Batch项目中实现ItemReader时如何打开Reader

Batch项目中实现ItemReader时如何打开Reader

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在Spring Batch项目中实现ItemReader时如何打开Reader？

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问题描述

在Spring Batch项目中，我需要用多行来编写记录。我正在实现 ItemReader 以在返回对象之前累积多行。在完成了几个示例项目之后，我将它拼凑在了一起，但我遇到了一个 ReaderNotOpenException 。

In a Spring Batch project I need to compose a record out of multiple lines. I'm implementing ItemReader to accumulate multiple lines before returning an object. After working through several example projects I have pieced this together but I am faced with a ReaderNotOpenException.

我已经三次检查文件的路径是否正确。当我调试委托包含我的配置文件中的资源和文件路径时。

I have triple checked the path to the file is correct. When I debug the delegate contains the resource and file path from my configuration file.

任何帮助表示赞赏。

配置文件：

    <bean id="cvsFileItemReader" class="com.mkyong.XYZFileRecordReader">
    <property name="delegate">
        <bean class="org.springframework.batch.item.file.FlatFileItemReader">
            <property name="resource" value="classpath:ma/report-headeronly.psv" />
            <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="|" />
                        </bean>
                    </property>
                    <property name="fieldSetMapper">
                        <bean class="org.springframework.batch.item.file.mapping.PassThroughFieldSetMapper" />
                    </property>
                </bean>
            </property>
        </bean>
    </property>
</bean>

我的读者：

package com.mkyong;

import org.springframework.batch.item.ExecutionContext;
import org.springframework.batch.item.ItemReader;
import org.springframework.batch.item.ItemStream;
import org.springframework.batch.item.ItemStreamException;
import org.springframework.batch.item.NonTransientResourceException;
import org.springframework.batch.item.ParseException;
import org.springframework.batch.item.UnexpectedInputException;
import org.springframework.batch.item.file.FlatFileItemReader;
import org.springframework.batch.item.file.transform.FieldSet;

import com.mkyong.model.XYZFileHeaderRecord;

public class XYZFileRecordReader implements ItemReader<XYZFileHeaderRecord>, ItemStream {

private FlatFileItemReader<FieldSet> delegate;

@Override
public XYZFileHeaderRecord read() throws Exception,
        UnexpectedInputException, ParseException,
        NonTransientResourceException {

    XYZFileHeaderRecord maFileHeaderRecord = new XYZFileHeaderRecord();

    for (FieldSet line = null; (line = this.delegate.read()) != null;) {
        String firstToken = line.readString(0);
        if (firstToken.equals("File ID")) {
            maFileHeaderRecord.setFileName( line.readString(1) );
        } else if (firstToken.equals("Date")) {
            maFileHeaderRecord.setDate( line.readString(1) );
            return maFileHeaderRecord;
        }
    }

    return null;
}

@Override
public void close() throws ItemStreamException {}

@Override
public void open(ExecutionContext arg0) throws ItemStreamException {}

@Override
public void update(ExecutionContext arg0) throws ItemStreamException {}

public FlatFileItemReader<FieldSet> getDelegate() {
    return delegate;
}

public void setDelegate(FlatFileItemReader<FieldSet> delegate) {
    this.delegate = delegate;
}
}

