java spring 批处理：没有 ItemWriter 的 Tasklet
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spring batch : Tasklet without ItemWriter
提问by Yassine EL AYACHI
I defined my tasklet without ItemWriter like this :
我在没有 ItemWriter 的情况下定义了我的 tasklet，如下所示：
<b:tasklet>
<b:chunk reader="baseReader" processor="baseProcessor" commit-interval="100" />
</b:tasklet>
and i got this error :
我收到了这个错误：
Configuration problem: The <b:chunk/>element has neither a 'writer' attribute nor a <writer/>element.
配置问题：该<b:chunk/>元素既没有“writer”属性也没有<writer/>元素。
Do you have any idea ? Thanks
你有什么主意吗 ？谢谢
回答by Cygnusx1
Well, in a chunk, A reader and a Writer are MANDATORY! however, The ItemProcessor is optional.
好吧，总而言之，读者和作家是强制性的！但是，ItemProcessor 是可选的。
This is from the official doc :
这是来自官方文档：
5.1.1. Configuring a Step
Despite the relatively short list of required dependencies for a Step, it is an extremely complex class that can potentially contain many collaborators. In order to ease configuration, the Spring Batch namespace can be used:
5.1.1. 配置步骤
尽管 Step 所需的依赖项列表相对较短，但它是一个极其复杂的类，可能包含许多协作者。为了简化配置，可以使用 Spring Batch 命名空间：
<job id="sampleJob" job-repository="jobRepository">
<step id="step1">
<tasklet transaction-manager="transactionManager">
<chunk reader="itemReader" writer="itemWriter" commit-interval="10"/>
</tasklet>
</step>
The configuration above represents the only required dependencies to create a item-oriented step:
reader - The ItemReader that provides items for processing.
writer - The ItemWriter that processes the items provided by the ItemReader.
transaction-manager - Spring's PlatformTransactionManager that will be used to begin and commit transactions during processing.
job-repository - The JobRepository that will be used to periodically store the StepExecution and ExecutionContext during processing (just before committing). For an in-line (one defined within a ) it is an attribute on the element; for a standalone step, it is defined as an attribute of the .
commit-interval - The number of items that will be processed before the transaction is committed.
It should be noted that, job-repository defaults to "jobRepository" and transaction-manager defaults to "transactionManger". Furthermore, the ItemProcessor is optional, not required, since the item could be directly passed from the reader to the writer.
上面的配置表示创建面向项目的步骤所需的唯一依赖项：
reader - 提供处理项目的 ItemReader。
writer - 处理 ItemReader 提供的项目的 ItemWriter。
事务管理器 - Spring 的 PlatformTransactionManager 将用于在处理期间开始和提交事务。
job-repository - JobRepository 将用于在处理期间（就在提交之前）定期存储 StepExecution 和 ExecutionContext。对于内联（在 a 中定义的），它是元素上的一个属性；对于独立步骤，它被定义为 .
commit-interval - 在提交事务之前将处理的项目数。
需要注意的是，job-repository 默认为“jobRepository”，而transaction-manager 默认为“transactionManger”。此外，ItemProcessor 是可选的，不是必需的，因为项目可以直接从读取器传递给写入器。
回答by Yassine EL AYACHI
We can define a chunk without writer (just a reader + processor), i managed to do so. It seems that in order to pass the writer step containing the chunk must inherit abstract step parents, like this :
我们可以定义一个没有写入器的块（只是一个读取器 + 处理器），我设法做到了。似乎为了通过包含块的 writer 步骤必须继承抽象步骤的父级，如下所示：
<b:step id="task" parent="Task">
<b:tasklet>
<b:chunk reader="baseReader" processor="baseProcessor" commit- interval="100" />
</b:tasklet>
</b:step>
<b:job id="batch" parent="Batch">
<b:step id="etape" parent="task" />
</b:job>
Problem solved, thanks!
问题已解决，谢谢！
