使用JAXB处理丢失的节点 [英] Handling missing nodes with JAXB
问题描述
我目前正在使用JAXB来解析xml文件。我通过xsd文件生成了所需的类。但是,我收到的xml文件不包含生成的类中声明的所有节点。以下是我的xml文件结构的示例:
I am currently using JAXB to parse xml files. I generated the classes needed through an xsd file. However, the xml files I receive do not contain all the nodes declared in the generated classes. The following is an example of my xml file's structure:
<root>
<firstChild>12/12/2012</firstChild>
<secondChild>
<firstGrandChild>
<Id>
</name>
<characteristics>Description</characteristics>
<code>12345</code>
</Id>
</firstGrandChild>
</secondChild>
</root>
我面临以下两种情况:
- 节点
< name>
存在于生成的类中但不存在于XML文件中 - 节点没有值
- The node
<name>
is present in the generated classes but not in the XML files - The node has no value
在这两种情况下,该值都设置为null。我希望能够区分XML文件中何时缺少节点以及何时存在但具有空值的节点。尽管我的搜索,我还没有找到办法。任何帮助都非常欢迎
In both cases, the value is set to null. I would like to be able to differentiate when the node is absent from the XML file and when it's present but has a null value. Despite my searches, I didn't figure out a way to do so. Any help is more than welcome
非常感谢您提前花时间和帮助
Thank you so much in advance for your time and help
问候
推荐答案
A JAXB(JSR-222) 实现不会为缺少的节点调用set方法。你可以在你的set方法中输入逻辑来跟踪它是否被调用。
A JAXB (JSR-222) implementation won't call the set method for absent nodes. You could put logic in your set method to track whether or not it has been called.
public class Foo {
private String bar;
private boolean barSet = false;
public String getBar() {
return bar;
}
public void setBar(String bar) {
this.bar = bar;
this.barSet = true;
}
}
UPDATE
JAXB还会将空节点视为空值 String
。
JAXB will also treat empty nodes as having a value of empty String
.
Java模型
import javax.xml.bind.annotation.XmlRootElement;
@XmlRootElement
public class Root {
private String foo;
private String bar;
public String getFoo() {
return foo;
}
public void setFoo(String foo) {
this.foo = foo;
}
public String getBar() {
return bar;
}
public void setBar(String bar) {
this.bar = bar;
}
}
演示
import java.io.File;
import javax.xml.bind.*;
public class Demo {
public static void main(String[] args) throws Exception {
JAXBContext jc = JAXBContext.newInstance(Root.class);
Unmarshaller unmarshaller = jc.createUnmarshaller();
File xml = new File("src/forum15839276/input.xml");
Root root = (Root) unmarshaller.unmarshal(xml);
Marshaller marshaller = jc.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
marshaller.marshal(root, System.out);
}
}
input.xml /输出
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<root>
<foo></foo>
</root>
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