启动Spring boot报错：nested exception is java.sql.SQLException: Field 'id' doesn't have a default value

　　先看具体日志：

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaConfiguration': Unsatisfied dependency expressed through constructor parameter ; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSource' defined in class path resource [org/springframework/boot/autoconfigure/jdbc/DataSourceConfiguration$Hikari.class]: Initialization of bean failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.boot.autoconfigure.jdbc.DataSourceInitializerInvoker': Invocation of init method failed; nested exception is org.springframework.jdbc.datasource.init.ScriptStatementFailedException: Failed to execute SQL script statement # of URL [jar:file:/home/wlf/springboot-0.0.-SNAPSHOT.jar!/BOOT-INF/classes!/schema.sql]: insert into t_user(user_name, pass_word, role_value) select 'admin', '', 'Admin' from dual where not exists(select user_name, pass_word, role_value from t_user where user_name='admin' and pass_word='' and role_value='Admin'); nested exception is java.sql.SQLException: Field 'id' doesn't have a default value
        at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$(AbstractBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$(AbstractBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:) ~[spring-context-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:) ~[spring-context-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:) ~[spring-context-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:) ~[spring-boot-2.1..RELEASE.jar!/:2.1..RELEASE]
        at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:) ~[spring-boot-2.1..RELEASE.jar!/:2.1..RELEASE]
        at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:) ~[spring-boot-2.1..RELEASE.jar!/:2.1..RELEASE]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:) ~[spring-boot-2.1..RELEASE.jar!/:2.1..RELEASE]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:) ~[spring-boot-2.1..RELEASE.jar!/:2.1..RELEASE]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:) ~[spring-boot-2.1..RELEASE.jar!/:2.1..RELEASE]
        at com.crocodile.springboot.SpringbootApplication.main(SpringbootApplication.java:) ~[classes!/:0.0.-SNAPSHOT]
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:) ~[na:na]
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:) ~[na:na]
        at java.base/java.lang.reflect.Method.invoke(Method.java:) ~[na:na]
        at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:) ~[springboot-0.0.-SNAPSHOT.jar:0.0.-SNAPSHOT]
        at org.springframework.boot.loader.Launcher.launch(Launcher.java:) ~[springboot-0.0.-SNAPSHOT.jar:0.0.-SNAPSHOT]
        at org.springframework.boot.loader.Launcher.launch(Launcher.java:) ~[springboot-0.0.-SNAPSHOT.jar:0.0.-SNAPSHOT]
        at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:) ~[springboot-0.0.-SNAPSHOT.jar:0.0.-SNAPSHOT]
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSource' defined in class path resource [org/springframework/boot/autoconfigure/jdbc/DataSourceConfiguration$Hikari.class]: Initialization of bean failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.boot.autoconfigure.jdbc.DataSourceInitializerInvoker': Invocation of init method failed; nested exception is org.springframework.jdbc.datasource.init.ScriptStatementFailedException: Failed to execute SQL script statement # of URL [jar:file:/home/wlf/springboot-0.0.-SNAPSHOT.jar!/BOOT-INF/classes!/schema.sql]: insert into t_user(user_name, pass_word, role_value) select 'admin', '', 'Admin' from dual where not exists(select user_name, pass_word, role_value from t_user where user_name='admin' and pass_word='' and role_value='Admin'); nested exception is java.sql.SQLException: Field 'id' doesn't have a default value
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$(AbstractBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        ...  common frames omitted
