【FAQ】SpingMVC实现集合参数（Could not instantiate bean class [java.util.List]）

需求，要求批量新增或者修改一个List，在Spring MVC中是不支持下面代码的写法

	@RequestMapping(value = "/update", method = RequestMethod.POST)
	public String update(List productCollocations ,HttpServletRequest request, RedirectAttributes redirectAttributes) {
		for (ProductCollocation productCollocation : productCollocations) {
			productCollocation.setModifyDate(DateUtil.getDate());
			productCollocationService.update(productCollocation, "create_date","product","collocation","description");
		}
		addFlashMessage(redirectAttributes, SUCCESS_MESSAGE);
		return "redirect:list.jhtml";
	}

会抛出异常

nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [java.util.List]: 

是否其实也很简单，Spring MVC 需要支持Form表单对象的方式映射，使用get set器来填充对象。

新增一个Form

public class ProductCollocationForm {
	List productCollocations;

	/**
	 * @return the productCollocations
	 */
	public List getProductCollocations() {
		return productCollocations;
	}

	/**
	 * @param productCollocations the productCollocations to set
	 */
	public void setProductCollocations(List productCollocations) {
		this.productCollocations = productCollocations;
	}
}

再使用Form来set对象

	@RequestMapping(value = "/update", method = RequestMethod.POST)
	public String update(ProductCollocationForm productCollocationForm ,HttpServletRequest request, RedirectAttributes redirectAttributes) {
		for (ProductCollocation productCollocation : productCollocationForm.getProductCollocations()) {
			productCollocation.setModifyDate(DateUtil.getDate());
			productCollocationService.update(productCollocation, "create_date","product","collocation","description");
		}
		addFlashMessage(redirectAttributes, SUCCESS_MESSAGE);
		return "redirect:list.jhtml";
	}

前台就可以使用索引的方式对后台对象设置值了