TIP 1. Never create the same JAXBContext more than once

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Always, always assign JAXBContext to a static final field. A JAXBContext object can be shared safely by multiple threads. This is a very expensive to create, so create it once, and share it.

8.1. Performance and thread-safety
The JAXBContext class is thread safe, but the Marshaller, Unmarshaller, and Validator classes are not thread safe.

For example, suppose you have a multi-thread server application that processes incoming XML documents by JAXB. In this case, for the best performance you should have just one instance of JAXBContext in your whole application like this:

Singleton JAXBContext
class MyServlet extends HttpServlet {   
    static final JAXBContext context = initContext();   
    private static JAXBContext initContext() {       
        return JAXBContext.newInstance(Foo.class,Bar.class);   
    }
}

And each time you need to unmarshal/marshal/validate a document. Just create a new Unmarshaller/Marshaller/Validator from this context, like this:

Thread local Unmarshaller
    public void doGet( HttpServletRequest req, HttpServletResponse ) {       
         Unmarshaller u = context.createUnmarshaller();       
          u.unmarshal(...);   
    }

This is the simplest safe way to use the JAXB RI from multi-threaded applications.

If you really care about the performance, and/or your application is going to read a lot of small documents, then creating Unmarshaller could be relatively an expensive operation. In that case, consider pooling Unmarshaller objects. Different threads may reuse one Unmarshaller instance, as long as you don't use one instance from two threads at the same time.

@XmlRootElement(name = "message")
@XmlAccessorType(XmlAccessType.PROPERTY)
@XmlType(propOrder = {"to", "from", "body"})
public class Message2 {
 private String to;

 private String from;

 private String body;
 
 @XmlElement(name = "TO")
 public String getTo() {
  return to;
 }
 public void setTo(String to) {
  this.to = to;
 }
 
 @XmlElement(name = "from")
 public String getFrom() {
  return from;
 }
 
 public void setFrom(String from) {
  this.from = from;
 }
 
 @XmlElement(name = "body")
 public String getBody() {
  return body;
 }
 
 public void setBody(String body) {
  this.body = body;
 }
}

         @Override
        public Accessor<BeanT,ValueT> optimize(JAXBContextImpl context) {
            if(getter==null || setter==null)
                // if we aren't complete, OptimizedAccessor won't always work
                return this;
            if(context!=null && context.fastBoot)
                // let's not waste time on doing this for the sake of faster boot.
                return this;

            Accessor<BeanT,ValueT> acc = OptimizedAccessorFactory.get(getter,setter);
            if(acc!=null)
                return acc;
            else
                return this;
        }
 

* 참고 : Accessor에 대한 개념 파악에 도움되는 글

Improving field get and set performance with ASM or Javassist

http://stackoverflow.com/questions/3022741/improving-field-get-and-set-performance-with-asm-or-javassist

@XmlRootElement(name = "message")
@XmlAccessorType(XmlAccessType.PROPERTY)
@XmlType(propOrder = {"to", "from", "body"})
public class Message2 {
 private String to;

 private String from;

 private String body;
 
 @XmlElement(name = "x")

 public String getTo() {
  return to;
 }
 public void setTo(String to) {
  this.to = to;
 }

[Loaded com.google.spring.bean.Message2$JaxbAccessorM_getBody_setBody_java_lang_String from __JVM_DefineClass__]
[Loaded com.google.spring.bean.Message2$JaxbAccessorM_getBody_setBody_java_lang_String from __JVM_DefineClass__]
[Loaded com.google.spring.bean.Message2$JaxbAccessorM_getFrom_setFrom_java_lang_String from __JVM_DefineClass__]
[Loaded com.google.spring.bean.Message2$JaxbAccessorM_getFrom_setFrom_java_lang_String from __JVM_DefineClass__]
[Loaded com.google.spring.bean.Message2$JaxbAccessorM_getTo_setTo_java_lang_String from __JVM_DefineClass__]
[Loaded com.google.spring.bean.Message2$JaxbAccessorM_getTo_setTo_java_lang_String from __JVM_DefineClass__]

@XmlRootElement(name = "message")
@XmlAccessorType(XmlAccessType.FIELD)
public class Message2 {
 public String to;

 public String from;

 public String body;
}