如何处理SpringBatch中ItemReader之后的逻辑相关行? [英] How to process logically related rows after ItemReader in SpringBatch?
问题描述
方案
为简单起见,假设我有一个返回25行的ItemReader。
前10行属于学生A
接下来的5个属于学生B
和剩下的10个属于学生C
我想逻辑地将它们聚合在一起,比如说按StudentId,然后将它们展平,以结束每个学生一行。
问题
如果我理解正确,将提交间隔设置为5将执行以下操作:
- 向处理器发送5行(它将聚合这些行或执行我告诉它的任何业务逻辑)。
- 处理后将写入5行。
- 然后它将在接下来的5行中再次执行此操作,依此类推。
我个人不会那样做。
- 在Spring Batch中处理此类情况的最佳实践是什么?
备用
有时我觉得编写一个常规的Spring JDBC主程序要容易得多,这样我就可以完全控制我想要做的事情了。但是,我希望利用作业的作业存储库状态监视、重新启动、跳过、作业和步骤侦听器的功能.
我的Spring批量编码
我的module-context.xml
<?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"
xsi:schemaLocation="http://www.springframework.org/schema/batch http://www.springframework.org/schema/batch/spring-batch-2.1.xsd
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
<description>Example job to get you started. It provides a skeleton for a typical batch application.</description>
<batch:job id="job1">
<batch:step id="step1" >
<batch:tasklet transaction-manager="transactionManager" start-limit="100" >
<batch:chunk reader="attendanceItemReader"
processor="attendanceProcessor"
writer="attendanceItemWriter"
commit-interval="10"
/>
</batch:tasklet>
</batch:step>
</batch:job>
<bean id="attendanceItemReader" class="org.springframework.batch.item.database.JdbcCursorItemReader">
<property name="dataSource">
<ref bean="sourceDataSource"/>
</property>
<property name="sql"
value="select s.student_name ,s.student_id ,fas.attendance_days ,fas.attendance_value from K12INTEL_DW.ftbl_attendance_stumonabssum fas inner join k12intel_dw.dtbl_students s on fas.student_key = s.student_key inner join K12INTEL_DW.dtbl_schools ds on fas.school_key = ds.school_key inner join k12intel_dw.dtbl_school_dates dsd on fas.school_dates_key = dsd.school_dates_key where dsd.rolling_local_school_yr_number = 0 and ds.school_code = ? and s.student_activity_indicator = 'Active' and fas.LOCAL_GRADING_PERIOD = 'G1' and s.student_current_grade_level = 'Gr 9' order by s.student_id"/>
<property name="preparedStatementSetter" ref="attendanceStatementSetter"/>
<property name="rowMapper" ref="attendanceRowMapper"/>
</bean>
<bean id="attendanceStatementSetter" class="edu.kdc.visioncards.preparedstatements.AttendanceStatementSetter"/>
<bean id="attendanceRowMapper" class="edu.kdc.visioncards.rowmapper.AttendanceRowMapper"/>
<bean id="attendanceProcessor" class="edu.kdc.visioncards.AttendanceProcessor" />
<bean id="attendanceItemWriter" class="org.springframework.batch.item.file.FlatFileItemWriter">
<property name="resource" value="file:target/outputs/passthrough.txt"/>
<property name="lineAggregator">
<bean class="org.springframework.batch.item.file.transform.PassThroughLineAggregator" />
</property>
</bean>
</beans>
我的读者支持类。
一个PreparedStatementSetter
package edu.kdc.visioncards.preparedstatements;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import org.springframework.jdbc.core.PreparedStatementSetter;
public class AttendanceStatementSetter implements PreparedStatementSetter {
public void setValues(PreparedStatement ps) throws SQLException {
ps.setInt(1, 7);
}
}
和RowMapper
package edu.kdc.visioncards.rowmapper;
import java.sql.ResultSet;
import java.sql.SQLException;
import org.springframework.jdbc.core.RowMapper;
import edu.kdc.visioncards.dto.AttendanceDTO;
public class AttendanceRowMapper<T> implements RowMapper<AttendanceDTO> {
public static final String STUDENT_NAME = "STUDENT_NAME";
