如何序列化HashTable< String，String>使用JAXB到XML？

问题描述：

我正在尝试使用JAXB将 HashTable< String，String> 序列化为XML。我是Java新手（来自C＃），所以我对此任务感到困惑。

I am trying to use JAXB to serialize a HashTable<String, String> to XML. I am very new to Java (came from C#), so I am kinda perplexed by this task.

我看过以下代码：

public static <T> String ObjectToXml(T object, Class<T> classType) throws JAXBException
{
  JAXBContext jaxbContext = JAXBContext.newInstance(classType);
  StringWriter writerTo = new StringWriter();
  Marshaller marshaller = jaxbContext.createMarshaller();
  marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true); 
  marshaller.marshal(object, writerTo); //create xml string from the input object
  return writerTo.toString();
}

这样调用： ObjectToXml（o， ClassOfO.class），但 HashTable< String，String> .class 错误（我已经知道）。

Which is invoked like so: ObjectToXml(o, ClassOfO.class), but HashTable<String, String>.class is wrong (that I already know).

那里的Java大师能告诉我如何调用这段代码吗？建议更简单的实现（当然还有调用示例）也是受欢迎的。

Can Java gurus out there show me how to invoke this code? Proposing a simpler implementation (along with an invocation example, of course) is most welcome as well.

谢谢。

答

您需要创建一个包装类来保留 Hashtable ：

You will need to create a wrapper class to hold onto the Hashtable:

package forum7534500;

import java.util.Hashtable;

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Wrapper {

    private Hashtable<String, String> hashtable;

    public Hashtable<String, String> getHashtable() {
        return hashtable;
    }

    public void setHashtable(Hashtable<String, String> hashtable) {
        this.hashtable = hashtable;
    }

}

然后你可以做以下事情：

Then you can do the following:

package forum7534500;

import java.io.StringWriter;
import java.util.Hashtable;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;

public class Demo {

    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(Wrapper.class);
        Wrapper wrapper = new Wrapper();
        Hashtable<String, String> hashtable = new Hashtable<String,String>();
        hashtable.put("foo", "A");
        hashtable.put("bar", "B");
        wrapper.setHashtable(hashtable);
        System.out.println(objectToXml(jc, wrapper));
    }

    public static String objectToXml(JAXBContext jaxbContext, Object object) throws JAXBException
    {
      StringWriter writerTo = new StringWriter();
      Marshaller marshaller = jaxbContext.createMarshaller();
      marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true); 
      marshaller.marshal(object, writerTo); //create xml string from the input object
      return writerTo.toString();
    }

}

这将产生以下输出：

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<wrapper>
    <hashtable>
        <entry>
            <key>bar</key>
            <value>B</value>
        </entry>
        <entry>
            <key>foo</key>
            <value>A</value>
        </entry>
    </hashtable>
</wrapper>

注意事项

JAXBContext 是一个线程安全的对象，应该创建一次并重复使用。

Hashtable 是同步的，如果你不需要这个，那么使用 HashMap 是常见的替代品。

约定是以小写字母开始Java方法名称。

JAXBContext is a thread-safe object and should be created once and reused.
Hashtable is synchronized, if you do not need this then using HashMap is the common replacement.
The convention is to start Java method names with a lower case letter.

自定义映射

您可以在JAXB中使用 XmlAdapter 来自定义任何类的映射。以下是我博客上帖子的链接，我将演示如何做到这一点：

You can use an XmlAdapter in JAXB to customize the mapping of any class. Below is an link to a post on my blog where I demonstrate how to do just that:

http://blog.bdoughan.com/2010/07/xmladapter-jaxbs-secret-weapon.html

http://blog.bdoughan.com/2010/07/xmladapter-jaxbs-secret-weapon.html

如何序列化HashTable< String，String>使用JAXB到XML？

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