缺少实际组成一个 writer 并将每个元素附加到字符串上。有没有办法让 JAXB 编码器编码一个对象列表，我可以在其中为其指定顶部元素的名称？

我觉得我很接近这个

//http://blog.bdoughan.com/2012/07/jaxb-no-annotations-required.html
public <T> String jaxb(Collection<T> o, Class<T> clazz, String plural){
    try {
        ArrayList<T> al = new ArrayList<T>(o.size());
        al.addAll(o);
        JAXBContext jc = JAXBContext.newInstance(ArrayList.class);
        JAXBElement<ArrayList> amenity = new JAXBElement(new QName(plural), ArrayList.class, al);
        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        StringWriter writer = new StringWriter();
        marshaller.marshal(amenity, writer);
        return writer.toString();
    } catch (JAXBException e) {
        throw new RuntimeException(e);
    }
}

但结果仍然是一个空列表

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<pluralName/>

有没有办法不用手动将 xml 字符串粘贴在一起就可以做到这一点？

更新

在 Michael Glavassevich 的帮助下，我已经能够做到这一点，但需要注意的是，各个元素是 <Item>

//http://blog.bdoughan.com/2012/07/jaxb-no-annotations-required.html
@SuppressWarnings({ "unchecked", "rawtypes" })
public <T> String jaxb(Collection<T> elements, Class<T> elementClass, String plural){
    try {
        T[] array = (T[]) Array.newInstance(elementClass, elements.size());
        elements.toArray(array);
        JAXBContext jc = JAXBContext.newInstance(array.getClass());
        JAXBElement<T[]> topElement = new JAXBElement(new QName(plural), array.getClass(), array);
        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        StringWriter writer = new StringWriter();
        marshaller.marshal(topElement, writer);
        return writer.toString();
    } catch (JAXBException e) {
        throw new RuntimeException(e);
    }
}

那么结果就变成了

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Basketballs>
    <item>basketball one</item>
    <item>basketball two</item>
</Basketballs>

最佳答案

如果您不想创建包装类，您可以将集合转换为数组，将该数组放在 JAXBElement 中，然后对其进行编码。

例如:

public class JAXBArrayWriter {

    public static class Item {
        @XmlValue
        protected String value;

        public Item() {}

        public Item(String value) {
            this.value = value;
        }
    }

    public static void main (String [] args) throws Exception {
        List<Item> items = new ArrayList<Item>();
        items.add(new Item("one"));
        items.add(new Item("two"));
        JAXBContext jc = JAXBContext.newInstance(Item[].class);
        JAXBElement<Item[]> root = new JAXBElement<Item[]>(new QName("items"), 
                Item[].class, items.toArray(new Item[items.size()]));
        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        StringWriter writer = new StringWriter();
        marshaller.marshal(root, writer);
        System.out.println(writer.toString());
    }
}

生成以下文档:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<items>
    <item>one</item>
    <item>two</item>
</items>

关于java - 我如何在不制作包装器类的情况下编码 Jaxb 元素列表？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/35444507/