JAXB编组-根元素的命名空间

Question

我有几个关于JAXB编组的简单问题。我正在尝试封送包含以下字段的类：

@XmlElementRef(name = "AlternateVerificationKeys", namespace = "http://schemas.microsoft.com/Azure/MediaServices/KeyDelivery/TokenRestrictionTemplate/v1", type = JAXBElement.class, required = false)
protected JAXBElement<ArrayOfTokenVerificationKey> alternateVerificationKeys;

@XmlElement(name = "Audience", required = true, nillable = true)
@XmlSchemaType(name = "anyURI")
protected String audience;

@XmlElement(name = "Issuer", required = true, nillable = true)
@XmlSchemaType(name = "anyURI")
protected String issuer;

@XmlElement(name = "PrimaryVerificationKey", required = true, nillable = true)
protected TokenVerificationKey primaryVerificationKey;

@XmlElementRef(name = "RequiredClaims", namespace = "http://schemas.microsoft.com/Azure/MediaServices/KeyDelivery/TokenRestrictionTemplate/v1", type = JAXBElement.class, required = false)
protected JAXBElement<ArrayOfTokenClaim> requiredClaims;

@XmlElement(name = "TokenType", required = true)
@XmlSchemaType(name = "string")
protected TokenType tokenType;

只需使用以下序列化代码：

public static String asString(JAXBContext pContext, Object pObject) throws JAXBException {
    StringWriter sw = new StringWriter();

    Marshaller marshaller = pContext.createMarshaller();
    marshaller.setProperty(Marshaller.JAXB_ENCODING, "UTF-8");
    marshaller.setProperty(Marshaller.JAXB_FRAGMENT, Boolean.TRUE);
    marshaller.marshal(pObject, sw);

    return sw.toString();
}

我得到的输出是：

<TokenRestrictionTemplate xmlns="http://schemas.microsoft.com/Azure/MediaServices/KeyDelivery/TokenRestrictionTemplate/v1">
    <ArrayOfTokenVerificationKey>
        <TokenVerificationKey
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="SymmetricVerificationKey">
            <KeyValue></KeyValue>
        </TokenVerificationKey>
    </ArrayOfTokenVerificationKey>
    <Audience>urn:test</Audience>
    <Issuer>http://testacs.com/</Issuer>
    <PrimaryVerificationKey
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="SymmetricVerificationKey">
        <KeyValue></KeyValue>
    </PrimaryVerificationKey>
    <ArrayOfTokenClaim>
        <TokenClaim>
            <ClaimType>urn:microsoft:azure:mediaservices:contentkeyidentifier</ClaimType>
            <ClaimValue
                xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:nil="true"/>
        </TokenClaim>
    </ArrayOfTokenClaim>
    <TokenType>SWT</TokenType>
</TokenRestrictionTemplate>

现在，我面临的问题如下：

>

我想要名称空间xmlns:xsi=”http://www.w3.org/2001/XMLSchema-instance“出现在根元素中，即TokenRestrictionTemplate中，而不是单个子元素中。如何实现这一点？

我有一些元素，例如带有@XmlElementRef（name="AlternateVerficationKeys"...）的JAXBElement，但是当我列表时，子元素的名称似乎是ArrayOfTokenVerficationKey而不是AlternateVerficationKeys。我如何解决这个问题？

Answer 1

我想要名称空间xmlns:xsi=”http://www.w3.org/2001/XMLSchema-instance“出现在根元素中，即TokenRestrictionTemplate中，而不是单个子元素中。如何实现这一点？

这是XML的核心特性。您可以通过使用一个抽象类和从第一个继承的多个具体类来实现这一点。您还应该使用@Xml瞬态和@XmlSeeAnd来注释抽象类，他们会收到具体类的列表。下面的示例。

1、使用这些注释创建一个名为TokenVerificationKey的抽象类。

@XmlTransient
@XmlSeeAlso({SymmetricVerificationKey.class, X509CertTokenVerificationKey.class})
public abstract class TokenVerificationKey {

}

2、最后，用这些注释定义具体类：

@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "SymmetricVerificationKey")
public class SymmetricVerificationKey extends TokenVerificationKey {

    @XmlElement(name = "KeyValue")
    private byte[] keyValue;

}

我有一些元素，例如带有@XmlElementRef（name="AlternateVerficationKeys"...）的JAXBElement，但是当我列表时，子元素的名称似乎是ArrayOfTokenVerficationKey而不是AlternateVerficationKeys。我如何解决这个问题？

您应该使用@XmlElementWrapper来创建集合（包装器）元素，并使用@XmlElement来设置Childs元素名称：

@XmlElementWrapper(name = "AlternateVerificationKeys")
@XmlElement(name = "TokenVerificationKey")
private List<TokenVerificationKey> alternateVerificationKeys;

