Skip to main content

JPA and Enums

There are different ways of configuring enums inside JPA entity which yields different results.

Let's consider we have this enum

public enum EmpType {

And the entity

public class Employee implements Serializable {

private static final long serialVersionUID = 1L;
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String name;
private EmpType empType;


To use enum we have to annotate field with @Enumerated

Employee e = new Employee();

the above code will save entity as follows
1 0 na

This is because all the enum's in EmpType are indexed starting from zero, so if we change order or introduce a new enum in middle we lose the context in Employee table.

Instead use this @Enumerated(EnumType.STRING) which save the above entity as


If you are looking for more advance mapping then consider this post
Advance Enums JPA 2.0


Riccardo said…
Hello, I use enums quite often and I find using EnumType.String very useful, not only for the fact that I can change the order, but also because sql queries are simpler to write this way and results easier to read (you don't have to lookup the code to know what does that '1' stand for!).

Do you think that theese advantages balance the greater database space use? I actually never ran in a situation where the size of those field is really an issue - a few bytes more by a few thousands record sum up as a few kilobytes after all, but a case with a table with many enums may be different.
Intesar said…
checkout this new custom enum value configuration
Riccardo said…
Yes, it is viable option.
Anonymous said…

Popular posts from this blog

JPA 2 new feature @ElementCollection explained

@ElementCollection is new annotation introduced in JPA 2.0, This will help us get rid of One-Many and Many-One shitty syntax.

Example 1: Stores list of Strings in an Entity

public class Users implements Serializable {

    private static final long serialVersionUID = 1L;
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    private List<String> certifications = new ArrayList<String>();

    public Long getId() {
        return id;

    public void setId(Long id) { = id;

    public List<String> getCertifications() {
        return certifications;

    public void setCertifications(List<String> certifications) {
        this.certifications = certifications;

        Users u = new Users();
        u.getCertifications().add("Sun Certified Java Programmer");

Generated Tables

Column --> ID
    Row             1


Validating CSV Files

What is CsvValidator ?
  A Java framework which validates any CSV files something similar to XML validation using XSD.

Why should I use this ?
  You don't have to use this and in fact its easy to write something your own and also checkout its source code for reference.

Why did I write this ?
  Some of our projects integrate with third party application which exchanges information in CSV files so I thought of writing a generic validator which can be hooked in multiple projects or can be used by QA for integration testing.

What is the license clause ?

Are there any JUnit test cases for me checkout ?
 Yes, source

How to integrate in my existing project ?

Just add the Jar which can be downloaded from here CsvValidator.jar and you are good.

Instantiate CsvValidator constructor which takes these 3 arguements

         // filename is the the file to be validated and here is a sample         // list - defines all the fields in the above csv file ( a field has index, type, isOptional, rege…

ArrayList vs LinkedList vs HashSet Performance Comparision

ConclusionsInserting & Reading sequentially from Collection prefer LinkedList/ArrayListInserting & Reading/Deleting by Search/equals from Collection prefer HashSetInserting, ArrayList & LinkedList performs best while HashSet takes double the timeReading, HashSet performs best while ArrayList & LinkedList are marginally lessDeleting, HashSet performs 10 times better than ArrayList & ArrayList performs 4 times better than LinkedList. LinkedList is slow because of sequencial search Bottom line : unless you are not going to iterate using for(Integer i : list ) then prefer HashSet
Inserting/Reading/Deleting integer's from zero till countJDK7Collectionactioncounttime msArrayListInsert1000/1LinkedListInsert1000/1HashSetInsert1000/1ArrayListInsert100005LinkedListInsert100004HashSetInsert100007ArrayListInsert10000011LinkedListInsert10000011HashSetInsert10000021ArrayListGet/Read1000LinkedListGet/Read1000HashSetGet/Read1000ArrayListGet/Read100004LinkedListGet/Read100003Has…