org.postgresql.util.PSQLException: ERROR: value too long for type character varying(255)

You try to save a string value more than 255 chars length. Just increase a column length

@Column(name = "xxx", length = 1024)

you need to alter a column length in the database too.

When you use

@Column(name = "xxx")

Hibernate uses a default column length.

You can use @Lob for a really large text data.

Please, use xxx_users in place of tblusers.

Use User in place of Users.

Use CascadeType.ALL on the @OneToMany part of the association.

Use a lazy loading on the @ManyToOne part of the association.

@ManyToOne(fetch = FetchType.Lazy)
pravate User user;

For String with more than 255 chars length you can increase column length :

@Column(length = 2048)
private String column;

For large size :

@Lob
private String column;

For unlimited size :

@Column(columnDefinition="text")
private String column;