StaxEventItemReader - skip XML fragments processed in previous Job executions

Question

When working with CSV files and restarting a FAILED Job, a StepExecutionListner and associated beforeStep( ....) method can be used to position the reader within the file. So the code could look something like:

public void beforeStep(StepExecution stepExecution) {

    ExecutionContext executionContext = stepExecution.getExecutionContext();

    if (executionContext.containsKey(getKey(LINES_READ_COUNT))) {

        long lineCount = executionContext.getLong(getKey(LINES_READ_COUNT));

        LineReader reader = getReader();
        Object record = "";
        while (reader.getPosition() < lineCount && record != null) {
            record = readLine();
        }
    }
} // Or something similar

My question is how do you achieve the same thing when working with a StaxEventItemReader?

My batch_step_execution_context looks something like {"string":"StaxEventItemReader.read.count","int":6}. So in my case the the first 5 XML fragment were successfully processed and upon restarting the Job I would like to start processing from XML fragment number 6 onwards.

Given the config below, how would I position the reader within the XML file?

<batch:job id="reportJob" restartable="true">
    <batch:step id="step1">
        <batch:tasklet>
            <batch:chunk reader="xmlItemReader" writer="cvsFileItemWriter" processor="filterReportProcessor"
                commit-interval="1">
            </batch:chunk>
            <batch:listeners>
                <batch:listener ref="step1Listener" />
            </batch:listeners>
        </batch:tasklet>
    </batch:step>
</batch:job>

<bean id="step1Listener" class="com.mkyong.listeners.Step1Listener" />

<bean id="filterReportProcessor" class="com.mkyong.processor.FilterReportProcessor" />

<bean id="xmlItemReader" class="org.springframework.batch.item.xml.StaxEventItemReader">
    <property name="fragmentRootElementName" value="record" />
    <property name="resource" value="classpath:xml/report.xml" />
    <property name="unmarshaller" ref="reportUnmarshaller" />
</bean>

<!-- Read and map values to object, via jaxb2 -->
<bean id="reportUnmarshaller" class="org.springframework.oxm.jaxb.Jaxb2Marshaller">
    <property name="classesToBeBound">
        <list>
            <value>com.mkyong.model.Report</value>
        </list>
    </property>
</bean>

Environment - spring-batch-core-2.2.0; spring-core-3.2.2

Test Input File

Convert a XML file into a CSV file.

<company>
    <record refId="1001">
        <name>mkyong</name>
        <age>31</age>
        <dob>31/8/1982</dob>
        <income>200,000</income>
    </record>
    <record refId="1002">
        <name>kkwong</name>
        <age>30</age>
        <dob>26/7/1983</dob>
        <income>100,999</income>
    </record>
    <record refId="1003">
        <name>joel</name>
        <age>29</age>
        <dob>21/8/1984</dob>
        <income>1,000,000</income>
    </record>
    <record refId="1004">
        <name>leeyy</name>
        <age>29</age>
        <dob>21/3/1984</dob>
        <income>80,000.89</income>
    </record>
    <record refId="1005">
        <name>Grant</name>
        <age>29</age>
        <dob>21/3/1984</dob>
        <income>80,000.89</income>
    </record>
</company>

Test Run 1

After processing two records in the input file, I forced a RunTimeException.

batch_job_execution --->>  "FAILED";"FAILED";"java.lang.RuntimeException: Get me out of here!

batch_step_execution_context --->> {"string":"StaxEventItemReader.read.count","int":2}

Output CSV file --->> 1001,mkyong,31,31/08/1982,200000
                      1002,kkwong,30,26/07/1983,100999

Test Run 2

Process all "remaining data", so expecting .... refId="1003", refId="1004", refId="1005"

batch_job_execution --->>  "COMPLETED";"COMPLETED";"''";"2015-01-25 16:18:08.587"

batch_step_execution_context --->>  {"string":"StaxEventItemReader.read.count","int":6}


Output CSV file --->> 1001,mkyong,31,31/08/1982,200000
                      1002,kkwong,30,26/07/1983,100999
                      1003,joel,29,21/08/1984,1000000
                      1004,leeyy,29,21/03/1984,80000.89
                      1005,Grant,29,21/03/1984,80000.89

Test Result

Unfortunately it looks like the StaxEventItemReader is reading from the beginning of the file, rather than re-positioning itself based on the value of StaxEventItemReader.read.count which is set to 2 after the first test.

Answer 1

You don't need to configure anything, this is already the default behavior of the StaxEventItemReader. When it opens it repositions itself from the read count in the step execution context.