Jaxb annotation初步使用
一.Jaxb处理java对象和xml之间转换常用的annotation有：
@XmlType
@XmlElement
@XmlRootElement
@XmlAttribute
@XmlAccessorType
@XmlAccessorOrder
@XmlTransient
@XmlJavaTypeAdapter
二.常用annotation使用说明
@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，经常使用的只有前两个属性。如：
@XmlType(name = “basicStruct”, propOrder = {
"intValue",
"stringArray",
"stringValue"
)
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。
2.@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。如：
@XmlElement(name=“Address”)
private String yourAddress;
3.@XmlRootElement
@XmlRootElement用于类级别的注解，对应xml的跟元素，常与 @XmlType 和 @XmlAccessorType一起使用。如：
@XmlType
@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement
public class Address {}
4.@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。如：
@XmlAttribute(name=“Country”)
private String state;
5.@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。
6.@XmlAccessorOrder
@XmlAccessorOrder用于对java对象生成的xml元素进行排序。它有两个属性值：
AccessorOrder.ALPHABETICAL：对生成的xml元素按字母书序排序
XmlAccessOrder.UNDEFINED:不排序
7.@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。
8.@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。
@XmlJavaTypeAdapter(value=xxx.class),value为自己定义的adapter类
XmlAdapter如下：
public abstract class XmlAdapter {
// Do-nothing constructor for the derived classes.
protected XmlAdapter() {}
// Convert a value type to a bound type.
public abstract BoundType unmarshal(ValueType v);
// Convert a bound type to a value type.
public abstract ValueType marshal(BoundType v);
}
三.示例
1.Shop.java
package jaxb.shop;
import java.util.Set;
import javax.xml.bind.annotation.XmlAccessOrder;
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;
import javax.xml.bind.annotation.XmlType;
import javax.xml.bind.annotation.XmlElementWrapper;
import javax.xml.bind.annotation.XmlAccessorOrder;
@XmlAccessorOrder(XmlAccessOrder.ALPHABETICAL)
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = “shop”, propOrder = { “name”, “number”, “describer”, “address”,“orders” })
@XmlRootElement(name = “CHMart”)
public class Shop {
@XmlAttribute
private String name;
// @XmlElement
private String number;
@XmlElement
private String describer;
@XmlElementWrapper(name = "orders")
@XmlElement(name = "order")
private Set<Order> orders;
@XmlElement
private Address address;
public Shop() {
}
public Shop(String name, String number, String describer, Address address) {
this.name = name;
this.number = number;
this.describer = describer;
this.address = address;
}
getter/setter略
//同时使用了@XmlType（propOrder={}）和@XmlAccessorOrder(XmlAccessOrder.ALPHABETICAL)，但是生成的xml只按照propOrder定义的顺序生成元素
2.Order.java
package jaxb.shop;
import java.math.BigDecimal;
import java.util.Date;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
@XmlType(name=“order”,propOrder={“shopName”,“orderNumber”,“price”,“amount”,“purDate”,“customer”})
@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement
public class Order {
// @XmlElement
private String shopName;
@XmlAttribute
private String orderNumber;
// @XmlElement
@XmlJavaTypeAdapter(value=DateAdapter.class)
private Date purDate;
// @XmlElement
private BigDecimal price;
// @XmlElement
private int amount;
// @XmlElement
private Customer customer;
public Order() {
}
public Order(String shopName, String orderNumber, Date purDate,
BigDecimal price, int amount) {
this.shopName = shopName;
this.orderNumber = orderNumber;
this.purDate = purDate;
this.price = price;
this.amount = amount;
}
getter/setter略
//@XmlAccessorType(XmlAccessType.FIELD)，所以此处注释掉了@XmlElement，xml中依然会生成这些元素
3.Customer.java
package jaxb.shop;
import java.util.Set;
import javax.xml.bind.annotation.XmlType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
@XmlType
@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement
public class Customer {
@XmlAttribute
private String name;
private String gender;
private String phoneNo;
private Address address;
private Set<Order> orders;
public Customer() {
}
public Customer(String name, String gender, String phoneNo, Address address) {
this.name = name;
this.gender = gender;
this.phoneNo = phoneNo;
this.address = address;
}
getter/setter略
4.Address.java
package jaxb.shop;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAccessOrder;
