Spring Boot启动失败：查询返回非唯一结果（JWT学习场景）

正在学习JWT技术，运行Spring Boot应用时启动失败，报错日志如下：

Error starting ApplicationContext. To display the condition evaluation report re-run your application with 'debug' enabled.
2023-11-27T15:30:20.048+09:00 ERROR 66171 --- [  restartedMain] o.s.boot.SpringApplication               : Application run failed

java.lang.IllegalStateException: Failed to execute CommandLineRunner
    at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:777) ~[spring-boot-3.1.4.jar:3.1.4]
    at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:758) ~[spring-boot-3.1.4.jar:3.1.4]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:322) ~[spring-boot-3.1.4.jar:3.1.4]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1309) ~[spring-boot-3.1.4.jar:3.1.4]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1298) ~[spring-boot-3.1.4.jar:3.1.4]
    at com.example.gametalk_2005025.Gametalk2005025Application.main(Gametalk2005025Application.java:19) ~[main/:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[na:na]
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Method.java:568) ~[na:na]
    at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:50) ~[spring-boot-devtools-3.1.4.jar:3.1.4]
Caused by: org.springframework.dao.IncorrectResultSizeDataAccessException: query did not return a unique result: 2
    at org.springframework.orm.jpa.EntityManagerFactoryUtils.convertJpaAccessExceptionIfPossible(EntityManagerFactoryUtils.java:382) ~[spring-orm-6.0.12.jar:6.0.12]
    at org.springframework.orm.jpa.vendor.HibernateJpaDialect.translateExceptionIfPossible(HibernateJpaDialect.java:234) ~[spring-orm-6.0.12.jar:6.0.12]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.translateExceptionIfPossible(AbstractEntityManagerFactoryBean.java:550) ~[spring-orm-6.0.12.jar:6.0.12]
    at org.springframework.dao.support.ChainedPersistenceExceptionTranslator.translateExceptionIfPossible(ChainedPersistenceExceptionTranslator.java:61) ~[spring-tx-6.0.12.jar:6.0.12]
    at org.springframework.dao.support.DataAccessUtils.translateIfNecessary(DataAccessUtils.java:243) ~[spring-tx-6.0.12.jar:6.0.12]
    at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:152) ~[spring-tx-6.0.12.jar:6.0.12]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) ~[spring-aop-6.0.12.jar:6.0.12]
    at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:135) ~[spring-data-jpa-3.1.4.jar:3.1.4]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) ~[spring-aop-6.0.12.jar:6.0.12]
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:97) ~[spring-aop-6.0.12.jar:6.0.12]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) ~[spring-aop-6.0.12.jar:6.0.12]
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:244) ~[spring-aop-6.0.12.jar:6.0.12]
    at jdk.proxy4/jdk.proxy4.$Proxy112.findByRole(Unknown Source) ~[na:na]
    at com.example.gametalk_2005025.Gametalk2005025Application.run(Gametalk2005025Application.java:24) ~[main/:na]
    at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:774) ~[spring-boot-3.1.4.jar:3.1.4]
    ... 10 common frames omitted
Caused by: jakarta.persistence.NonUniqueResultException: query did not return a unique result: 2
    at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:128) ~[hibernate-core-6.2.9.Final.jar:6.2.9.Final]
    at org.hibernate.query.spi.AbstractSelectionQuery.getSingleResult(AbstractSelectionQuery.java:482) ~[hibernate-core-6.2.9.Final.jar:6.2.9.Final]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[na:na]
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Method.java:568) ~[na:na]
    at org.springframework.orm.jpa.SharedEntityManagerCreator$DeferredQueryInvocationHandler.invoke(SharedEntityManagerCreator.java:405) ~[spring-orm-6.0.12.jar:6.0.12]
    at jdk.proxy4/jdk.proxy4.$Proxy120.getSingleResult(Unknown Source) ~[na:na]
    at org.springframework.data.jpa.repository.query.JpaQueryExecution$SingleEntityExecution.doExecute(JpaQueryExecution.java:223) ~[spring-data-jpa-3.1.4.jar:3.1.4]
    at org.springframework.data.jpa.repository.query.JpaQueryExecution.execute(JpaQueryExecution.java:92) ~[spring-data-jpa-3.1.4.jar:3.1.4]
    at org.springframework.data.jpa.repository.query.AbstractJpaQuery.doExecute(AbstractJpaQuery.java:148) ~[spring-data-jpa-3.1.4.jar:3.1.4]
    at org.springframework.data.jpa.repository.query.AbstractJpaQuery.execute(AbstractJpaQuery.java:136) ~[spring-data-jpa-3.1.4.jar:3.1.4]
    at org.springframework.data.repository.core.support.RepositoryMethodInvoker.doInvoke(RepositoryMethodInvoker.java:136) ~[spring-data-commons-3.1.4.jar:3.1.4]
    at org.springframework.data.repository.core.support.RepositoryMethodInvoker.invoke(RepositoryMethodInvoker.java:120) ~[spring-data-commons-3.1.4.jar:3.1.4]
    at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.doInvoke(QueryExecutorMethodInterceptor.java:164) ~[spring-data-commons-3.1.4.jar:3.1.4]
    at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.invoke(QueryExecutorMethodInterceptor.java:143) ~[spring-data-commons-3.1.4.jar:3.1.4]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) ~[spring-aop-6.0.12.jar:6.0.12]
    at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:72) ~[spring-data-commons-3.1.4.jar:3.1.4]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) ~[spring-aop-6.0.12.jar:6.0.12]
    at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:123) ~[spring-tx-6.0.12.jar:6.0.12]
    at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:391) ~[spring-tx-6.0.12.jar:6.0.12]
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:119) ~[spring-tx-6.0.12.jar:6.0.12]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) ~[spring-aop-6.0.12.jar:6.0.12]
    at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:137) ~[spring-tx-6.0.12.jar:6.0.12]
    ... 19 common frames omitted

2023-11-27T15:30:20.056+09:00  INFO 66171 --- [  restartedMain] j.LocalContainerEntityManagerFactoryBean : Closing JPA EntityManagerFactory for persistence unit 'default'
2023-11-27T15:30:20.058+09:00  INFO 66171 --- [  restartedMain] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...
2023-11-27T15:30:20.187+09:00  INFO 66171 --- [  restartedMain] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.

Process finished with exit code 0

问题定位 #

核心错误是jakarta.persistence.NonUniqueResultException: query did not return a unique result: 2，说明：

• 启动类Gametalk2005025Application.java第24行调用了Repository的findByRole方法
• 该方法被设计为返回单个实体（比如返回User或Optional<User>），但数据库中匹配该role条件的记录有2条，导致查询结果不唯一，触发异常

解决建议 #

• 检查JPA Repository的findByRole方法定义：如果允许返回多条结果，将返回类型改为List<T>或Stream<T>；如果只需要一条，改用findFirstByRole或findTopByRole
• 清理数据库：查看对应表中匹配该role的数据，删除重复记录或调整数据使其唯一
• 调整启动类逻辑：确认调用findByRole后的代码是否能处理多条结果，若不能则修改查询方式

我是技术新手，不清楚还需提供哪些信息来定位问题，若有需要请告知。

内容的提问来源于stack exchange，提问作者snowman