Deleting existing data from table before running the JdbcBatchItemWriter with INSERTs

[rihards]

I am struggling to create Job that is loading classifiers from flat file.

I have configured FlatFileItemReader and JdbcBatchItemWriter to do the INSERTs and everything is fine up to the moment when I have to reload classifiers (run Job again with updated flat file).

What I would like to do is to run "setup" step (DELETE FROM t1) before doing INSERT t1 values (a,b,c) again.

How is this supposed to be done using Spring batch?

[scottishfiction]

I'm assuming you have already defined an SQL statement for inserting the values (e.g. INSERT INSERT t1 values (a,b,c))

Why not just add a DELETE or TRUNCATE statement to the beginning of the INSERT statement?

[rihards]

Having DELETE prepended would not work because it would by executed for every chunk that I am getting from reader?

I believe having of some kind of tasklet with customizable SQL statement that can be executed before or after loading of data might be good idea...

I ended up by creating my own tasklet (postgresql specific) to do the job...

public class TablePrepareTasklet implements Tasklet, InitializingBean {

    private DataSource dataSource;
    private String table;

    @Override
    public RepeatStatus execute(StepContribution contribution,
            ChunkContext chunkContext) throws Exception {
        dataSource.getConnection().createStatement().execute("DELETE FROM "+table);
        dataSource.getConnection().createStatement().execute("VACUUM "+table);
        return RepeatStatus.FINISHED;
    }

    public void setDataSource(DataSource dataSource) {
        this.dataSource = dataSource;
    }

    public DataSource getDataSource() {
        return dataSource;
    }

    public void setTable(String table) {
        this.table = table;
    }

    public String getTable() {
        return table;
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        Assert.notNull(dataSource,"datasource must be set");
        Assert.notNull(table,"table name must be set");
    }
}