I’m using Viritin and its pretty nifty LazyList in combination with a slightly modified ListContainer as the data source for my Grid. I’ve provided the LazyList with an EntityProvider that fetches new rows from the database as needed. It works smoothly most of the time, but then I ran into a situation when a problem occurred during a database search for a particular page. The question is, how to handle this in a graceful way? I already log the exception and show an error message to the user, but an exception is still thrown from the Vaadin internals. If I return an empty list from
findEntities(int firstRow)
, I end up with the following:
SEVERE:
java.lang.IndexOutOfBoundsException: Index: 0
at java.util.Collections$EmptyList.get(Collections.java:3212)
at org.vaadin.viritin.LazyList.get(LazyList.java:173)
at java.util.SubList.get(AbstractList.java:641)
at com.vaadin.server.communication.data.RpcDataProviderExtension.pushRowData(RpcDataProviderExtension.java:379)
at com.vaadin.server.communication.data.RpcDataProviderExtension.access$900(RpcDataProviderExtension.java:65)
at com.vaadin.server.communication.data.RpcDataProviderExtension$2.requestRows(RpcDataProviderExtension.java:293)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.__invoke(DelegatingMethodAccessorImpl.java:43)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java)
at java.lang.reflect.Method.invoke(Method.java:601)
If I return null, I end up with the following:
SEVERE:
java.lang.NullPointerException
at com.vaadin.ui.Grid$RowDataGenerator.writeData(Grid.java:2192)
at com.vaadin.ui.Grid$RowDataGenerator.generateData(Grid.java:2152)
at com.vaadin.server.communication.data.RpcDataProviderExtension.getRowData(RpcDataProviderExtension.java:395)
at com.vaadin.server.communication.data.RpcDataProviderExtension.pushRowData(RpcDataProviderExtension.java:383)
at com.vaadin.server.communication.data.RpcDataProviderExtension.access$900(RpcDataProviderExtension.java:65)
at com.vaadin.server.communication.data.RpcDataProviderExtension$2.requestRows(RpcDataProviderExtension.java:293)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.__invoke(DelegatingMethodAccessorImpl.java:43)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java)
at java.lang.reflect.Method.invoke(Method.java:601)The exceptions are not logged (nor should they), but they cause visual problems. The Grid is rendered full of empty rows (as
EntityProvider.size()
worked properly), with the columns squeezed really narrow, and the component error marker (exclamation mark) appears next to the grid. Question is, can I avoid this somehow? I’d like the Grid to be rendered as empty without any rows, and no component error markers. The problem is that I have no way of catching those exceptions and handling them.