How to use #BeforeStep Job Parameters in JdbcCursorItemReader for named Query - spring-batch

Question

I have the code like below
#Bean
public JdbcCursorItemReader<Map<String, Object>> itemReader() {
return new JdbcCursorItemReader<Map<String, Object>>() {
private JobParameters jobParameter;
String sql = "select EMPLOYEE_ID as empId, EMPLOYEE_NAME as empName EMPLOYEE_AGE as age from EMPLOYEE EMPLOYEE_DEPT =:empDept and EMPLOYEE_SAL > :empSal";
Map<String, Object> namedParameters = null;
#PostConstruct
public void initialize() throws Exception
{
setDataSource(dataSource);
setSql("select 1 from dual");
setRowMapper(new ColumnMapRowMapper());
}
#BeforeStep
public void retrieveExecutionContext(StepExecution stepExecution)
{
jobParameter = stepExecution.getJobParameters();
namedParameters = new HashMap<String, Object>() {
{
put("bstd", jobParameter.getString("empDept"));
put("bwtn", jobParameter.getString("empSal"));
}
};
jobParameter.getParameters().forEach((k, v) -> System.out.println("key =" + k + ", Value:" + v));
}
#Override
public void afterPropertiesSet() throws Exception {
setSql(NamedParameterUtils.substituteNamedParameters(sql, new MapSqlParameterSource(namedParameters)));
setPreparedStatementSetter(new ListPreparedStatementSetter(
Arrays.asList(NamedParameterUtils.buildValueArray(sql, namedParameters))));
setRowMapper(new ColumnMapRowMapper());
setDataSource(dataSource);
super.afterPropertiesSet();
}
};
}
Tried using calling afterPropertiesSet, but still seeing below exception
Caused by: org.springframework.dao.InvalidDataAccessApiUsageException: No value supplied for the SQL parameter 'empDept': No value registered for key 'empDept'
at org.springframework.jdbc.core.namedparam.NamedParameterUtils.buildValueArray(NamedParameterUtils.java:361) ~[spring-jdbc-5.3.22.jar:5.3.22]
at org.springframework.jdbc.core.namedparam.NamedParameterUtils.buildValueArray(NamedParameterUtils.java:485) ~[spring-jdbc-5.3.22.jar:5.3.22]
Requirement is dynamic query, so don't have control of the Select query and the where conditions.
Thanks in advance,

Answer 1

You can use a SpEL expression to inject and use job parameters in your item reader bean definition as follows:
#Bean
#StepScope
public JdbcCursorItemReader<Map<String, Object>> itemReader(#Value("#{jobParameters['empDept']}") String empDept, #Value("#{jobParameters['empSal']}") String empSal) {
JdbcCursorItemReader<Map<String, Object>> itemReader = new JdbcCursorItemReader<>();
// use parameters 'empDept' and 'empSal' in your sql query as needed
return itemReader;
}
Note that the item reader should be step-scoped for that to work. For more details, please refer to the documentation: Late Binding of Job and Step Attributes.