JAXB使用经验总结

使用JAXB首先要知道它是干什么的 
   当然，切入正题 
      很多时候我们需要把认知世界转化为我们熟悉的java对象，以供方便操作。这里，JAXB可以把xml对象转化为我们的java对象，也可以把java对象转化为xml对象。这时候我们就得知道它的两个转化方法。 
      一个是unmarshal()，一个是marshal() 

unmarshal()是把xml对象转化为我们需要的java对象的方法，自然marshal()是把java对象转化为xml对象的一个过程。 

   我们需要的估计就是这两个方法的精华，只需要用到这么多就可以完成很多的事情了。下面看代码： 

   

private static <T> T unmarshal(File templateFile, JAXBContext context) throws JAXBException {

       final Unmarshaller unmarshaller = context.createUnmarshaller();

       // Unmarshal the XML in the stringWriter back into an object
       final T chart = (T) unmarshaller.unmarshal(templateFile);

       return chart;
   }

   @SuppressWarnings("unchecked")
   private static <T> T unmarshal(String template, JAXBContext context) throws JAXBException {

       final Unmarshaller unmarshaller = context.createUnmarshaller();

       // Unmarshal the XML in the stringWriter back into an object
       final T chart = (T) unmarshaller.unmarshal(new StringReader(template));

       return chart;
   }

这里templateFile 和 template 都是xml文件对象，这样的两个overload method就可以完成由xml对象转化为java对象了。 

private static <T> String marshal(JAXBContext context, final T chart) throws JAXBException {
        // Create the marshaller, this is the nifty little thing that will
        // actually transform the object into XML
        final Marshaller marshaller = context.createMarshaller();

        // Create a stringWriter to hold the XML
        final StringWriter stringWriter = new StringWriter();

        // Marshal the javaObject and write the XML to the stringWriter
        marshaller.marshal(chart, stringWriter);

        String chartXml = stringWriter.toString();
        return chartXml;
    }

marshal()方法也贡献上。

方法都具备了 可以开工了。 

  public static <T> String process(File templateFile, Class<T> type, ChartFiller<T> filler) {
       String chartXml = null;

       try {
           JAXBContext context = JAXBContext.newInstance(type);

           final T chart = (T) unmarshal(templateFile, context);

           filler.fill(chart);

           chartXml = marshal(context, chart);

       } catch (JAXBException e) {
           log.error(e.getMessage(), e);
       }
       return chartXml;
   }

   public static <T> String process(String template, Class<T> type, ChartFiller<T> filler) {
       String chartXml = null;

       try {
           JAXBContext context = JAXBContext.newInstance(type);

           final T chart = (T) unmarshal(template, context);

           filler.fill(chart);

           chartXml = marshal(context, chart);

       } catch (JAXBException e) {
           log.error(e.getMessage(), e);
       }
       return chartXml;
   }

public interface ChartFiller<T> {
       void fill(T chart);
   }

工具方法都上齐了，你就可以在你需要的地方调用了。当然，我还没讲我们的java操作对象。 

下面举个例子，比如上面出现的chart 就是我们需要操纵的对象，它可能是一个xml对象，而我们需要操作的是java对象，晕了吧： 
   比如我们的chart是在页面需要显示的图形，比如fusioncharts 的某个图，先定义为chart，它会是一个接口类，是所有xxxChart的父类。 比如我的具体chart名叫GaugeChart。 

代码如下，别说晕说郁闷了： 

public interface Chart {

}

@XmlRootElement(name = "chart")
public class GaugeChart implements Chart {

    @XmlAttribute
    private String lowerLimit;

    @XmlAttribute
    private String upperLimit;

    @XmlAttribute
    private String lowerLimitDisplay;

    @XmlAttribute
    private String upperLimitDisplay;

    @XmlAttribute
    private String majorTMNumber;

    @XmlAttribute
    private String majorTMColor;

    @XmlAttribute
    private String majorTMHeight;

    @XmlAttribute
    private String minorTMNumber;

    @XmlAttribute
    private String minorTMColor;

    @XmlAttribute
    private String minorTMHeight;

    @XmlAttribute
    private String displayValueDistance;

    @XmlAttribute
    private String tickValueDistance;

    @XmlAttribute
    private String gaugeStartAngle;

    @XmlAttribute
    private String gaugeEndAngle;

    @XmlAttribute
    private String palette;

