## 4.0.0-alpha.2 -> 4.0.0-alpha.3
**New**
A **Response Engine** gives you the freedom to create/change the
render/response writer for
- `context.JSON`
- `context.JSONP`
- `context.XML`
- `context.Text`
- `context.Markdown`
- `context.Data`
- `context.Render("my_custom_type",mystructOrData{},
iris.RenderOptions{"gzip":false,"charset":"UTF-8"})`
- `context.MarkdownString`
- `iris.ResponseString(...)`
**Fix**
- https://github.com/kataras/iris/issues/294
**Small changes**
- `iris.Config.Charset`, before alpha.3 was `iris.Config.Rest.Charset` &
`iris.Config.Render.Template.Charset`, but you can override it at
runtime by passinth a map `iris.RenderOptions` on the `context.Render`
call .
- `iris.Config.IsDevelopment` , before alpha.1 was
`iris.Config.Render.Template.IsDevelopment`
**Websockets changes**
No need to import the `github.com/kataras/iris/websocket` to use the
`Connection` iteral, the websocket moved inside `kataras/iris` , now all
exported variables' names have the prefix of `Websocket`, so the old
`websocket.Connection` is now `iris.WebsocketConnection`.
Generally, no other changes on the 'frontend API', for response engines
examples and how you can register your own to add more features on
existing response engines or replace them, look
[here](https://github.com/iris-contrib/response).
**BAD SIDE**: E-Book is still pointing on the v3 release, but will be
updated soon.
**Sessions were re-written **
- Developers can use more than one 'session database', at the same time,
to store the sessions
- Easy to develop a custom session database (only two functions are
required (Load & Update)), [learn
more](https://github.com/iris-contrib/sessiondb/blob/master/redis/database.go)
- Session databases are located
[here](https://github.com/iris-contrib/sessiondb), contributions are
welcome
- The only frontend deleted 'thing' is the: **config.Sessions.Provider**
- No need to register a database, the sessions works out-of-the-box
- No frontend/API changes except the
`context.Session().Set/Delete/Clear`, they doesn't return errors
anymore, btw they (errors) were always nil :)
- Examples (master branch) were updated.
```sh
$ go get github.com/iris-contrib/sessiondb/$DATABASE
```
```go
db := $DATABASE.New(configurationHere{})
iris.UseSessionDB(db)
```
> Note: Book is not updated yet, examples are up-to-date as always.
