java - org.springframework.batch.item.ItemStreamException : File already exists: [SpringBatch-Partitioner-Example\csv\outputs\users.processed21-30.csv]

Question

我正在开发Spring Batch Partitioning示例，在这个示例中我尝试创建一个“Partitioner”作业，它有10个线程，每个线程都会根据提供的'id'范围从数据库读取记录。我引用了 http://www.mkyong.com/spring-batch/spring-batch-partitioning-example/

当我第一次运行代码时，它工作正常，但下次当我再次运行代码时，它会显示以下错误，我希望每个运行文件都应该重新创建，那么我需要为此做什么？我需要做哪些额外配置？

org.springframework.batch.item.ItemStreamException: File already exists: [C:\Users\userpc\Documents\workspace-sts-3.6.4.RELEASE\SpringBatch-Partitioner-Example\csv\outputs\users.processed21-30.csv]
    at org.springframework.batch.item.util.FileUtils.setUpOutputFile(FileUtils.java:61)
    at org.springframework.batch.item.file.FlatFileItemWriter$OutputState.initializeBufferedWriter(FlatFileItemWriter.java:559)
    at org.springframework.batch.item.file.FlatFileItemWriter$OutputState.access$000(FlatFileItemWriter.java:399)
    at org.springframework.batch.item.file.FlatFileItemWriter.doOpen(FlatFileItemWriter.java:333)
    at org.springframework.batch.item.file.FlatFileItemWriter.open(FlatFileItemWriter.java:323)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
    at org.springframework.aop.support.DelegatingIntroductionInterceptor.doProceed(DelegatingIntroductionInterceptor.java:133)
    at org.springframework.aop.support.DelegatingIntroductionInterceptor.invoke(DelegatingIntroductionInterceptor.java:121)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:207)
    at com.sun.proxy.$Proxy5.open(Unknown Source)
    at org.springframework.batch.item.support.CompositeItemStream.open(CompositeItemStream.java:96)
    at org.springframework.batch.core.step.tasklet.TaskletStep.open(TaskletStep.java:310)
    at org.springframework.batch.core.step.AbstractStep.execute(AbstractStep.java:197)
    at org.springframework.batch.core.partition.support.TaskExecutorPartitionHandler$1.call(TaskExecutorPartitionHandler.java:139)
    at org.springframework.batch.core.partition.support.TaskExecutorPartitionHandler$1.call(TaskExecutorPartitionHandler.java:136)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.lang.Thread.run(Thread.java:745)

Apr 06, 2016 12:07:29 AM org.springframework.batch.core.step.AbstractStep execute
SEVERE: Encountered an error executing step slave in job partitionJob

用户.java

public class User implements Serializable{
    private static final long serialVersionUID = 1L;

    private int id;
    private String username;
    private String password;
    private int age;
    // setters and getters
}

UserRowMapper.java

public class UserRowMapper implements RowMapper<User> {

    @Override
    public User mapRow(ResultSet rs, int rowNum) throws SQLException {
        User user = new User();
        user.setId(rs.getInt("id"));
        user.setUsername(rs.getString("username"));
        user.setPassword(rs.getString("password"));
        user.setAge(rs.getInt("age"));

        return user;
    }
}

RangePartitioner.java

public class RangePartitioner implements Partitioner {

    @Override
    public Map<String, ExecutionContext> partition(int gridSize) {

        Map<String, ExecutionContext> result = new HashMap<String, ExecutionContext>();

        int range = 10;
        int fromId = 1;
        int toId = range;

        for (int i = 1; i <= gridSize; i++) {
            ExecutionContext value = new ExecutionContext();

            System.out.println("\nStarting : Thread" + i);
            System.out.println("fromId : " + fromId);
            System.out.println("toId : " + toId);

            value.putInt("fromId", fromId);
            value.putInt("toId", toId);

            // give each thread a name
            value.putString("name", "Thread" + i);

            result.put("partition" + i, value);

            fromId = toId + 1;
            toId += range;
        }
        return result;
    }
}

