XML Validation Schema

##As mentioned in the previous article Yes, through DTD we can easily judge whether the XML to be verified conforms to the specifications we have defined (the relationship between elements, whether the values of attributes are correct), but if we want to verify the content of elements, DTD is powerless, so people study A new verification method - Schema.

In addition to the above advantages,

Schemais even more impressive thanDTDThe exciting thing is that it is itself a well-formedXMLdocument, so it is very easy to writeSchema. Compared with DTDwhich has its own independent syntax, it is very difficult to write and maintain.A Schema file is an XML file, so the corresponding

Schema

## written byXMLThe process of # is to writeXML againstXML. In this case, it is very easy to write Schema. The following demonstrates how to write the corresponding Schema against XMLOriginal XML file (test2.xml)

  George Bush  John Adams Oxford Street
 London UK   Empire Burlesque Special Edition 1 10.90   Hide your heart 1 9.90

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##For the aboveXMLLet’s start creating aSchema. The principle to follow is how to write the originalXMLand then describe the correspondingSchema, just like you are face to face with a person. The description is the same.

Schema code is as follows (shiporder.xsd)

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Code analysis:

The first line is all

XMLThe statement needs no elaboration.

The second line does this

XML(Schemaitself is aXML) defines a namespace.

Starting from the fourth line are some requirements for the original

XML:

首先定义了根元素为shiporder（行4），其次因为shiporder元素有一个属性，其中包含其他的元素所以其为复合类型（行5）。然后通过sequence元素按照顺序包围其子元素（行10---行15），描述元素的名称以及元素的类型（行11----行14），如果需要描述元素的限制条件（行22）。描述根元素的属性，由于是必选属性所以选择required关键字，需要注意的是这个属性必须放在最后（行29）

通过Schema验证XML的代码和前面文章中的DTD验证大同小异，代码如下：

package ValidateXml; import java.io.File; import java.io.IOException; import javax.xml.XMLConstants; import javax.xml.transform.stream.StreamSource; import javax.xml.validation.Schema; import javax.xml.validation.SchemaFactory; import javax.xml.validation.Validator; import org.xml.sax.ErrorHandler; import org.xml.sax.SAXException; importcom.sun.org.apache.xml.internal.utils.DefaultErrorHandler; public class XmlValidator { private String xsdFilePath; public XmlValidator(String xsdFilePath) { this.xsdFilePath =xsdFilePath; } public String validata(String xmlFilePath,ErrorHandler errorHandler) { String msg = null; SchemaFactoryfactory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI); try { Schema schema = factory.newSchema(new File(xsdFilePath)); Validator validator = schema.newValidator(); validator.setErrorHandler(errorHandler); validator.validate(new StreamSource(new File(xmlFilePath))); } catch (SAXExceptione) { msg = e.getMessage(); e.printStackTrace(); } catch (IOExceptione) { msg = e.getMessage(); e.printStackTrace(); } return msg; } public static void main(String[] args) { String xmlFilePath ="d://test2.xml"; String xsdFilePath ="d://shiporder.xsd"; XmlValidator my =new XmlValidator(xsdFilePath); String msg =my.validata(xmlFilePath, new DefaultErrorHandler()); System.out.println(msg == null); } }

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如果原XML文件符合Schema文件中的描述则返回true；否则抛出异常进行描述哪里不符合，并且返回false。（具体的操作可在实际工程中自行定制，这里只是进行简单的描述）