kotlin使用spring mvc（一）

過濾器Filter，是Servlet的一種技術。可經過Filter，對請求進行攔截，好比判斷用戶是否登陸、驗證黑名單等而且可對請求進行預處理。

接下來介紹使用WebFilter配置過濾器並實現讀取cookie判斷用戶是否登錄

編寫Filter類

/註冊器名稱爲customFilter,攔截的url爲全部
@WebFilter(filterName = "customFilter",urlPatterns = ["/*"])
class CustomFilter:Filter {
    var logger = LoggerFactory.getLogger(this::class.java)!!
    override fun destroy() {
        logger.info("CustomFilter destroy")
    }

    override fun doFilter(request: ServletRequest?, response: ServletResponse?, chain: FilterChain?) {

        val httpServletRequest = request as? HttpServletRequest
        if (httpServletRequest != null && response != null) {
            //獲取用戶cookie
            val userCookie = httpServletRequest.cookies?.firstOrNull { it.name?.toLowerCase() == "userid" }
            //檢查cookie的正確性
            val userId = userCookie?.value?.toIntOrNull() ?: 0
            if(userId <= 0){
                val accept = httpServletRequest.getHeader("Accept")
                if (accept?.contains("json") == true) {
                    response.contentType = MediaType.APPLICATION_JSON_VALUE
                    val str = ObjectMapperExtension.instance.writeValueAsString(CommonResult(null, false, "No Access Token"))
                    response.writer.print(str)

                } else {
                    response.contentType = MediaType.ALL_VALUE
                    response.writer.print("No Access Token")
                }
                return
            }
        }
        logger.info("CustomFilter start")
        chain?.doFilter(request,response)
        logger.info("CustomFilter complete")
    }

    override fun init(filterConfig: FilterConfig?) {
        logger.info("CustomFilter init")
    }
}

而後在啓動類加入@ServletComponentScan註解，確保能夠掃描到CustomFilter

@SpringBootApplication
@ServletComponentScan
class Demo1Application

fun main(args: Array<String>) {
    runApplication<Demo1Application>(*args)
}

隨便請求一下，發現返回，咱們的過濾器生效了

HTTP/1.1 200
Content-Type: */*;charset=ISO-8859-1
Content-Length: 15
Date: Thu, 18 Oct 2018 07:23:58 GMT

No Access Token

那麼試一下接受json格式，添加請求頭

Accept: application/json

返回了咱們想要的json

HTTP/1.1 200
Content-Type: application/json;charset=ISO-8859-1
Content-Length: 52
Date: Thu, 18 Oct 2018 07:27:08 GMT

{"data":null,"succes":false,"msg":"No Access Token"}

若是加上Cookie（以下），那麼就能夠正常經過咱們的過濾器了

Cookie: userid=3;