XEO Web Components - Introducing the API

In the previous chapters you generated viewers using XEO Studio's Scaffolding tool and went through an explanation of the basics of XEO Viewers as well as customized an edit viewer for the LIB_Book Object Model. In this chapter we'll introduce the Java API to use when creating your own custom viewers and beans, before that, however, you should create some instances of Object Models so that some of things you'll do in this chapter are visible.

Go the Main_Library.xvw viewer and add an entry for the list viewer of the LIB_Publisher Object Model with the following code:

<xvw:menu text='Publishers'
 value="{viewerName:'LIB_Publisher/list.xvw', boql:select LIB_Publisher}"
 target='Tab' serverAction="#{viewBean.listObject}" icon='resources/LIB_Publisher/ico16.gif'/>

And create a publisher with any name you like (Wrox Press, for example). Now add two book instances (for example book Beggining Spring Framework 2 and Professional Apache Tomcat 6), for the author you can use the previously created "John Doe" (or create a new one) and for the publisher use the newly created "Wrox Press" instance. The task in this section is to add a new tab to the LIB_Publisher and LIB_Author edit viewers, to display the list of each books that publishe/author has worked on. This will also be used to introduce the Java API that can be used.

Start by creating a new java class in the org.examples.viewer.beans package with the name LibPublisherEditBean and make it extend the netgest.bo.xwc.xeo.beans.XEOEditBean class, then open the LIB_Publisher/edit.xvw file and change the classBean property to org.viewers.examples.viewers.beans.LibPublisherEditBean this will associate the viewer with this bean.

Next, add a new tab element, to the tabs container already present in the viewer, just like the following:

<xvw:tabs>
<xvw:tab label="Nucleus">
      <xeo:bridge bridgeName='nucleus' >
          <xvw:columns>
              <xvw:columnAttribute width="150" label="Nucleus" dataField="SYS_CARDID"/>
          </xvw:columns>
      </xeo:bridge>
      </xvw:tab>
                    
          <xvw:tab label="Published Books">
          </xvw:tab>
</xvw:tabs>

In order to display a list of Object Model instances you'll use the xeo:list component which is essentially like xeo:bridge component used before, but tailored to display any list of instances (and not only lists that come from collection attributes). Since you'll be displaying books just use the title for the column, use the following code:

<xvw:tab label="Published Books">
   <xeo:list targetList="#{viewBean.dataList}" >
       <xvw:columns>
           <xvw:columnAttribute width="150" dataField="title"/>
        </xvw:columns>
   </xeo:list>
</xvw:tab>

Notice the "targetList='#{viewBean.dataList}'" property. It tells the xeo:list component that its data source should come from the dataList property of the current bean. Switch the LibPublisherBean and create a method like the following (you'll need to import netgest.bo.xwc.components.connectors.DataListConnector):

public DataListConnector getDataList(){ }

The DataListConnector interface represents a list of elements to display in a xvw:gridPanel component (or any component that derives from the xvw:gridPanel component, actually, like the xeo:bridge and xeo:list component. For the xeo:bridge and xeo:list components there's an implementation of the interface that allows to use elements from a boObjectList instance. Compose the method with the following:

public DataListConnector getDataList(){
        String boqlExpression = "";
        boObjectList listBooksOfPublisher = ObjectListManager.list(getEboContext(), boqlExpression);
        return new XEOObjectListConnector(listBooksOfPublisher);
    }

Essentially, to create a list of instances, you only need a XEOQL (BOQL) expression an a Context to pass to the list method of the ObjectListManager class. The resulting set of instances is passed to the constructor of the XEOObjectListConnector which an implementation of the DataListConnector interface for lists of instances.The getEBoContext() method is available for any bean that extends the XEOBaseBean (which is the case of the XEOEditBean which is the bean you're extending in this situation)

The only situation here is what will be the XEOQL expression to retrieve all books from the current publisher, to do that, use the following query:

String boqlExpression = "select LIB_Book where publisher = " + getXEOObject().getBoui();

The getXEOObject() method is available in the XEOEditBean, which returns the current boObject instance being edited (in this situation, the publisher instance); since relations between instances are done using the instance's BOUI (Business Object Unique Identifier), you use the getBoui() method to complete the query. If the BOUI of the current publisher is 12345, the query would be select LIB_Book where publisher = 12345.

If you do this, and now open the list of Publishers, open the "Wrox Press" instance and select the "Published Books" tab you should see the list of books like depicted in figure XWCIA.1.

Figure XWCIA.1 - List of books published by "Wrox Press"

A note before moving on to the next viewer. List (xeo:list) components are usually found inside list viewers which are associated with the XEOBaseList bean, and that bean as a specific method to open an edit viewer from a double click of an item in the list. The XEOEditBean does not have such a method and if you try double clicking on a line of the "Published Books" list it will trigger an error, to prevent that from happenning you'll either have to implement a method to respond to the double click event, or disabled that via the onRowDblClick property, like in the following code:

<xeo:list targetList="#{viewBean.dataList}" <em>onRowDoubleClick=""</em>>
    <xvw:columns>
      <xvw:columnAttribute width="150" dataField="title"/>
   </xvw:columns>
</xeo:list>

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