JPA 数据库已经设置默认值了. 为什么保存时报错 Column cannot be null ？

Question

错误信息：

 Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.dao.DataIntegrityViolationException: could not execute statement; SQL [n/a]; constraint [null]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement] with root cause
java.sql.SQLIntegrityConstraintViolationException: Column 'aaa' cannot be null
        at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:117)
        at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122)

数据库字段信息：

    `aaa` VARCHAR(255) NOT NULL DEFAULT ''  COLLATE 'utf8mb4_general_ci',

public class XXX { 
    @Column(name = "`aaa`")
    private String aaa;
}

请问在数据库提供了默认值的情况下，为什么还会报 Column cannot be null 呢？

Answer 1

JPA默认是全量操作字段，所以这里实际生成的SQL语句还是会向aaa字段插入nul值，如果你想空值就不插入使用数据库默认值，给字段打上@DynamicInsert注解