Question

我正在使用Spring批量项阅读器。在Item阅读器中读取方法调用存储过程。一旦我们从存储过程中得到结果，它就会返回到writer。但它又会读取方法。所以读取是反复执行。

任何人都可以建议我如何限制read方法只调用一次作业执行。

*注意：StoredprocedureitemReader不是我们的要求。我们需要使用itemreader只读

请帮助解决此问题

Answer 1

如果我理解正确，你需要阅读一次并写多次。您可以使用存储过程在第一次调用read()方法时获取结果，并且所有剩余时间都可以逐个返回已重命名的对象。

Answer 2

这是一个读取器的示例，它一次加载一个项目队列，并从同一队列中读取。这类似于一次调用存储过程和多次“写入”的用例。

package de.incompleteco.spring.batch.item;

import java.util.PriorityQueue;
import java.util.Queue;
import java.util.UUID;

import org.springframework.batch.item.ItemReader;
import org.springframework.batch.item.NonTransientResourceException;
import org.springframework.batch.item.ParseException;
import org.springframework.batch.item.UnexpectedInputException;

import de.incompleteco.spring.batch.domain.Record;

public class SingleItemReader implements ItemReader<Record> {

    private Queue<String> values = null;

    public Record read() throws Exception, UnexpectedInputException,ParseException, NonTransientResourceException {
        //check the queue
        if (values == null) {
            //load
            loadQueue();
        }//end if
        //return
        return getRecord(values.poll());
    }

    private Record getRecord(String value) {
        //init
        Record record = null;
        //check for null
        if (value != null) {
            record = new Record();
            record.setId(UUID.randomUUID());
            record.setValue(value);
        }//end if
        //return
        return record;      
    }

    private synchronized void loadQueue() {
        //generate a bunch of data and add to the queue
        if (values == null) {
            System.out.println("calling load of the queue");
            values = new PriorityQueue<String>();
            for (int i=0;i<100;i++) {
                values.add("hello " + i);
            }//end for
        }//end if
    }

}

这是示例的作者

package de.incompleteco.spring.batch.item;

import java.util.List;

import org.springframework.batch.item.ItemWriter;

import de.incompleteco.spring.batch.domain.Record;

public class SystemItemWriter implements ItemWriter<Record> {

    public void write(List<? extends Record> items) throws Exception {
        System.out.println("starting write...");
        System.out.println(items);
        System.out.println("...finished write");
    }

}

批量配置如下;

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:batch="http://www.springframework.org/schema/batch"
    xmlns:task="http://www.springframework.org/schema/task"
    xmlns:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="http://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task.xsd
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/batch http://www.springframework.org/schema/batch/spring-batch.xsd
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd">

    <batch:job id="singleReadJob">
        <batch:step id="singleReadJob.step1">
            <batch:tasklet>
                <batch:chunk reader="singleReader" writer="multiWriter" commit-interval="10"/>
            </batch:tasklet>
        </batch:step>
    </batch:job>

    <bean id="singleReader" class="de.incompleteco.spring.batch.item.SingleItemReader"/>

    <bean id="multiWriter" class="de.incompleteco.spring.batch.item.SystemItemWriter"/>

    <bean id="jobRepository"
        class="org.springframework.batch.core.repository.support.MapJobRepositoryFactoryBean"/>

    <bean id="jobLauncher"
        class="org.springframework.batch.core.launch.support.SimpleJobLauncher">
        <property name="jobRepository" ref="jobRepository"/>
        <property name="taskExecutor" ref="taskExecutor"/>
    </bean>

    <bean id="jobExplorer"
        class="org.springframework.batch.core.explore.support.MapJobExplorerFactoryBean">
        <property name="repositoryFactory" ref="&amp;jobRepository"/>
    </bean>

    <task:executor id="taskExecutor"/>

    <bean id="transactionManager"
        class="org.springframework.batch.support.transaction.ResourcelessTransactionManager"/>
</beans>

Spring Batch Itemreader重复执行问题

2 个答案: