Question

<bean id="itemReader" class="org.springframework.batch.item.adapter.ItemReaderAdapter">
  <property name="targetObject" ref="fooService" />
  <property name="targetMethod" value="generateFoo" />
</bean>

鉴于这个简单的设置，fooService是一个简单的pojo spring bean。

如果fooService实现了ItemStream并且我实现了openclin和open方法，那么我的ItemReader是否可以重启？

此致

Answer 1

好的，我终于回答了我自己的问题。

我发现ItemReaderAdapter非常有用，因为大多数时候我们已经有某种DAO或服务可以访问我们需要的数据。

但我的测试告诉我，如果我使用ItemReaderAdapter impl。开箱即用，它们不能重新启动，因为它们没有实现ItemStream！

因此，如果你们中任何人想要使用具有可重启功能的ItemReaderAdapter，那么这就是我的解决方案。

经过测试和工作; - ）

1）创建自己的ItemReaderAdapter实现：

package xxx.readers.adapters;

import java.math.BigDecimal;

import org.apache.log4j.Logger;
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.adapter.AbstractMethodInvokingDelegator;
import org.springframework.beans.factory.annotation.Autowired;


/**
* Invokes a custom method on a delegate plain old Java object which itself
* provides an item.
* 
* overriden to implements the ItemStream interface
* 
* @author Benoit Campeau
*/
public class MyItemReaderAdapter<T> extends AbstractMethodInvokingDelegator<T>  implements ItemReader<T>, ItemStream {

private static final Logger log = Logger.getLogger(MyItemReaderAdapter.class);

private long currentCount = 0;

private final String CONTEXT_COUNT_KEY = "ReglementAdapter.count"; 

/**
 * @return return value of the target method.
 */
public T read() throws Exception {

    super.setArguments(new Long[]{currentCount++});
    return invokeDelegateMethod();
}
@Override
public void open(ExecutionContext executionContext)
        throws ItemStreamException {
    currentCount = executionContext.getLong(CONTEXT_COUNT_KEY,0);
    log.info("Open Stream current count : " + currentCount);

}


@Override
public void update(ExecutionContext executionContext) throws ItemStreamException {
    executionContext.putLong(CONTEXT_COUNT_KEY, currentCount);
    log.info("Update Stream current count : " + currentCount);
}


@Override
public void close() throws ItemStreamException {
    // TODO Auto-generated method stub

}

}

2）现在使用你的impl将Reader配置为适配器。（MyItemReaderAdapter）。

<bean id="MyReader" class="xxx.readers.adapters.MyItemReaderAdapter"> <property name="targetObject" ref="someAdapter" /> <property name="targetMethod" value="next" /> </bean>

3）最后，创建一个将作为Adapter委托类的Component：

package fcdq.iemt.batch.validation.reglement.readers.adapters; import java.util.List; import org.apache.log4j.Logger; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Component; @Component("someAdapter") public class SomeAdapter { private static final Logger log = Logger.getLogger(SomeAdapter .class); @Autowired private SomeService srv1; private List<Transaction> listTrx; public void init() { log.info("Initializing " + SomeAdapter.class.toString() ); listTrx = srv1.findByTimestampAndStatus(context.getBeginTSCutoff(), context.getEndTSCutoff(), TransactionTypeEnum.TRANSFER_COMPLETE); } /** * read method delegate * @return */ public Transaction next(Long index) { if (listTrx != null && listTrx.size() > index ) { return listTrx.get(index.intValue()); } else { return null; } } }

注意事项：

注意MyItemReaderAdapter中的setArguments。这必须将execution_context中存储的currentCount的值传递给委托read（）方法

请注意，MyItemReaderAdapter不实现InitializingBean接口。我使用stepListener代替，因为我想初始化我要及时阅读的项目列表。

希望它会帮助别人。

此致

Answer 2

实现相同目标的另一种方法是扩展AbstractItemCountingItemStreamItemReader

来自文档::

ItemReaders的抽象超类，支持通过存储重新启动 ExecutionContext中的项目计数（因此需要项目排序在运行之间保留）。子类本质上不是线程安全

示例代码：

package com.***.batch.reader;

import java.util.List;

import org.apache.log4j.LogManager;
import org.apache.log4j.Logger;
import org.springframework.batch.item.support.AbstractItemCountingItemStreamItemReader;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import com.mivim.campaignmanager.data.model.custom.CustomCampaignSubscriberEmail;
import com.mivim.campaignmanager.service.CampaignSubscriberService;


@Component
public class CampaignSubscriberItemReader extends
        AbstractItemCountingItemStreamItemReader<CustomCampaignSubscriberEmail> {

    private Logger logger = LogManager.getLogger(CampaignSubscriberItemReader.class);

    @Autowired
    CampaignSubscriberService campaignSubscriberService;

    List<CustomCampaignSubscriberEmail> customCampaignSubscriberEmails;

    final String ecName = "csItemReaderContext";

    public CampaignSubscriberItemReader() {
        setName(ecName);
    }

    @Override
    protected CustomCampaignSubscriberEmail doRead() throws Exception {
        CustomCampaignSubscriberEmail customCampaignSubscriberEmail = customCampaignSubscriberEmails
                .get(getCurrentItemCount() - 1);
        return customCampaignSubscriberEmail;
    }

    @Override
    protected void doOpen() throws Exception {
        customCampaignSubscriberEmails = campaignSubscriberService.getPendingCampaignSubscriber();

        setMaxItemCount(customCampaignSubscriberEmails.size());

    }

    @Override
    protected void doClose() throws Exception {
        customCampaignSubscriberEmails.clear();
        setMaxItemCount(0);
        setCurrentItemCount(0);
    }


}

ItemReaderAdapter和ItemStream

2 个答案: