Spring Batch Dynamic Insert and Update with DB to DB - spring-boot

Question

There is scenario where we want to load data from DB to DB .
But we want to check if data is already present in target system then update it otherwise insert it into DB.
We are using below approach:
#Bean
ItemWriter<Student> onosItemWriter1() {
JdbcBatchItemWriter<Student> databaseItemWriter = new JdbcBatchItemWriter<>();
databaseItemWriter.setDataSource(dataSource);
databaseItemWriter.setJdbcTemplate(namedParameterJdbcTemplate);
databaseItemWriter.setSql(INSERT_QUERY);
ItemPreparedStatementSetter<Student> valueSetter = new ItemPreparedStatementSetter<Student>() {
#Override
public void setValues(Student student, PreparedStatement statement) throws SQLException {
if (Student.getId() < 0) {
log.info("Inserting!");
databaseItemWriter.setSql(INSERT_QUERY);
statement.setString(1, student.getName());
statement.setString(2, student.getEmail());
} else {
log.info("updateing!!!!");
databaseItemWriter.setSql(UPDATE_QUERY);
statement.setString(1, student.getName());
statement.setString(2, student.getEmail());
}
}
};
databaseItemWriter.setItemPreparedStatementSetter(valueSetter);
return databaseItemWriter;
}
above its working only for insert. How I can do it with one JDBC batch Item writer to update it as well dynamically. if record is already present in chunks.

Answer 1

The code you shared won't work, because you are configuring the query on the item writer based on a runtime information from the item itself (Student.getId() < 0).
we want to check if data is already present in target system then update it otherwise insert it into DB
I would keep it simple and write a custom item writer like follows:
public class StudentItemWriter implements ItemWriter<Student> {
private static final String INSERT_QUERY = "insert into student ...";
private static final String UPDATE_QUERY = "update student set ... where id = ?";
private JdbcTemplate jdbcTemplate;
public StudentItemWriter(DataSource dataSource) {
this.jdbcTemplate = new JdbcTemplate(dataSource);
}
public void write(List<? extends Student> students) throws Exception {
for(Student student : students) {
int updated = jdbcTemplate.update(UPDATE_QUERY,...);
if(updated == 0) {
jdbcTemplate.update(INSERT_QUERY,...);
}
}
}
}