使用Hibernate元数据构建表单校验功能

public class ValidationInterceptor extends HandlerInterceptorAdapter {

	@Resource(name = "&sessionFactory")
	private LocalSessionFactoryBean sessionFactory;

	@Override
	@SuppressWarnings("unchecked")
	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
		final String uri = request.getRequestURI();
		//通过请求的URI找到对应的校验实体类，这个需要在外部进行配置
		final String entityName = getValidation(uri);
		//没有配置说明这个请求不需要校验
		if (entityName == null)
			return true;
		//通过实体名返回Hibernate的PersistentClass
		final PersistentClass clazz = sessionFactory.getConfiguration().getClassMapping(entityName);
		//对应的表的元数据
		final Table table = clazz.getTable();
		final Iterator<Column> iterator = table.getColumnIterator();
		final Map<String, String> errors = new HashMap<String, String>();
		while (iterator.hasNext()) {
			//对应的列的元数据
			final Column column = iterator.next();
			//列名
			final String name = column.getName();
			//这是数据库列映射到JAVA中的属性
			final Property property = clazz.getProperty(name);
			//这是前台表单提交上来的值
			final String value = request.getParameter(name);
			//如果值为空，跳过该字段的校验
			if (value == null)
				continue;
			//校验非空
			if (!column.isNullable() && "".equals(value.trim())) {
				errors.put(name, "字段"+name+"的值不能为空！");
			} 
			//校验字符串长度
			else if (property.getType() instanceof StringType) {
				if (value.length() > column.getLength()) {
					errors.put(name, "字段"+name+"的值超长了！");
				}
			} 
			//校验日期类型
			else if (property.getType() instanceof DateType) {
				final SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
				try {
					format.parse(value);
				} catch (Exception e){
					errors.put(name, "字段"+name+"必须是日期类型！");
				}
			} 
			//校验数字类型，包括浮点数
			else if (property.getType() instanceof BigDecimalType) {
				int precision = column.getPrecision();
				int scale = column.getScale();
				int front = precision - scale;
				String patten = "";
				for (int i = 0; i < front; i++) {
					patten += "#";
				}
				if (scale > 0) {
					patten += ".";
					for (int i = 0; i < scale; i++) {
						patten += "#";
					}
				}
				final NumberFormat format = new DecimalFormat(patten);
				try {
					format.parse(value);
				} catch (Exception e) {
					errors.put(name, "字段"+name+"必须是数字类型("+patten"+")！");
				}
			}
		}
		//如果没有错误，直接放行
		if (errors.isEmpty())
			return true;
		//有错了，生成描述错误信息的JSON串，返回前台
		response.setContentType("text/json;charset=UTF-8");
		response.getWriter().write(JSONObject.fromObject(errors).toString());
		response.getWriter().close();
		return false;
	}
}

/test/save_log.do=com.coolfancy.blog.entity.Log
/test/save_reply.do=com.coolfancy.blog.entity.Reply