import javax.xml.bind.annotation.XmlAccessorOrder;
@XmlType(propOrder={“state”,“province”,“city”,“street”,“zip”})
@XmlAccessorOrder(XmlAccessOrder.ALPHABETICAL)
@XmlAccessorType(XmlAccessType.NONE)
@XmlRootElement
public class Address {
@XmlAttribute
private String state;
@XmlElement
private String province;
@XmlElement
private String city;
@XmlElement
private String street;
@XmlElement
private String zip;
public Address() {
super();
}
public Address(String state, String province, String city, String street,
String zip) {
super();
this.state = state;
this.province = province;
this.city = city;
this.street = street;
this.zip = zip;
}
getter/setter略
//注意：虽然@XmlAccessorType为XmlAccessType.NONE,但是在java类的私有属性上加了@XmlAttribute和@XmlElement注解后，这些私有成员会映射生成xml的元素
5.DateAdapter.java
package jaxb.shop;
import java.util.Date;
import java.text.SimpleDateFormat;
import javax.xml.bind.annotation.adapters.XmlAdapter;
public class DateAdapter extends XmlAdapter {
private String pattern = "yyyy-MM-dd HH:mm:ss";
SimpleDateFormat fmt = new SimpleDateFormat(pattern);
@Override
public Date unmarshal(String dateStr) throws Exception {
return fmt.parse(dateStr);
}
@Override
public String marshal(Date date) throws Exception {
return fmt.format(date);
}
}
//用于格式化日期在xml中的显示格式，并且由xml unmarshal为java对象时，将字符串解析为Date对象
6.ShopTest.java
package jaxb.shop;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.math.BigDecimal;
import java.util.Date;
import java.util.HashSet;
import java.util.Set;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;
public class ShopTest {
public static void main(String[] args) throws JAXBException, IOException{
Set<Order> orders = new HashSet<Order>();
Address address1 = new Address("China", "ShangHai", "ShangHai", "Huang", "200000");
Customer customer1 = new Customer("Jim", "male", "13699990000", address1);
Order order1 = new Order("Mart", "LH59900", new Date(), new BigDecimal(60), 1);
order1.setCustomer(customer1);
Address address2 = new Address("China", "JiangSu", "NanJing", "ZhongYangLu", "210000");
Customer customer2 = new Customer("David", "male", "13699991000", address2);
Order order2 = new Order("Mart", "LH59800", new Date(), new BigDecimal(80), 1);
order2.setCustomer(customer2);
orders.add(order1);
orders.add(order2);
Address address3 = new Address("China", "ZheJiang", "HangZhou", "XiHuRoad", "310000");
Shop shop = new Shop("CHMart", "100000", "EveryThing",address3);
shop.setOrder(orders);
FileWriter writer = null;
JAXBContext context = JAXBContext.newInstance(Shop.class);
try {
Marshaller marshal = context.createMarshaller();
marshal.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
marshal.marshal(shop, System.out);
writer = new FileWriter("shop.xml");
marshal.marshal(shop, writer);
} catch (Exception e) {
e.printStackTrace();
}
Unmarshaller unmarshal = context.createUnmarshaller();
FileReader reader = new FileReader("shop.xml") ;
Shop shop1 = (Shop)unmarshal.unmarshal(reader);
Set<Order> orders1 = shop1.getOrder();
for(Order order : orders1){
System.out.println("***************************");
System.out.println(order.getOrderNumber());
System.out.println(order.getCustomer().getName());
System.out.println("***************************");
}
}
}
7.生成的xml文件
<number>100000</number>
<describer>EveryThing</describer>
<address state="China">
<province>ZheJiang</province>
<city>HangZhou</city>
<street>XiHuRoad</street>
<zip>310000</zip>
</address>
<orders>
<order orderNumber="LH59800">
<shopName>Mart</shopName>
<price>80</price>
<amount>1</amount>
<purDate>2012-03-25 12:57:23</purDate>
<customer name="David">
<gender>male</gender>
<phoneNo>13699991000</phoneNo>
<address state="China">
<province>JiangSu</province>
<city>NanJing</city>
<street>ZhongYangLu</street>
<zip>210000</zip>
</address>
</customer>
</order>
<order orderNumber="LH59900">
<shopName>Mart</shopName>
<price>60</price>
<amount>1</amount>
<purDate>2012-03-25 12:57:23</purDate>
<customer name="Jim">
<gender>male</gender>
<phoneNo>13699990000</phoneNo>
<address state="China">
<province>ShangHai</province>
<city>ShangHai</city>
<street>Huang</street>
<zip>200000</zip>
</address>
</customer>
</order>
</orders>
以上是以一个简单的商店订单模型作为示例。