Java 使用泛型和基类时，Jaxb XML名称空间不正确

我在两个名称空间中有四个类，一个包中的两个用作另一个包中两个的基类，例如：

@XmlAccessorType(XmlAccessType.FIELD)
public class Foo<T extends Bar> {

    @XmlElement(name="Bar")
    private List<T> bar;

}

派生类如下所示：

@XmlType(name="Foo" namespace="urn:foo/Bar")
@XmlRootElement(name="Foo")
public class DerivedFoo extends Foo<DerivedBar> {
    // something
}

在包含基类的包中，没有

package info.java

或任何包含名称空间信息的内容。包含派生类的包具有所有命名空间信息

输出XML对

DerivedFoo

类进行了适当的（排序）命名，但将

DerivedBar

类分配给了一个未命名的名称空间，基本上：

<Response xmlns:ns2="urn:foo/Bar">
  <ns2:Foo>
    <Bar>
    </Bar>
  </ns2:Foo>
</Response>

---

我认为您需要的是和的组合。使用

@xmlementref

注释就像说“这里有一件事；看看它的

@XmlRootElement

注释，找出如何序列化它。”

下面的设置似乎符合您的要求。基类：

package base;

@XmlAccessorType(XmlAccessType.FIELD)
public class Foo<T extends Bar> {

    @XmlElementRef
    public List<T> bar;

}

---

从我的测试来看很不错：

@Test
public void tryIt() throws Exception {
    JAXBContext context = JAXBContext.newInstance(Request.class, DerivedFoo.class, DerivedBar.class);

    Marshaller marshaller = context.createMarshaller();
    marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);

    Request request = new Request();
    DerivedFoo foo = new DerivedFoo();
    request.foo = foo;
    foo.bar = new ArrayList<DerivedBar>();
    foo.bar.add(new DerivedBar());

    marshaller.marshal(request, System.out);
}

---

嵌套类型可能不太在意，但我打赌使用

Request

的人可能不会识别这些元素名称。

您能否分享重现问题的步骤（可能是命令行调用或maven插件配置）？

package base;

@XmlAccessorType(XmlAccessType.FIELD)
public class Foo<T extends Bar> {

    @XmlElementRef
    public List<T> bar;

}

package base;

@XmlAccessorType(XmlAccessType.FIELD)
public class Bar {
    // something
}

package base;

@XmlRootElement(name = "Request")
@XmlAccessorType(XmlAccessType.FIELD)
public class Request {

    @XmlElementRef
    public Foo<?> foo;
}

package derived;

@XmlRootElement(name = "Foo", namespace = "urn:foo/Bar")
public class DerivedFoo extends Foo<DerivedBar> {
    // something
}

package derived;

@XmlRootElement(name = "Bar", namespace = "urn:foo/Bar")
public class DerivedBar extends Bar {
    // something
}

@Test
public void tryIt() throws Exception {
    JAXBContext context = JAXBContext.newInstance(Request.class, DerivedFoo.class, DerivedBar.class);

    Marshaller marshaller = context.createMarshaller();
    marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);

    Request request = new Request();
    DerivedFoo foo = new DerivedFoo();
    request.foo = foo;
    foo.bar = new ArrayList<DerivedBar>();
    foo.bar.add(new DerivedBar());

    marshaller.marshal(request, System.out);
}

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Request xmlns:ns2="urn:foo/Bar">
    <ns2:Foo>
        <ns2:Bar/>
    </ns2:Foo>
</Request>

<Request xmlns:ns2="urn:rock/roll" xmlns:ns3="urn:yummy">
    <ns2:FooFighters>
        <ns3:TikiBar/>
    </ns2:FooFighters>
</Request>