    @XmlAttribute
    private String showValue;

    @XmlAttribute
    private String numberSuffix;

    @XmlElementWrapper(name = "colorRange")
    @XmlElement(name = "color")
    private List<Color> colors;

    @XmlElementWrapper(name = "dials")
    @XmlElement(name = "dial")
    private List<Dial> dials;

    @XmlElementWrapper(name = "annotations")
    @XmlElement(name = "annotationGroup")
    private List<AnnotationGroup> annotations;

    public void addAnnotationGroup(AnnotationGroup annotationGroup) {
        if (annotations == null)
            annotations = new LinkedList<AnnotationGroup>();
        this.annotations.add(annotationGroup);
    }

    public void addDials(Dial dial) {
        if (dials == null)
            dials = new LinkedList<Dial>();
        this.dials.add(dial);
    }

    public void setAnnotations(List<AnnotationGroup> annotations) {
        this.annotations = annotations;
    }

    public void setDials(List<Dial> dials) {
        this.dials = dials;
    }

    public void setColors(List<Color> colors) {
        this.colors = colors;
    }

    public void addColor(Color color) {
        if (color == null)
            colors = new LinkedList<Color>();
        this.colors.add(color);
    }

    public void setLowerLimit(String lowerLimit) {
        this.lowerLimit = lowerLimit;
    }

    public void setUpperLimit(String upperLimit) {
        this.upperLimit = upperLimit;
    }

    public void setLowerLimitDisplay(String lowerLimitDisplay) {
        this.lowerLimitDisplay = lowerLimitDisplay;
    }

    public void setUpperLimitDisplay(String upperLimitDisplay) {
        this.upperLimitDisplay = upperLimitDisplay;
    }

    public void setMajorTMNumber(String majorTMNumber) {
        this.majorTMNumber = majorTMNumber;
    }

    public void setMajorTMColor(String majorTMColor) {
        this.majorTMColor = majorTMColor;
    }

    public void setMajorTMHeight(String majorTMHeight) {
        this.majorTMHeight = majorTMHeight;
    }

    public void setMinorTMNumber(String minorTMNumber) {
        this.minorTMNumber = minorTMNumber;
    }

    public void setMinorTMColor(String minorTMColor) {
        this.minorTMColor = minorTMColor;
    }

    public void setMinorTMHeight(String minorTMHeight) {
        this.minorTMHeight = minorTMHeight;
    }

    public void setDisplayValueDistance(String displayValueDistance) {
        this.displayValueDistance = displayValueDistance;
    }

    public void setTickValueDistance(String tickValueDistance) {
        this.tickValueDistance = tickValueDistance;
    }

    public void setGaugeStartAngle(String gaugeStartAngle) {
        this.gaugeStartAngle = gaugeStartAngle;
    }

    public void setGaugeEndAngle(String gaugeEndAngle) {
        this.gaugeEndAngle = gaugeEndAngle;
    }

    public void setPalette(String palette) {
        this.palette = palette;
    }

    public void setShowValue(String showValue) {
        this.showValue = showValue;
    }

    public void setNumberSuffix(String numberSuffix) {
        this.numberSuffix = numberSuffix;
    }

    @Override
    public String toString() {
        return ToStringBuilder.reflectionToString(this);
    }
}

  上面那一堆的注解来自jaxb的jar包，下哪些包我就不说了。估计应该能看懂个所以然吧，那些属性都是这个gaugeChart所需要的图形显示属性，不必去细究，它需要什么，我们按上面添加就是了，不过貌似没有get()方法，不需要这个。里面注解的像这样的@XmlElement(name = "annotationGroup") ，这个annotationGroup也是像GaugeChart这样的java对象，需要被定义。 


接下来我们可以在action中调用了。 
  
  

private String getXxxXml() {

       String template = getTemplate();
       String chartXml = JAXBUtils.process(template, GaugeChart.class,
               new JAXBUtils.ChartFiller<GaugeChart>() {

                   public void fill(final GaugeChart chart) {
                       Dial dial1 = new Dial();
                       dial1.setValue("");
                       dial1.setRearExtension("10");
                       chart.addDials(dial1);
                   }
               });
       return chartXml;
   }

这样的一个方法返回的就是一个xml的string型对象了，我们只需要在页面拿到这个string型的xml ，就可以通过fusioncharts（当然是我这里用了fusioncharts）来调用它并显示相应的图形了。