Hibernate: Dealing with unique contraints

Question

I have a table called Topic with two columns: Id(Primary key) and topic(Unique key).

I need to avoid duplicate entries to column 'topic'.

Here is the domain class for the table.

@Entity @Table(name="TOPIC",uniqueConstraints = {@UniqueConstraint(columnNames = "TOPIC") }) @DynamicUpdate ublic class Topic { @Id @GeneratedValue @Column(name="ID") private long id; @Column(name="TOPIC",unique=true) private String topic; //getters and setters

When I'am inserting duplicate entry,it is trowing sql exception (org.hibernate.engine.jdbc.spi.SqlExceptionHelper - Duplicate entry ).So iam catching that exception and showing a message "item already exists)

 try { topicService.save(tp); } catch (Exception e) { System.out.print("item already exists"); }

is this the correct method for dealing with unique constraints in Spring data JPA?

Rafik BELDI · Accepted Answer · 2014-07-11 06:56:46Z

if it is a one column then this should be enough:

@Column(name="TOPIC",unique=true) private String topic;

if unique applies to more than one column combined together , let's say : TOPIC and REF :@Entity

@Table(name="TOPIC",uniqueConstraints = @UniqueConstraint(columnNames = {"TOPIC","REF"}) ) @DynamicUpdate public class Topic { @Id @GeneratedValue @Column(name="ID") private long id; @Column(name="TOPIC") private String topic; @Column(name="REF") private String ref; //getters and setters

if you have multiple combined unique constraints for example :{TOPIC ,REF } AND {VERSION,"TOPIC"}

 @Table(name="TOPIC",uniqueConstraints ={ @UniqueConstraint(columnNames = {"TOPIC","REF"}),@UniqueConstraint(columnNames = {"TOPIC","VERSION"})}) public class Topic { @Id @GeneratedValue @Column(name="ID") private long id; @Column(name="TOPIC") private String topic; @Column(name="REF") private String ref; //getters and setters @Column(name="VERSION") private String version;

ok. But when I'am adding the duplicate data its trowing sql exception.Wont hibernate handle this by itself without trowing exception?
no you have to handle that byyourself, at the DAO level for exampl: try { save your entity }catch(DataIntegrityViolationException e){ //handle it here }

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