在转换器中注入ManagedBean [英] Injecting a managedBean in a converter

问题描述

我正在尝试为我的selectonemenu列表编写一个转换器，以便可以从ManagedBean的getter getDatasetList()中检索要显示的列表. 我的ManagedBean是viewScoped.

I'm trying to write a converter for my selectonemenu list so the list that i want to display can be retrieved from a managedBean's getter getDatasetList() . My managedBean is viewScoped.

这是转换器的代码:

@FacesConverter(value = "datasetConverter")
public class DatasetConverter implements Converter{

@ManagedProperty(value="#{projectCampaignManagementMB}")
private ProjectCampaignManagementMB campaignManagementMB;

@Override
public Object getAsObject(FacesContext context, UIComponent component,
        String value) {

     List <DataSet>  datasetList=campaignManagementMB.getDatasetList();

     DataSet dataSet;
     String dataSetName;
     if (datasetList!=null){
            for(int i=0 ;i<datasetList.size();i++)
            {   
                dataSet=datasetList.get(i);
                dataSetName=dataSet.getName();

            if  (dataSetName.equals(value))
                return dataSet;
            System.out.println("getasobject dataset"+dataSet.getName());
            }
     }
            return null;
}

@Override
public String getAsString(FacesContext context, UIComponent component,
        Object value) {

 if (value==null) return ""; 
    System.out.println("getastring dataset"+((DataSet) value).getName());
 return ((DataSet) value).getName();
}

但是我在此行上收到一个java.lang.NullPointerException

But i'm getting a java.lang.NullPointerException on this line

  List <DataSet>  datasetList=campaignManagementMB.getDatasetList();

因此，注入的managedBean为Null，

So the injected managedBean is Null,

我尝试了没有意义但可以解决的问题，但是我想做正确的事情. 我用了这个

i tried something that has no sense but it works ,but i want something correct . i used this

@ManagedProperty(value="#{projectCampaignManagementMB}")
private ProjectCampaignManagementMB campaignManagementMB =
    new ProjectCampaignManagementMB();

代替

@ManagedProperty(value="#{projectCampaignManagementMB}")
private ProjectCampaignManagementMB campaignManagementMB

任何帮助将不胜感激

推荐答案

当您要在转换器中使用托管属性时，请使转换器成为托管bean，就像这样

When you want to use managed properties inside your convertor make your convertor a managed bean, like this

@ManagedBean
@SessionScoped
public class DatasetConverter implements Converter{

比起将其用作xhtml页面中的转换器，只需使用绑定

Than to use it as convertor in your xhtml page just use binding

像这样

<h:inputText converter="#{datasetConverter}"

这篇关于在转换器中注入ManagedBean的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！