jx

#jx

jx - a simple json storage engine by Golang.

jx is a storage engine use simple json by kv map encoded as documentation. It provides simple api methods to operate value in storage. It can be used as embedded storage.

Getting Started

jx saves real data in files. so create a *jx.Storage in directory.

import "github.com/fuxiaohei/jx"

s,e := jx.NewStorage("data")
if e != nil{
    panic(e) // remember error
}

It creates storage directory for saving data. But it doesn't load existing data now.

1. Sync

Then sync a struct to storage, so storage can save the struct value.

type User struct {
    Id       int64    `jx:"pk-auto"`
    UserName string 
    Password string
    Email    string 
}

type School struct {
    Id      int64 `jx:"pk"`
    Address string
    Rank    int 
}

e := s.Sync(new(User),new(School))

s.Sync(...) only support struct pointer type.

jx:"pk" means primary key for this field, only support int64, string, float64 type.

jx:"pk-auto" means auto-increment primary key for this field, only support int64 type.Insert

The pk field is unique, so if two "pk" tag in struct, the last one is assigned.

Notice:

When sync a struct, it creates default data files if not exist yet.

Or it reads old data for memory as preparation.

2. Insert

Insert a new struct value into storage:

u := new(User)
u.UserName = "abcdef"
u.Password = "12345678"
u.Email = "abcdef@xyz.com"

e := s.Put(u) // u.Id is auto increasing.

Insert only support struct pointer.

The pk field u.Id is assigned as max id in storage and increasing one by one.

If pk-auto tag, no matter the pk you set in struct, use storage max pk int.

s := new(School)
s.Id = 123
s.Address = "address"
S.Rank = 4

e := s.Put(s) // pk field 
if e == jx.Conflict{
    // means the pk is used in storage.
}
if e == jx.Wrong{
    // means the pk field is wrong value, type error and empty
}

When s.Insert(u), it checks pk field value unique.

Then write data to chunk files.

3. Get

Now only support get value by pk field

u := &User{Id:100}
e := s.Get(u)
if e == jx.Nil{
    println("get no data")
}else{
    println(u.UserName) // if found, field is filled.
}

Get only support struct pointer and by pk field.

If value is not synced, return error.

If value is found, u is filled by value.

4. Update

Only support update value by pk field:

u := new(User)
u.Id = 1
u.UserName = "mnopq"
u.Password = "9876543"
u.Email = "xyz@abc.com"

e := s.Update(u)

5. Delete

Delete value by pk:

u := new(User)
u.Id = 1

e := s.Delete(u)