From CREATE TABLE to JPA Entity: the type mapping

Transcribing DDL into a JPA Entity is mechanical work full of small decisions: which Java type for NUMERIC? IDENTITY or SEQUENCE? Does nullable go in the annotation or do you trust the database? Here's the mapping Schemint uses and the reasoning behind each choice.

PostgreSQL to Java type table

PostgreSQL	Java	Note
`BIGSERIAL` / `BIGINT`	`Long`	generated id: `@GeneratedValue(strategy = IDENTITY)`
`SERIAL` / `INTEGER`	`Integer`
`VARCHAR(n)` / `TEXT`	`String`	`@Column(length = n)` when there's a limit
`NUMERIC(p,s)`	`BigDecimal`	never `double` for money
`BOOLEAN`	`Boolean`
`TIMESTAMP`	`LocalDateTime`
`TIMESTAMPTZ`	`Instant`	a real instant, normalized to UTC
`DATE`	`LocalDate`
`UUID`	`UUID`
`JSONB`	`String`	or `@JdbcTypeCode(SqlTypes.JSON)` with your own type

Wrapper types (Long, not long): a nullable column has to be able to represent absence, and a primitive with a magic 0 value is a bug waiting to happen.

The generated skeleton

@Entity
@Table(name = "customers")
public class CustomerEntity {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(nullable = false, length = 120)
    private String name;

    @Column(nullable = false, unique = true, length = 180)
    private String email;
}

IDENTITY, not AUTO: with a Postgres BIGSERIAL/identity column, IDENTITY reflects what the database actually does. AUTO lets Hibernate pick and can end up on a sequence table.
nullable/unique/length in the annotation: they don't change runtime (the database is what validates), but they document the contract on the class and let Hibernate validate the schema at boot (hibernate.ddl-auto=validate).
FK as a plain column first: generating customer_id Long instead of @ManyToOne avoids deciding fetch/cascade automatically; a relationship is a modeling decision, not a transcription one.

Paste your CREATE TABLE into Schemint and get back the Entity, request/response records, repository, Flyway migration, ER diagram and the schema warnings. It runs in the browser and nothing is stored.