使用 java 从 mysql 中的 bit(2) 列存储和检索值

Question

I need to add values something like 0 - ACTIVE, 1 - INACTIVE, 2 - DISCHARGED

In my database and the column datatype I am using is bit(2) I am able to store it in database using enum

Here is my enum

public enum Status {
  ACTIVE,
  INACTIVE,
  DISCHARGED
}

I am able to store the value in database using Status.ACTIVE.ordinal() but not able to fetch the value from DB.

How can I fetch the value from database in java?

Answer 1

Quick answer: https://spring.io/guides/gs/accessing-data-jpa/

Full answer:

add jpa and mysql-connector dependency to your pom.xml file:

<!-- JPA -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<!-- MySQL connector -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>

After that, you should create interface (for example, SomeDataRepository), that extends CrudRepository.

public interface SomeDataRepository extends CrudRepository<Status, Integer> {
}

Then you fetching data from database becomes pretty easy (also as other work with db):

@Autowired
SomeDataRepository someDataRepository;
public List<Status> getData() {
    return someDataRepository.findAll();
}

Answer 2

To fetch the value of bit(2) column as integer from DB we need to use the CAST() function

SELECT CAST(colName AS unsigned int) as aliasName FROM tableName