JAXB注解使用
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:
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:
@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement
public class Address {}
4.@XmlAttribute
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<ValueType,BoundType> {
// 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<String, Date> { 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
<?xml version= "1.0" encoding= "UTF-8" standalone= "yes" ?> <CHMart name= "CHMart" > <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> </CHMart> |
以上是以一个简单的商店订单模型作为示例。
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