Java反射通过getter和setter方法实现类的拷贝

     private User copyFieldValues(User userData, User user) {
         Field[] fields = user.getClass().getDeclaredFields();
         String[] fieldNames = getFieldNames(fields);
         for (int i = 0; i < fieldNames.length; i++) {
             Object value = getFieldValueByName(fieldNames[i], user);
             if (value != null) {
                 setFieldValueByName(fieldNames[i], userData, value,fields[i].getType());
             }
         }
         return userData;
     }

     private String[] getFieldNames(Field[] fields) {
         String[] fieldNames = new String[fields.length];
         for (int i = 0; i < fields.length; i++) {
             fieldNames[i] = fields[i].getName();
         }
         return fieldNames;
     }

     private Object getFieldValueByName(String fieldName, Object o) {
         Object value = null;
         try {
             String getter = "get" + initStr(fieldName);
             Method method = o.getClass().getMethod(getter);
             value = method.invoke(o);
         } catch (Exception e) {
             e.printStackTrace();
         }
         return value;
     }

     private void setFieldValueByName(String fieldName, Object o, Object value, Class<?> type) {
         try {
             String setter = "set" + initStr(fieldName);
             Method method = o.getClass().getMethod(setter, type);
             method.invoke(o, value);
         } catch (Exception e) {
             e.printStackTrace();
         }
     }

     private String initStr(String fieldName) {
         return fieldName.substring(0, 1).toUpperCase() + fieldName.substring(1);
     }