Spring Batch – Read Date Field as a String in Readers and Convert it to Other Format

Are you tired of dealing with date fields in your Spring Batch application? Do you find yourself struggling to read date fields as strings and convert them to other formats? Well, worry no more! In this article, we’ll show you how to read date fields as strings in readers and convert them to other formats with ease.

Understanding the Problem

When working with date fields in Spring Batch, you might encounter issues when reading date fields as strings. By default, Spring Batch reads date fields as java.util.Date objects, which can lead to formatting issues. For instance, if your input file contains a date field in the format “yyyy-mm-dd”, Spring Batch might interpret it as “mm-dd-yyyy” instead. This can cause problems when processing data.

To overcome this issue, you need to read date fields as strings and then convert them to the desired format. But how do you do that?

The Solution

The solution lies in using a custom FieldSetMapper and a CustomDateEditor. But before we dive into the code, let’s understand the concept.

A FieldSetMapper is an interface in Spring Batch that allows you to map input fields to objects. By implementing this interface, you can tailor the mapping process to your needs. In our case, we’ll use it to read date fields as strings.

A CustomDateEditor, on the other hand, is a property editor that allows you to customize the way date fields are converted. We’ll use it to convert the string date field to the desired format.

Step 1: Create a Custom FieldSetMapper

public class CustomFieldSetMapper implements FieldSetMapper<MyObject> {

    @Override
    public MyObject mapFieldSet(FieldSet fieldSet) throws BindException {
        MyObject myObject = new MyObject();
        
        // Read date field as a string
        String dateString = fieldSet.readString("dateField");
        
        // Convert the string date field to the desired format
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-mm-dd");
        Date date = sdf.parse(dateString);
        
        // Set the date field in the object
        myObject.setDateField(date);
        
        // Set other fields
        myObject.setField1(fieldSet.readString("field1"));
        myObject.setField2(fieldSet.readString("field2"));
        
        return myObject;
    }
}

In the above code, we’re reading the date field as a string using the readString() method of the FieldSet interface. We then use a SimpleDateFormat object to parse the string date field to a Date object.

Step 2: Create a CustomDateEditor

public class CustomDateEditor extends PropertyEditorSupport {

    @Override
    public void setAsText(String text) throws IllegalArgumentException {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-mm-dd");
        try {
            Date date = sdf.parse(text);
            setValue(date);
        } catch (ParseException e) {
            throw new IllegalArgumentException("Invalid date format");
        }
    }
}

In the above code, we’re extending the PropertyEditorSupport class and overriding the setAsText() method. This method is called when the editor is set with a string value. We use a SimpleDateFormat object to parse the string date field to a Date object.

Step 3: Register the CustomDateEditor

@Bean
public CustomFieldSetMapper customFieldSetMapper() {
    CustomFieldSetMapper fieldSetMapper = new CustomFieldSetMapper();
    return fieldSetMapper;
}

@Bean
public CustomDateEditor customDateEditor() {
    CustomDateEditor dateEditor = new CustomDateEditor();
    return dateEditor;
}

@Bean
public JobBuilderFactory jobs() {
    return new JobBuilderFactory();
}

@Bean
public StepBuilderFactory steps() {
    return new StepBuilderFactory();
}

@Bean
public JobExecutionListener listener() {
    return new JobExecutionListener();
}

@Bean
public JobLauncher jobLauncher() {
    return new SimpleJobLauncher();
}

@Bean
public JobRepository jobRepository() {
    return new SimpleJobRepository();
}

@Bean
public PlatformTransactionManager transactionManager() {
    return new ResourcelessTransactionManager();
}

@Bean
public JobRegistry jobRegistry() {
    return new MapJobRegistry();
}

@Bean
public JobOperator jobOperator() {
    return new SimpleJobOperator();
}

@Configuration
@EnableBatchProcessing
public class AppConfig {
    
    @Autowired
    private JobBuilderFactory jobs;
    
    @Autowired
    private StepBuilderFactory steps;
    
    @Bean
    public Job job() {
        return jobs.get("myJob")
                .start(step1())
                .build();
    }
    
    @Bean
    public Step step1() {
        return steps.get("step1")
                .<MyObject, MyObject>chunk(10)
                .reader(itemReader())
                .processor(itemProcessor())
                .writer(itemWriter())
                .build();
    }
    
    @Bean
    public ItemReader<MyObject> itemReader() {
        FlatFileItemReader<MyObject> reader = new FlatFileItemReader<>();
        reader.setResource(new ClassPathResource("input.txt"));
        reader.set LineMapper(new DelimitedLineMapper<MyObject>());
        reader.setLineTokenizer(new DelimitedLineTokenizer());
        
        // Register the custom field set mapper
        reader.setFieldSetMapper(customFieldSetMapper());
        
        return reader;
    }
    
    @Bean
    public ItemProcessor<MyObject, MyObject> itemProcessor() {
        return new ItemProcessor<MyObject, MyObject>() {
            @Override
            public MyObject process(MyObject item) throws Exception {
                return item;
            }
        };
    }
    
    @Bean
    public ItemWriter<MyObject> itemWriter() {
        return new ConsoleItemWriter<>();
    }
}

In the above code, we’re registering the custom FieldSetMapper and CustomDateEditor as beans. We then use the FieldSetMapper in the ItemReader to read the date field as a string and convert it to a Date object using the CustomDateEditor.

Conclusion

In this article, we’ve shown you how to read date fields as strings in readers and convert them to other formats using a custom FieldSetMapper and CustomDateEditor. By following these steps, you can easily handle date fields in your Spring Batch application and avoid common formatting issues.

Common Pitfalls

When working with date fields in Spring Batch, it’s easy to fall into common pitfalls. Here are a few things to keep in mind:

• Make sure to register the custom FieldSetMapper and CustomDateEditor as beans in your application context.
• Verify that the date format in your input file matches the format specified in the SimpleDateFormat object.
• Handle exceptions properly when parsing date fields to avoid errors.

Best Practices

Here are some best practices to keep in mind when working with date fields in Spring Batch:

1. Use a consistent date format throughout your application.
2. Verify the input data to ensure that it matches the expected date format.
3. Use a custom FieldSetMapper and CustomDateEditor to handle date fields.
4. Test your application thoroughly to ensure that date fields are being processed correctly.

Format	Description
yyyy-mm-dd	Year-month-day format
mm-dd-yyyy	Month-day-year format
dd-mm-yyyy	Day-month-year format

In conclusion, reading date fields as strings in readers and converting them to other formats is a common task in Spring Batch. By following the steps outlined in this article and adhering to best practices, you can easily handle date fields in your application and avoid common formatting issues.

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