Let me take you to, how to do dynamic pagination using rich:dataTable, rich:datascroller, org.ajax4jsf.model.SerializableDataModel. We will get into a step by step approach on implementing Lazy Pagination using JSF-Richfaces-SEAM.
Please Note: For Richfaces 4 usage, after downloading DynamicDataModel.java. Please do following two bullet points change to java class file. SerializableDataModel was removed in release of Richfaces 4.
- Replace extends class from org.ajax4jsf.model.SerializableDataModel to org.ajax4jsf.model.ExtendedDataModel
- Remove following method from class file
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/* (non-Javadoc) * @see org.ajax4jsf.model.SerializableDataModel#update() */ @Override public void update() { // ignore } |
How to do Step by Step approach!
Step 1:
Create a Class DynamicDataModel extending org.ajax4jsf.model.SerializableDataModel; with all overridden methods.
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public class DynamicDataModel extends SerializableDataModel { @Override public void update() { // TODO Auto-generated method stub } @Override public Object getRowKey() { // TODO Auto-generated method stub return null; } @Override public void setRowKey(Object key) { // TODO Auto-generated method stub } @Override public void walk(FacesContext context, DataVisitor visitor, Range range, Object argument) throws IOException { // TODO Auto-generated method stub } @Override public int getRowCount() { // TODO Auto-generated method stub return 0; } @Override public Object getRowData() { // TODO Auto-generated method stub return null; } @Override public int getRowIndex() { // TODO Auto-generated method stub return 0; } @Override public Object getWrappedData() { // TODO Auto-generated method stub return null; } @Override public boolean isRowAvailable() { // TODO Auto-generated method stub return false; } @Override public void setRowIndex(int rowIndex) { // TODO Auto-generated method stub } @Override public void setWrappedData(Object data) { // TODO Auto-generated method stub } } |
Step 2:
Declare below given local variables to manipulate the pagination in the class.
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private Integer rowId; private Map wrappedData = new HashMap(); private List wrappedKeys = null; private Integer totalRows = 0; private Integer firstRow = 0; private Integer numberOfRows = 0; |
Step 3:
And now we have to implement following methods to achieve dynamic loading of limited data required to display on the page.
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@Override public Object getRowKey() { return rowId; } @Override public void setRowKey(Object key) { this.rowId = (Integer) key; } @Override public int getRowCount() { if (null == rowCount) { return rowCount.intValue(); } return 0; } @Override public Object getRowData() { if (null == rowId) { return null; } return wrappedData.get(rowId); } public SerializableDataModel getSerializableModel(Range range) { if (null != wrappedKeys) { return this; } return null; } |
Step 4:
Ignore following methods since they are never invoked by framework. However you can make use of it on need basis.
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@Override public int getRowIndex() { return 0; } @Override public Object getWrappedData() { throw new UnsupportedOperationException(); } @Override public boolean isRowAvailable() { if (rowId == null) { return false; } else { return dataProvider.hasItemByRowId(rowId); } } @Override public void setRowIndex(int rowIndex) { // ignore } @Override public void setWrappedData(Object data) { throw new UnsupportedOperationException(); } |
Step 5:
Now I’m gonna explain the method walk(), vital part of implementation.
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public void walk(FacesContext context, DataVisitor visitor, Range range, Object argument) throws IOException { // This is method we have to populate a data for DataTable //Range parameter provides the firstRow value and no. of rows value. Extract those values to local variables this.firstRow = ((SequenceRange) range).getFirstRow(); this.numberOfRows = ((SequenceRange) range).getRows(); //we can populate the data from Service Call/Web Service Call For eg. Data from database or Search results using Range values //Define getItemsByrange() method to extract the required data by passing the range values List sampleDataList = getItemsByrange(this.firstRow, this.numberOfRows.intValue()); // Now store the data to wrappedKeys & wrappedData components for the framework to make use of. wrappedKeys = new ArrayList(); if (!sampleDataList.isEmpty()) { for (SampleData item : sampleDataList) { wrappedKeys.add(item.getId()); wrappedData.put(item.getId(), item); visitor.process(context, item.getId(), argument); } } } |
Step 6:
We have completed Java part; let’s move on to JSF code snippet to invoke the Java class
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<rich:panel> <rich:datascroller for="sampleData" maxpages="10" id="dsTop" fastcontrols="hide" renderifsinglepage="false" rerender="dsBtm"></rich:datascroller> <rich:datatable id="sampleData" rowclasses="greyBg, whiteBg" styleclass="tablesorter" value="#{dynamicDataModel}" var="item" rowkeyvar="row" rows="10" width="674" border="0" cellspacing="0" cellpadding="0"> <rich:column sortable="true" sortby="#{item.id}"> <f:facet styleclass="header" name="header"> <h:outputtext value="ID"> </h:outputtext> </f:facet> <h:outputtext value="#{item.id}"></h:outputtext> </rich:column> <rich:column sortable="true" sortby="#{item.firstName}"> <f:facet styleclass="header" name="header"> <h:outputtext value="First Name"></h:outputtext> </f:facet> <h:outputtext value="#{item.firstName}"></h:outputtext> </rich:column> <rich:column sortable="true" sortby="#{item.lastName}"> <f:facet styleclass="header" name="header"> <h:outputtext value="Last Name"></h:outputtext> </f:facet> <h:outputtext value="#{item.lastName}"></h:outputtext> </rich:column> </rich:datatable> <rich:datascroller for="sampleData" maxpages="10" id="dsBtm" fastcontrols="hide" renderifsinglepage="false" rerender="dsTop"></rich:datascroller> </rich:panel> |
That’s all we have to do above steps to achieve dynamic data model pagination through Lazy Pagination using JSF-Richfaces-SEAM. This approach could minimize the weight on presentation layer loading the required data for the page rather loading all the data; that are yet to be displayed in forthcoming pages assuming the data extraction calls are not so expensive.
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