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Splitting XML Messages

XPathMessageSplitter supports messages with either String or Document payloads. The splitter uses the provided XPath expression to split the payload into a number of nodes. By default, this results in each Node instance becoming the payload of a new message. When each message should be a Document, you can set the createDocuments flag. Where a String payload is passed in, the payload is converted and then split before being converted back to a number of String messages. The XPath splitter implements MessageHandler and should therefore be configured in conjunction with an appropriate endpoint (see the namespace support example after the following example for a simpler configuration alternative). The following example configures a bean that uses an XPathMessageSplitter:

<bean id="splittingEndpoint"
      class="org.springframework.integration.endpoint.EventDrivenConsumer">
    <constructor-arg ref="orderChannel" />
    <constructor-arg>
        <bean class="org.springframework.integration.xml.splitter.XPathMessageSplitter">
            <constructor-arg value="/order/items" />
            <property name="documentBuilder" ref="customisedDocumentBuilder" />
            <property name="outputChannel" ref="orderItemsChannel" />
        </bean>
    </constructor-arg>
</bean>

XPath splitter namespace support lets you create a message endpoint with an input channel and output channel, as the following example shows:

<!-- Split the order into items and create a new message for each item node -->
<int-xml:xpath-splitter id="orderItemSplitter"
                       input-channel="orderChannel"
                       output-channel="orderItemsChannel">
    <int-xml:xpath-expression expression="/order/items"/>
</int-xml:xpath-splitter>

<!-- Split the order into items, create a new document for each item-->
<int-xml:xpath-splitter id="orderItemDocumentSplitter"
                       input-channel="orderChannel"
                       output-channel="orderItemsChannel"
                       create-documents="true">
    <int-xml:xpath-expression expression="/order/items"/>
    <int:poller fixed-rate="2000"/>
</int-xml:xpath-splitter>

Starting with version 4.2, the XPathMessageSplitter exposes the outputProperties (such as OutputKeys.OMIT_XML_DECLARATION) property for an javax.xml.transform.Transformer instance when a request payload is not of type org.w3c.dom.Node. The following example defines a property and uses it with the output-properties property:

<util:properties id="outputProperties">
	<beans:prop key="#{T (javax.xml.transform.OutputKeys).OMIT_XML_DECLARATION}">yes</beans:prop>
</util:properties>

<xpath-splitter input-channel="input"
             output-properties="outputProperties">
    <xpath-expression expression="/orders/order"/>
</xpath-splitter>

Starting with version 4.2, the XPathMessageSplitter exposes an iterator option as a boolean flag (defaults to true). This allows the “streaming” of split nodes in the downstream flow. With the iterator mode set to true, each node is transformed while iterating. When false, all entries are first transformed, before the split nodes start being sent to the output channel. (You can think of the difference as “transform, send, transform, send” versus “transform, transform, send, send”.) See Splitter for more information.