# JAXB 将 Java 对象写入 XML 示例
> 原文: [https://howtodoinjava.com/jaxb/write-object-to-xml/](https://howtodoinjava.com/jaxb/write-object-to-xml/)
**将 Java 对象写入 XML** 的 Java 示例。 Java 对象字段中存储的信息可以写入 **XML 文件**,也可以写入 **XML 字符串**。
## 1)将 Java 对象转换为 XML 字符串
要将 Java 对象写入 XML `String`,请首先获取`JAXBContext`。 它是 JAXB API 的入口点,并提供了解组,组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,文件或流。
```java
package com.howtodoinjava.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, "Lokesh", "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();
}
}
}
```
程序输出。
```java
101
IT
Lokesh
1
Gupta
```
## 2)将 Java 对象转换为 XML 文件
将 XML 写入文件与上面的示例非常相似。 您只需要提供要在其中写入文件的 XML 文件位置即可。
```java
package com.howtodoinjava.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, "Lokesh", "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();
}
}
}
```
程序输出:
```java
101
IT
Lokesh
1
Gupta
```
## 3)阅读 XML 范例
如果要再次从文件读取 XML 到 Java 对象,请使用此方法。
```java
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();
}
}
```
程序输出:
```java
Employee [id=1, firstName=Lokesh, lastName=Gupta, department=Department [id=101, name=IT]]
```
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