Mastering PowerBuilder

Connecting from Client App to Middle Tier App

In the client application, i.e., the application located in product.pbl, we have created a connection object, but we haven't coded anything to connect to the middle tier application.

Open the application object and declare a global variable as shown below:

nuo_connection g_connection

In the application Open event, append the following code.

// Object: pms Application Object // Event: Open IF not IsValid( g_Connection ) THEN g_Connection = CREATE nuo_Connection End IF IF g_Connection.of_ConnectToServer() <> 1 THEN HALT CLOSE END IF w_mdi_frame.SetMicroHelp( "Connected to DPB Server " )

Now, add ncst_product_master instance variable to w_product_master window.

ncst_product_master incst_product_master

Comment any code that is referring to any DataWindow in the w_product_master Open event and add the following code.

// Object: w_product_master // Event: Open IF g_Connection.CreateInstance(incst_product_master) <> 0 THEN MessageBox("Error", "Unable to create instance of " + & " Product master service object!") Return END IF

Replace ue_retrieve event code with the following:

// Object: w_product_master // Event: ue_retrieve long ll_rowCount Blob lbl_data ll_rowCount = incst_product_master.of_retrieve(lbl_data) dw_product1.SetFullState(lbl_data) // Error Handling

In the above code, we are calling of_retrieve() function that is declared in ncst_product_master. You may recall that ncst_product_master is residing in product-server.pbl which will eventually be moved to another machine. However, you have the proxy for ncst_product_master sitting in product-proxy.pbl, which is in your current application library list. Later, we are making using of DataWindow synchronization functions.

Replace ue_save event code with the following.

// Object: w_product_master // Event: ue_retrieve BLOB lblob_changes long ll_rc int lUserAnswer, lUpdateStatus lUserAnswer = MessageBox( "Update", & "Apply Changes ?", Question!,YesNo!,2) if lUserAnswer = 1 then SetPointer( HourGlass! ) dw_product1.getChanges(lblob_changes) ll_rc = incst_product_master.of_Update( lblob_changes ) if ll_rc = 1 then dw_product1.ResetUpdate() else SetPointer( Arrow! ) MessageBox( "Update", "Error while " + & "applying changes to the database" ) return 0 end if end if SetPointer( Arrow! )

The logic here is similar to ue_retrieve event. Here we are calling ue_update instead of of_retrieve. We are reading the changes into the BLOB variable and sending to the middle-tier object by calling of_update(). Later, we are resetting the status flags for dw_product.

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