ThreadLocal实现session中用户信息 的线程间共享（精）

 @SuppressWarnings("unchecked")  
public class UserSession {  
      
    private static final ThreadLocal SESSION_MAP = new ThreadLocal();  
  
      
    protected UserSession() {  
    }  
  
      
    public static Object get(String attribute) {  
        Map map = (Map) SESSION_MAP.get(); 
        return map.get(attribute);  
    }  
  
      
    public static <T> T get(String attribute, Class<T> clazz) {  
        return (T) get(attribute);  
    }  
  
      
    public static void set(String attribute, Object value) {  
        Map map = (Map) SESSION_MAP.get();  
  
        if (map == null) {  
            map = new HashMap();  
            SESSION_MAP.set(map);  
        }  
  
        map.put(attribute, value);  
    }  
}