JAXB Annotation初步使用

JAXB(Java Architecture for XML Binding简称JAXB)允许Java开发人员将Java类映射为XML表示方式。JAXB提供两种主要特性:将一个Java对象序列化为XML,以及反向操作,将XML解析成Java对象。换句话说,JAXB允许以XML格式存储和读取数据,而不需要程序的类结构实现特定的读取XML和保存XML的代码。


一.Jaxb常用annotation

@XmlType

@XmlElement

@XmlRootElement

@XmlAttribute

@XmlAccessorType

@XmlAccessorOrder

@XmlTransient

@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<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:

Shop.java

package jaxb2;

import javax.xml.bind.annotation.*;
import java.util.Set;


@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;
    }

    public String getName() {
        return name;
    }

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

    public String getNumber() {
        return number;
    }

    public void setNumber(String number) {
        this.number = number;
    }

    public String getDescriber() {
        return describer;
    }

    public void setDescriber(String describer) {
        this.describer = describer;
    }

    public Set<Order> getOrders() {
        return orders;
    }

    public void setOrders(Set<Order> orders) {
        this.orders = orders;
    }

    public Address getAddress() {
        return address;
    }

    public void setAddress(Address address) {
        this.address = address;
    }
}


Order.java

package jaxb2;

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;
    }

    public String getShopName() {
        return shopName;
    }

    public void setShopName(String shopName) {
        this.shopName = shopName;
    }

    public String getOrderNumber() {
        return orderNumber;
    }

    public void setOrderNumber(String orderNumber) {
        this.orderNumber = orderNumber;
    }

    public Date getPurDate() {
        return purDate;
    }

    public void setPurDate(Date purDate) {
        this.purDate = purDate;
    }

    public BigDecimal getPrice() {
        return price;
    }

    public void setPrice(BigDecimal price) {
        this.price = price;
    }

    public int getAmount() {
        return amount;
    }

    public void setAmount(int amount) {
        this.amount = amount;
    }

    public Customer getCustomer() {
        return customer;
    }

    public void setCustomer(Customer customer) {
        this.customer = customer;
    }
}


Customer.java

package jaxb2;

import java.util.Set;
import javax.xml.bind.annotation.XmlType;
import javax.xml.bind.annotation.XmlAttribute;
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;
    }

    public String getName() {
        return name;
    }

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

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public String getPhoneNo() {
        return phoneNo;
    }

    public void setPhoneNo(String phoneNo) {
        this.phoneNo = phoneNo;
    }

    public Address getAddress() {
        return address;
    }

    public void setAddress(Address address) {
        this.address = address;
    }

    public Set<Order> getOrders() {
        return orders;
    }

    public void setOrders(Set<Order> orders) {
        this.orders = orders;
    }
}


Address.java

package jaxb2;

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;
    }

    public String getState() {
        return state;
    }

    public void setState(String state) {
        this.state = state;
    }

    public String getProvince() {
        return province;
    }

    public void setProvince(String province) {
        this.province = province;
    }

    public String getCity() {
        return city;
    }

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

    public String getStreet() {
        return street;
    }

    public void setStreet(String street) {
        this.street = street;
    }

    public String getZip() {
        return zip;
    }

    public void setZip(String zip) {
        this.zip = zip;
    }
}


DateAdapter.java

package jaxb2;

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);
    }
 
}


最后做一个测试:

package jaxb2;

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

/**
 * Created with IntelliJ IDEA.
 * User: ASUS
 * Date: 14-7-2
 * Time: 下午6:10
 * To change this template use File | Settings | File Templates.
 */
public class Test {

    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.setOrders(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.getOrders();
        for (Order order : orders1) {
            System.out.println("***************************");
            System.out.println(order.getOrderNumber());
            System.out.println(order.getCustomer().getName());
            System.out.println("***************************");
        }
    }
}

以上是以一个简单的商店订单模型作为示例。

====END====

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