在GSP中導入和使用groovy代碼

Question

我試圖在GSP中使用groovy函數。 請幫忙，因為我要把頭發弄到這里。

在我的GSP頂部，我有<%@ page import = company.ConstantsFile %>

在我的GSP里面我有

<p>
I have been in the heating and cooling business for <%(ConstantsFile.daysBetween())%>
</p>

和我的ConstantsFile.groovy

package company

import static java.util.Calendar.*

class ConstantsFile {

    def daysBetween() {
        def startDate = Calendar.instance
        def m = [:]
        m[YEAR] = 2004
        m[MONTH] = "JUNE"
        m[DATE] = 26
        startDate.set(m)
        def today = Calendar.instance

        render today - startDate
    }
}

我也嘗試將renter更改為puts，system.out等，但這不是我的主要問題。

Error 500: Internal Server Error
URI
/company/
Class
java.lang.NullPointerException
Message
Cannot invoke method daysBetween() on null object

所以我試試

<p>
    I have been in the heating and cooling business for <%(new ConstantsFile.daysBetween())%>
    </p>

但后來我明白了

Class: org.codehaus.groovy.control.MultipleCompilationErrorsException

unable to resolve class ConstantsFile.daysBetween @ line 37, column 1. (new ConstantsFile.daysBetween()) ^ 1 error

請有人幫助我或指向一個顯示該做什么的網站..我已經嘗試了谷歌搜索和一切談論ag：選擇或其他類型的標簽...我只想輸出像我用過的功能的結果在JSP中。

Answer 1

首先，您的GSP導入應該是：

<%@ page import="company.ConstantsFile" %>

其次，你的daysBetween應該是靜態的（它更有意義）並且你不會從控制器以外的任何東西渲染：

class ConstantsFile {

    static daysBetween() {
        def startDate = Calendar.instance
        def m = [:]
        m[YEAR] = 2004
        m[MONTH] = "JUNE"
        m[DATE] = 26
        startDate.set(m)
        def today = Calendar.instance

        return today - startDate
    }
}

第三，通過以下方式訪問它：

<p>I have been in the heating and cooling business for ${ConstantsFile.daysBetween}</p>

最后，你應該使用taglib。 我正在編輯我的帖子以添加一個例子

class MyTagLib {

  static namespace = "my"

  def daysBetween = { attr ->
     out << ConstantsFile.daysBetween()
  }
}

然后在您的GSP中使用

<p>I have been in the heating and cooling business for <my:daysBetween /></p>