无法使用Spring batch写入FlatFile

<bean id="itemReader" class="org.springframework.batch.item.file.FlatFileItemReader">
    <property name="resource" value="classpath:data.csv" />
    <property name="lineMapper">
        <bean class="org.springframework.batch.item.file.mapping.DefaultLineMapper">
            <property name="lineTokenizer">
                <bean class="org.springframework.batch.item.file.transform.DelimitedLineTokenizer">
                    <property name="delimiter" value="," />
                    <property name="names" value="id,name,age" />
                </bean>
            </property>
            <property name="fieldSetMapper">
                <bean class="com.example.FieldSetMapper" />
            </property>
        </bean>
    </property>
</bean>

<bean id="itemProcessor" class="com.example.ItemProcessor" />

<bean id="itemWriter" class="org.springframework.batch.item.file.FlatFileItemWriter">
    <property name="resource" value="file:output.csv" />
    <property name="lineAggregator">
        <bean class="org.springframework.batch.item.file.transform.DelimitedLineAggregator">
            <property name="delimiter" value="," />
            <property name="fieldExtractor">
                <bean class="org.springframework.batch.item.file.transform.BeanWrapperFieldExtractor">
                    <property name="names" value="id,name,age" />
                </bean>
            </property>
        </bean>
    </property>
</bean>

<batch:job id="myJob">
    <batch:step id="step1">
        <batch:tasklet>
            <batch:chunk reader="itemReader" processor="itemProcessor" writer="itemWriter" commit-interval="10" />
        </batch:tasklet>
    </batch:step>
</batch:job>