2023-06-10 21:29:04.460  WARN 24060 --- [           main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]: Invocation of init method failed; nested exception is javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory; nested exception is org.hibernate.MappingException: Could not get constructor for org.hibernate.persister.entity.SingleTableEntityPersister
2023-06-10 21:29:04.468  INFO 24060 --- [           main] com.alibaba.druid.pool.DruidDataSource   : {dataSource-1} closed
2023-06-10 21:29:04.509  INFO 24060 --- [           main] o.apache.catalina.core.StandardService   : Stopping service [Tomcat]

无法初始化 JPA EntityManagerFactory：无法创建请求的服务 [org.hibernate.engine.jdbc.env.spi.JdbcEnvironment]

或者

Could not get constructor for org.hibernate.persister.entity.SingleTableEntityPersister

或

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/zero/xunwuproject/config/JpaConfig.class]: Invocation of init method failed; nested exception is javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory; nested exception is org.hibernate.MappingException: Could not get constructor for org.hibernate.persister.entity.SingleTableEntityPersister

这个错误有多种原因导致，在网上查了一下， 大概有以下几种原因：

1. 实体类的属性对象没有设置setter或者getter。

   http://stackoverflow.com/questions/18042247/could-not-get-constructor-for-org-hibernate-persister-entity-singletableentitype

2. 没有导入javassist的jar文件 (javassist-3.15.0-GA.jar什么的）

   http://blog.csdn.net/xiaochangwei789/article/details/7712725

3. 实体类中的属性对象名和映射文件的property name不一致。

   https://blog.csdn.net/liuzhengyang1/article/details/23127629

而我这里是第二个原因，缺少javassist的jar包，于是在pom文件中引入：

<dependency>
    <groupId>org.javassist</groupId>
    <artifactId>javassist</artifactId>
    <version>3.23.1-GA</version>
</dependency>

解决办法：缺少  javassist-3.15.0-GA.jar  包，版本未定。引入了这个jar包后，启动就正常了。