JAXB对XML的编组方式与OutputStream和StringWriter不同

如果回答了这个问题,我很抱歉,但是我一直使用的搜索词(即 jaxb@xmltattribute压缩 或 JAXB XML封送到字符串不同的结果 )什么都没想出来。

我正在使用JAXB取消/封送带注释的对象 @XmlElement 和 @XmlAttribute 注释。我有一个格式化程序类,它提供了两个方法——一个方法包装marshal方法并接受要封送的对象,另一个方法 OutputStream 另一个只接受对象并以字符串形式返回XML输出。不幸的是,这些方法不能为相同的对象提供相同的输出。封送到文件时,内部用标记的简单对象字段 @ XmlAttribute 印制为:

<element value="VALUE"></element>

当封送到字符串时,它们是:

<element value="VALUE"/>

对于这两种情况,我更喜欢第二种格式,但我对如何控制差异很好奇,不管怎样,我都会满足于它们是相同的。我甚至创建了一个静态封送拆收器,两个方法都使用它来消除不同的实例值。格式代码如下:

/** Marker interface for classes which are listed in jaxb.index */
public interface Marshalable {}

/** Local exception class */
public class XMLMarshalException extends BaseException {}

/** Class which un/marshals objects to XML */
public class XmlFormatter {
    private static Marshaller marshaller = null;
    private static Unmarshaller unmarshaller = null;

    static {
        try {
            JAXBContext context = JAXBContext.newInstance("path.to.package");
            marshaller = context.createMarshaller();
            marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
            marshaller.setProperty(Marshaller.JAXB_ENCODING, "UTF-8");

            unmarshaller = context.createUnmarshaller();
        } catch (JAXBException e) {
            throw new RuntimeException("There was a problem creating a JAXBContext object for formatting the object to XML.");
        }
    }

    public void marshal(Marshalable obj, OutputStream os) throws XMLMarshalException {
        try {
            marshaller.marshal(obj, os);
        } catch (JAXBException jaxbe) {
            throw new XMLMarshalException(jaxbe);
        }
    }

    public String marshalToString(Marshalable obj) throws XMLMarshalException {
        try {
            StringWriter sw = new StringWriter();
            return marshaller.marshal(obj, sw);
        } catch (JAXBException jaxbe) {
            throw new XMLMarshalException(jaxbe);
        }
    }
}

/** Example data */
@XmlType
@XmlAccessorType(XmlAccessType.FIELD)
public class Data {

    @XmlAttribute(name = value)
    private String internalString;
}

/** Example POJO */
@XmlType
@XmlRootElement(namespace = "project/schema")
@XmlAccessorType(XmlAccessType.FIELD)
public class Container implements Marshalable {

    @XmlElement(required = false, nillable = true)
    private int number;

    @XmlElement(required = false, nillable = true)
    private String word;

    @XmlElement(required = false, nillable = true)
    private Data data;
}

呼叫的结果 marshal(container, new FileOutputStream("output.xml")) 和 marshalToString(container) 如下:

输出到文件

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>  
<ns2:container xmlns:ns2="project/schema">  
    <number>1</number>  
    <word>stackoverflow</word>  
    <data value="This is internal"></data>  
</ns2:container>

和

输出到字符串

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>  
<ns2:container xmlns:ns2="project/schema">  
    <number>1</number>  
    <word>stackoverflow</word>  
    <data value="This is internal"/>  
</ns2:container>