使用空字段的JAXB编组 [英] JAXB Marshalling with null fields

问题描述

这是一个非常简单的请求，但我没有办法做到这一点。

This is a pretty simple request, but I just didn't find a way to do it.

我基本上是想在JAXB中设置一个角色表示只要遇到空字段，而不是在输出中忽略它，就将其设置为空值。所以对于班级来说：

I'm basically trying to set up a role in JAXB which says that whenever an null field is encountered, instead of ignoring it in the output, set it to an empty value. So for the class :

@XMLRootElement
Class Foo {
   Integer num;
   Date date;
….
}

如果日期字段为空，则已将此编组到XML文件中，我的输出中没有该元素。我想要做的是包括输出中的所有字段;如果它们为null，则将它们替换为 - 例如空白。所以输出应该是：

When this has been marshalled into the XML file if the date field is null, my output does not have that element in it. What I want to do is include all the fields in the output; and if they are null, replace them with - say a blank. So the output should be :

<foo>
  <num>123</num>
  <date></date>
</foo>

谢谢，

Jalpesh。

推荐答案

谢谢你的回答。

Chris Dail - 我试过你的方法，它并没有真正做我想要的。尽管为我的字段定义了一个默认值，JAXB仍然忽略了我的空值。

Chris Dail - I tried your approach, and it didn't really do what I wanted. JAXB was still ignoring my null values, in spite of defining a default value for my fields.

在泽西论坛的某个人向我指出文档后，我偶然发现了答案部分 2.2.12.8无价值。

I did stumble across the answer after somebody in the Jersey forums pointed me to documentation section 2.2.12.8 No Value.

基本上，我所要做的就是将以下内容添加到我的字段中：

Basically, all I had to do was to add the following to my fields :

@XmlElement(nillable = true) 

一旦我添加了它，JAXB会显示这些字段当将它们编组为XML时：

Once I added that, JAXB would show up those fields when marshalling them to XML like this:

...
<num>5</num>
<date xsi:nil="true" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"/>
....

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