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.boot.autoconfigure.jdbc.DataSourceInitializerInvoker': Invocation of init method failed; nested exception is org.springframework.jdbc.datasource.init.ScriptStatementFailedException: Failed to execute SQL script statement # of URL [jar:file:/home/wlf/springboot-0.0.-SNAPSHOT.jar!/BOOT-INF/classes!/schema.sql]: insert into t_user(user_name, pass_word, role_value) select 'admin', '', 'Admin' from dual where not exists(select user_name, pass_word, role_value from t_user where user_name='admin' and pass_word='' and role_value='Admin'); nested exception is java.sql.SQLException: Field 'id' doesn't have a default value
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$(AbstractBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveNamedBean(DefaultListableBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveBean(DefaultListableBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.boot.autoconfigure.jdbc.DataSourceInitializerPostProcessor.postProcessAfterInitialization(DataSourceInitializerPostProcessor.java:) ~[spring-boot-autoconfigure-2.1..RELEASE.jar!/:2.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsAfterInitialization(AbstractAutowireCapableBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        ...  common frames omitted
Caused by: org.springframework.jdbc.datasource.init.ScriptStatementFailedException: Failed to execute SQL script statement # of URL [jar:file:/home/wlf/springboot-0.0.-SNAPSHOT.jar!/BOOT-INF/classes!/schema.sql]: insert into t_user(user_name, pass_word, role_value) select 'admin', '123456, 'Admin' from dual where not exists(select user_name, pass_word, role_value from t_user where user_name='admin' and pass_word='' and role_value='Admin'); nested exception is java.sql.SQLException: Field 'id' doesn't have a default value
        at org.springframework.jdbc.datasource.init.ScriptUtils.executeSqlScript(ScriptUtils.java:) ~[spring-jdbc-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.jdbc.datasource.init.ResourceDatabasePopulator.populate(ResourceDatabasePopulator.java:) ~[spring-jdbc-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.jdbc.datasource.init.DatabasePopulatorUtils.execute(DatabasePopulatorUtils.java:) ~[spring-jdbc-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.boot.autoconfigure.jdbc.DataSourceInitializer.runScripts(DataSourceInitializer.java:) ~[spring-boot-autoconfigure-2.1..RELEASE.jar!/:2.1..RELEASE]
        at org.springframework.boot.autoconfigure.jdbc.DataSourceInitializer.createSchema(DataSourceInitializer.java:) ~[spring-boot-autoconfigure-2.1..RELEASE.jar!/:2.1..RELEASE]
        at org.springframework.boot.autoconfigure.jdbc.DataSourceInitializerInvoker.afterPropertiesSet(DataSourceInitializerInvoker.java:) ~[spring-boot-autoconfigure-2.1..RELEASE.jar!/:2.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:) ~[spring-beans-5.1..RELEASE.jar!/:5.1..RELEASE]
        ...  common frames omitted
Caused by: java.sql.SQLException: Field 'id' doesn't have a default value
        at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:) ~[mysql-connector-java-8.0..jar!/:8.0.]
        at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:) ~[mysql-connector-java-8.0..jar!/:8.0.]
        at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:) ~[mysql-connector-java-8.0..jar!/:8.0.]
        at com.mysql.cj.jdbc.StatementImpl.executeInternal(StatementImpl.java:) ~[mysql-connector-java-8.0..jar!/:8.0.]
        at com.mysql.cj.jdbc.StatementImpl.execute(StatementImpl.java:) ~[mysql-connector-java-8.0..jar!/:8.0.]
        at com.zaxxer.hikari.pool.ProxyStatement.execute(ProxyStatement.java:) ~[HikariCP-3.2..jar!/:na]
        at com.zaxxer.hikari.pool.HikariProxyStatement.execute(HikariProxyStatement.java) ~[HikariCP-3.2..jar!/:na]
        at org.springframework.jdbc.datasource.init.ScriptUtils.executeSqlScript(ScriptUtils.java:) ~[spring-jdbc-5.1..RELEASE.jar!/:5.1..RELEASE]
        ...  common frames omitted

