Package net.sf.jasperreports.engine.data

Class AbstractXmlDataSource<T extends AbstractXmlDataSource<?>>

java.lang.Object
net.sf.jasperreports.engine.data.JRAbstractTextDataSource
net.sf.jasperreports.engine.data.AbstractXmlDataSource<T>
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 Details

    • PROPERTY_FIELD_EXPRESSION

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

  • Constructor Details

    • AbstractXmlDataSource

      public AbstractXmlDataSource()

  • Method Details

    • 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()

    • getSelectObject

      public abstract Object getSelectObject(Node currentNode, String expression) throws JRException
      Throws:
      JRException

    • getFieldValue

      public Object getFieldValue(JRField jrField) throws JRException
      Description copied from interface: JRDataSource
      Gets the field value for the current position.
      Specified by:
      getFieldValue in interface JRDataSource
      Returns:
      an object containing the field value. The object type must be the field object type.
      Throws:
      JRException

    • 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:

    • subDataSource

      public T subDataSource() throws JRException
      Creates a sub data source using the current node (record) as the root of the document. The data source will contain exactly one record consisting of the document node itself.
      Specified by:
      subDataSource in interface HierarchicalDataSource<T extends AbstractXmlDataSource<?>>
      Returns:
      the xml sub data source
      Throws:
      JRException - if the data source cannot be created
      See Also:

    • 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:

    • dataSource

      public T dataSource() throws JRException
      Creates a sub data source using as root document the document used by "this" data source. The data source will contain exactly one record consisting of the document node itself.
      Returns:
      the xml sub data source
      Throws:
      JRException - if the data source cannot be created
      See Also:

    • 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)