chalice 。如何使用嵌套列表保存实体？

Question

有以下实体:

class Letter {
    String email          
    String subject
    String content

    List attachments

    static hasMany = [attachments : Attachment]

    static constraints = {
        subject nullable:true, blank:true
        content nullable:true
        email email:true
        attachments nullable:true
    }

和

class Attachment {
    String fileName
    Integer size
    byte[] data
    Letter letter

    static belongsTo = [letter:Letter]
    static constraints = {
        fileName nullable: true, blank: true
        size nullable: true, blank: true
        data nullable: true, maxSize: 1024*1024*5 /*5MB*/
    }

}

在单独的模块中创建一封信，并将附件添加到此列表中。没有坚持。代码:

public Letter createLetterFromMessage(Message message) {
    Letter letter = new Letter()

    def addr = message.getFrom()[0]
    if (addr instanceof InternetAddress) {
        def inAddr = addr as InternetAddress
        letter.email = inAddr.address
    }

    letter.subject = message.subject

    def part = message as Part
    letter.attachments = getAttachmetList(letter,part.getContent())//list of not persisted attaches

    return letter
}

在另一个模块中，我需要保存一封已添加附件列表的信件。
代码:

    public void onSuccess(List<Letter> letters) {
        for (Letter letter : letters) {
            if(letterService.save(letter)){
                log.debug "Letter saved with id = ${letter.id}."
                //do some work
            } else
                log.debug "Letter not saved and not added to execution context!"
        }
   }

这该怎么做？

文档中的示例在这里不起作用。

def book = new Book(title: 'Misery')
author.addToBooks(book)
author.save()

Answer 1

我想如果您只是将字母实例分配给 letter每个附件的属性，然后保存字母实例，它应该将保存传播到每个附件:

letter.attachments.each{ it.letter = letter }
letter.save()

这本质上是 addTo*方法确实