将 Java 对象转换为 XML 字符串

要将 Java 对象写入 XML String，首先要获取 JAXBContext。
它是 JAXB API 的入口点，并提供解组、编组和验证操作的方法。

现在从 JAXBContext获取 Marshaller实例。
marshal()方法将 Java 对象编组为 XML。
现在可以将此 XML 写入不同的输出，例如字符串、文件或者流。

package com.onitroad.demo;
import java.io.File;
import java.io.StringWriter;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
public class JaxbExample 
{
	public static void main(String[] args) 
	{
		//Java object. We will convert it to XML.
		Employee employee = new Employee(1, "JackLi", "Gupta", new Department(101, "IT"));

		//Method which uses JAXB to convert object to XML
		jaxbObjectToXML(employee);
	}
	private static void jaxbObjectToXML(Employee employee) 
	{
	    try 
	    {
	    	//Create JAXB Context
	        JAXBContext jaxbContext = JAXBContext.newInstance(Employee.class);

	        //Create Marshaller
	        Marshaller jaxbMarshaller = jaxbContext.createMarshaller();
	        //Required formatting??
	        jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
	        //Print XML String to Console
	        StringWriter sw = new StringWriter();

	        //Write XML to StringWriter
	        jaxbMarshaller.marshal(employee, sw);

	        //Verify XML Content
	        String xmlContent = sw.toString();
	        System.out.println( xmlContent );
	    } catch (JAXBException e) {
	        e.printStackTrace();
	    }
	}
}

将 Java 对象转换为 XML 文件

我们只需要提供要写入文件的 XML 文件位置。

package com.onitroad.demo;
import java.io.File;
import java.io.StringWriter;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
public class JaxbExample 
{
	public static void main(String[] args) 
	{
		//Java object. We will convert it to XML.
		Employee employee = new Employee(1, "JackLi", "Gupta", new Department(101, "IT"));

		//Method which uses JAXB to convert object to XML
		jaxbObjectToXML(employee);
	}
	private static void jaxbObjectToXML(Employee employee) 
	{
	    try 
	    {
	    	//Create JAXB Context
	        JAXBContext jaxbContext = JAXBContext.newInstance(Employee.class);

	        //Create Marshaller
	        Marshaller jaxbMarshaller = jaxbContext.createMarshaller();
	        //Required formatting??
	        jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
	       //Store XML to File
	        File file = new File("employee.xml");

	        //Writes XML file to file-system
	        jaxbMarshaller.marshal(employee, file);	
	    } 
	    catch (JAXBException e) 
	    {
	        e.printStackTrace();
	    }
	}
}

Java 读取 XML 示例

如果我们想再次将 XML 从文件读取到 Java 对象，则使用此方法。

String fileName = "employee.xml";
//Call method which read the XML file above
jaxbXmlFileToObject(fileName);
private static void jaxbXmlFileToObject(String fileName) {

		File xmlFile = new File(fileName);

		JAXBContext jaxbContext;
		try 
		{
			jaxbContext = JAXBContext.newInstance(Employee.class);
			Unmarshaller jaxbUnmarshaller = jaxbContext.createUnmarshaller();
			Employee employee = (Employee) jaxbUnmarshaller.unmarshal(xmlFile);

			System.out.println(employee);
		}
		catch (JAXBException e) 
		{
			e.printStackTrace();
		}
	}