使用Marshaller 將Java對象轉化爲XML格式

一、
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
/**
*實體類
*/
@XmlRootElement(name = "User")//根節點
public class User {
    private Integer id;
    private String name;
    @XmlElement //xml元素
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }
    @XmlElement
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}
/**
* 測試類
*/
public class BeanToXml {

    public static void main(String[] args) throws JAXBException {
        JAXBContext jbt = JAXBContext.newInstance(User.class);
        User user = new User();
        user.setId(1);
        user.setName("user1");

        Marshaller ms = jbt.createMarshaller();
        ms.marshal(user,System.out);//輸出到控制檯
    }

}
測試結果:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
    <User>
        <id>1</id>
        <name>user1</name>
    </User>
/**
* pom.xml添加依賴
*/
    <dependency>
      <groupId>javax.xml.bind</groupId>
      <artifactId>jaxb-api</artifactId>
      <version>2.3.1</version>
    </dependency>
可能出現的問題:java.lang.ClassNotFoundException: javax.xml.bind.JAXBException
https://blog.csdn.net/hadues/article/details/79188793

補充:

1.輸出到Write,設置屬性值等

        Marshaller ms = jbt.createMarshaller();
        //設置編碼等屬性
        ms.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT,true);
        ms.setProperty(Marshaller.JAXB_ENCODING,"UTF-8");
        //輸出到Write
        StringWriter write = new StringWriter();
        ms.marshal(user,write);
        System.out.println(write);

2.當爲給實體類設置有效屬性值:比如,設置實體類字段值爲null時,轉化XML時會出現節點丟失問題(null值得屬性不會轉化爲節點並輸出到文件),可採取一下措施:親測可用,其他方式遇見持續更新,再次做記錄,方便後期回顧

1)編寫監聽方法
import javax.xml.bind.Marshaller;
import java.lang.reflect.Field;

/**
 * 監聽類
 */
public class MarshallerListener extends Marshaller.Listener {
    public static final String BLANK_CHAR = "";
    @Override
    public void beforeMarshal(Object source) {
        super.beforeMarshal(source);
        //反射 獲取所有屬性
        Field[] fields = source.getClass().getDeclaredFields();
        for(Field field : fields){
            //允許獲取私有屬性
            field.setAccessible(true);
            try {
                //只針對String類型的,其他類型單獨處理
                if(field.getType() == String.class && field.get(source) == null){
                    //設置屬性值
                    field.set(source,BLANK_CHAR);
                }
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
        }
    }
}
2.編寫工具類
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import java.io.StringWriter;

/**
 * java實體類轉XML工具類
 */
public class JavaBeanToXml {
    public static String beanToXmlUtf8(Object obj,Class<?> load) throws JAXBException {
        JAXBContext jbt = JAXBContext.newInstance(load);
        Marshaller ms = jbt.createMarshaller();
        ms.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT,true);
        ms.setProperty(Marshaller.JAXB_ENCODING,"UTF-8");

        MarshallerListener listener = new MarshallerListener();
        ms.setListener(listener);

        StringWriter write = new StringWriter();
        ms.marshal(obj,write);
        String xmlStr = write.toString();
        return xmlStr;
    }
}
//實體類
@XmlRootElement(name = "User")
public class User {
    private Integer id;
    private String name;
    @XmlElement
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }
    @XmlElement
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}
//測試類
/**
 * Unit test for simple App.
 */
public class AppTest 
{
    @Test
    public void beanToXml() throws JAXBException {
        User user = new User();
        user.setId(2);
        user.setName(null);

        String xmlStr = JavaBeanToXml.beanToXmlUtf8(user,user.getClass());
        System.out.println(xmlStr);
    }
}