如何使用JAXB为XML中的空元素生成自关闭标记

Question

使用JAXB-API2.3.1和Java 8使用StringWriterforJAXBMarshaller:

@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "", propOrder = {
    "currencyCode",
    "discountValue",
    "setPrice"
})
@XmlRootElement(name = "countryData")
public class CountryData {
    protected String currencyCode;
    protected String discountValue = "";
    protected String setPrice = "";

    // setters and setters
}

StringWriter sw = new StringWriter();
jaxbMarshaller.marshal(countryDataObject, sw);
sw.toString();

<currencyCode>GBP</currencyCode>
<discountValue/>
<setPrice/>

<currencyCode>GBP</currencyCode>
<discountValue></discountValue>
<setPrice></setPrice>




Answer 1

不要初始化变量。使用nillable属性并将其值设置为true

@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "", propOrder = { "currencyCode", "discountValue", "setPrice" })
@XmlRootElement(name = "countryData")
public class CountryData {
    @XmlElement(nillable=true)
    protected String currencyCode;
    @XmlElement(nillable=true)
    protected String discountValue;
    @XmlElement(nillable=true)
    protected String setPrice;
    // getters and setters
}

输出

<currencyCode>GBP</currencyCode>
<discountValue xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:nil="true"/>
<setPrice xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:nil="true"/>