Howto deal with fixed fields text record and JPA Entity

If the persistance layer is realized with JPA, we can mapping record fields directly to Entity fields

Fixefid is a java library wich permits to define a fixed fields text record with Java Bean or Java Enum. Often a text record must be retrieved from data persisted on a database. Or a text record must be persisted on a database.

The solution is to define a mapping from the record’s fields with the persistence model. If the persistance layer is realized with JPA Entities, the mapping can be done directly to the JPA Entity with the Fixefid annotations. Infact a JPA Entity is a POJO, that’s a Java Bean. And so, we can annotate the JPA Entity with the Fixefid annotations to realize the mapping, without the need to create two models, one for the record and another one for the JPA Entity.

The environment is as a follows:

  • Java 8
  • Spring Boot 2.3.4.RELEASE
  • Spring Data JPA
  • Fixefid 1.1.0
  • H2 Database

For example we can have a Customer bean like this one:

@Entity
@FixefidRecord
public class Customer {
	@Id
	@GeneratedValue(strategy = GenerationType.AUTO)
	@FixefidField(fieldLen = 19, fieldOrdinal = 0, fieldType = FieldType.N)
	private Long id;
	
	@FixefidField(fieldLen = 50, fieldOrdinal = 1, fieldType = FieldType.AN)
	private String firstName;
	
	@FixefidField(fieldLen = 50, fieldOrdinal = 2, fieldType = FieldType.AN)
	private String lastName;

	protected Customer() {
	}

	public Customer(String firstName, String lastName) {
		this.firstName = firstName;
		this.lastName = lastName;
	}

	@Override
	public String toString() {
		return String.format("Customer[id=%d, firstName='%s', lastName='%s']", id, firstName, lastName);
	}

	public Long getId() {
		return id;
	}

	public String getFirstName() {
		return firstName;
	}

	public String getLastName() {
		return lastName;
	}
}

The Customer above is annotated with Entity and FixefidRecord. The fields are annotated with FixefidField and other JPA annotations. To obtain the record from the database:

Customer customer = repository.findById(1L);
String record = new BeanRecord(customer).toString();

To save the record to the database:

String newRecord = "0000000000000000001Paul                                              Robinson                                          ";
Customer newCustomer = new Customer();
new BeanRecord(newCustomer, newRecord);
repository.save(newCustomer);

I made a video tutorial where the example above is explained in the detail way.

Here the project of the example on github.

Howto deal with fixed fields text record without substring

Howto avoid substring approach to deal with fixed fields formatted text records. The solution is the Java library Fixefid

Often we have to develop Java methods to deal with fixed fields formatted text records. The format is often used nowadays yet to files transfer between mainframe and unix machines. Almost always the approach is using substring like this:

String address = record.substring(10, 20);
String location = record.substring(20, 30);

But that is an error prone pattern. The records are length thousands of chars with many many fields and make a mistake with the offset is not so rarely. And moreover when you have to format the fields to create the record, you have to deal with string right padding, zero lead numeric left padding, boolean format, date format, decimal format, decimal separator, etc etc…

The solution is using a Java library like Fixefid, wich permits to start from a specification in excel, model the record with Java Bean or Java Enum and deal with fields by getter, setter and toString Java methods.

I’ve made a video tutorial where I explain in the detail way the process to start from an excel like this:

to create a Java Bean model like this:

to obtain a records txt file like this:

In this way we can using the standard java bean development to deal with fixed fields formatted text files.

For example you can create a Java Bean like this:

@FixefidRecord(recordLen = 600)
public class Student extends Person {
@FixefidField(fieldLen = 10, fieldOrdinal = 8, fieldType = FieldType.N,       
         fieldMandatory = FieldMandatory.INOUT)
private Long studentId;
….
}

and create a BeanRecord like this:

Student student = createStudent();
BeanRecord studentRecord = new BeanRecord(student, null, null, 
       createStudentMapFieldExtendedProperties());
studentRecord.toNormalize();
String studentRecordAsString = studentRecord.toString();
System.out.println("Student Record=[" + studentRecordAsString + "]");

The video tutorial explains the whole process in the detail way.

Here the java project developed on the video tutorial.

If you don’t want to use Java Bean, the same record can be modeled with Java Enum.