Spring Batch Reader is reading alternate records - spring-boot

Question

I have created a sample spring batch application which is trying to read record from a DB and in writer, it displays those records. However, I could see that only even numbered (alternate) records are printed.
It's not the problem of database as the behavior is consistent with both H2 database or Oracle database.
There are total 100 records in my DB.
With JDBCCursorItemReader, only 50 records are read and that too alternate one as can be seen from log snapshot
With JdbcPagingItemReader, only 5 records are read and that too alternate one as can be seen from log snapshot
My code configurations are given below. Why reader is skipping odd numbered records?
#Bean
public ItemWriter<Safety> safetyWriter() {
return items -> {
for (Safety item : items) {
log.info(item.toString());
}
};
}
#Bean
public JdbcCursorItemReader<Safety> cursorItemReader() throws Exception {
JdbcCursorItemReader<Safety> reader = new JdbcCursorItemReader<>();
reader.setSql("select * from safety " );
reader.setDataSource(dataSource);
reader.setRowMapper(new SafetyRowMapper());
reader.setVerifyCursorPosition(false);
reader.afterPropertiesSet();
return reader;
}
#Bean
JdbcPagingItemReader<Safety> safetyPagingItemReader() throws Exception {
JdbcPagingItemReader<Safety> reader = new JdbcPagingItemReader<>();
reader.setDataSource(dataSource);
reader.setFetchSize(10);
reader.setRowMapper(new SafetyRowMapper());
H2PagingQueryProvider queryProvider = new H2PagingQueryProvider();
queryProvider.setSelectClause("*");
queryProvider.setFromClause("safety");
Map<String, Order> sortKeys = new HashMap<>(1);
sortKeys.put("id", Order.ASCENDING);
queryProvider.setSortKeys(sortKeys);
reader.setQueryProvider(queryProvider);
return reader;
}
#Bean
public Step importSafetyDetails() throws Exception {
return stepBuilderFactory.get("importSafetyDetails")
.<Safety, Safety>chunk(chunkSize)
//.reader(cursorItemReader())
.reader(safetyPagingItemReader())
.writer(safetyWriter())
.listener(new StepListener())
.listener(new ChunkListener())
.build();
}
#Bean
public Job job() throws Exception {
return jobBuilderFactory.get("job")
.start(importSafetyDetails())
.build();
}
Domain classes looks like below:
#NoArgsConstructor
#AllArgsConstructor
#Data
public class Safety {
private int id;
}
public class SafetyRowMapper implements RowMapper<Safety> {
#Override
public Safety mapRow(ResultSet resultSet, int i) throws SQLException {
if(resultSet.next()) {
Safety safety = new Safety();
safety.setId(resultSet.getInt("id"));
return safety;
}
return null;
}
}
#SpringBootApplication
#EnableBatchProcessing
public class SpringBatchSamplesApplication {
public static void main(String[] args) {
SpringApplication.run(SpringBatchSamplesApplication.class, args);
}
}
application.yml configuration is as below:
spring:
application:
name: spring-batch-samples
main:
allow-bean-definition-overriding: true
datasource:
url: jdbc:h2:mem:testdb;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=FALSE
username: sa
password:
driver-class-name: org.h2.Driver
hikari:
connection-timeout: 20000
maximum-pool-size: 10
h2:
console:
enabled: true
batch:
initialize-schema: never
server:
port: 9090
sqls are as below:
CREATE TABLE safety (
id int NOT NULL,
CONSTRAINT PK_ID PRIMARY KEY (id)
);
INSERT INTO safety (id) VALUES (1);
...100 records are inserted
Listeners classes are as below:
#Slf4j
public class StepListener{
#AfterStep
public ExitStatus afterStep(StepExecution stepExecution) {
log.info("In step {} ,Exit Status: {} ,Read Records: {} ,Committed Records: {} ,Skipped Read Records: {} ,Skipped Write Records: {}",
stepExecution.getStepName(),
stepExecution.getExitStatus().getExitCode(),
stepExecution.getReadCount(),
stepExecution.getCommitCount(),
stepExecution.getReadSkipCount(),
stepExecution.getWriteSkipCount());
return stepExecution.getExitStatus();
}
}
#Slf4j
public class ChunkListener {
#BeforeChunk
public void beforeChunk(ChunkContext context) {
log.info("<< Before the chunk");
}
#AfterChunk
public void afterChunk(ChunkContext context) {
log.info("<< After the chunk");
}
}

