JAXB使用经验总结 unmarshal与marshal

很多时候我们需要把认知世界转化为我们熟悉的java对象，以供方便操作。这里，JAXB可以把xml对象转化为我们的java对象，也可以把java对象转化为xml对象。这时候我们就得知道它的两个转化方法。
一个是unmarshal()，一个是marshal()
unmarshal()是把xml对象转化为我们需要的java对象的方法，自然marshal()是把java对象转化为xml对象的一个过程。

<?xml version="1.0" encoding="utf-8"?>

<root>
  <girl city="深圳">
    <name>zs</name>
    <age>1</age>
  </girl>
  <boy>
    <name>ls</name>
    <age>1</age>
  </boy>
</root>

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.StringReader;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;

public class XmlUtil {

	@SuppressWarnings({ "restriction", "unchecked" })
	public static <T> T toObject(File file, Class<T> type) throws JAXBException {
		JAXBContext jc = JAXBContext.newInstance(type);
		return (T) jc.createUnmarshaller().unmarshal(file);
	}

	@SuppressWarnings({ "restriction", "unchecked" })
	public static <T> T toObject(String context, Class<T> type) throws JAXBException {
		JAXBContext jc = JAXBContext.newInstance(type);
		return (T) jc.createUnmarshaller().unmarshal(new StringReader(context));
	}

	@SuppressWarnings("restriction")
	public static void toXml(Object object, String FilePath) throws JAXBException, IOException {
		JAXBContext jc = JAXBContext.newInstance(object.getClass());
		OutputStream outputStream = new FileOutputStream(new File(FilePath));
		jc.createMarshaller().marshal(object, outputStream);
		outputStream.close();
	}
}

import javax.xml.bind.JAXBException;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

@XmlAccessorType(XmlAccessType.FIELD)
class People {

	@XmlElement(name = "name")
	private String name;

	@XmlElement(name = "age")
	private int age;

	@XmlAttribute(name = "city")
	private String city;

	public People() {
	}

	public People(String name, int age) {
		this.name = name;
		this.age = age;
	}

	public People(String name, int age, String city) {
		this.name = name;
		this.age = age;
		this.city = city;
	}

	@Override
	public String toString() {
		return name + "," + age + "," + city + "\n";
	}

	public int getAge() {
		return age;
	}

	public String getCity() {
		return city;
	}

	public void setCity(String city) {
		this.city = city;
	}

	public void setAge(int age) {
		this.age = age;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}
}

@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement(name = "root")
class Root {
	@XmlElement(name = "girl")
	private List<People> girls;
	@XmlElement(name = "boy")
	private List<People> boys;

	@Override
	public String toString() {
		StringBuilder sb = new StringBuilder();
		for (People girl : girls) {
			sb.append(girl.toString());
		}
		for (People girl : boys) {
			sb.append(girl.toString());
		}
		return sb.toString();
	}

	public List<People> getGirls() {
		return girls;
	}

	public void setGirls(List<People> girls) {
		this.girls = girls;
	}

	public List<People> getBoys() {
		return boys;
	}

	public void setBoys(List<People> boys) {
		this.boys = boys;
	}
}

	public static void main(String[] args) throws JAXBException, IOException {
		Root root = new Root();
		List<People> list = new ArrayList<People>();
		list.add(new People("zs", 1, "深圳"));
		root.setGirls(list);

		list = new ArrayList<People>();
		list.add(new People("ls", 1));
		root.setBoys(list);

		XmlUtil.toXml(root, "F:\\t.xml");

		root = XmlUtil.toObject(new File("F:\\t.xml"), root.getClass());
		System.out.println(root);
	}

从最里层开始(girl)，把我们想要的节点标记好了：@XmlElement(name = “xxx”)，并且给出他的get,set方法。

同时，要给Girl这个class加上@XmlAccessorType(XmlAccessType.FIELD) ，表示使用这个类中的 private 非静态字段作为 XML 的序列化的属性或者元素。 也就是说，咱们把里边的Girl类中的name来表示xml文件中的name，非常简单。当然，我们需要在name的头上加一顶小帽子@XmlElement(name = “name”)