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

@RequestMapping(value = "/update", method = RequestMethod.POST) 
public String update(List<ProductCollocation> 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"; 
}

这样写会抛出如下异常:

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<ProductCollocation> productCollocations; 
 
    /** 
     * @return the productCollocations 
     */ 
    public List<ProductCollocation> getProductCollocations() { 
        return productCollocations; 
    } 
 
    /** 
     * @param productCollocations the productCollocations to set 
     */ 
    public void setProductCollocations(List<ProductCollocation> 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"; 
}

前台就能够使用索引的方式对后台对象设置值了

<td> 
  <input type="text" name="productCollocations[${productCollocation_index}].displayName" class="text" maxlength="200"  style="width:100px"  value="${productCollocation.displayName}"/> 
  <input type="hidden" name="productCollocations[${productCollocation_index}].id" class="text" maxlength="200" value="${productCollocation.id}"/> 
</td>

上面页面中name的值为:productCollocations[${productCollocation_index}].displayName,其实也相当于productCollocations[0].displayName、productCollocations[1].displayName类似这种的写法

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在使用springMVC时,我使用了@Service这样的注解,发现使用注解@Transactional声明的事务不起作用详解
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