java - 如何通过 Spring-Expression-Language 或其他方式根据 jobParameters 有条件地注入(inject) bean？

Question

我正在尝试创建一个包含多个 FlatFileItemWriter 的 CustomWriter。配置是通过xml。我希望根据 jobParameters 中的值将 FlatFileItemWriters 注入(inject)到 CustomWriter 中；像这样-

<bean id="customWriter" class="com.company.writer.CustomDataWriter" scope="step">
    <property name="chapatiDataWriter" ref="#{jobParameters['chapatiSection'] != null ? chapatiDataWriter : null}"/>
    <property name="anotherDataWriter" ref="anotherDataWriter"/>
    <property name="batchJobConfiguration" value="#{jobParameters['product_configuration']}"/>
</bean>

当我尝试运行该应用程序时，我得到；

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'scopedTarget.customWriter' defined in URL [file:./conf/context.xml]: Cannot resolve reference to bean '#{jobParameters['chapatiSection'] != null ? chapatiDataWriter : null}' while setting bean property 'chapatiDataWriter'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'org.springframework.batch.item.file.FlatFileItemWriter@19cb8309' available

Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'org.springframework.batch.item.file.FlatFileItemWriter@19cb8309' available
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanDefinition(DefaultListableBeanFactory.java:805)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getMergedLocalBeanDefinition(AbstractBeanFactory.java:1279)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:297)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:330)
    ... 52 common frames omitted

如何根据 jobParameters 有条件地注入(inject) chapatiDataWriter？

Answer 1

尽管 SpEL 非常强大，但我不建议在字符串中使用复杂的代码。我将使用 FactoryBean 创建自定义编写器并在 XML 配置中使用工厂 bean:

<bean id="customWriter" class="com.company.writer.CustomDataWriterFactoryBean" scope="step"/>