects(Load(x))
u2:=dbm2.Users[0]
u2.Print()
u2.Name="KURT"
u2.Print()
d2:=dbm2.Domains[0]
d2.Print()
d2.User.Name="ZIG"
u2.Print()
}
func main() {
testState()
}
开心每一天1111
TA贡献1836条经验 获得超13个赞
使用encoding/json包
元帅：
// Marshal is a function that marshals the object into an
// io.Reader.
// By default, it uses the JSON marshaller.
var Marshal = func(v interface{}) (io.Reader, error) {
b, err := json.MarshalIndent(v, "", "\t")
if err != nil {
return nil, err
}
return bytes.NewReader(b), nil
}
解组：
// Unmarshal is a function that unmarshals the data from the
// reader into the specified value.
// By default, it uses the JSON unmarshaller.
var Unmarshal = func(r io.Reader, v interface{}) error {
return json.NewDecoder(r).Decode(v)
}
不确定还有更多，
您可以做的另一件事是，将所有这些存储为 json 格式的字符串。
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