UserProcessor.java

@Component("itemProcessor")
@Scope(value = "step")
public class UserProcessor implements ItemProcessor<User, User> {

    @Value("#{stepExecutionContext[name]}")
    private String threadName;

    @Override
    public User process(User item) throws Exception {
        System.out.println(threadName + " processing : " + item.getId() + " : " + item.getUsername());
        return item;
    }

    public String getThreadName() {
        return threadName;
    }

    public void setThreadName(String threadName) {
        this.threadName = threadName;
    }
}

数据库.xml

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:jdbc="http://www.springframework.org/schema/jdbc" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans 
        http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
        http://www.springframework.org/schema/jdbc 
        http://www.springframework.org/schema/jdbc/spring-jdbc-3.2.xsd">

    <!-- connect to database -->
    <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="com.mysql.jdbc.Driver" />
        <property name="url" value="jdbc:mysql://localhost:3306/toga" />
        <property name="username" value="root" />
        <property name="password" value="root" />
    </bean>

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

    <!-- create job-meta tables automatically 
    <jdbc:initialize-database data-source="dataSource">
        <jdbc:script location="org/springframework/batch/core/schema-drop-mysql.sql" />
        <jdbc:script location="org/springframework/batch/core/schema-mysql.sql" />
    </jdbc:initialize-database>
    -->
</beans>

上下文.xml

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans 
        http://www.springframework.org/schema/beans/spring-beans-3.2.xsd">

    <!-- stored job-meta in memory --> 
    <bean id="jobRepository"
        class="org.springframework.batch.core.repository.support.MapJobRepositoryFactoryBean">
        <property name="transactionManager" ref="transactionManager" />
    </bean>

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

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

作业分区器.xml

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

    <!-- spring batch core settings -->
    <import resource="../config/context.xml" />

    <!-- database settings -->
    <import resource="../config/database.xml" />

    <!-- ============= partitioner job ========== -->
    <job id="partitionJob" xmlns="http://www.springframework.org/schema/batch">

        <!-- master step, 10 threads (grid-size)  -->
        <step id="masterStep">
            <partition step="slave" partitioner="rangePartitioner">
                <handler grid-size="10" task-executor="taskExecutor" />
            </partition>
        </step>

    </job>

    <!-- ======= Jobs to run ===== -->
    <step id="slave" xmlns="http://www.springframework.org/schema/batch">
        <tasklet>
            <chunk reader="pagingItemReader" writer="flatFileItemWriter"
                   processor="itemProcessor" commit-interval="1" />
        </tasklet>
    </step>


    <bean id="rangePartitioner" class="com.mkyong.partition.RangePartitioner" />

    <bean id="taskExecutor" class="org.springframework.core.task.SimpleAsyncTaskExecutor" />

    <bean id="itemProcessor" class="com.mkyong.processor.UserProcessor" scope="step">
        <property name="threadName" value="#{stepExecutionContext[name]}" />
    </bean>


    <!-- ========== Paging Item Reader -->
    <bean id="pagingItemReader" class="org.springframework.batch.item.database.JdbcPagingItemReader" scope="step">
        <property name="dataSource" ref="dataSource" />

        <property name="queryProvider">
            <bean class="org.springframework.batch.item.database.support.SqlPagingQueryProviderFactoryBean">
                <property name="dataSource" ref="dataSource" />
                <property name="selectClause" value="select id, username,password, age" />
                <property name="fromClause" value="from user" />
                <property name="whereClause" value="where id &gt;= :fromId and id &lt;= :toId" />
                <property name="sortKey" value="id" />
            </bean>
        </property>

        <!-- Inject via the ExecutionContext in rangePartitioner -->
        <property name="parameterValues">
            <map>
                <entry key="fromId" value="#{stepExecutionContext[fromId]}" />
                <entry key="toId" value="#{stepExecutionContext[toId]}" />
            </map>
        </property>

