H2 database: NULL not allowed for column "ID" when inserting record using jdbcTemplate

Try to use strategy=GenerationType.IDENTITY instead of the strategy=GenerationType.AUTO

Also could be wrong hibernate.dialect Try the

hibernate.dialect=org.hibernate.dialect.H2Dialect

Hibernate 5.2.x (Spring Boot 2.x) change default strategy for sequences, if DB supported one. So, with strategy=GenerationType.AUTO, hibernate_sequence is created, but id is not autoincremented, based on this sequence, as must be:

create table users (id integer not null, ...) 

instead of

create table table_name(id int default hibernate_sequence.nextval primary key, ...);

(see HHH-13268). There are several solutions:

• change @GeneratedValue to strategy = GenerationType.IDENTITY
• set spring.jpa.properties.hibernate.id.new_generator_mappings=false (spring-boot alias spring.jpa.hibernate.use-new-id-generator-mappings)
• insert with nextval: INSERT INTO TABLE(ID, ...) VALUES (hibernate_sequence.nextval, ...)