build-web-application-with-golang/6.3.md

#6.3 session存储 上一节我们介绍了Session管理器的实现原理，定义了存储session的接口，这小节我们将示例一个基于内存的session存储接口的实现，其他的存储方式，读者可以自行参考示例来实现，内存的实现请看下面的例子代码

package memory

import (
	"github.com/astaxie/session/"
	"time"
	"container/list"
)

var d = &Provider{list:list.New()}

type SessionStore struct {
	sid          string                      //session id唯一标示	  	
	timeAccessed time.Time                   //最后访问时间	  	
	value        map[interface{}]interface{} //session里面存储的值
}

func (this *SessionStore) Set(key, value interface{}) bool {
	this.value[key] = value
	d.SessionUpdate(this.sid)
	return true
}

func (this *SessionStore) Get(key interface{}) interface{} {
	d.SessionUpdate(this.sid)
	if v, ok := this.value[key]; ok {
		return v
	} else {
		return ""
	}
}

func (this *SessionStore) Del(key interface{}) bool {
	delete(this.value, key)
	d.SessionUpdate(this.sid)
	return true
}

type Provider struct {
	lock     sync.Mutex               //用来锁
	sessions map[string]*SessionStore //用来存储在内存
	list     *list.List               //用来做gc
}

func (this *Provider) SessionInit(sid string) (session.Session, error) {
	this.lock.Lock()
	defer this.lock.Unlock()
	v := make(map[interface{}]interface{}, 0)
	newsess := &SessionStore{"sid": sid, "timeAccessed": time.Now(), "value": v}
	this.sessions[sid] = newsess
	this.list.Push(newsess)
	return newsess
}

func (this *Provider) SessionRead(sid string) (session.Session, error) {
	if s, ok := this.sessions[sid]; ok {
		return s, nil
	} else {
		sess, err := this.SessionInit(sid)
		return sess, err
	}
}

func (this *Provider) SessionDestroy(sid string) bool {
	if s, ok := this.sessions[sid]; ok {
		delete(this.table, sid)
		this.list.Remove(s)
		return true
	} else {
		return false
	}
}

func (this *Provider) SessionGC(maxlifetime int64) {
	this.lock.Lock()
	defer this.lock.Unlock()

	for {
		element := this.list.Back()
		if element == nil {
			break
		}
		if (element.Value.(*SessionStore).timeAccessed.Unix() + maxlifetime) < time.Now().Unix() {
			this.list.Remove(element)
			delete(this.table, element.Value.(*SessionStore).sid)
		} else {
			break
		}
	}
}

func (this *Provider) SessionUpdate(sid string) bool {
	this.lock.Lock()
	defer this.lock.Unlock()
	if element, ok := this.sessions[sid]; ok {
		element.Value.(*SessionStore).value = s.value
		this.moveToFront(element)
		return true
	} else {
		return false
	}
}

func (this *Provider) moveToFront(element *list.Element) {
	this.lock.Lock()
	defer this.lock.Unlock()
	element.Value.(*SessionStore).timeAccessed = time.Now()
	this.list.MoveToFront(element)
}

func init() {
	session.Register("memory", d)
}

上面这个代码实现了一个内存存储的session机制。通过init函数注册到session管理器中。这样就可以方便的调用了。

links

• 目录
• 上一节: Go如何使用session
• 下一节: 预防session劫持

LastModified

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