Java&Xml教程（九）Java中通过XSD校验XML合法性

怼烎@ 2022-08-20 02:29 204阅读 0赞

Java XML校验API能够通过XSD（XML Schema Definition）校验XML文件内容的合法性。在下面的案例中使用javax.xml.validation.Validator 类通过一个xsd文件来鉴定XML内容合法性。  
下面是我们将要用于校验的xsd文件和xml文件的内容。  
Employee.xsd

<?xml version="1.0" encoding="UTF-8"?>
    <schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.journaldev.com/Employee" xmlns:empns="http://www.journaldev.com/Employee" elementFormDefault="qualified">
    
        <element name="empRequest" type="empns:empRequest"></element>
    
        <element name="empResponse" type="empns:empResponse"></element>
    
        <complexType name="empRequest">
            <sequence>
                <element name="id" type="int"></element>
            </sequence>
        </complexType>
    
        <complexType name="empResponse">
            <sequence>
                <element name="id" type="int"></element>
                <element name="role" type="string"></element>
                <element name="fullName" type="string"></element>
            </sequence>
        </complexType>
    </schema>

需要注意的是上面的XSD包含两种根元素，同时具有命名空间，下面两种xml文件内容都是合法的：  
EmployeeRequest.xml

<?xml version="1.0" encoding="UTF-8"?>
    <empns:empRequest xmlns:empns="http://www.journaldev.com/Employee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.journaldev.com/Employee Employee.xsd ">
      <empns:id>5</empns:id>
    </empns:empRequest>

EmployeeResponse.xml

<?xml version="1.0" encoding="UTF-8"?>
    <empns:empResponse xmlns:empns="http://www.journaldev.com/Employee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.journaldev.com/Employee Employee.xsd ">
      <empns:id>1</empns:id>
      <empns:role>Developer</empns:role>
      <empns:fullName>Pankaj Kumar</empns:fullName>
    </empns:empResponse>

下面的一个xml文件内容是不满足XSD约束的：  
employee.xml

<?xml version="1.0"?>
    <Employee>
        <name>Pankaj</name>
        <age>29</age>
        <role>Java Developer</role>
        <gender>Male</gender>
    </Employee>

接下来看如何通过程序来校验这三个xml文件内容是否满足XSD的约束，validateXMLSchema方法接受两个参数，分别是xsd和xml文件的路径，如果xml文件内容是合法的，该方法返回true，否则返回false。  
XMLValidation.java

package com.journaldev.xml;
    
    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.SAXException;
    
    public class XMLValidation {
    
        public static void main(String[] args) {
    
          System.out.println("EmployeeRequest.xml validates against Employee.xsd? "+validateXMLSchema("Employee.xsd", "EmployeeRequest.xml"));
          System.out.println("EmployeeResponse.xml validates against Employee.xsd? "+validateXMLSchema("Employee.xsd", "EmployeeResponse.xml"));
          System.out.println("employee.xml validates against Employee.xsd? "+validateXMLSchema("Employee.xsd", "employee.xml"));
    
          }
    
        public static boolean validateXMLSchema(String xsdPath, String xmlPath){
    
            try {
                SchemaFactory factory = 
                        SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
                Schema schema = factory.newSchema(new File(xsdPath));
                Validator validator = schema.newValidator();
                validator.validate(new StreamSource(new File(xmlPath)));
            } catch (IOException | SAXException e) {
                System.out.println("Exception: "+e.getMessage());
                return false;
            }
            return true;
        }
    }

运行上面程序，控制台输出：

EmployeeRequest.xml validates against Employee.xsd? true
    EmployeeResponse.xml validates against Employee.xsd? true
    Exception: cvc-elt.1: Cannot find the declaration of element 'Employee'.
    employee.xml validates against Employee.xsd? false