java 使用 JAXB 编组 LocalDate
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Marshalling LocalDate using JAXB
提问by pwaring
I'm building a series of linked classes whose instances I want to be able to marshall to XML so I can save them to a file and read them in again later.
我正在构建一系列链接类，我希望能够将它们的实例编组为 XML，以便我可以将它们保存到文件中，并在以后再次读取它们。
At present I'm using the following code as a test case:
目前我使用以下代码作为测试用例：
import javax.xml.bind.annotation.*;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import java.time.LocalDate;
public class LocalDateExample
{
@XmlRootElement
private static class WrapperTest {
public LocalDate startDate;
}
public static void main(String[] args) throws JAXBException
{
WrapperTest wt = new WrapperTest();
LocalDate ld = LocalDate.of(2016, 3, 1);
wt.startDate = ld;
marshall(wt);
}
public static void marshall(Object jaxbObject) throws JAXBException
{
JAXBContext context = JAXBContext.newInstance(jaxbObject.getClass());
Marshaller marshaller = context.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
marshaller.marshal(jaxbObject, System.out);
}
}
The XML output is:
XML 输出是：
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<wrapperTest>
<startDate/>
</wrapperTest>
Is there a reason why the startDateelement is empty? I would like it to contain the string representation of the date (i.e. toString()). Do I need to write some code of my own in order to do this?
startDate元素为空是否有原因？我希望它包含日期的字符串表示（即toString()）。我是否需要编写一些自己的代码才能做到这一点？
The output of java -versionis:
的输出java -version是：
openjdk version "1.8.0_66-internal"
OpenJDK Runtime Environment (build 1.8.0_66-internal-b17)
OpenJDK 64-Bit Server VM (build 25.66-b17, mixed mode)
回答by nyname00
You will have to create an XmlAdapterlike this:
你将不得不创建一个XmlAdapter这样的：
public class LocalDateAdapter extends XmlAdapter<String, LocalDate> {
public LocalDate unmarshal(String v) throws Exception {
return LocalDate.parse(v);
}
public String marshal(LocalDate v) throws Exception {
return v.toString();
}
}
And annotate your field using
并使用注释您的字段
@XmlJavaTypeAdapter(value = LocalDateAdapter.class)
See also javax.xml.bind.annotation.adapters.XmlJavaTypeAdaptersif you want to define your adapters on a package level.
另请参阅javax.xml.bind.annotation.adapters.XmlJavaTypeAdapters是否要在包级别定义适配器。
回答by R. Gulbrandsen
http://blog.bdoughan.com/2011/05/jaxb-and-joda-time-dates-and-times.htmldescribes the hole setup.
http://blog.bdoughan.com/2011/05/jaxb-and-joda-time-dates-and-times.html描述了孔设置。
Joda-Time provides an alternative to the Date and Calendar classes currently provided in Java SE. Since they are provided in a separate library JAXB does not provide a default mapping for these classes.
Joda-Time 提供了 Java SE 中当前提供的 Date 和 Calendar 类的替代方案。由于它们是在单独的库中提供的，因此 JAXB 不为这些类提供默认映射。
To register the adapter for all files in a package. you can add package-info.java in the package you want to register it.
为包中的所有文件注册适配器。您可以在要注册的包中添加 package-info.java 。
@XmlJavaTypeAdapters({
@XmlJavaTypeAdapter(type=LocalDate.class,
value=LocalDateAdapter.class),
})
package PACKAGE_NAME;
import java.time.LocalDate;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapters;
The adapter looks like:
适配器看起来像：
import javax.xml.bind.annotation.adapters.XmlAdapter;
import java.time.LocalDate;
public class LocalDateAdapter extends XmlAdapter<String, LocalDate>{
public LocalDate unmarshal(String v) throws Exception {
return LocalDate.parse(v);
}
public String marshal(LocalDate v) throws Exception {
return v.toString();
}
}
