Question

我一直在尝试弹簧批量示例，我无法通过itemwriter删除数据库中的记录。 itemreader工作正常，但在itemwriter我不知道如何工作，因为我刚接触春季批次可能会犯一些错误。我尝试了一些示例中的以下代码，但它不起作用。我是否必须写一些其他课程？

<bean id="itemWriter" class="org.springframework.batch.item.database.JdbcBatchItemWriter">
    <property name="dataSource" ref="dataSource" />
    <property name="sql">
        <!-- Why CDATA? 

             because < etc. is not allowed for xml values
             when you use &lt; xml parser will work, but
             now the sql won't because of the & spring assumes
             a placeholder, see
             - AbstractSqlPagingQueryProvider.init(...)
             - JdbcParameterUtils.countParameterPlaceholders(...)

             -->
        <value>
            <![CDATA[
                DELETE FROM TEST
                WHERE id = ? 
                and sub.id = ?
                and ... 
            ]]>
        </value>
    </property>
    <property name="itemPreparedStatementSetter">
        <bean class="...FieldSetItemPreparedStatementSetter" />
    </property>        
</bean>

ItemPreparedStatementSetter

的实施

/**
 * Implementation for {@link ItemPreparedStatementSetter}, 
 * sets the values from {@link FieldSet}.
 * 
 */
public class FieldSetItemPreparedStatementSetter implements ItemPreparedStatementSetter<FieldSet> {

    /** {@inheritDoc} */
    @Override
    public void setValues(FieldSet item, PreparedStatement ps) throws SQLException {
        for (int i = 0; i < item.getValues().length; i++) {
            // PreparedStatements start with 1
            ps.setObject(i + 1, item.getValues()[i]);
        }
    }
}

我的错误是： -

 Encountered an error executing the step
java.lang.ClassCastException: com.mkyong.User cannot be cast to org.springframework.batch.item.file.transform.FieldSet
at com.mkyong.FieldSetItemPreparedStatementSetter.setValues(FieldSetItemPreparedStatementSetter.java:1)
at org.springframework.batch.item.database.JdbcBatchItemWriter$1.doInPreparedStatement(JdbcBatchItemWriter.java:190)
at org.springframework.jdbc.core.JdbcTemplate.execute(JdbcTemplate.java:589)
at org.springframework.jdbc.core.JdbcTemplate.execute(JdbcTemplate.java:617)
at org.springframework.batch.item.database.JdbcBatchItemWriter.write(JdbcBatchItemWriter.java:186)
at org.springframework.batch.core.step.item.SimpleChunkProcessor.writeItems(SimpleChunkProcessor.java:175)
at org.springframework.batch.core.step.item.SimpleChunkProcessor.doWrite(SimpleChunkProcessor.java:151)
at org.springframework.batch.core.step.item.SimpleChunkProcessor.write(SimpleChunkProcessor.java:274)
at org.springframework.batch.core.step.item.SimpleChunkProcessor.process(SimpleChunkProcessor.java:199)
at org.springframework.batch.core.step.item.ChunkOrientedTasklet.execute(ChunkOrientedTasklet.java:75)
at org.springframework.batch.core.step.tasklet.TaskletStep$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.run(App.java:34)
at com.mkyong.App.main(App.java:16)

Dec 06, 2013 3:50:56 PM org.springframework.batch.core.launch.support.SimpleJobLauncher$1 run
INFO: Job: [FlowJob: [name=testJob]] completed with the following parameters: [{}] and the following status: [FAILED]
Exit Status : FAILED
Exit Status : [java.lang.ClassCastException: com.mkyong.User cannot be cast to org.springframework.batch.item.file.transform.FieldSet]
Done

Answer 1

代码已“正式更正”，但您必须使用ItemPreparedStatementSetter而不是User声明FieldSet，因为ItemWriter使用{{1}创建的同一对象}};我想你的读者会返回ItemReader类型的对象。

根据新的通用有界类型替换为User和ItemPreparedStatementSetter<User>。

Answer 2

也许，您的问题解释缺少一些信息，但在步骤定义中，您必须授予读取时返回的对象的匹配并传递给编写器。更好的解释：

阅读并创建一个MyCustomInputPOJO：

public class MyCustomFieldSetMapper implements FieldSetMapper<MyCustomInputPOJO> {

    @Override
    public MyCustomPOJO mapFieldSet(FieldSet fs) throws BindException {
        MyCustomInputPOJO pojo = new MyCustomInputPOJO();
        pojo.setAnAttribute(fs.readString("anAttribute"));
        return pojo;
    }
}

将MyCustomInputPOJO传递给处理器（如果有），并转换为MyCustomOutputPOJO：

@Component("MyProcessor")
public class MyCustomProcessor implements ItemProcessor<MyCustomInputPOJO, MyCustomOutputPOJO> {
    public MyCustomOutputPOJO doProcess(MyCustomInputPOJO input) {
        MyCustomOutputPOJO output = ConverterLogic.convert(input);
        return output
    }
}

现在你必须将MyCustomOutputPOJO传递给JdbcBatchItemWriter使用的ItemPreparedStatementSetter实现：

public class MyCustomItemPreparedStatementSetter implements ItemPreparedStatementSetter<MyCustomOutputPOJO> {
    public void setValues(MyCustomOutputPOJO output, PreparedStatement ps) throws SQLException {
        ps.setString(1, output.getAnAttribute());
    }
}

您的步骤配置：

<job id="MyJob">
    <step id="lerArquivoSaldos" >
            <tasklet>
                <chunk 
                    reader="MyReader" 
                    processor = "MyProcessor"
                    writer="MyWriter" 
                    commit-interval="10" 
                >
                </chunk>
            </tasklet>
        </step>
</job>

其中MyReader和MyProcessor是分别引用MyCustomFieldSetMapper和MyCustomItemPreparedStatementSetter的自定义bean。

Answer 3

public class FieldSetItemPreparedStatementSetter implements ItemPreparedStatementSetter<com.mkyong.User > {
    /** {@inheritDoc} */
    @Override
    public void setValues(com.mkyong.User item, PreparedStatement ps) throws SQLException {
        for (int i = 0; i < item.getValues().length; i++) {
            // PreparedStatements start with 1
            ps.setObject(i + 1, item.getValues()[i]);
        }
    }
}

将FieldSet类替换为com.mkyong.User abd，分别更改setter / getter。

Spring批量项目编写器在mysql中删除记录

3 个答案: