XSD中的use="required"

XSD中的use="required"用于指定一个元素是必需的，即必须在实例文档中出现。如果一个元素的use属性未指定或指定为"optional"，则该元素是可选的，即可以在实例文档中出现，也可以不出现。而如果一个元素的use属性指定为"prohibited"，则该元素是禁止的，即不能在实例文档中出现。

相关问题

<?xml version="1.0" encoding="UTF-8"?> <!-- Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to You under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. --> <tomcat-users xmlns="http://tomcat.apache.org/xml" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://tomcat.apache.org/xml tomcat-users.xsd" version="1.0"> <!-- By default, no user is included in the "manager-gui" role required to operate the "/manager/html" web application. If you wish to use this app, you must define such a user - the username and password are arbitrary. Built-in Tomcat manager roles: - manager-gui - allows access to the HTML GUI and the status pages - manager-script - allows access to the HTTP API and the status pages - manager-jmx - allows access to the JMX proxy and the status pages - manager-status - allows access to the status pages only The users below are wrapped in a comment and are therefore ignored. If you wish to configure one or more of these users for use with the manager web application, do not forget to remove the <!.. ..> that surrounds them. You will also need to set the passwords to something appropriate. --> <!-- <user username="admin" password="<must-be-changed>" roles="manager-gui"/> <user username="robot" password="<must-be-changed>" roles="manager-script"/> --> <!-- The sample user and role entries below are intended for use with the examples web application. They are wrapped in a comment and thus are ignored when reading this file. If you wish to configure these users for use with the examples web application, do not forget to remove the <!.. ..> that surrounds them. You will also need to set the passwords to something appropriate. --> <role rolename="tomcat"/> <role rolename="role1"/> <user username="tomcat" password="tomcat" roles="tomcat"/> <user username="both" password="tomcat" roles="tomcat,role1"/> <user username="role1" password="tomcat" roles="role1"/> </tomcat-users> 出现cvc-elt.1.a: Cannot find the declaration of element 'tomcat-users'.如何修改

从你提供的`server.xml`文件来看，`tomcat-users`元素是在`http://tomcat.apache.org/xml`命名空间下定义的，因此需要使用相应的命名空间前缀来引用该元素。

根据你的配置文件内容，将以下行：

<tomcat-users xmlns="http://tomcat.apache.org/xml"
              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
              xsi:schemaLocation="http://tomcat.apache.org/xml tomcat-users.xsd"
              version="1.0">

修改为：

<tomcat-users xmlns="http://tomcat.apache.org/xml"
              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
              xsi:schemaLocation="http://tomcat.apache.org/xml tomcat-users.xsd"
              version="1.0"
              xmlns:ns2="http://tomcat.apache.org/xml">

然后，在以下行中添加命名空间前缀 `ns2`：

<role rolename="tomcat"/>
<role rolename="role1"/>
<user username="tomcat" password="tomcat" roles="tomcat"/>
<user username="both" password="tomcat" roles="tomcat,role1"/>
<user username="role1" password="tomcat" roles="role1"/>

修改为：

<ns2:role rolename="tomcat"/>
<ns2:role rolename="role1"/>
<ns2:user username="tomcat" password="tomcat" roles="tomcat"/>
<ns2:user username="both" password="tomcat" roles="tomcat,role1"/>
<ns2:user username="role1" password="tomcat" roles="role1"/>

这样修改后，`tomcat-users`元素及其子元素应该能被正确识别了。记得保存修改后的文件并重新启动Tomcat服务器。如果还有其他问题，请提供更多错误信息以便我能够帮助你进一步调试。

在“学生信息.xsd”中定义一个名为“姓名”的全局简单类型，并将其用作“姓名”元素的类型

以下是修改后的“学生信息.xsd”文件，使用了一个名为“姓名类型”的全局简单类型，并将其用作“姓名”元素的类型：

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">

  <xs:simpleType name="姓名类型">
    <xs:restriction base="xs:string">
      <xs:minLength value="2" />
      <xs:maxLength value="10" />
    </xs:restriction>
  </xs:simpleType>

  <xs:element name="学生信息">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="学生" minOccurs="1" maxOccurs="unbounded">
          <xs:complexType>
            <xs:sequence>
              <xs:element name="姓名" type="姓名类型" minOccurs="1" maxOccurs="1" />
              <xs:element name="性别">
                <xs:simpleType>
                  <xs:restriction base="xs:string">
                    <xs:enumeration value="男" />
                    <xs:enumeration value="女" />
                  </xs:restriction>
                </xs:simpleType>
              </xs:element>
              <xs:element name="年龄" type="xs:integer">
                <xs:simpleType>
                  <xs:restriction base="xs:integer">
                    <xs:minInclusive value="18" />
                    <xs:maxInclusive value="35" />
                  </xs:restriction>
                </xs:simpleType>
              </xs:element>
            </xs:sequence>
            <xs:attribute name="学号" type="xs:ID" use="required" />
          </xs:complexType>
        </xs:element>
      </xs:sequence>
    </xs:complexType>
  </xs:element>

</xs:schema>

在这个XSD文件中，我们定义了一个名为“姓名类型”的全局简单类型，它基于字符串类型，并限制了其最小长度为2，最大长度为10。然后在“学生”元素的复杂类型中，我们将“姓名”元素的类型指定为“姓名类型”。这样就避免了使用匿名类型定义“姓名”元素时可能出现的问题。