grails - Grails findBy返回(未保存)对象，导致render()出现空问题

Question

我正在尝试将GSP模板呈现为PDF并通过电子邮件发送，但遇到了一个奇怪的问题。我使用Grails findBy*方法获取数据，

def fax(Integer id) {
    def transcriptInstance = Transcript.findById(id)
    def userInstance = User.findById(transcriptInstance.submitter)

    def m = [userInstance: userInstance, transcriptInstance: transcriptInstance]

    ByteArrayOutputStream bytes = pdfRenderingService.render(template: "/transcript/_pdf", model: m)

    mailService.sendMail {
        to <my email> // for testing
        from <my email> // for testing
        subject "PDF Attachment";
        attachBytes "transcript.pdf", "application/pdf", bytes.toByteArray()
        body "PDF attachment"
    }
}

但是用户实例返回为 User : (unsaved)，而我在 Cannot invoke method render() on null object行上收到错误 ByteArrayOutputStream bytes = pdfRenderingService.render(template: "/transcript/_pdf", model: m)。用户肯定保存在数据库中，这是我第一次遇到此问题。知道出了什么问题吗？

编辑:

这段代码现在生成一个pdf，但是我无法通过mailService发送它。

def fax(Integer id) {
    def transcriptInstance  = Transcript.findById(id)
    def userInstance = User.findById(transcriptInstance.submitter)

    def m = [userInstance: userInstance, transcriptInstance: transcriptInstance]

    ByteArrayOutputStream pdfBytes = pdfRenderingService.render(template: '/transcript/pdf', model: m)
    new File('test.pdf').withOutputStream { 
        it.write pdfBytes.toByteArray()
    }

    mailService.sendMail {
        multipart true
        to <my email> // for testing
        from <my email> // for testing
        subject "PDF Attachment";
        attachBytes "transcript.pdf", "application/pdf", <WHAT DO I PUT HERE?>
        body "PDF attachment"
    }
}

我已经尝试了一些尝试，但是没有任何效果。有任何想法吗？

Answer 1

获得ByteArrayOutputStream后，可以调用toByteArray()以获取mailService所需的字节。

def fax(Integer id) {
    def transcriptInstance  = Transcript.findById(id)
    def userInstance = User.findById(transcriptInstance.submitter)

    def m = [userInstance: userInstance, transcriptInstance: transcriptInstance]

    ByteArrayOutputStream pdfBytes = pdfRenderingService.render(template: '/transcript/pdf', model: m)

    mailService.sendMail {
        multipart true
        to <my email> // for testing
        from <my email> // for testing
        subject "PDF Attachment";
        attachBytes "transcript.pdf", "application/pdf", pdfBytes.toByteArray()
        body "PDF attachment"
    }
}