Package net.sf.jasperreports.engine.data

Class AbstractXmlDataSource<T extends AbstractXmlDataSource<?>>

  • All Implemented Interfaces:
    HierarchicalDataSource<T>, RandomAccessDataSource, JRDataSource, JRRewindableDataSource
    Direct Known Subclasses:
    JaxenXmlDataSource, JRXmlDataSource, XalanXmlDataSource
    public abstract class AbstractXmlDataSource<T extends AbstractXmlDataSource<?>>
extends JRAbstractTextDataSource
implements RandomAccessDataSource, HierarchicalDataSource<T>
    Abstract XML data source implementation that allows to access the data from a xml document using XPath expressions.

    The data source is constructed around a node set (record set) selected by an XPath expression from the xml document.

    Each field can provide an additional XPath expression that will be used to select its value. This expression must be specified using the PROPERTY_FIELD_EXPRESSION custom property at field level. The use of the field description to specify the XPath expression is still supported, but is now discouraged, the above mentioned custom property taking precedence over the field description. In case no XPath expression is specified, the name of the field will be used for the selection of the value. The expression is evaluated in the context of the current node thus the expression should be relative to the current node.

    To support subreports, sub data sources can be created. There are two different methods for creating sub data sources. The first one allows to create a sub data source rooted at the current node. The current node can be seen as a new document around which the sub data source is created. The second method allows to create a sub data source that is rooted at the same document that is used by the data source but uses a different XPath select expression.

    Example: 

     <A>
        <B id="0">
                <C>
                <C>
        </B>
        <B id="1">
                <C>
                <C>
        </B>
        <D id="3">
                <E>
                <E>
        </D>
 </A>

    Data source creation

    • new JRXmlDataSource(document, "/A/B") - creates a data source with two nodes of type /A/B
    • new JRXmlDataSource(document, "/A/D") - creates a data source with two nodes of type /A/D
    Field selection
    • @id - will select the "id" attribute from the current node
    • C - will select the value of the first node of type C under the current node.
    Sub data source creation
    • "((net.sf.jasperreports.engine.data.JRXmlDataSource)$P{REPORT_DATA_SOURCE}).subDataSource("/B/C") - in the context of the node B, creates a data source with elements of type /B/C
    • "((net.sf.jasperreports.engine.data.JRXmlDataSource)$P{REPORT_DATA_SOURCE}).dataSource("/A/D") - creates a data source with elements of type /A/D

    Generally the full power of XPath expression is available. As an example, "/A/B[@id > 0"] will select all the nodes of type /A/B having the id greater than 0. You'll find a short XPath tutorial here.

    Note on performance. Due to the fact that all the XPath expression are interpreted the data source performance is not great. For the cases where more speed is required, consider implementing a custom data source that directly accesses the Document through the DOM API.

    Author:
    Narcis Marcu (narcism@users.sourceforge.net)

    • Field Detail

      • PROPERTY_FIELD_EXPRESSION

        public static final String PROPERTY_FIELD_EXPRESSION
        Property specifying the XPath expression for the dataset field.
        See Also:
        Constant Field Values

    • Constructor Detail

      • AbstractXmlDataSource

        public AbstractXmlDataSource()

    • Method Detail

      • getDocument

        public Document getDocument()
        Access the document that this data source is based on.
        Returns:
        the document used by this data source

      • getCurrentNode

        public abstract Node getCurrentNode()

      • subDataSource

        public abstract T subDataSource​(String selectExpr)
                         throws JRException
        Creates a sub data source using the current node (record) as the root of the document. An additional XPath expression specifies the select criteria applied to this new document and that produces the nodes (records) for the data source.
        Specified by:
        subDataSource in interface HierarchicalDataSource<T extends AbstractXmlDataSource<?>>
        Parameters:
        selectExpr - the XPath select expression
        Returns:
        the xml sub data source
        Throws:
        JRException - if the sub data source couldn't be created
        See Also:
        JRXmlDataSource(Document, String)

      • subDocument

        public abstract Document subDocument()
                              throws JRException
        Creates a document using the current node as root.
        Returns:
        a document having the current node as root
        Throws:
        JRException

      • dataSource

        public abstract T dataSource​(String selectExpr)
                      throws JRException
        Creates a sub data source using as root document the document used by "this" data source. An additional XPath expression specifies the select criteria applied to this document and that produces the nodes (records) for the data source.
        Parameters:
        selectExpr - the XPath select expression
        Returns:
        the xml sub data source
        Throws:
        JRException - if the sub data source couldn't be created
        See Also:
        JRXmlDataSource(Document, String)

      • getText

        public String getText​(Node node)
        Return the text that a node contains. This routine:
        • Ignores comments and processing instructions.
        • Concatenates TEXT nodes, CDATA nodes, and the results of recursively processing EntityRef nodes.
        • Ignores any element nodes in the sublist. (Other possible options are to recurse into element sublists or throw an exception.)
        Parameters:
        node - a DOM node
        Returns:
        a String representing node contents or null

      • getFieldExpression

        protected String getFieldExpression​(JRField field)