Spring Batch - One or more ItemWriter among a list

问题

What I want to do is use one or more ItemWriter for a single step, depending on the batch configuration.

What I need is a behaviour between a classic CompositeItemWriter (which calls all writers) and a classic ClassifierCompositeItemWriter (which calls only one writer); this behaviour would let me call one or more writer, with an external condition for each of the writers specified as delegates.

One of the solution I thought about is using a ClassifierCompositeItemWriter which contains as delegates the list of all possible combination of my writers. To create combinations of writers, I'd need to declare as many CompositeItemWriter as needed (2ⁿ - (n + 1), where n is the total number of "real" writers). Then the Classifier would be custom-made to return a code formatted as a bit-word with each bit is the statuts of a writer (activation could depend on properties configuration or jobParameters, etc.)

Here's an example with 2 writers :

<bean class="ClassifierCompositeItemWriter">
    <property name="matcherMap">
        <map>
            <entry key="10">
                <bean ref="writer1" />
            </entry>
            <entry key="01">
                <bean ref="writer2" />
            </entry>
            <entry key="11">
                <bean ref="writer1and2" />
            </entry>
        </map>
    </property>
</bean>

<bean id="writer1" />
<bean id="writer2" />

<bean id="writer1and2" class="CompositeItemWriter">
    <property name="delegates">
        <bean ref="writer1" />
        <bean red="writer2" />
    </property>
</bean>

This solution is actually working but requires a great number of CompositeItemReader as the number of "real" writers grows.

Is there a more efficient solution?

来源：https://stackoverflow.com/questions/34180075/spring-batch-one-or-more-itemwriter-among-a-list

标签

java

spring-batch