Answer 1

I tried to reproduce your problem, but I couldn't. Maybe it would be great if you could share more code.
Meanwhile I created a simple job to read 100 records from "safety" table a print them to the console. And it is working fine.
.
#SpringBootApplication
#EnableBatchProcessing
public class ReaderWriterProblem implements CommandLineRunner {
#Autowired
DataSource dataSource;
#Autowired
StepBuilderFactory stepBuilderFactory;
#Autowired
JobBuilderFactory jobBuilderFactory;
#Autowired
private JobLauncher jobLauncher;
#Autowired
private ApplicationContext context;
public static void main(String[] args) {
String[] arguments = new String[]{LocalDateTime.now().toString()};
SpringApplication.run(ReaderWriterProblem.class, arguments);
}
#Bean
public ItemWriter<Safety> safetyWriter() {
return new ItemWriter<Safety>() {
#Override
public void write(List<? extends Safety> items) throws Exception {
for (Safety item : items) {
//log.info(item.toString());
System.out.println(item);
}
}
};
}
// #Bean
// public JdbcCursorItemReader<Safety> cursorItemReader() throws Exception {
// JdbcCursorItemReader<Safety> reader = new JdbcCursorItemReader<>();
//
// reader.setSql("select * from safety ");
// reader.setDataSource(dataSource);
// reader.setRowMapper(new SafetyRowMapper());
// reader.setVerifyCursorPosition(false);
// reader.afterPropertiesSet();
//
// return reader;
// }
#Bean
JdbcPagingItemReader<Safety> safetyPagingItemReader() throws Exception {
JdbcPagingItemReader<Safety> reader = new JdbcPagingItemReader<>();
reader.setDataSource(dataSource);
reader.setFetchSize(10);
reader.setRowMapper(new SafetyRowMapper());
PostgresPagingQueryProvider queryProvider = new PostgresPagingQueryProvider();
queryProvider.setSelectClause("*");
queryProvider.setFromClause("safety");
Map<String, Order> sortKeys = new HashMap<>(1);
sortKeys.put("id", Order.ASCENDING);
queryProvider.setSortKeys(sortKeys);
reader.setQueryProvider(queryProvider);
return reader;
}
#Bean
public Step importSafetyDetails() throws Exception {
return stepBuilderFactory.get("importSafetyDetails")
.<Safety, Safety>chunk(5)
//.reader(cursorItemReader())
.reader(safetyPagingItemReader())
.writer(safetyWriter())
.listener(new MyStepListener())
.listener(new MyChunkListener())
.build();
}
#Bean
public Job job() throws Exception {
return jobBuilderFactory.get("job")
.listener(new JobListener())
.start(importSafetyDetails())
.build();
}
#Override
public void run(String... args) throws Exception {
JobParametersBuilder jobParametersBuilder = new JobParametersBuilder();
jobParametersBuilder.addString("date", LocalDateTime.now().toString());
try {
Job job = (Job) context.getBean("job");
jobLauncher.run(job, jobParametersBuilder.toJobParameters());
} catch (JobExecutionAlreadyRunningException | JobRestartException | JobInstanceAlreadyCompleteException | JobParametersInvalidException e) {
e.printStackTrace();
}
}
public static class JobListener implements JobExecutionListener {
#Override
public void beforeJob(JobExecution jobExecution) {
System.out.println("Before job");
}
#Override
public void afterJob(JobExecution jobExecution) {
System.out.println("After job");
}
}
private static class SafetyRowMapper implements RowMapper<Safety> {
#Override
public Safety mapRow(ResultSet resultSet, int i) throws SQLException {
Safety safety = new Safety();
safety.setId(resultSet.getLong("ID"));
return safety;
}
}
public static class MyStepListener implements StepExecutionListener {
#Override
public void beforeStep(StepExecution stepExecution) {
System.out.println("Before Step");
}
#Override
public ExitStatus afterStep(StepExecution stepExecution) {
System.out.println("After Step");
return ExitStatus.COMPLETED;
}
}
private static class MyChunkListener implements ChunkListener {
#Override
public void beforeChunk(ChunkContext context) {
System.out.println("Before Chunk");
}
#Override
public void afterChunk(ChunkContext context) {
System.out.println("After Chunk");
}
#Override
public void afterChunkError(ChunkContext context) {
}
}
}
Hope this helps