JSF中的访问器/获取器方法内部的业务逻辑 [英] Business logic inside an accessor / getter method in JSF
问题描述
我在MySQL数据库中有三个表.
I have three tables in MySQL database.
- 类别(此问题排除在外)
- sub_category
- 产品
这些表之间的关系很直观-按它们出现的顺序一对多.
The relationship between these tables is intuitive - one-to-many in the order in which they appear.
我正在使用 遍历SubCategory
,List<SubCategory>
的列表c2> 如下.
I'm iterating through a list of SubCategory
, List<SubCategory>
using <p:dataGrid>
as follows.
<p:dataGrid var="row" value="#{featuredProductManagedBean}" rows="4" first="0" columns="1" rowIndexVar="rowIndex" paginator="true" paginatorAlwaysVisible="false" pageLinks="10" lazy="true" rowsPerPageTemplate="5,10,15">
<h:panelGrid columns="1" style="width:100%;">
<p:carousel value="#{featuredProductManagedBean.getProducts(row.subCatId)}" var="prodRow" numVisible="4" pageLinks="5" headerText="#{row.subCatName}" style="text-align: left;">
<!--Display product image in <p:graphicImage>-->
</p:carousel>
<h:outputLink rendered="#{featuredProductManagedBean.count gt 4}" value="xxx">View More</h:outputLink>
</h:panelGrid>
<p:ajax event="page" onstart="PF('blockDataPanelUIWidget').block()" oncomplete="PF('blockDataPanelUIWidget').unblock()"/>
</p:dataGrid>
有一个与 </p:carousel>
的value属性关联的参数化吸气方法. a> featuredProductManagedBean.getProducts(row.subCatId)
.
多次调用该方法,导致多次调用昂贵的业务服务.
The method is called several times causing the expensive business service(s) to be invoked several times.
托管bean:
@ManagedBean
@ViewScoped
public final class FeaturedProductManagedBean extends LazyDataModel<SubCategory> implements Serializable
{
@EJB
private final FeaturedProductBeanLocal service=null;
private Product selectedProduct; //Getter and setter.
private Long count; //Getter and setter.
private static final long serialVersionUID = 1L;
public FeaturedProductManagedBean() {}
public List<Product>getProducts(Long subCatId)
{
List<Product>products=null;
if(FacesContext.getCurrentInstance().getCurrentPhaseId().getOrdinal()==6)
{
setCount(service.countProducts(subCatId));
products=service.getProductList(subCatId);
}
return products;
}
@Override
public List<SubCategory> load(int first, int pageSize, String sortField, SortOrder sortOrder, Map<String, String> filters)
{
int rowCount = service.rowCount().intValue();
setRowCount(rowCount);
if(pageSize<=0)
{
FacesMessage message = new FacesMessage(FacesMessage.SEVERITY_FATAL, Utility.getMessage("faces.message.error"), Utility.getMessage("pageSize.error.message"));
FacesContext.getCurrentInstance().addMessage(null, message);
return Collections.emptyList();
}
else if(first>=pageSize&&rowCount<=Utility.currentPage(first, pageSize)*pageSize-pageSize) {
first-=pageSize;
}
setPageSize(pageSize);
return service.getList(first, pageSize);
}
}
在这里不能使用@PostConstruct
非延迟加载.目前,我已经进行了条件检查if(FacesContext.getCurrentInstance().getCurrentPhaseId().getOrdinal()==6)
,以防止多次调用服务方法.此条件检查是否执行正确的操作?有副作用吗?
Neither @PostConstruct
not lazy loading can be used here. Currently I have put a conditional check if(FacesContext.getCurrentInstance().getCurrentPhaseId().getOrdinal()==6)
to prevent the service methods from being called multiple times. Does this conditional check perform the right thing? Does it have some side effects?
此答案维护Map
,但是维护大型数据源的Map
则很昂贵.
This answer maintains a Map
but maintaining a Map
for large data sources is expensive.
是否存在防止此类业务逻辑多次执行的精确方法?
Is there a precise way to prevent such business logic from being executed multiple times?
推荐答案
我建议将当前加载的subCategory
的产品存储在Map
中,紧接着是<p:dataGrid>
的惰性模型加载它们之后. Map永远不会增长太多,因为您每次调用load
方法时都会将其清空:
I suggest to store the products of the currently loaded subCategory
in a Map
, just after they are loaded by the lazy model of <p:dataGrid>
. The Map will never grow too much because you'll empty it at each invocation of the load
method:
@ManagedBean
@ViewScoped
public final class FeaturedProductManagedBean extends LazyDataModel<SubCategory> implements Serializable
{
@EJB
private final FeaturedProductBeanLocal service=null;
private Product selectedProduct; //Getter and setter.
private Long count; //Getter and setter.
private Map<Long, Product> productsBySubCategory = new HashMap<>(); //Getter only.
private static final long serialVersionUID = 1L;
@Override
public List<SubCategory> load(int first, int pageSize, String sortField, SortOrder sortOrder, Map<String, String> filters)
{
int rowCount = service.rowCount().intValue();
setRowCount(rowCount);
List<SubCategory> subCategories = service.getList(first, pageSize);
productsBySubCategory.clear();
for (SubCategory sc : subCategories)
{
productsBySubCategory.put(sc.getSubCatId(), service.getProductList(sc.getSubCatId());
}
return subCategories;
}
}
然后直接从EL中访问Map
:
And access directly the Map
from EL:
<p:carousel value="#{featuredProductManagedBean.productsBySubCategory[row.subCatId]}" />
请注意,您不需要检查页面边界并设置页面大小的所有样板.
Note that you don't need all that boilerplate that checks page boundaries and sets pagesize.
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