根据JAXB官方文档改进JAXBContext的使用

src/main/java/me/chanjar/weixin/util/xml/XmlTransformer.java

@@ -8,84 +8,91 @@ import java.io.Writer;
 import java.util.HashMap;
 import java.util.Map;
 
-import javax.xml.bind.JAXBContext;
-import javax.xml.bind.JAXBException;
-import javax.xml.bind.Marshaller;
-import javax.xml.bind.Unmarshaller;
+import javax.xml.bind.*;
 
+import me.chanjar.weixin.bean.*;
 import org.xml.sax.InputSource;
 
 import com.sun.xml.bind.marshaller.CharacterEscapeHandler;
 
 public class XmlTransformer {
 
+  protected static final JAXBContext jaxbContext = initJAXBContext();
+
   /**
    * xml -> pojo
+   *
    * @param clazz
-   * @param object
+   * @param xml
    * @return
-   * @throws JAXBException 
+   * @throws JAXBException
    */
   @SuppressWarnings("unchecked")
   public static <T> T fromXml(Class<T> clazz, String xml) throws JAXBException {
-    JAXBContext context = getJAXBContext(clazz);
+    JAXBContext context = jaxbContext;
     Unmarshaller um = context.createUnmarshaller();
     T object = (T) um.unmarshal(new StringReader(xml));
     return object;
   }
-  
+
   @SuppressWarnings("unchecked")
   public static <T> T fromXml(Class<T> clazz, InputStream is) throws JAXBException {
-    JAXBContext context = getJAXBContext(clazz);
+    JAXBContext context = jaxbContext;
     Unmarshaller um = context.createUnmarshaller();
     InputSource inputSource = new InputSource(is);
     inputSource.setEncoding("utf-8");
     T object = (T) um.unmarshal(inputSource);
     return object;
   }
-  
+
   /**
    * pojo -> xml
+   *
    * @param clazz
+   * @param object
    * @return
-   * @throws JAXBException 
+   * @throws JAXBException
    */
   public static <T> String toXml(Class<T> clazz, T object) throws JAXBException {
     StringWriter stringWriter = new StringWriter();
     toXml(clazz, object, stringWriter);
     return stringWriter.getBuffer().toString();
   }
-  
+
   public static <T> void toXml(Class<T> clazz, T object, Writer writer) throws JAXBException {
-    JAXBContext context = getJAXBContext(clazz);
+    JAXBContext context = jaxbContext;
     Marshaller m = context.createMarshaller();
     m.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
     m.setProperty(CharacterEscapeHandler.class.getName(), characterUnescapeHandler);
     m.marshal(object, writer);
   }
-  
+
   protected static CharacterEscapeHandler characterUnescapeHandler = new CharacterUnescapeHandler();
-  
+
   protected static class CharacterUnescapeHandler implements CharacterEscapeHandler {
     public void escape(char[] ac, int i, int j, boolean flag, Writer writer) throws IOException {
       writer.write(ac, i, j);
     }
   }
-  
-  protected static Map<Class<?>, JAXBContext> jaxbContexts = new HashMap<Class<?>, JAXBContext>();
-  
-  protected static JAXBContext getJAXBContext(Class<?> clazz){
-	//JAXBContext是线程安全的,且创建相对比较耗性能,使用map缓存,并发下多次创建没问题.
-	JAXBContext context = jaxbContexts.get(clazz);
-	if(context == null){
-	  try {
-	    context = JAXBContext.newInstance(clazz);
-	  } catch (JAXBException e) {
-	    throw new RuntimeException("创建JAXBContext实例失败:" + clazz.getName(), e);
-	  }
-	  jaxbContexts.put(clazz, context);
-	}
-	return context;
+
+  private static JAXBContext initJAXBContext() {
+    /*
+     * JAXBContext对象是线程安全的，根据官方文档的建议将对象作为全局实例
+     * https://jaxb.java.net/guide/Performance_and_thread_safety.html
+     */
+    try {
+      return JAXBContext.newInstance(
+          WxXmlOutMessage.class,
+          WxXmlOutImageMessage.class,
+          WxXmlOutMewsMessage.class,
+          WxXmlOutMusicMessage.class,
+          WxXmlOutTextMessage.class,
+          WxXmlOutVideoMessage.class,
+          WxXmlOutVoiceMessage.class,
+          WxXmlMessage.class);
+    } catch (JAXBException e) {
+      throw new RuntimeException(e);
+    }
   }
-  
+
 }

src/test/java/me/chanjar/weixin/bean/WxXmlMessageTest.java

@@ -1,11 +1,9 @@
 package me.chanjar.weixin.bean;
 
-import me.chanjar.weixin.bean.WxXmlMessage;
+import me.chanjar.weixin.api.WxConsts;
 import org.testng.Assert;
 import org.testng.annotations.Test;
 
-import me.chanjar.weixin.api.WxConsts;
-
 @Test
 public class WxXmlMessageTest {