用于base64Binary的XmlAdapter导致String [英] XmlAdapter for base64Binary results in String

问题描述

我有一个包含以下内容的XSD文件：

I've an XSD file containing this:

<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:jaxb="http://java.sun.com/xml/ns/jaxb"
xmlns:xjc="http://java.sun.com/xml/ns/jaxb/xjc"
jaxb:extensionBindingPrefixes="xjc"
elementFormDefault="qualified"
targetNamespace="http://example.org/">

<xsd:complexType name="Certificate">
    <xsd:sequence>
        <xsd:element name="certificate" type="xsd:base64Binary">
            <xsd:annotation>
                <xsd:appinfo>
                    <xjc:javaType name="java.security.cert.X509Certificate" adapter="adapters.X509CertificateAdapter" />
                </xsd:appinfo>
            </xsd:annotation>
        </xsd:element>
    </xsd:sequence>
</xsd:complexType>

</xsd:schema>

当我使用xjc生成java代码时，它会生成：

and when I generate java code with xjc, it produces this:

public class Certificate {

    @XmlElement(required = true, type = String.class)
    @XmlJavaTypeAdapter(X509CertificateAdapter.class)
    @XmlSchemaType(name = "base64Binary")
    protected X509Certificate certificate;

    ....
}

并且适配器工作正常很好。

and the adapter works fine.

我的问题是为什么 @XmlElement（required = true，type = String.class）？为什么 type = String.class 而不是 byte [] ？

My question is why @XmlElement(required = true, type = String.class) ? Why type = String.class and not byte[]?

推荐答案

对于以下内容：

@XmlElement(required = true, type = String.class)
@XmlJavaTypeAdapter(X509CertificateAdapter.class)
@XmlSchemaType(name = "base64Binary")
protected X509Certificate certificate;

有几点需要注意：

1. @XmlElement 上的类型设置是多余的，因为 X509CertificateAdapter 已经指定用于编组&解组它将 X508Certificate 转换为 String 。


2. X509CertificateAdapter 转换为 String 而不是 byte [] 最有可能出于性能目的，因为转换为 byte [] 会导致JAXB额外转换为 String 在XML中正确呈现它。


3. @XmlSchemaType 注释用于确保XML Schema时生成的节点类型显示为 base64Binary 而不是 string 。

1. The type setting on @XmlElement is redundant since the X509CertificateAdapter already specifies that for the purposes of marshalling & unmarshalling it is going to convert X508Certificate to/from a String.
2. The X509CertificateAdapter converts to/from a String instead of a byte[] most likely for the purposes of performance, as a conversion to a byte[] would cause JAXB to do an additional conversion to String to render it correctly in the XML.
3. The @XmlSchemaType annotation is used to ensure that when an XML Schema is generated that the node type shows up as base64Binary and not string.

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