7.6 Session

Go 语言实现操作session不像cookie那样，net/http包里有现成函数可以很方便的使用，一些web服务用到session的话，没办法地自己敲代码实现。

Go具体实现session:

• 服务端可以通过内存、redis、数据库等存储session数据(本例只有内存)。
• 通过cookie将唯一SessionID发送到客户端

session.go

package session
import (
    "crypto/rand"
    "encoding/base64"
    "fmt"
    "io"
    "net/http"
    "net/url"
    "sync"
    "time"
)
//session存储方式接口
type Provider interface {
    //初始化一个session，sid根据需要生成后传入
    SessionInit(sid string) (Session, error)
    //根据sid,获取session
    SessionRead(sid string) (Session, error)
    //销毁session
    SessionDestroy(sid string) error
    //回收
    SessionGC(maxLifeTime int64)
}
//Session操作接口
type Session interface {
    Set(key, value interface{}) error
    Get(key interface{}) interface{}
    Delete(ket interface{}) error
    SessionID() string
}
type Manager struct {
    cookieName  string
    lock        sync.Mutex //互斥锁
    provider    Provider   //存储session方式
    maxLifeTime int64      //有效期
}
//示例化一个session管理器
func NewSessionManager(provideName, cookieName string, maxLifeTime int64) (*Manager, error) {
    provide, ok := provides[provideName]
    if !ok {
        return nil, fmt.Errorf("session: unknown provide %q ", provideName)
    }
    return &Manager{cookieName: cookieName, provider: provide, maxLifeTime: maxLifeTime}, nil
}
//注册 由实现Provider接口的结构体调用
func Register(name string, provide Provider) {
    if provide == nil {
        panic("session: Register provide is nil")
    }
    if _, ok := provides[name]; ok {
        panic("session: Register called twice for provide " + name)
    }
    provides[name] = provide
}
var provides = make(map[string]Provider)
//生成sessionId
func (manager *Manager) sessionId() string {
    b := make([]byte, 32)
    if _, err := io.ReadFull(rand.Reader, b); err != nil {
        return ""
    }
    //加密
    return base64.URLEncoding.EncodeToString(b)
}
//判断当前请求的cookie中是否存在有效的session，存在返回，否则创建
func (manager *Manager) SessionStart(w http.ResponseWriter, r *http.Request) (session Session) {
    manager.lock.Lock() //加锁
    defer manager.lock.Unlock()
    cookie, err := r.Cookie(manager.cookieName)
    if err != nil || cookie.Value == "" {
        //创建一个
        sid := manager.sessionId()
        session, _ = manager.provider.SessionInit(sid)
        cookie := http.Cookie{
            Name:     manager.cookieName,
            Value:    url.QueryEscape(sid), //转义特殊符号@#￥%+*-等
            Path:     "/",
            HttpOnly: true,
            MaxAge:   int(manager.maxLifeTime),
            Expires:  time.Now().Add(time.Duration(manager.maxLifeTime)),
            //MaxAge和Expires都可以设置cookie持久化时的过期时长，Expires是老式的过期方法，
            // 如果可以，应该使用MaxAge设置过期时间，但有些老版本的浏览器不支持MaxAge。
            // 如果要支持所有浏览器，要么使用Expires，要么同时使用MaxAge和Expires。
        }
        http.SetCookie(w, &cookie)
    } else {
        sid, _ := url.QueryUnescape(cookie.Value) //反转义特殊符号
        session, _ = manager.provider.SessionRead(sid)
    }
    return session
}
//销毁session 同时删除cookie
func (manager *Manager) SessionDestroy(w http.ResponseWriter, r *http.Request) {
    cookie, err := r.Cookie(manager.cookieName)
    if err != nil || cookie.Value == "" {
        return
    } else {
        manager.lock.Lock()
        defer manager.lock.Unlock()
        sid, _ := url.QueryUnescape(cookie.Value)
        manager.provider.SessionDestroy(sid)
        expiration := time.Now()
        cookie := http.Cookie{
            Name:     manager.cookieName,
            Path:     "/",
            HttpOnly: true,
            Expires:  expiration,
            MaxAge:   -1}
        http.SetCookie(w, &cookie)
    }
}
func (manager *Manager) GC() {
    manager.lock.Lock()
    defer manager.lock.Unlock()
    manager.provider.SessionGC(manager.maxLifeTime)
    time.AfterFunc(time.Duration(manager.maxLifeTime), func() { manager.GC() })
}

