问题描述
让我们以下面的 XML 为例:
Let's take the following example XML:
<device>
<name>NiceDevice</name>
<value>123</value>
</device>
<user>
<name>user1</name>
<usesDevice>NiceDevice</usesDevice>
</user>
<user>
<name>user2</name>
<usesDevice>NiceDevice</usesDevice>
</user>
已通过此 XSD 验证:
validated by this XSD:
<xs:element name="device" minOccurs="0" maxOccurs="unbounded">
<xs:complexType>
<element name="name" type="xs:string"/>
<element name="value" type="xs:integer"/>
</xs:complexType>
</xs:element>
<xs:element name="user" minOccurs="0" maxOccurs="unbounded">
<xs:complexType>
<element name="name" type="xs:string"/>
<element name="usesDevice" type="xs:string"/>
</xs:complexType>
</xs:element>
我现在要做的是仅验证 user/usesDevice
的值在某处也显示为 device/value
的 xml.或者换句话说:我只想允许使用在某处定义的设备.
What I now want to do is validate only xmls where the value of user/usesDevice
also appears somewhere as device/value
.Or in other words: I want to only allow the use of devices which were defined somewhere.
意味着以下 XML 应该有效:
Meaning the following XML should not be valid:
<device>
<name>NiceDevice</name>
<value>123</value>
</device>
<user>
<name>user1</name>
<usesDevice>NiceDevice</usesDevice>
</user>
<user>
<name>user2</name>
<usesDevice>BadDevice</usesDevice>
</user>
因为 BadDevice
从未用作 device/name
.
推荐答案
使用 xs:key
和 xs:keyref
来约束 usesDevices
有一个 device
name
的值:
Use xs:key
and xs:keyref
to constrain usesDevices
to have a value of a device
name
:
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="r">
<xs:complexType>
<xs:sequence>
<xs:element name="device" minOccurs="0" maxOccurs="unbounded">
<xs:complexType>
<xs:sequence>
<xs:element name="name" type="xs:string"/>
<xs:element name="value" type="xs:integer"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="user" minOccurs="0" maxOccurs="unbounded">
<xs:complexType>
<xs:sequence>
<xs:element name="name" type="xs:string"/>
<xs:element name="usesDevice" type="xs:string"/>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
<xs:key name="deviceKey" >
<xs:selector xpath="device"/>
<xs:field xpath="name" />
</xs:key>
<xs:keyref name="deviceKeyRef" refer="deviceKey">
<xs:selector xpath="user" />
<xs:field xpath="usesDevice" />
</xs:keyref>
</xs:element>
</xs:schema>
那么这个 XML 将是有效的:
Then this XML will be valid:
<?xml version="1.0" encoding="UTF-8"?>
<r xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:noNamespaceSchemaLocation="try.xsd">
<device>
<name>NiceDevice</name>
<value>123</value>
</device>
<user>
<name>user1</name>
<usesDevice>NiceDevice</usesDevice>
</user>
<user>
<name>user2</name>
<usesDevice>NiceDevice</usesDevice>
</user>
</r>
但是这个 XML,
<?xml version="1.0" encoding="UTF-8"?>
<r xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:noNamespaceSchemaLocation="try.xsd">
<device>
<name>NiceDevice</name>
<value>123</value>
</device>
<user>
<name>user1</name>
<usesDevice>NiceDevice</usesDevice>
</user>
<user>
<name>user2</name>
<usesDevice>BadDevice</usesDevice>
</user>
</r>
不会,
[错误] try.xml:16:5: cvc-identity-constraint.4.3: 没有为元素r"的标识约束找到值为BadDevice"的键deviceKeyRef".
根据要求.
请注意,我已向您的 XML 添加了一个根元素,这是您的 XML 格式良好所必需的.
Note that I've added to your XML a single root element, which is required for your XML to be well-formed.
这篇关于只允许 XSD 中的其他现有 XML 值?(xs:key 和 xs:keyref)的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!