如何在更新期间将null设置为QueryDSL时间戳列？

Question

I have the following table in Postgre:

CREATE TABLE user_attempts
(
    id INT PRIMARY KEY NOT NULL,
    username VARCHAR(50) NOT NULL,
    attempts SMALLINT NOT NULL,
    lastmodified TIMESTAMP,
    FOREIGN KEY ( username ) REFERENCES users ( username )
);

I would like to update the lastmodified field through QueryDSL and Spring Data JDBC Extension as follow:

template.update(userAttempts, update -> update
                .set(userAttempts.attempts, (short) 0)
                .set(userAttempts.lastmodified, null) // compilation error here
                .where(userAttempts.username.eq(username))
                .execute();

However, it seems that QueryDSL's set method can't accept null because it will match more than one function signatures.

Answer 1

Based on this QueryDSL issue: https://github.com/querydsl/querydsl/issues/846

I should use setNull method instead:

template.update(userAttempts, update -> update
                .set(userAttempts.attempts, (short) 0)
                .setNull(userAttempts.lastmodified)
                .where(userAttempts.username.eq(username))
                .execute()
);

Answer 2

You'll probably have to cast null to the type of lastmodified . Eg:

.set(userAttempts.lastmodified, (Timestamp) null)

The reason for this is that the null literal is ambiguous when calling overloaded generic methods.