memory.go

package memory
import (
    "container/list"
    "example/example/public/session"
    "sync"
    "time"
)
var pder = &FromMemory{list: list.New()}
func init() {
    pder.sessions = make(map[string]*list.Element, 0)
    //注册  memory 调用的时候一定有一致
    session.Register("memory", pder)
}
//session实现
type SessionStore struct {
    sid              string                      //session id 唯一标示
    LastAccessedTime time.Time                   //最后访问时间
    value            map[interface{}]interface{} //session 里面存储的值
}
//设置
func (st *SessionStore) Set(key, value interface{}) error {
    st.value[key] = value
    pder.SessionUpdate(st.sid)
    return nil
}
//获取session
func (st *SessionStore) Get(key interface{}) interface{} {
    pder.SessionUpdate(st.sid)
    if v, ok := st.value[key]; ok {
        return v
    } else {
        return nil
    }
    return nil
}
//删除
func (st *SessionStore) Delete(key interface{}) error {
    delete(st.value, key)
    pder.SessionUpdate(st.sid)
    return nil
}
func (st *SessionStore) SessionID() string {
    return st.sid
}
//session来自内存 实现
type FromMemory struct {
    lock     sync.Mutex               //用来锁
    sessions map[string]*list.Element //用来存储在内存
    list     *list.List               //用来做 gc
}
func (frommemory *FromMemory) SessionInit(sid string) (session.Session, error) {
    frommemory.lock.Lock()
    defer frommemory.lock.Unlock()
    v := make(map[interface{}]interface{}, 0)
    newsess := &SessionStore{sid: sid, LastAccessedTime: time.Now(), value: v}
    element := frommemory.list.PushBack(newsess)
    frommemory.sessions[sid] = element
    return newsess, nil
}
func (frommemory *FromMemory) SessionRead(sid string) (session.Session, error) {
    if element, ok := frommemory.sessions[sid]; ok {
        return element.Value.(*SessionStore), nil
    } else {
        sess, err := frommemory.SessionInit(sid)
        return sess, err
    }
    return nil, nil
}
func (frommemory *FromMemory) SessionDestroy(sid string) error {
    if element, ok := frommemory.sessions[sid]; ok {
        delete(frommemory.sessions, sid)
        frommemory.list.Remove(element)
        return nil
    }
    return nil
}
func (frommemory *FromMemory) SessionGC(maxLifeTime int64) {
    frommemory.lock.Lock()
    defer frommemory.lock.Unlock()
    for {
        element := frommemory.list.Back()
        if element == nil {
            break
        }
        if (element.Value.(*SessionStore).LastAccessedTime.Unix() + maxLifeTime) <
            time.Now().Unix() {
            frommemory.list.Remove(element)
            delete(frommemory.sessions, element.Value.(*SessionStore).sid)
        } else {
            break
        }
    }
}
func (frommemory *FromMemory) SessionUpdate(sid string) error {
    frommemory.lock.Lock()
    defer frommemory.lock.Unlock()
    if element, ok := frommemory.sessions[sid]; ok {
        element.Value.(*SessionStore).LastAccessedTime = time.Now()
        frommemory.list.MoveToFront(element)
        return nil
    }
    return nil
}

memory.go里面是sesson.go 的Provider 和Session 接口的具体实现，通过这种方式可以灵活的扩展存取session数据的方式。

调用示例：

main.go

package main
import (
    _ "example/example/public/memory"  //这里修改成你存放menory.go相应的目录
    "example/example/public/session" //这里修改成你存放session.go相应的目录
    "fmt"
    "log"
    "net/http"
)
var globalSessions *session.Manager
func init() {
    var err error
    globalSessions, err = session.NewSessionManager("memory", "goSessionid", 3600)
    if err != nil {
        fmt.Println(err)
        return
    }
    go globalSessions.GC()
    fmt.Println("fd")
}
func sayHelloHandler(w http.ResponseWriter, r *http.Request) {
    cookie, err := r.Cookie("name")
    if err == nil {
        fmt.Println(cookie.Value)
        fmt.Println(cookie.Domain)
        fmt.Println(cookie.Expires)
    }
    //fmt.Fprintf(w, "Hello world!\n") //这个写入到w的是输出到客户端的
}
func login(w http.ResponseWriter, r *http.Request) {
    sess := globalSessions.SessionStart(w, r)
    val := sess.Get("username")
    if val != nil {
        fmt.Println(val)
    } else {
        sess.Set("username", "jerry")
        fmt.Println("set session")
    }
}
func loginOut(w http.ResponseWriter, r *http.Request) {
    //销毁
    globalSessions.SessionDestroy(w, r)
    fmt.Println("session destroy")
}
func main() {
    http.HandleFunc("/", sayHelloHandler) //    设置访问路由
    http.HandleFunc("/login", login)
    http.HandleFunc("/loginout", loginOut) //销毁
    log.Fatal(http.ListenAndServe(":8080", nil))
}

memory 包的应用方式用下划线，只需执行 memory的init方法即可。

运行 main.go

访问 http://localhost:8080/login 设置session

服务端输出：

set session

jerry

访问http://localhost:8080/loginout 销毁session

服务端输出：

session destroy

links

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