java、xsd 和编码 : jre bug, 我的错还是 xsd 问题？

Question

我在将 JAXB 模型树编码为 xml 文件时遇到问题。

我使用 xjc 创建了这些模型类。 我无法修改这些 xml 模式 - 它们是在外部定义的(类似于 this 问题，缺少答案)。

根据 xjc(和其他 xml 工具)，xml 模式文件似乎是有效的。 我在问是否

• 这是一个 java/jre 错误或
• 我做错了什么或者
• 如果模式文件有些错误

以及如何解决这个问题。

我得到的异常是:

com.sun.istack.internal.SAXException2: "com.mypackage.A" is substituting "com.mypackage.BaseType", but "com.mypackage.A" is bound to an anonymous type.
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.reportError(XMLSerializer.java:237)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsXsiType(XMLSerializer.java:652)
    at com.sun.xml.internal.bind.v2.runtime.property.SingleElementNodeProperty.serializeBody(SingleElementNodeProperty.java:143)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:343)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsXsiType(XMLSerializer.java:685)
    at com.sun.xml.internal.bind.v2.runtime.property.ArrayElementNodeProperty.serializeItem(ArrayElementNodeProperty.java:54)
    at com.sun.xml.internal.bind.v2.runtime.property.ArrayElementProperty.serializeListBody(ArrayElementProperty.java:157)
    at com.sun.xml.internal.bind.v2.runtime.property.ArrayERProperty.serializeBody(ArrayERProperty.java:144)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:343)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:335)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsXsiType(XMLSerializer.java:685)
    at com.sun.xml.internal.bind.v2.runtime.property.SingleElementNodeProperty.serializeBody(SingleElementNodeProperty.java:143)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:343)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:335)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsXsiType(XMLSerializer.java:685)
    at com.sun.xml.internal.bind.v2.runtime.property.SingleElementNodeProperty.serializeBody(SingleElementNodeProperty.java:143)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:343)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsXsiType(XMLSerializer.java:685)
    at com.sun.xml.internal.bind.v2.runtime.property.SingleElementNodeProperty.serializeBody(SingleElementNodeProperty.java:143)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:343)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsXsiType(XMLSerializer.java:685)
    at com.sun.xml.internal.bind.v2.runtime.property.SingleElementNodeProperty.serializeBody(SingleElementNodeProperty.java:143)
    at com.sun.xml.internal.bind.v2.runtime.ElementBeanInfoImpl$1.serializeBody(ElementBeanInfoImpl.java:146)
    at com.sun.xml.internal.bind.v2.runtime.ElementBeanInfoImpl$1.serializeBody(ElementBeanInfoImpl.java:116)
    at com.sun.xml.internal.bind.v2.runtime.ElementBeanInfoImpl.serializeBody(ElementBeanInfoImpl.java:318)
    at com.sun.xml.internal.bind.v2.runtime.ElementBeanInfoImpl.serializeRoot(ElementBeanInfoImpl.java:325)
    at com.sun.xml.internal.bind.v2.runtime.ElementBeanInfoImpl.serializeRoot(ElementBeanInfoImpl.java:61)
    at com.sun.xml.internal.bind.v2.runtime.property.ArrayReferenceNodeProperty.serializeListBody(ArrayReferenceNodeProperty.java:103)
    at com.sun.xml.internal.bind.v2.runtime.property.ArrayERProperty.serializeBody(ArrayERProperty.java:144)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:343)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsXsiType(XMLSerializer.java:685)
    at com.sun.xml.internal.bind.v2.runtime.property.SingleElementNodeProperty.serializeBody(SingleElementNodeProperty.java:143)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:343)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsXsiType(XMLSerializer.java:685)
    at com.sun.xml.internal.bind.v2.runtime.property.ArrayElementNodeProperty.serializeItem(ArrayElementNodeProperty.java:54)
    at com.sun.xml.internal.bind.v2.runtime.property.ArrayElementProperty.serializeListBody(ArrayElementProperty.java:157)
    at com.sun.xml.internal.bind.v2.runtime.property.ArrayERProperty.serializeBody(ArrayERProperty.java:144)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:343)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsXsiType(XMLSerializer.java:685)
    at com.sun.xml.internal.bind.v2.runtime.ElementBeanInfoImpl$1.serializeBody(ElementBeanInfoImpl.java:141)
    at com.sun.xml.internal.bind.v2.runtime.ElementBeanInfoImpl$1.serializeBody(ElementBeanInfoImpl.java:116)
    at com.sun.xml.internal.bind.v2.runtime.ElementBeanInfoImpl.serializeBody(ElementBeanInfoImpl.java:318)
    at com.sun.xml.internal.bind.v2.runtime.ElementBeanInfoImpl.serializeRoot(ElementBeanInfoImpl.java:325)
    at com.sun.xml.internal.bind.v2.runtime.ElementBeanInfoImpl.serializeRoot(ElementBeanInfoImpl.java:61)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsRoot(XMLSerializer.java:483)
    at com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.write(MarshallerImpl.java:308)
    at com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.marshal(MarshallerImpl.java:236)
    at javax.xml.bind.helpers.AbstractMarshallerImpl.marshal(AbstractMarshallerImpl.java:95)

