Spring Batch — call existing Service

On this example, we’ll see how to call the existing service and get its data in the ItemReader and process it.

ItemReaderAdapter — Invokes a custom method on a delegate plain old Java object which itself provides an item.

CustomerService.java

@Component
public class CustomerService {
    private int curIndex;
    private List<Customer> customers;


    private String[] firstNames = {"Michael", "Warren", "Ann", "Terrence", "Erica", "Laura", "Steve", "Larry"};
    private String middleInitial = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    private String[] lastNames = {"Gates", "Darrow", "Donnelly", "Jobs", "Buffett", "Ellison", "Obama"};

    private String[] streets = {"4th Street", "Wall Street", "Fifth Avenue", "Mt. Lee Drive", "Jeopardy Lane",
            "Infinite Loop Drive", "Farnam Street", "Isabella Ave", "S. Greenwood Ave"};

    private String[] cities = {"Chicago", "New York", "Hollywood", "Aurora", "Omaha", "Atherton"};
    private String[] states = {"IL", "NY", "CA", "NE"};

    private Random generator = new Random();

    public CustomerService() {
        curIndex = 0;
        customers = new ArrayList<>();
        for (int i = 0; i < 100; i++) {
            customers.add(buildCustomer());
        }
    }

    private Customer buildCustomer() {
        Customer customer = new Customer();
        customer.setId((long) generator.nextInt(Integer.MAX_VALUE));
        customer.setFirstName(firstNames[generator.nextInt(firstNames.length - 1)]);
        customer.setMiddleInitial(String.valueOf(middleInitial.charAt(generator.nextInt(middleInitial.length() - 1))));
        customer.setLastName(lastNames[generator.nextInt(lastNames.length - 1)]);
        customer.setAddress(generator.nextInt(9999) + " " + streets[generator.nextInt(streets.length - 1)]);
        customer.setCity(cities[generator.nextInt(cities.length - 1)]);
        customer.setState(states[generator.nextInt(states.length - 1)]);
        customer.setZipCode(String.valueOf(generator.nextInt(99999)));
        return customer;
    }

    public Customer getCustomer() {
        Customer cust = null;
        if (curIndex < customers.size()) {
            cust = customers.get(curIndex);
            curIndex++;
        }
        return cust;
    }
}

Customer.java

@Data
@NoArgsConstructor
public class Customer {
    private Long id;
    private String city;
    private String state;
    private String zipCode;
    private String address;
    private String lastName;
    private String firstName;
    private String middleInitial;

    @Override
    public String toString() {
        return "Customer{" +
                "id=" + id + ", firstName='" + firstName + '\'' + ", middleInitial='" + middleInitial + '\'' +
                ", lastName='" + lastName + '\'' + ", city='" + city + '\'' +
                ", state='" + state + '\'' + ", zipCode='" + zipCode + '\'' + '}';
    }
}

ExistingServiceApplication.java

@EnableBatchProcessing
@SpringBootApplication
public class ExistingServiceApplication {

    @Autowired
    private JobBuilderFactory jobBuilderFactory;

    @Autowired
    private StepBuilderFactory stepBuilderFactory;

    @Bean
    public ItemReaderAdapter<Customer> customerItemReader(CustomerService customerService) {
        ItemReaderAdapter<Customer> adapter = new ItemReaderAdapter<>();
        adapter.setTargetObject(customerService);
        adapter.setTargetMethod("getCustomer");
        return adapter;

    }

    @Bean
    public ItemWriter<Customer> itemWriter() {
        return (items) -> items.parallelStream().forEach(out::println);
    }

    @Bean
    public Step copyFileStep() {
        return this.stepBuilderFactory.get("copyFileStep")
                .<Customer, Customer>chunk(10)
                .reader(this.customerItemReader(null))
                .writer(this.itemWriter())
                .build();
    }


    @Bean
    public Job job() {
        return this.jobBuilderFactory.get("job")
                .start(this.copyFileStep())
                .build();
    }

    public static void main(String[] args) {
        SpringApplication.run(ExistingServiceApplication.class, args);
    }
}