Question

这是我的转换代码。当我们处理大数据时，这需要很长时间......调用方法几乎一百万次......我们可以清楚地看到它正在保持一段时间的线程。

请告诉我一些改善表现的方法！

public class GenericObjectXMLConverter<T> {

  private T t = null;
  private static JAXBContext jaxbContext =null;
  public GenericObjectXMLConverter() {

  }
  public GenericObjectXMLConverter(T obj){
    t = obj;
  }

  protected final Logger  log = Logger.getLogger(getClass());

  /**
   * Converts the java Object and into a xml string message type.
   * @param object the object to convert
   * @return String the converted xml message as string
   */
  public String objectToXMLMessage(T object) {
    StringWriter stringWriter = new StringWriter();
    //JAXBContext jaxbContext=null;
    try {
      jaxbContext = JAXBContext.newInstance(object.getClass());
      Marshaller jaxbMarshaller = jaxbContext.createMarshaller();
      jaxbMarshaller.marshal(object, stringWriter);
    } catch (JAXBException e) {
      log.warn("JAXBException occured while converting the java object into xml string :"+e.getMessage());
    }
       /*if(log.isDebugEnabled())
         log.debug("xml string after conversion:"+stringWriter.toString());*/
       return stringWriter.toString();
  }

  /**
   * Converts a xml string message into a Java Object
   * @param string the string message to convert
   * @return Object the result as Java Object. If the message parameter is null then
     *  this method will simply return null.
   */
  @SuppressWarnings("unchecked")
  public T xmlToObject(String message) {
    if(message.equals("") || message.equals(" ") || message.length()==0){
      return null;
    }else{
      T object=null;
      try {
        jaxbContext = JAXBContext.newInstance(t.getClass());
        StringReader reader = new StringReader(message);
        Unmarshaller jaxbUnmarshaller = jaxbContext.createUnmarshaller();
        object = (T)jaxbUnmarshaller.unmarshal(reader);
        } catch (JAXBException e) {
        log.warn("JAXBException occured while converting the xml string into a Java Object :"+e.getMessage());
        }
       /* if(log.isDebugEnabled()){
          log.debug("Java object after conversion:"+object.toString());
        }*/
      return object;
    }
  }

}

Answer 1

性能和JAXB运行时类

您应该避免反复创建相同的JAXBContext。 JAXBContext是线程安全的，应该重用以提高性能。
Marshaller / Unmarshaller不是线程安全的，但可以快速创建。重复使用它并不是什么大不了的事。

Answer 2

您应该为您的bean类创建单个JAXBContext对象。这是我的版本，用于维护每个bean类的JAXBContext单例对象。

public class MyJAXBUtil {
    public static final Map<String, JAXBContext> JAXB_MAP = new HashMap<>();
    public static JAXBContext getJAXBContext(Object object) {
        if(JAXB_MAP.get(object.getClass().getCanonicalName()) != null) {
            return JAXB_MAP.get(object.getClass().getCanonicalName());
        }else {
            try {
                JAXBContext jaxbContext = JAXBContext.newInstance(object.getClass());
                JAXB_MAP.put(object.getClass().getCanonicalName(), jaxbContext);
                return jaxbContext;
            } catch (JAXBException e) {
                e.printStackTrace();
                return null;
            }
        }
    }
}

当您需要bean类的getJAXBContext并在本地创建JAXBContext时，可以调用Marshaller/Unmarshaller方法。

如何提高JAXB性能？

2 个答案: