[英]JAXB unmarshalling with java generics
我正在尝试使用JAXB从旧版系统中解组XML文档。 我有一个xml结构,如下所示:
<response>
<id>000000</id>
<results>
<result>
<!-- Request specific xml content -->
<year>2003</year>
<title>Lorem Ipsum</title>
<items>
<item>I1</item>
<item>I2</item>
</items>
</result>
<result>
<year>2007</year>
<title>Dolor sit amet</title>
<items>
<item>K1</item>
<item>K2</item>
</items>
</result>
</results>
</response>
<result>
标签指定的零件内部的标签将根据我的要求而更改。 由于内容可能会更改,因此我决定对结果项使用泛型,并准备了带有注释的Java Bean,如下所示:
// imports here
@XmlRootElement(name="response")
@XmlAccessorType(XmlAccessType.FIELD)
public class XResponse<T>{
private String id;
@XmlElementWrapper(name="results")
@XmlElement(name="result")
private List<T> results;
// setters and getters
}
...
@XmlRootElement(name="result")
@XmlAccessorType(XmlAccessType.FIELD)
public class X1Result{
private String year;
private String title;
@XmlElementWrapper(name="items")
@XmlElement(name="item")
private List<String> items;
// setters and getters
}
...
我尝试通过以下代码解组xml文档:
JAXBContext context = JAXBContext.newInstance(XResponse.class, X1Result.class);
Unmarshaller um = context.createUnmarshaller();
XResponse<X1Result> response = (XResponse<X1Result>) um.unmarshal( xmlContent );
List<X1Result> results = unmarshal.getResults();
for (X1Result object : results) {
System.out.println(object.getClass());
}
我在解组期间遇到问题,它无法将列表项转换为X1Result
类。 相反,它使用org.apache.xerces.dom.ElementNSImpl
。
如何使JAXB Unmarshaller使用X1Result
类?
提前致谢
我认为您应该使用继承而不是泛型。 给定这样的XML:
<?xml version="1.0" encoding="UTF-8"?>
<response xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<id>000000</id>
<results>
<result xsi:type="X1Result">
<year>2003</year>
<title>Lorem Ipsum</title>
<items>
<item>I1</item>
<item>I2</item>
</items>
</result>
<result xsi:type="X1Result">
<year>2007</year>
<title>Dolor sit amet</title>
<items>
<item>K1</item>
<item>K2</item>
</items>
</result>
</results>
</response>
您可以动态绑定您的<result>
条目。 您具有顶级类型:
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "XResult")
@XmlSeeAlso({
X1Result.class
})public abstract class XResult {
}
并且您有实现类:
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "X1Result")
public class X1Result extends XResult {
@XmlElement(name = "year")
private String year;
@XmlElement(name = "title")
private String title;
@XmlElementWrapper(name = "items")
@XmlElement(name = "item")
private List<String> items;
...
}
在XResponse类中使用顶级类型:
@XmlRootElement(name = "response")
@XmlAccessorType(XmlAccessType.FIELD)
public class XResponse {
@XmlElement(name = "id")
private String id;
@XmlElementWrapper(name = "results")
@XmlElement(name = "result")
private List<XResult> results;
...
}
您可以使用顶级类型取消编组:
context = JAXBContext.newInstance(XResponse.class, XResult.class);
Unmarshaller unmarshaller = context.createUnmarshaller();
XResponse response = (XResponse) unmarshaller.unmarshal(new File("testfile.xml"));
List<XResult> results = response.getResults();
for (XResult object : results) {
System.out.println(object.getClass());
}
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