JAXB注解使用

一.Jaxb处理java对象和xml之间转换常用的annotation有：

1. @XmlType
2. @XmlElement
3. @XmlRootElement
4. @XmlAttribute
5. @XmlAccessorType
6. @XmlAccessorOrder
7. @XmlTransient
8. @XmlJavaTypeAdapter

　二.常用annotation使用说明

 

1. @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 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 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 orders = new HashSet();

        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 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

"1.0" encoding= "UTF-8" standalone= "yes" ?>
"CHMart" >
    100000
    EveryThing
    "China" >
        ZheJiang
        HangZhou
        XiHuRoad
        310000


        "LH59800" >
            Mart
            80
            1
            2012 - 03 - 25 12 : 57 : 23
            "David" >
                male
                13699991000
                "China" >
                    JiangSu
                    NanJing
                    ZhongYangLu
                    210000



        "LH59900" >
            Mart
            60
            1
            2012 - 03 - 25 12 : 57 : 23
            "Jim" >
                male
                13699990000
                "China" >
                    ShangHai
                    ShangHai
                    Huang
                    200000

　　以上是以一个简单的商店订单模型作为示例。