此设置与前一个设置相结合，会产生如下输出。

使用此技术，您将获得以下输出：

<TokenRestrictionTemplate xmlns="http://schemas.microsoft.com/Azure/MediaServices/KeyDelivery/TokenRestrictionTemplate/v1" xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
    <AlternateVerificationKeys>
        <TokenVerificationKey i:type="SymmetricVerificationKey">
            <KeyValue>cGVwZXBlZGtkZGllZGpkamRqZGplaWRqZWVpZGplaWRqaWpkZWltZGVpbWRlaWRpZWQ=</KeyValue>
        </TokenVerificationKey>
        <TokenVerificationKey i:type="X509CertTokenVerificationKey">
            <RawBody>MIIDqDCCAxGgAwIBAgIJAMAU1MJasjgBMA0GCSqGSIb3DQEBBQUAMIGVMQswCQYDVQQGEwJBUjENMAsGA1UECBMEQlNBUzENMAsGA1UEBxMEQ0FCQTEXMBUGA1UEChMOU291dGh3b3JrcyBTUkwxGTAXBgNVBAsTEERldmVsb3BtZW50IFVuaXQxCzAJBgNVBAMTAkVWMScwJQYJKoZIhvcNAQkBFhh2ZWNjaGlvZW1hbnVlbEBnbWFpbC5jb20wHhcNMTUwNzE0MTc1MjQ0WhcNMTgwNDEwMTc1MjQ0WjCBlTELMAkGA1UEBhMCQVIxDTALBgNVBAgTBEJTQVMxDTALBgNVBAcTBENBQkExFzAVBgNVBAoTDlNvdXRod29ya3MgU1JMMRkwFwYDVQQLExBEZXZlbG9wbWVudCBVbml0MQswCQYDVQQDEwJFVjEnMCUGCSqGSIb3DQEJARYYdmVjY2hpb2VtYW51ZWxAZ21haWwuY29tMIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDJC2kNjNnBw2hyyI3Hbu30PRXw17GGfHytyvgB89nuakoFE2Oe7Ic8NDPN5/WeA7MROH7dDKole+MFOjDeSO/8d7ylWieVu08/yVpJwcgM3hV7X9Jbc5Zl0XsMXUxXaLvYAaLb3Kc8LrPPBJtTI2bXesV7AGxYKqcDIpwfQ7BGHwIDAQABo4H9MIH6MB0GA1UdDgQWBBTKcw3CsHdNrjqsOPKCoD+59Nh9ijCBygYDVR0jBIHCMIG/gBTKcw3CsHdNrjqsOPKCoD+59Nh9iqGBm6SBmDCBlTELMAkGA1UEBhMCQVIxDTALBgNVBAgTBEJTQVMxDTALBgNVBAcTBENBQkExFzAVBgNVBAoTDlNvdXRod29ya3MgU1JMMRkwFwYDVQQLExBEZXZlbG9wbWVudCBVbml0MQswCQYDVQQDEwJFVjEnMCUGCSqGSIb3DQEJARYYdmVjY2hpb2VtYW51ZWxAZ21haWwuY29tggkAwBTUwlqyOAEwDAYDVR0TBAUwAwEB/zANBgkqhkiG9w0BAQUFAAOBgQBVuuFO3cyOPKSE1nvNyshAeRqhRD+igICeCHGP2zpFQ05k4lzRoio/+1/zdkwZ7g1jHSXz+QkGPRjAxMKGoK8huiTvJwJ1jDVNqyJqfnCW4S2AoNCwziKgGriL7luSDZ+PG3MxoNaCB63B6M6OKOezXhFk4VeLJ/NY1Eohe9E1ew==</RawBody>
        </TokenVerificationKey>
    </AlternateVerificationKeys>
    <Audience>http://audience.com</Audience>
    <Issuer>https://issuer.com</Issuer>
    <PrimaryVerificationKey i:type="SymmetricVerificationKey">
        <KeyValue>cGVwZXBlZGtkZGllZGpkamRqZGplaWRqZWVpZGplaWRqaWpkZWltZGVpbWRlaWRpZWQ=</KeyValue>
    </PrimaryVerificationKey>
    <RequiredClaims>
        <TokenClaim>
            <ClaimType>urn:microsoft:azure:mediaservices:contentkeyidentifier</ClaimType>
            <ClaimValue i:nil="true"/>
        </TokenClaim>
    </RequiredClaims>
    <TokenType>SWT</TokenType>
</TokenRestrictionTemplate> 

您可能希望在XML的开头定义一次命名空间。您应该定义"com.sun.xml.bind.namespacePrefix Mapper"属性。您还可以为命名空间设置首选前缀。

顺便说一句：的Azure SDK。NET中，使用“i”作为前缀。

    Marshaller m = context.createMarshaller();
    m.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
    m.setProperty("com.sun.xml.bind.namespacePrefixMapper", new    NamespacePrefixMapper() {
        @Override
        public String[] getPreDeclaredNamespaceUris() {
            return new String[] {
                    // "http://www.w3.org/2001/XMLSchema-instance"
                    XMLConstants.W3C_XML_SCHEMA_INSTANCE_NS_URI
                    };
        }

        @Override
        public String getPreferredPrefix(String namespaceUri, String suggestion, boolean requirePrefix) {
            // "http://www.w3.org/2001/XMLSchema-instance"
            if (namespaceUri.equals(XMLConstants.W3C_XML_SCHEMA_INSTANCE_NS_URI)) {
                return "i";
            }
            return suggestion;
        }
    });