　　从上述日志中看到，启动Spring boot时先去初始化Spring data JPA，但没有加载到数据源DataSource对象。那为啥数据源会加载失败，其实引发的原因是执行初始化脚本执行失败。先看application.properties文件配置的数据源：

#mysql数据库配置
spring.datasource.url=jdbc:mysql://localhost:3306/test?useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC
spring.datasource.username=root
spring.datasource.password=
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.initialization-mode=always

　　最后一行指定了数据源初始化时必须去执行我的预置脚本schema.sql：

create table if not exists t_user (
    id bigint not null auto_increment,
    user_name varchar() not null,
    pass_word varchar() not null,
    role_value varchar() not null,
    primary key (id)
);

insert into t_user(user_name, pass_word, role_value) select 'admin', '', 'admin' from dual where not exists(select user_name, pass_word, role_value from t_user where user_name='admin' and pass_word='' and role_value='admin');

　　重启Spring boot时为防止重复建表用了if not exists、重复插入用了insert into...select from dual where not exists，都是先看有没有，没有了再操作。因为这里的id是自增长的，所以就算我的插入语句不指定id，mysql也会默认自动给id赋一个自增长的值。如果真按以上执行了，那应该不会出现问题才对。但事实很明显，Spring boot不按此套路来。看下我的实体类中主键ID的定义：

@Entity
@Table(name = "T_USER")
public class User implements Serializable {
    @Id
    @GeneratedValue
　　 private Long id;

    private String userName;

    private String passWord;

    private String roleValue;

    ...
}

　　以上实例类中我们指定ID是自增长的，可是这个增长不是mysql的自增，而是Spring Data JPA去设置的。我们看下@GeneratedValue究竟给我们设置了怎样的生成策略：

@Target({ElementType.METHOD, ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
public @interface GeneratedValue {
    GenerationType strategy() default GenerationType.AUTO;

    String generator() default "";
}

　　它默认是GenerationType.AUTO，若想让mysql接手设置自动增长，必须用这个：

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

　　生成类型有四种：

• TABLE：使用一个特定的数据库表来保存主键，也就是你可以自己指定哪张表。
• SEQUENCE：根据底层数据库的序列来生成主键，当然条件是得数据库支持序列的生成。
• IDENTITY：主键由数据库自动生成（主要是自动增长型），比如mysql就会设置扩展属性为auto_increment
• AUTO：主键由程序控制，程序自动生成表，比如在mysql里会自动创建表hibernate_sequence，每次新增都会读取next_val值作为自增长ID。

　　我们看下使用AUTO生成的表结构：

mysql> desc t_user;
+------------+--------------+------+-----+---------+-------+
| Field      | Type         | Null | Key | Default | Extra |
+------------+--------------+------+-----+---------+-------+
| id         | bigint()   | NO   | PRI | NULL    |       |
| pass_word  | varchar() | YES  |     | NULL    |       |
| role_value | varchar() | YES  |     | NULL    |       |
| user_name  | varchar() | YES  |     | NULL    |       |
+------------+--------------+------+-----+---------+-------+
 rows in set (0.00 sec)

　　直接insert不带主键默认值必然报错：

mysql> insert into t_user(user_name, pass_word, role_value) values ('wlf', '', 'sales');
ERROR  (HY000): Field 'id' doesn't have a default value

　　换IDENTITY试试：

mysql> desc t_user;
+------------+--------------+------+-----+---------+----------------+
| Field      | Type         | Null | Key | Default | Extra          |
+------------+--------------+------+-----+---------+----------------+
| id         | bigint()   | NO   | PRI | NULL    | auto_increment |
| user_name  | varchar() | NO   |     | NULL    |                |
| pass_word  | varchar() | NO   |     | NULL    |                |
| role_value | varchar() | NO   |     | NULL    |                |
+------------+--------------+------+-----+---------+----------------+
 rows in set (0.01 sec)

　　我们看到mysql的自增长属性带上了，这时再使用不带自增长的id字段入库成功了：

mysql> insert into t_user(user_name, pass_word, role_value) values('aaa', '', 'sales');
Query OK,  row affected (0.02 sec)

　　另外需要注意，mysql里没有建表前你指定主键生成策略为IDENTITY会加上自增长属性，但如果你开始是AUTO的，后来再改为IDENTITY的，那么你需要手动去mysql里修改约束，自己加上自增长属性，或者drop表重来。