        <property name="pageSize" value="10" />
        <property name="rowMapper">
            <bean class="com.mkyong.UserRowMapper" />
        </property>
    </bean>


    <!-- ================= csv file writer ============== -->
    <bean id="flatFileItemWriter" class="org.springframework.batch.item.file.FlatFileItemWriter" scope="step" >
        <property name="resource"
            value="file:csv/outputs/users.processed#{stepExecutionContext[fromId]}-#{stepExecutionContext[toId]}.csv" />

        <property name="appendAllowed" value="false" />

        <property name="lineAggregator">
            <bean class="org.springframework.batch.item.file.transform.DelimitedLineAggregator">
                <property name="delimiter" value="," />
                <property name="fieldExtractor">
                    <bean class="org.springframework.batch.item.file.transform.BeanWrapperFieldExtractor">
                        <property name="names" value="id, username, password, age" />
                    </bean>
                </property>
            </bean>
        </property>
    </bean>



    <!-- ========= Mongo Item Reader ========-->
    <bean id="mongoItemReader" class="org.springframework.batch.item.data.MongoItemReader" scope="step">
        <property name="template" ref="mongoTemplate" />
        <property name="targetType" value="com.mkyong.User" />
        <property name="query"
            value="{ 
                    'id':{$gt:#{stepExecutionContext[fromId]}, $lte:#{stepExecutionContext[toId]} 
            } }" />
        <property name="sort">
            <util:map id="sort">
                <entry key="id" value="" />
            </util:map>
        </property>
    </bean>
</beans>

请帮我解决这个问题。

应用程序.java

public class App {

    public static void main(String[] args) {
        App obj = new App();
        obj.run();
    }

    private void run() {
        final String[] springConfig = { "spring/batch/jobs/job-partitioner.xml" };

        ApplicationContext context = new ClassPathXmlApplicationContext(springConfig);

        JobLauncher jobLauncher = (JobLauncher) context.getBean("jobLauncher");
        Job job = (Job) context.getBean("partitionJob");

        try {
            System.out.println("-----------------------------------------------");
            JobExecution execution = jobLauncher.run(job, new JobParameters());
            System.out.println("Exit Status : " + execution.getStatus());
            System.out.println("Exit Status : " + execution.getAllFailureExceptions());
            System.out.println("-----------------------------------------------");
        } catch (Exception e) {
            e.printStackTrace();
        }
        System.out.println("Done");
    }
}

添加了项目结构:

Answer 1

去掉appendAllowed配置即可生效(append默认为false，参见source of flatfileitemwriter)

<bean id="flatFileItemWriter" class="org.springframework.batch.item.file.FlatFileItemWriter" scope="step" >
    <property name="resource"
        value="file:csv/outputs/users.processed#{stepExecutionContext[fromId]}-#{stepExecutionContext[toId]}.csv" />

   <!-- ******* remove this line ***** --><property name="appendAllowed" value="false" /> 

    <property name="lineAggregator">
        <bean class="org.springframework.batch.item.file.transform.DelimitedLineAggregator">
            <property name="delimiter" value="," />
            <property name="fieldExtractor">
                <bean class="org.springframework.batch.item.file.transform.BeanWrapperFieldExtractor">
                    <property name="names" value="id, username, password, age" />
                </bean>
            </property>
        </bean>
    </property>
</bean>

至于为什么这样可以解决问题，原因在于 FlatFileItemWriter 内部

/**
 * Flag to indicate that the target file should be appended if it already
 * exists. If this flag is set then the flag
 * {@link #setShouldDeleteIfExists(boolean) shouldDeleteIfExists} is
 * automatically set to false, so that flag should not be set explicitly.
 * Defaults value is false.
 * 
 * @param append the flag value to set
 */
public void setAppendAllowed(boolean append) {
    this.append = append;
    this.shouldDeleteIfExists = false;
}

独立于附加值，shouldDeleteIfExists将设置为 false，这会导致您的问题

看起来像一个错误，它是在 BATCH-2495 创建的