JAXB中各种常见注解小结

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:

Java代码


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;

}

}

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:

Java代码


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);

}

}

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,

Java代码


@XmlRootElement

@XmlAccessorType(XmlAccessType.FIELD)

public class Customer {

@XmlList

private List<String> emailAddresses;

}

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>