JAXB之xml与javabean的相互转换
1.JAXB常用注解
（1）@XmlRootElement
@XmlRootElement用于类级别的注解，对应xml的根元素，常与 @XmlType 和 @XmlAccessorType一起使用。
（2）@XmlType
@XmlType用在class类的注解，常与@XmlRootElement，@XmlAccessorType一起使用。它有三个属性：name、propOrder、namespace，其中propOrder属性用来指定序列成的xml节点顺序，在使用@XmlType的propOrder 属性时，必须列出JavaBean对象中的所有属性，否则会报错。
（3）@XmlAccessorType
@XmlAccessorType用于指定由java对象生成xml文件时对java对象属性的访问方式。常与@XmlRootElement、@XmlType一起使用。它的属性值是XmlAccessType的4个枚举值，分别为：
XmlAccessType.FIELD:java对象中的所有成员变量
XmlAccessType.PROPERTY：java对象中所有通过getter/setter方式访问的成员变量
XmlAccessType.PUBLIC_MEMBER：java对象中所有的public访问权限的成员变量和通过getter/setter方式访问的成员变量
XmlAccessType.NONE:java对象的所有属性都不映射为xml的元素
注意：@XmlAccessorType的默认访问级别是XmlAccessType.PUBLIC_MEMBER，因此，如果java对象中的private成员变量设置了public权限的getter/setter方法，就不要在private变量上使用@XmlElement和@XmlAttribute注解，否则在由java对象生成xml时会报同一个属性在java类里存在两次的错误。同理，如果@XmlAccessorType的访问权限为XmlAccessType.NONE，如果在java的成员变量上使用了@XmlElement或@XmlAttribute注解，这些成员变量依然可以映射到xml文件。
（4）@XmlElement
@XmlElement将java对象的属性映射为xml的节点，在使用@XmlElement时，可通过name属性改变java对象属性在xml中显示的名称。
（5）@XmlAttribute
@XmlAttribute用于把java对象的属性映射为xml的属性,并可通过name属性为生成的xml属性指定别名。
（6）@XmlTransient
@XmlTransient用于标示在由java对象映射xml时，忽略此属性。即，在生成的xml文件中不出现此元素。
（7）@XmlJavaTypeAdapter
@XmlJavaTypeAdapter常用在转换比较复杂的对象时，如map类型或者格式化日期等。使用此注解时，需要自己写一个adapter类继承XmlAdapter抽象类，并实现里面的方法。
2.案例
@XmlType(propOrder={"id","name","age","birthday","teacherList","teacher","data","dataList"}) //指定序列成的xml节点顺序
@XmlAccessorType(value=XmlAccessType.FIELD) //访问类型改为字段
@XmlRootElement //根元素
public class Student {
@XmlElement //子元素
private String id;
@XmlElement
private String name;
@XmlElement
private Integer age;
@XmlElement
@XmlJavaTypeAdapter(DateAdapter.class)
private Date birthday;
@XmlElementWrapper(name = "teacherList")
@XmlElement(name= "teacher")
private List teacherList;
@XmlElement
private Teacher teacher;
@XmlElement
@XmlJavaTypeAdapter(MapAdapter.class)
private Map data;
@XmlElement
@XmlJavaTypeAdapter(MapListAdapter.class)
private List> dataList;
@XmlAttribute //Student根元素属性
private Integer sex;
@XmlTransient //该属性不加入序列化/反序列化中
private Float weight;
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
public List getTeacherList() {
return teacherList;
}
public void setTeacherList(List teacherList) {
this.teacherList = teacherList;
}
public Teacher getTeacher() {
return teacher;
}
public void setTeacher(Teacher teacher) {
this.teacher = teacher;
}
public Map getData() {
return data;
}
public void setData(Map map) {
this.data = map;
}
public Integer getSex() {
return sex;
}
public void setSex(Integer sex) {
this.sex = sex;
}
public Float getWeight() {
return weight;
}
public void setWeight(Float weight) {
this.weight = weight;
}
public List> getDataList() {
return dataList;
}
public void setDataList(List> dataList) {
this.dataList = dataList;
}
@Override
public String toString() {
return "Student{" +
"id='" + id + '\'' +
", name='" + name + '\'' +
", age=" + age +
", birthday=" + birthday +
", teacherList=" + teacherList +
", teacher=" + teacher +
", data=" + data +
", dataList=" + dataList +
", sex=" + sex +
", weight=" + weight +
'}';
}
}
@XmlAccessorType(value=XmlAccessType.FIELD)
@XmlType(propOrder={"id","name","age"})
public class Teacher {
@XmlElement
private String id;
@XmlElement
private String name;
@XmlElement
private Integer age;
public Teacher() {
}
public Teacher(String id, String name, Integer age) {
this.id = id;
this.name = name;
this.age = age;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
@Override
public String toString() {
return "Teacher{" +
"id='" + id + '\'' +
", name='" + name + '\'' +
", age=" + age +
'}';
}
}
/**
* 自定义时间适配器类
*/
public class DateAdapter extends XmlAdapter {
@Override
public Date unmarshal(String str) throws Exception {
SimpleDateFormat sdf = getSimpleDateFormat("yyyy-MM-dd HH:mm:ss");
return str == null ? null : sdf.parse(str);
}
@Override
public String marshal(Date date) throws Exception {
SimpleDateFormat sdf = getSimpleDateFormat("yyyy-MM-dd HH:mm:ss");
return date == null ? null : sdf.format(date);
}