public static final String STUDENT_ID = "STUDENT_ID";
public static final String ATTENDANCE_DAYS = "ATTENDANCE_DAYS";
public static final String ATTENDANCE_VALUE = "ATTENDANCE_VALUE";
public AttendanceDTO mapRow(ResultSet rs, int rowNum) throws SQLException {
AttendanceDTO dto = new AttendanceDTO();
dto.setStudentId(rs.getString(STUDENT_ID));
dto.setStudentName(rs.getString(STUDENT_NAME));
dto.setAttDays(rs.getInt(ATTENDANCE_DAYS));
dto.setAttValue(rs.getInt(ATTENDANCE_VALUE));
return dto;
}
}
我的处理器
package edu.kdc.visioncards;
import java.util.HashMap;
import java.util.Map;
import org.springframework.batch.item.ItemProcessor;
import edu.kdc.visioncards.dto.AttendanceDTO;
public class AttendanceProcessor implements ItemProcessor<AttendanceDTO, Map<Integer, AttendanceDTO>> {
private Map<Integer, AttendanceDTO> map = new HashMap<Integer, AttendanceDTO>();
public Map<Integer, AttendanceDTO> process(AttendanceDTO dto) throws Exception {
if(map.containsKey(new Integer(dto.getStudentId()))){
AttendanceDTO attDto = (AttendanceDTO)map.get(new Integer(dto.getStudentId()));
attDto.setAttDays(attDto.getAttDays() + dto.getAttDays());
attDto.setAttValue(attDto.getAttValue() + dto.getAttValue());
}else{
map.put(new Integer(dto.getStudentId()), dto);
}
return map;
}
}
我对上面代码的关注
在处理器中,我创建了一个HashMap,在处理行时,我检查Map中是否已经有该学员,如果没有,我会添加它。如果它已经存在,我将获取它,获取我感兴趣的值,并将它们与我当前正在处理的行相加。
之后,Spring Batch Framework根据我的配置写入文件
我的问题如下:
- 我不想让它给作者。我想处理所有剩余的行。如何在内存中保留为需要通过同一处理器的下一组行创建的映射呢?每次通过AttendanceProcessor处理一行时,都会初始化Map。我是否应该将地图初始化放入静电挡路?
推荐答案
在我的应用程序中,我创建了一个CollectingJdbcCursorItemReader
,它扩展了标准JdbcCursorItemReader
并执行您需要的功能。在内部,它使用MyCollectingRowMapper
:将多个相关行映射到一个对象的标准RowMapper
的扩展。
这里是ItemReader的代码,CollectingRowMapper
接口的代码,以及它的抽象实现,可以在我的another answer中找到。
import java.sql.ResultSet;
import java.sql.SQLException;
import org.springframework.batch.item.ReaderNotOpenException;
import org.springframework.batch.item.database.JdbcCursorItemReader;
import org.springframework.jdbc.core.RowMapper;
/**
* A JdbcCursorItemReader that uses a {@link CollectingRowMapper}.
* Like the superclass this reader is not thread-safe.
*
* @author Pino Navato
**/
public class CollectingJdbcCursorItemReader<T> extends JdbcCursorItemReader<T> {
private CollectingRowMapper<T> rowMapper;
private boolean firstRead = true;
/**
* Accepts a {@link CollectingRowMapper} only.
**/
@Override
public void setRowMapper(RowMapper<T> rowMapper) {
this.rowMapper = (CollectingRowMapper<T>)rowMapper;
super.setRowMapper(rowMapper);
}
/**
* Read next row and map it to item.
**/
@Override
protected T doRead() throws Exception {
if (rs == null) {
throw new ReaderNotOpenException("Reader must be open before it can be read.");
}
try {
if (firstRead) {
if (!rs.next()) { //Subsequent calls to next() will be executed by rowMapper
return null;
}
firstRead = false;
} else if (!rowMapper.hasNext()) {
return null;
}
T item = readCursor(rs, getCurrentItemCount());
return item;
}
catch (SQLException se) {
throw getExceptionTranslator().translate("Attempt to process next row failed", getSql(), se);
}
}
@Override
protected T readCursor(ResultSet rs, int currentRow) throws SQLException {
T result = super.readCursor(rs, currentRow);
setCurrentItemCount(rs.getRow());
return result;
}
}
您可以像经典JdbcCursorItemReader
一样使用它:唯一的要求是您向它提供CollectingRowMapper
而不是经典的RowMapper
。
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