JSF 2.1 and JBoss RichFaces 4.1.0 make it easy to do server-side paging and sorting, which improves performance of Java EE web applications significantly compared to returning list of all rows from the database and filtering it later in the application.
By implementing
ExtendedDataModel, the
data model can be used directly by
rich:dataTable and
rich:dataScroller JSF components.
ExtendedDataModel for Spring Data Neo4j Finder/Query Methods To implement this on
Neo4j graph database, by using
Spring Data Neo4j finder methods we can implement ExtendedDataModel like below: (in
Scala programming language)
package com.satukancinta.webimport collection.JavaConversions._ import org.ajax4jsf.model.ExtendedDataModelimport javax.faces.context.FacesContext import org.springframework.data.domain.Pageimport org.ajax4jsf.model.DataVisitor import org.springframework.data.neo4j.repository.GraphRepositoryimport org.springframework.data.domain.PageRequest import org.springframework.data.neo4j.aspects.core.NodeBackedimport org.ajax4jsf.model.Range import org.ajax4jsf.model.SequenceRangeimport org.slf4j.LoggerFactory import org.springframework.data.domain.Sortimport org.springframework.data.domain.Sort.Direction import org.springframework.data.domain.Pageableabstract class FinderModel[E]() extends ExtendedDataModel[E] { private lazy val log = LoggerFactory.getLogger(classOf[FinderModel[E]]) private lazy val rowCount: Int = { val result= getRowCountLazy log.debug("Total rows: {}", result) result } private var rowIndex: Int = _ private var page: Page[E] = _ private var pageData: List[E] = _ private var lastRange: (Int, Int) = _ log.trace("Created {}", this.getClass) def getRowCountLazy: Int def find(pageable: Pageable): Page[E] def setRowKey(key: Object): Unit = setRowIndex(key.asInstanceOf[Int]) def getRowKey: Object = getRowIndex: java.lang.Integer private def loadData(range: Range): Unit = { val seqRange = range.asInstanceOf[SequenceRange] val curRange = (seqRange.getFirstRow, seqRange.getRows) if (lastRange == curRange) { log.debug("loadData returning cached") return } lastRange = curRange val pageNum = seqRange.getFirstRow / seqRange.getRows // ORDER BY name is painfully slow: https://groups.google.com/group/neo4j/t/f2219df41f5500a9 val pageReq = new PageRequest(pageNum, seqRange.getRows/*, Direction.ASC, "y.name"*/) log.debug("loadData({}, {}) -> PageRequest({}, {})", Array[Object](seqRange.getFirstRow: java.lang.Long, seqRange.getRows: java.lang.Long, pageNum: java.lang.Long, seqRange.getRows: java.lang.Long)) val startTime = System.currentTimeMillis page = find(pageReq) val findTime = System.currentTimeMillis - startTime log.debug("Page has {} rows of {} total in {} pages, took {}ms", Array[Object](page.getSize: java.lang.Long, page.getTotalElements: java.lang.Long, page.getTotalPages: java.lang.Long, findTime: java.lang.Long)) pageData = page.toList // val pageIds = pageData.map( _.asInstanceOf[NodeBacked].getNodeId )// log.debug("Node IDs: {}", pageIds); } def walk(context: FacesContext, visitor: DataVisitor, range: Range, argument: Object): Unit = { loadData(range) for (val index <- 0 to pageData.size - 1) { visitor.process(context, index, argument) } } def isRowAvailable: Boolean = rowIndex < pageData.length def getRowCount: Int = rowCount def getRowData: E = { val result = pageData(rowIndex) // repository.findOne(rowKey.asInstanceOf[Long]) val node = result.asInstanceOf[NodeBacked] log.trace("getRowData({}) = #{}: {}", Array[Object](rowIndex: java.lang.Long, node.getNodeId: java.lang.Long, node)) result } def getRowIndex: Int = rowIndex def setRowIndex(index: Int): Unit = rowIndex = index def getWrappedData: Object = { null } def setWrappedData(wrappedData: Object): Unit = { /* dummy */ }} To use the FinderModel, it's much easier if we create a repository first and add some finder/query methods returning count and Page:
public interface InterestRepository extends GraphRepository<Interest> { @Query("START u=node({userId}) MATCH u-[:LIKE]->y RETURN COUNT(y)") public Long findUserLikeCount(@Param("userId") long userId); // ORDER BY name is still slow: https://groups.google.com/group/neo4j/t/f2219df41f5500a9 // @Query("START u=node({userId}) MATCH u-[:LIKE]->y RETURN y ORDER BY y.name") @Query("START u=node({userId}) MATCH u-[:LIKE]->y RETURN y") public Page<Interest> findUserLikes(@Param("userId") long userId, Pageable pageable); }How to create a FinderModel instance from Java :
@Inject InterestRepository interestRepo; private FinderModel<Interest> userLikesModel; @PostConstruct public void init() { userLikesModel = new FinderModel<Interest>() { @Override public int getRowCountLazy() { return interestRepo.findUserLikeCount(user.getNodeId()).intValue(); } @Override public Page<Interest> find(Pageable pageable) { return interestRepo.findUserLikes(user.getNodeId(), pageable); } }; }And how to use this data model from a JSF Template .xhtml file:
<rich:dataTable id="interestTable" var="interest" value="#{userLikes.userLikesModel}" rows="20"> <rich:column> <f:facet name="header">Name</f:facet> <h:link outcome="/interests/show?id=#{interest.nodeId}" value="#{interest.name}"/> </rich:column> <f:facet name="footer"><rich:dataScroller/></f:facet> </rich:dataTable>Quite practical, isn't it?
ExtendedDataModel for Spring Data Neo4j RepositoryFinderModel can then be further subclassed to handle any
Spring Data Neo4j repository:
class GraphRepositoryModel[E]() extends FinderModel[E] { private var repository: GraphRepository[E] = _ def getRowCountLazy: Int = repository.count.toInt def find(pageable: Pageable): Page[E] = repository.findAll(pageable) override def getWrappedData: Object = repository override def setWrappedData(wrappedData: Object): Unit = repository = wrappedData.asInstanceOf[GraphRepository[E]] }And use it like this:
@Inject InterestRepository interestRepo; private GraphRepositoryModel<Interest> interestModel; @PostConstruct public void init() { interestModel = new GraphRepositoryModel<Interest>(); interestModel.setWrappedData(interestRepo);} Hope this helps.
To learn more about Scala programming, I recommend Programming in Scala: A Comprehensive Step-by-Step Guide, 2nd Edition.
