Java 使用JAXB，如何将具有属性定义类型的XMLelement解组到基于该属性的对象？

我的应用程序正在接收编组为XML的对象负载，例如：

<targetedMessage>
   <sender>external application</sender>
   <payload class="class.path.from.external.application.Foo">
      <id>1</id>
   </payload>
</targetedMessage>

枚举可用于根据外部类路径查找对象的本地类：

public enum ForeignClass {

FOO("class.path.from.external.application.Foo", Foo.class),
BAR("class.path.from.external.application.Bar", Bar.class);

public static getClassFromForeignClassPath(String foreignClassPath) {
  // return class
}

我还有一个

TargetedMessage

类来捕获有关消息本身的元信息：

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class TargetedMessage {
    private String sender;
    private Baz baz;
}

正确解组XML需要什么注释？我尝试在

TargetedMessage

类中的

Baz

字段上使用XmlAdapter，但ValueType参数始终为null

---

@xmldattribute

似乎也不起作用，因为

类

属性的值与其对应的本地类名不同。

您至少有两个选项。首先，可以将“class”属性映射到字符串枚举，并在TargetedMessage的#getBaz（）方法中实现实例化逻辑。XSD如下所示（根据需要重命名类型）：

其次，您可以转换初始XML，以便根据其“class”属性内容重命名“payload”元素。例如，它可以是“payloadFoo”、“payloadBar”等。然后，您可以将其直接映射到所需的类。相应的XSD如下所示

<?xml version="1.0" encoding="UTF-8"?>
<schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.example.org/XMLSchema" xmlns:tns="http://www.example.org/XMLSchema" elementFormDefault="qualified">

    <simpleType name="simpleTypeFoo">
        <restriction base="string">
            <enumeration value="class.path.from.external.application.Foo"></enumeration>
        </restriction>
    </simpleType>

    <simpleType name="simpleTypeBar">
        <restriction base="string">
            <enumeration value="class.path.from.external.application.Bar"></enumeration>
        </restriction>
    </simpleType>

    <complexType name="payloadTypeFoo">
        <sequence>
            <element name="id" type="string"></element>
        </sequence>
        <attribute name="class" type="tns:simpleTypeFoo"></attribute>
    </complexType>

    <complexType name="payloadTypeBar">
        <sequence>
            <element name="id" type="string"></element>
        </sequence>
        <attribute name="class" type="tns:simpleTypeBar"></attribute>
    </complexType>

    <complexType name="payloadType">
        <choice>
            <element name="payloadFoo" type="tns:payloadTypeFoo" minOccurs="0" maxOccurs="1"></element>
            <element name="payloadBar" type="tns:payloadTypeBar" minOccurs="0" maxOccurs="1"></element>
        </choice>
    </complexType>

    <complexType name="targetedMessageType">
        <sequence>
            <element name="sender" type="string"></element>
            <element name="payload" type="tns:payloadType"></element>
        </sequence>
    </complexType>
</schema>

<?xml version="1.0" encoding="UTF-8"?>
<schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.example.org/XMLSchema" xmlns:tns="http://www.example.org/XMLSchema" elementFormDefault="qualified">

    <include schemaLocation=""></include>

    <simpleType name="simpleTypeClass">
        <restriction base="string">
            <enumeration value="class.path.from.external.application.Foo"></enumeration>
            <enumeration value="class.path.from.external.application.Bar"></enumeration>
        </restriction>
    </simpleType>

    <complexType name="payloadType">
        <sequence>
            <element name="id" type="string"></element>
        </sequence>
        <attribute name="class" type="tns:simpleTypeClass"></attribute>
    </complexType>

    <complexType name="targetedMessageType">
        <sequence>
            <element name="sender" type="string"></element>
            <element name="payload" type="tns:payloadType"></element>
        </sequence>
    </complexType>
</schema>

<?xml version="1.0" encoding="UTF-8"?>
<schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.example.org/XMLSchema" xmlns:tns="http://www.example.org/XMLSchema" elementFormDefault="qualified">

    <simpleType name="simpleTypeFoo">
        <restriction base="string">
            <enumeration value="class.path.from.external.application.Foo"></enumeration>
        </restriction>
    </simpleType>

    <simpleType name="simpleTypeBar">
        <restriction base="string">
            <enumeration value="class.path.from.external.application.Bar"></enumeration>
        </restriction>
    </simpleType>

    <complexType name="payloadTypeFoo">
        <sequence>
            <element name="id" type="string"></element>
        </sequence>
        <attribute name="class" type="tns:simpleTypeFoo"></attribute>
    </complexType>

    <complexType name="payloadTypeBar">
        <sequence>
            <element name="id" type="string"></element>
        </sequence>
        <attribute name="class" type="tns:simpleTypeBar"></attribute>
    </complexType>

    <complexType name="payloadType">
        <choice>
            <element name="payloadFoo" type="tns:payloadTypeFoo" minOccurs="0" maxOccurs="1"></element>
            <element name="payloadBar" type="tns:payloadTypeBar" minOccurs="0" maxOccurs="1"></element>
        </choice>
    </complexType>

    <complexType name="targetedMessageType">
        <sequence>
            <element name="sender" type="string"></element>
            <element name="payload" type="tns:payloadType"></element>
        </sequence>
    </complexType>
</schema>