我的堆栈跟踪：

SEVERE: Encountered an error executing the step
org.springframework.batch.item.ReaderNotOpenException: Reader must be open before it can be read.
    at org.springframework.batch.item.file.FlatFileItemReader.readLine(FlatFileItemReader.java:195)
    at org.springframework.batch.item.file.FlatFileItemReader.doRead(FlatFileItemReader.java:173)
    at org.springframework.batch.item.support.AbstractItemCountingItemStreamItemReader.read(AbstractItemCountingItemStreamItemReader.java:83)
    at com.mkyong.XYZFileRecordReader.read(XYZFileRecordReader.java:26)
    at com.mkyong.XYZFileRecordReader.read(XYZFileRecordReader.java:1)
    at org.springframework.batch.core.step.item.SimpleChunkProvider.doRead(SimpleChunkProvider.java:91)
    at org.springframework.batch.core.step.item.SimpleChunkProvider.read(SimpleChunkProvider.java:155)
    at org.springframework.batch.core.step.item.SimpleChunkProvider$1.doInIteration(SimpleChunkProvider.java:114)
    at org.springframework.batch.repeat.support.RepeatTemplate.getNextResult(RepeatTemplate.java:368)
    at org.springframework.batch.repeat.support.RepeatTemplate.executeInternal(RepeatTemplate.java:215)
    at org.springframework.batch.repeat.support.RepeatTemplate.iterate(RepeatTemplate.java:144)
    at org.springframework.batch.core.step.item.SimpleChunkProvider.provide(SimpleChunkProvider.java:108)
    at org.springframework.batch.core.step.item.ChunkOrientedTasklet.execute(ChunkOrientedTasklet.java:69)
    at org.springframework.batch.core.step.tasklet.TaskletStep$ChunkTransactionCallback.doInTransaction(TaskletStep.java:395)
    at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:131)
    at org.springframework.batch.core.step.tasklet.TaskletStep$2.doInChunkContext(TaskletStep.java:267)
    at org.springframework.batch.core.scope.context.StepContextRepeatCallback.doInIteration(StepContextRepeatCallback.java:77)
    at org.springframework.batch.repeat.support.RepeatTemplate.getNextResult(RepeatTemplate.java:368)
    at org.springframework.batch.repeat.support.RepeatTemplate.executeInternal(RepeatTemplate.java:215)
    at org.springframework.batch.repeat.support.RepeatTemplate.iterate(RepeatTemplate.java:144)
    at org.springframework.batch.core.step.tasklet.TaskletStep.doExecute(TaskletStep.java:253)
    at org.springframework.batch.core.step.AbstractStep.execute(AbstractStep.java:195)
    at org.springframework.batch.core.job.SimpleStepHandler.handleStep(SimpleStepHandler.java:137)
    at org.springframework.batch.core.job.flow.JobFlowExecutor.executeStep(JobFlowExecutor.java:64)
    at org.springframework.batch.core.job.flow.support.state.StepState.handle(StepState.java:60)
    at org.springframework.batch.core.job.flow.support.SimpleFlow.resume(SimpleFlow.java:152)
    at org.springframework.batch.core.job.flow.support.SimpleFlow.start(SimpleFlow.java:131)
    at org.springframework.batch.core.job.flow.FlowJob.doExecute(FlowJob.java:135)
    at org.springframework.batch.core.job.AbstractJob.execute(AbstractJob.java:301)
    at org.springframework.batch.core.launch.support.SimpleJobLauncher$1.run(SimpleJobLauncher.java:134)
    at org.springframework.core.task.SyncTaskExecutor.execute(SyncTaskExecutor.java:49)
    at org.springframework.batch.core.launch.support.SimpleJobLauncher.run(SimpleJobLauncher.java:127)
    at com.mkyong.App.main(App.java:27)
Apr 25, 2014 5:35:56 PM org.springframework.batch.core.launch.support.SimpleJobLauncher$1 run
INFO: Job: [FlowJob: [name=reportJob]] completed with the following parameters: [{}] and the following status: [FAILED]
Exit Status : FAILED
Done


推荐答案

您的代表没有被打开。解决此问题的最简单方法是更新打开，关闭和更新也可以在委托上调用相应的方法。这也允许重新启动（当前版本不会因为代理的状态没有被保存）：

Your delegate isn't getting opened. The easiest way to address this is to update the open, close, and update methods to call the corresponding methods on the delegate as well. This also allows for restartability (which your current version would not because the state of the delegate is not being saved):

@Override
public void close() throws ItemStreamException {
   delegate.close();
}

@Override
public void open(ExecutionContext arg0) throws ItemStreamException {
    delegate.open(arg0);
}

@Override
public void update(ExecutionContext arg0) throws ItemStreamException {
    delegate.update(arg0);
}

另一种方法是注册你的 FlatFileItemReader 作为您步骤中的流。如果你想走那条路，你必须将它拉出到一个单独的bean定义。

The alternative is to register your FlatFileItemReader as a stream in your step. You'll have to pull it out to a separate bean definition if you want to go that route.

你可以阅读更多关于 ItemStream的信息 s以及它们的生命周期如何工作以及如何通过委托来影响它：

You can read more about ItemStreams and how their lifecycle works and how it is impacted via delegation here: http://docs.spring.io/spring-batch/reference/html-single/index.html#itemStream

这篇关于在Spring Batch项目中实现ItemReader时如何打开Reader？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！

08-20 12:07
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