C# - XML 架构验证器

• 下载源代码文件 - 3.65 Kb

引言

你是否曾经在利用 Web Services、XML 和 Schema 的项目中工作过？那么你可能需要确保传递给 Web Service 的 XML 是否符合 Schema 的有效性。本文展示了如何使用 .NET 的 XmlValidatingReader 来使用 Schema 验证 XML。

使用代码

1. 创建 XmlSchemaValidator 类。
2. 创建 XML Schema。
3. 创建一个 WebService 并添加 ValidateXML 方法。

注意：所有代码都可通过可下载的 zip 文件获得。

XmlSchemaValidator 类

XmlSchemaValidator 类包含一个重载的公共方法 ValidXmlDoc。此方法允许调用者传递一个 XML 的 string、一个 XmlDocument 或一个 XML 的 StringReader。其他参数是用于验证 XML 的 Schema 的命名空间和 URI。该方法返回一个布尔值，如果 XML 有效则返回 true，如果 XML 无效则返回 false。还有一个公共的 string "ValidationError"，其中包含验证错误。

using System;
using System.Xml;
using System.Xml.Schema;
using System.IO;


namespace YourNameSpace.GoesHere
{
    /// <SUMMARY>
    /// This class validates an xml string or xml document against an xml
        /// schema.
    /// It has public methods that return a boolean value depending on 
        /// the validation
    /// of the xml.
    /// </SUMMARY>
    public class XmlSchemaValidator
    {
        private bool isValidXml = true;
        private string validationError = "";

        /// <SUMMARY>
        /// Empty Constructor.
        /// </SUMMARY>
        public XmlSchemaValidator()
        {
            
        }

        /// <SUMMARY>
        /// Public get/set access to the validation error.
        /// </SUMMARY>
        public String ValidationError
        {
            get
            {
                return "<VALIDATIONERROR>" + this.validationError 
                       + "</VALIDATIONERROR>";
            }
            set
            {
                this.validationError = value;
            }
        }

        /// <SUMMARY>
        /// Public get access to the isValidXml attribute.
        /// </SUMMARY>
        public bool IsValidXml
        {
            get
            {
                return this.isValidXml;
            }
        }

        /// <SUMMARY>
        /// This method is invoked when the XML does not match
        /// the XML Schema.
        /// </SUMMARY>
        /// <PARAM name="sender"></PARAM>
        /// <PARAM name="args"></PARAM>
        private void ValidationCallBack(object sender, 
                                   ValidationEventArgs args)
        {
            // The xml does not match the schema.
            isValidXml = false;
            this.ValidationError = args.Message;
        }  


        /// <SUMMARY>
        /// This method validates an xml string against an xml schema.
        /// </SUMMARY>
        /// <PARAM name="xml">XML string</PARAM>
        /// <PARAM name="schemaNamespace">XML Schema Namespace</PARAM>
        /// <PARAM name="schemaUri">XML Schema Uri</PARAM>
        /// <RETURNS>bool</RETURNS>
        public bool ValidXmlDoc(string xml, 
               string schemaNamespace, string schemaUri)
        {
          try
          {
               // Is the xml string valid?
               if(xml == null || xml.Length <  1)
               {
                   return false;
               }

               StringReader srXml = new StringReader(xml);
               return ValidXmlDoc(srXml, schemaNamespace, schemaUri);
          }
          catch(Exception ex)
          {
              this.ValidationError = ex.Message;
              return false;
          }
        }

        /// <SUMMARY>
        /// This method validates an xml document against an xml 
                /// schema.
        public bool ValidXmlDoc(XmlDocument xml, 
               string schemaNamespace, string schemaUri)
        {
            try
            {
                // Is the xml object valid?
                if(xml == null)
                {
                    return false;
                }

                // Create a new string writer.
                StringWriter sw = new StringWriter();
                // Set the string writer as the text writer 
                                // to write to.
                XmlTextWriter xw = new XmlTextWriter(sw);
                // Write to the text writer.
                xml.WriteTo(xw);
                // Get 
                string strXml = sw.ToString();

                StringReader srXml = new StringReader(strXml);

                return ValidXmlDoc(srXml, schemaNamespace, schemaUri);
            }
            catch(Exception ex)
            {
                this.ValidationError = ex.Message;
                return false;
            }
        }

        /// <SUMMARY>
        /// This method validates an xml string against an xml schema.
        /// </SUMMARY>
        /// <PARAM name="xml">StringReader containing xml</PARAM>
        /// <PARAM name="schemaNamespace">XML Schema Namespace</PARAM>
        /// <PARAM name="schemaUri">XML Schema Uri</PARAM>
        /// <RETURNS>bool</RETURNS>
        public bool ValidXmlDoc(StringReader xml, 
               string schemaNamespace, string schemaUri)
        {
            // Continue?
            if(xml == null || schemaNamespace == null || schemaUri == null)
            {
                return false;
            }

            isValidXml = true;
            XmlValidatingReader vr;
            XmlTextReader tr;
            XmlSchemaCollection schemaCol = new XmlSchemaCollection();
            schemaCol.Add(schemaNamespace, schemaUri);

            try 
            { 
                // Read the xml.
                tr = new XmlTextReader(xml);
                // Create the validator.
                vr = new XmlValidatingReader(tr);
                // Set the validation tyep.
                vr.ValidationType = ValidationType.Auto;
                // Add the schema.
                if(schemaCol != null)
                {
                    vr.Schemas.Add(schemaCol);
                }
                // Set the validation event handler.
                vr.ValidationEventHandler += 
                   new ValidationEventHandler(ValidationCallBack);
                // Read the xml schema.
                while(vr.Read()) 
                { 
                } 

                vr.Close(); 

                return isValidXml;
            } 
            catch(Exception ex) 
            { 
                this.ValidationError = ex.Message;
                return false; 
            } 
            finally
            {
                // Clean up...
                vr = null;
                tr = null;
            }
        }
    }
}

XmlSchema 示例

以下代码是一个用于验证示例 XML 的示例 Schema 文件

<xs:schema id="XSDSchemaTest"
  xmlns:xs="http://www.w3.org/2001/XMLSchema" 
  elementFormDefault="qualified" 
  attributeFormDefault="unqualified"
>

 <xs:simpleType name="FamilyMemberType">
  <xs:restriction base="xs:string">
   <xs:enumeration value="384" />
   <xs:enumeration value="385" />
   <xs:enumeration value="386" />
   <xs:enumeration value="" />
  </xs:restriction>        
 </xs:simpleType>

   <xs:element name="Answer">
     <xs:complexType>
    <xs:sequence>
      <xs:element name="ShortDesc" type="FamilyMemberType" />
      <xs:element name="AnswerValue" type="xs:int" />
     </xs:sequence>
      </xs:complexType>
     </xs:element>
</xs:schema>

XML 示例

根据 Schema 验证的示例 XML

<Answer>
    <ShortDesc>385</ShortDesc> 
    <AnswerValue>1</AnswerValue> 
</Answer>

WebService 示例

WebService 具有一个公共方法，用于验证 XML。此方法提供了一个示例，说明验证器对象可以使用的多种方式之一。请记住，ValidXmlDoc 方法有三个重载。

[WebMethod]
public string ValidateXml(string xml)
{
    XmlSchemaValidator validator = new XmlSchemaValidator();

    string retVal = "<VALIDXML>" + 
           validator.ValidXmlDoc(xml, "", 
           Server.MapPath("XSDSchemaTest.xsd")).ToString() + 
           "</VALIDXML>";

    if(!validator.IsValidXml)
    {
        retVal = retVal + validator.ValidationError;
    }

    return retVal;
}