(java 7 更新 45)

Answer 1

长话短说

java, xsd & marshalling: jre bug, my fault or xsd issues?

这是你的错:)。继续阅读原因。

---

Java 模型

下面是一个 Java 模型，它基于您问题中暗示的模型，可用于产生与您所看到的相同的异常。

根

下面是一个具有一个属性的根对象。该属性的类型有两个子类。其中一个子类 (B) 对应命名类型，另一个 (A) 对应匿名类型。

package com.mypackage;

import javax.xml.bind.annotation.XmlRootElement;
@XmlRootElement
public class Root {

    private BaseType baseType;

    public BaseType getBaseType() {
        return baseType;
    }

    public void setBaseType(BaseType baseType) {
        this.baseType = baseType;
    }

}

基本类型

这是父类(super class)。它有两个子类:A 和 B。

package com.mypackage;

import javax.xml.bind.annotation.XmlSeeAlso;

@XmlSeeAlso({A.class, B.class})
public class BaseType {

}

一个

A 类对应于匿名复杂类型。匿名类型用 @XmlType(name="") 注释表示。

package com.mypackage;

import javax.xml.bind.annotation.XmlType;

@XmlType(name="")
public class A extends BaseType {

}

B

B 类对应于命名的复杂类型b。默认值与 @XmlType(name="b") 相同。

package com.mypackage;

public class B extends BaseType {

}

演示代码 - 重现错误

演示

当 Root 类的 baseType 属性是子类之一时，将添加 xsi:type 属性来限定元素 (类似于 Java 中的强制转换)。该实例需要对应于命名的复杂类型。在这种情况下，A 没有。

package com.mypackage;

import javax.xml.bind.*;

public class Demo {

    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(Root.class);

        Root root = new Root();
        BaseType baseType = new A(); // Invalid Value
        root.setBaseType(baseType);

        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.marshal(root, System.out);
    }

}

异常

这会导致以下异常。如异常所述 A 不是 BaseType 的有效替代品，因为它对应于匿名复杂类型，因为它对应于匿名类型，所以它没有xsi:type 属性的必要值。

Exception in thread "main" javax.xml.bind.MarshalException
 - with linked exception:
[com.sun.istack.internal.SAXException2: Instance of "com.mypackage.A" is substituting "com.mypackage.BaseType", but "com.mypackage.A" is bound to an anonymous type.]
    at com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.write(MarshallerImpl.java:311)
    at com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.marshal(MarshallerImpl.java:236)
    at javax.xml.bind.helpers.AbstractMarshallerImpl.marshal(AbstractMarshallerImpl.java:95)
    at com.mypackage.Demo.main(Demo.java:16)
Caused by: com.sun.istack.internal.SAXException2: Instance of "com.mypackage.A" is substituting "com.mypackage.BaseType", but "com.mypackage.A" is bound to an anonymous type.
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.reportError(XMLSerializer.java:237)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsXsiType(XMLSerializer.java:652)
    at com.sun.xml.internal.bind.v2.runtime.property.SingleElementNodeProperty.serializeBody(SingleElementNodeProperty.java:143)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:343)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsSoleContent(XMLSerializer.java:582)
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeRoot(ClassBeanInfoImpl.java:325)
    at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsRoot(XMLSerializer.java:483)
    at com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.write(MarshallerImpl.java:308)
    ... 3 more

演示代码 - 有效

演示

如果您指定了另一个子类 B 而不是 A，它对应于一个命名的复杂类型。

package com.mypackage;

import javax.xml.bind.*;

public class Demo {

    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(Root.class);

        Root root = new Root();
        BaseType baseType = new B(); // Valid Value
        root.setBaseType(baseType);

        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.marshal(root, System.out);
    }

}

输出

然后您将看到一切都按预期工作，并且在编码 baseType 属性时包含类型名称。

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<root>
    <baseType xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="b"/>
</root>