如何让XJC将XSD无类型元素生成为String而非Object？

背景 #

使用XJC配合maven-jaxb2-plugin生成JAXB类时，XSD中未指定类型的元素默认会被生成为Java的Object类型，需改为String类型，且尽量不修改原XSD文件。

当前配置 #

绑定文件（binding.xjb） #

<jxb:bindings
        version="1.0"
        xmlns:xs="http://www.w3.org/2001/XMLSchema"
        xmlns:jxb="http://java.sun.com/xml/ns/jaxb"
        xmlns:xjc="http://java.sun.com/xml/ns/jaxb/xjc">

    <jxb:globalBindings typesafeEnumMaxMembers="1000" collectionType="java.util.ArrayList">
        <xjc:simple/>
    </jxb:globalBindings>
    <jxb:bindings schemaLocation="../xsd/SOME_OTHER_XSD.xsd">
        <jxb:bindings node="//xs:complexType[@name='SOME_OTHER_TYPE']">
            <jxb:bindings node=".//xs:attribute[@name='Version']">
                <jxb:property name="VersionAttribute"/>
            </jxb:bindings>
        </jxb:bindings>
    </jxb:bindings>
    <jxb:bindings schemaLocation="../xsd/XSD_IN_QUESTION.xsd">
        <jxb:bindings node="//xs:complexType[@name='TYPE_IN_QUESTION']">
            <jxb:bindings node=".//xs:element[@name='Version']">
                <jxb:javaType name="java.lang.String" parseMethod="javax.xml.bind.annotation.adapters.CollapsedStringAdapter"/>
            </jxb:bindings>
        </jxb:bindings>
    </jxb:bindings>
</jxb:bindings>

XSD文件结构 #

<xs:schema
        xmlns:xs="http://www.w3.org/2001/XMLSchema"
        xmlns:ns2="ns2"
        xmlns="ns"
        targetNamespace="ns"
        elementFormDefault="qualified" attributeFormDefault="unqualified">

    <xs:element name="PARENT_ELEMENT" type="TYPE_IN_QUESTION"/>
    <xs:complexType name="TYPE_IN_QUESTION">
        <xs:sequence>
            <xs:element name="Version"/> <!-- No Type specified -->
        </xs:sequence>
    </xs:complexType>
</xs:schema>

遇到的错误 #

[ERROR] Error while parsing schema(s).Location [ file:/C:/[PATH]/src/main/resources/META-INF/binding/binding.xjb{25,128}].
com.sun.istack.SAXParseException2: compiler was unable to honor this javaType customization. It is attached to a wrong place, or its inconsistent with other bindings.
...
[ERROR] Error while parsing schema(s).Location [ file:/C:/[PATH]/src/main/resources/META-INF/xsd/XSD_IN_QUESTION.xsd{93,41}].
com.sun.istack.SAXParseException2: (the above customization is attached to the following location in the schema)

解决方案 #

错误原因 #

XSD中未指定类型的元素默认对应xsd:anyType，直接在元素节点上使用<jxb:javaType>是无效的，该自定义绑定不能直接附着在元素节点上。

1. 单个元素修复方案 #

在绑定文件中，针对目标元素通过<jxb:baseType>指定其基础类型为xs:string：

<jxb:bindings schemaLocation="../xsd/XSD_IN_QUESTION.xsd">
    <jxb:bindings node="//xs:complexType[@name='TYPE_IN_QUESTION']">
        <jxb:bindings node=".//xs:element[@name='Version']">
            <jxb:property>
                <jxb:baseType name="xs:string"/>
            </jxb:property>
        </jxb:bindings>
    </jxb:bindings>
</jxb:bindings>

2. 全局解决方案（推荐） #

如果需要所有未指定类型的元素都生成为String，修改<globalBindings>，添加全局类型映射，将xsd:anyType直接映射为java.lang.String：

<jxb:globalBindings typesafeEnumMaxMembers="1000" collectionType="java.util.ArrayList">
    <xjc:simple/>
    <!-- 全局映射xsd:anyType到String，同时使用CollapsedStringAdapter处理字符串 -->
    <xjc:javaType name="java.lang.String" xmlType="xs:anyType"
        parseMethod="javax.xml.bind.annotation.adapters.CollapsedStringAdapter.unmarshal"
        printMethod="javax.xml.bind.annotation.adapters.CollapsedStringAdapter.marshal"/>
</jxb:globalBindings>

该配置会自动将所有XSD中未指定类型的元素生成为String类型，无需逐个元素配置。

内容的提问来源于stack exchange，提问作者Jonas Seidl