在JAXB中(用于JAVA对象和xml之间的转换),经常出现各类的 @XmlElement这样的标记,
下面就来以一个例子小结下,加深学习:
[code="java"]
import java.util.*;
import javax.xml.bind.annotation.*;
@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class Customer {
private List<String> emailAddresses;
public Customer() {
emailAddresses = new ArrayList<String>();
}
public List<String> getEmailAddresses() {
return emailAddresses;
}
public void setEmailAddresses(List<String> emailAddresses) {
this.emailAddresses = emailAddresses;
}
}
[/code]
这个是一个典型的POJO了,其中引用了对象emailAddress,是一个List,那么下面演示各类用法:
先看默认的调用代码如下:
[code="java"]
import javax.xml.bind.JAXBContext;
import javax.xml.bind.Marshaller;
public class Demo {
public static void main(String[] args) throws Exception {
JAXBContext jc = JAXBContext.newInstance(Customer.class);
Customer customer = new Customer();
customer.getEmailAddresses().add("janed@example.com");
customer.getEmailAddresses().add("jdoe@example.org");
Marshaller marshaller = jc.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
marshaller.marshal(customer, System.out);
}
}
[/code]
默认的把这个对象输出为一般的XML:
<customer>
<emailAddresses>janed@example.com</emailAddresses>
<emailAddresses>jdoe@example.org</emailAddresses>
</customer>
下面逐一看每个注解的用法
1) @XmlElement
@XmlElement(name="email-address")
private List<String> emailAddresses;
加上这个注解的话,则按自定义的xml标签名去输出某个属性,如下:
<customer>
<email-address>janed@example.com</email-address>
<email-address>jdoe@example.org</email-address>
</customer>
2) @XmlElementWrapper
这个注解等于在最外面再包一层了,
@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class Customer {
@XmlElementWrapper(name="email-addresses")
@XmlElement(name="email-address")
private List<String> emailAddresses;
}
输出:
<customer>
<email-addresses>
<email-address>janed@example.com</email-address>
<email-address>jdoe@example.org</email-address>
</email-addresses>
</customer>
3) @XmlList
这个等于是在同一行中,把list中的输出,以空格形式分隔开来,
[code="java"]
@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class Customer {
@XmlList
private List<String> emailAddresses;
}
[/code]
输出:
<customer>
<emailAddresses>janed@example.com jdoe@example.org</emailAddresses>
</customer>
4)
@XmlList和 @XmlAttribute混合使用
@XmlList
@XmlAttribute
private List<String> emailAddresses;
输出:
<customer
emailAddresses="janed@example.com jdoe@example.org"/>
看到没?就是同一行中逗号输出,并作为customer的一个属性
5)
@XmlList 和 @XmlValue混用
@XmlList
@XmlValue
private List<String> emailAddresses;
就是把emailAddress的list的值,作为<customer>的value 输出,结果如下:
<customer>janed@example.com jdoe@example.org</customer>
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