java – jaxb可以解析系统属性吗？

我们使用JAXB来配置XML对象.我想知道JAXB是否有办法解析系统属性.例如,如果我有一个属性颜色的bean,我希望能够这样做：

<mybean color="${mycolor.in.data.property}" />

但是如果我这样做,JAXB创建mybean对象,颜色将等于字符串：
mycolor.in.data.property

JAXB在春天是否有相应的PropertyPlaceholderConfigurer,以便我的系统属性可以解决？

解决方法:

XmlAdapter是一种JAXB (JSR-222)机制,允许您在编组/解组时将对象转换为另一个对象.您可以编写一个XmlAdapter,将系统属性名称转换为实际值.

import javax.xml.bind.annotation.adapters.XmlAdapter;

public class ColorAdapter extends XmlAdapter<String, String> {

    @Override
    public String unmarshal(String v) throws Exception {
        return System.getProperty(v);
    }

    @Override
    public String marshal(String v) throws Exception {
        return v;
    }

}

然后使用@XmlJavaTypeAdapter批注为您的属性配置XmlAdapter.

@XmlJavaTypeAdapter(ColorAdapter.class)
public String getColor() {
    return color;
}

欲获得更多信息

> http://blog.bdoughan.com/2011/05/jaxb-and-joda-time-dates-and-times.html

UPDATE

Ok thanks. Actually I do not have access to the class, as this is part
of an imported library. So I was more looking of a way to configure
this directly in the xml file, but it is probably not possible.

如果无法修改类,则可以使用StreamReaderDelegate修改XML输入.有一些方法可以处理文本/字符数据,因此您可能需要进行实验以确保覆盖最适合您正在使用的JAXB实现的方法.

import javax.xml.bind.*;
import javax.xml.stream.*;
import javax.xml.stream.util.StreamReaderDelegate;
import javax.xml.transform.stream.StreamSource;

public class Demo {

    public static void main(String[] args) throws Exception {

        JAXBContext jc = JAXBContext.newInstance(MyBean.class);

        XMLInputFactory xif = XMLInputFactory.newFactory();
        StreamSource source = new StreamSource("input.xml");
        XMLStreamReader xsr = xif.createXMLStreamReader(source);
        xsr = new StreamReaderDelegate(xsr) {

            @Override
            public String getText() {
                String text = super.getText();
                if(text.contains("${")) {
                    text = System.getProperty(text);
                }
                return text;
            }

        };

        Unmarshaller unmarshaller = jc.createUnmarshaller();
        unmarshaller.unmarshal(xsr);
    }

}

标签：java,properties,xml,jaxb,unmarshalling
来源： https://codeday.me/bug/20190629/1329307.html