private SimpleDateFormat getSimpleDateFormat(String pattern) {
SimpleDateFormat sdf = new SimpleDateFormat(pattern);
return sdf;
}
}
@XmlType(propOrder = {"key", "value"})
@XmlAccessorType(value=XmlAccessType.FIELD)
public class Entry {
@XmlAttribute
private String key;
@XmlValue
private String value;
public String getKey() {
return key;
}
public void setKey(String key) {
this.key = key;
}
public String getValue() {
return value;
}
public void setValue(String value) {
this.value = value;
}
}
@XmlAccessorType(value=XmlAccessType.FIELD)
public class MapConvertor {
@XmlElement(name="result")
public List entryList = new ArrayList<>();
}
public class MapAdapter extends XmlAdapter> {
@Override
public Map unmarshal(MapConvertor mapConvertor) throws Exception {
Map map = new HashMap<>();
if (mapConvertor != null) {
List entryList = mapConvertor.entryList;
for (Entry entry : entryList) {
map.put(entry.getKey(), entry.getValue());
}
return map;
}
return null;
}
@Override
public MapConvertor marshal(Map map) throws Exception {
MapConvertor mapConvertor = new MapConvertor();
if (map != null) {
for (Map.Entry entry : map.entrySet()) {
Entry en = new Entry();
en.setKey(entry.getKey());
en.setValue(entry.getValue());
mapConvertor.entryList.add(en);
}
return mapConvertor;
}
return null;
}
}
@XmlAccessorType(value=XmlAccessType.FIELD)
public class MapListConvertor {
@XmlElement(name="resultList")
public List mapList = new ArrayList<>();
}
public class MapListAdapter extends XmlAdapter>> {
private MapAdapter mapAdapter = new MapAdapter();
@Override
public List> unmarshal(MapListConvertor mapListConvertor) throws Exception {
List> mapList = new ArrayList<>();
if (mapListConvertor != null) {
List list = mapListConvertor.mapList;
for (MapConvertor mapConvertor : list) {
Map map = this.mapAdapter.unmarshal(mapConvertor);
mapList.add(map);
}
return mapList;
}
return null;
}
@Override
public MapListConvertor marshal(List> mapList) throws Exception {
MapListConvertor mapListConvertor = new MapListConvertor();
if (mapList != null) {
for (Map map : mapList) {
MapConvertor mapConvertor = this.mapAdapter.marshal(map);
mapListConvertor.mapList.add(mapConvertor);
}
return mapListConvertor;
}
return null;
}
}
public class Main {
public static void main(String[] args) {
Student stu = new Student();
initData(stu);
try {
//javabean转换为xml
JAXBContext context = JAXBContext.newInstance(Student.class);
Marshaller marshaller = context.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
marshaller.setProperty(Marshaller.JAXB_ENCODING, "UTF-8");
StringWriter writer = new StringWriter();
marshaller.marshal(stu, writer);
System.out.println(writer.toString());
//xml转换为javabean
JAXBContext context2 = JAXBContext.newInstance(Student.class);
Unmarshaller unmarshaller = context2.createUnmarshaller();
String xmlStr = "\n" +
"\n" +
" 007 \n" +
" 小西 \n" +
" 25 \n" +
" 2018-12-01 16:12:02 \n" +
" \n" +
" \n" +
" 1 \n" +
" 小明 \n" +
" 22 \n" +
" \n" +
" \n" +
" 2 \n" +
" 小红 \n" +
" 22 \n" +
" \n" +
" \n" +
" 3 \n" +
" 小志 \n" +
" 22 \n" +
" \n" +
" \n" +
" \n" +
" 1 \n" +
" 佳佳 \n" +
" 22 \n" +
" \n" +
" \n" +
" 小罗 \n" +
" 小嘉 \n" +
" 小敏 \n" +
" \n" +
" \n" +
" ";
Student s = (Student) unmarshaller.unmarshal(new StringReader(xmlStr));
System.out.println(s.toString());
} catch (Exception e) {
e.printStackTrace();
}
}
public static void initData(Student stu) {
stu.setId("007");
stu.setName("小西");
stu.setAge(25);
stu.setBirthday(new Date());
stu.setSex(0);
stu.setWeight(62.5f);
//list集合，set集合一样
ArrayList list = new ArrayList<>();
list.add(new Teacher("1","小明",22));
list.add(new Teacher("2","小红",22));
list.add(new Teacher("3","小志",22));
stu.setTeacherList(list);
//在javaBean中添加javaBean
Teacher teacher = new Teacher("1","佳佳",22);
stu.setTeacher(teacher);
//添加map集合
Map map = new HashMap<>();
map.put("1", "小罗");
map.put("2", "小嘉");
map.put("3", "小敏");
stu.setData(map);
//添加map泛型的list
List> dataList = new ArrayList<>();
Map map2 = new HashMap<>();
map2.put("1", "小周");
map2.put("2", "小蕾");
dataList.add(map);
dataList.add(map2);
stu.setDataList(dataList);
}
}