Spring 启动 BookStore 项目“org.springframework.beans.factory.BeanCreationException：创建名为“bookStoreRepo”的 bean 时出错”

Question

I'm trying to create the backend of a bookstore using spring boot and MySQL. I'm tasked to create a book browsing feature however I keep getting "Error creating bean with name" throughout the project and I can't connect to postman to test my code. The Problem started after I implemented the service and repo package/classes. I messed around with many suggestions online but im having little luck.

terminal

"C:\Program Files\Java\jdk-17.0.1\bin\java.exe" "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2022.1.3\lib\idea_rt.jar=54086:C:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2022.1.3\bin" -Dfile.encoding=UTF-8 -classpath C:\Users\Arthur\Documents\GitHub\BookStore\target\classes;C:\Users\Arthur\.m2\repository\org\springframework\boot\spring-boot-starter-data-jpa\2.7.2\spring-boot-starter-data-jpa-2.7.2.jar;C:\Users\Arthur\.m2\repository\org\springframework\boot\spring-boot-starter-aop\2.7.2\spring-boot-starter-aop-2.7.2.jar;C:\Users\Arthur\.m2\repository\org\springframework\spring-aop\5.3.22\spring-aop-5.3.22.jar;C:\Users\Arthur\.m2\repository\org\aspectj\aspectjweaver\1.9.7\aspectjweaver-1.9.7.jar;C:\Users\Arthur\.m2\repository\org\springframework\boot\spring-boot-starter-jdbc\2.7.2\spring-boot-starter-jdbc-2.7.2.jar;C:\Users\Arthur\.m2\repository\com\zaxxer\HikariCP\4.0.3\HikariCP-4.0.3.jar;C:\Users\Arthur\.m2\repository\org\springframework\spring-jdbc\5.3.22\spring-jdbc-5.3.22.jar;C:\Users\Arthur\.m2\repository\jakarta\transaction\jakarta.transaction-api\1.3.3\jakarta.transaction-api-1.3.3.jar;C:\Users\Arthur\.m2\repository\jakarta\persistence\jakarta.persistence-api\2.2.3\jakarta.persistence-api-2.2.3.jar;C:\Users\Arthur\.m2\repository\org\hibernate\hibernate-core\5.6.10.Final\hibernate-core-5.6.10.Final.jar;C:\Users\Arthur\.m2\repository\org\jboss\logging\jboss-logging\3.4.3.Final\jboss-logging-3.4.3.Final.jar;C:\Users\Arthur\.m2\repository\net\bytebuddy\byte-buddy\1.12.12\byte-buddy-1.12.12.jar;C:\Users\Arthur\.m2\repository\antlr\antlr\2.7.7\antlr-2.7.7.jar;C:\Users\Arthur\.m2\repository\org\jboss\jandex\2.4.2.Final\jandex-2.4.2.Final.jar;C:\Users\Arthur\.m2\repository\com\fasterxml\classmate\1.5.1\classmate-1.5.1.jar;C:\Users\Arthur\.m2\repository\org\hibernate\common\hibernate-commons-annotations\5.1.2.Final\hibernate-commons-annotations-5.1.2.Final.jar;C:\Users\Arthur\.m2\repository\org\glassfish\jaxb\jaxb-runtime\2.3.6\jaxb-runtime-2.3.6.jar;C:\Users\Arthur\.m2\repository\org\glassfish\jaxb\txw2\2.3.6\txw2-2.3.6.jar;C:\Users\Arthur\.m2\repository\com\sun\istack\istack-commons-runtime\3.0.12\istack-commons-runtime-3.0.12.jar;C:\Users\Arthur\.m2\repository\com\sun\activation\jakarta.activation\1.2.2\jakarta.activation-1.2.2.jar;C:\Users\Arthur\.m2\repository\org\springframework\data\spring-data-jpa\2.7.2\spring-data-jpa-2.7.2.jar;C:\Users\Arthur\.m2\repository\org\springframework\data\spring-data-commons\2.7.2\spring-data-commons-2.7.2.jar;C:\Users\Arthur\.m2\repository\org\springframework\spring-orm\5.3.22\spring-orm-5.3.22.jar;C:\Users\Arthur\.m2\repository\org\springframework\spring-context\5.3.22\spring-context-5.3.22.jar;C:\Users\Arthur\.m2\repository\org\springframework\spring-tx\5.3.22\spring-tx-5.3.22.jar;C:\Users\Arthur\.m2\repository\org\springframework\spring-beans\5.3.22\spring-beans-5.3.22.jar;C:\Users\Arthur\.m2\repository\org\slf4j\slf4j-api\1.7.36\slf4j-api-1.7.36.jar;C:\Users\Arthur\.m2\repository\org\springframework\spring-aspects\5.3.22\spring-aspects-5.3.22.jar;C:\Users\Arthur\.m2\repository\org\springframework\boot\spring-boot-starter-web\2.7.2\spring-boot-starter-web-2.7.2.jar;C:\Users\Arthur\.m2\repository\org\springframework\boot\spring-boot-starter\2.7.2\spring-boot-starter-2.7.2.jar;C:\Users\Arthur\.m2\repository\org\springframework\boot\spring-boot\2.7.2\spring-boot-2.7.2.jar;C:\Users\Arthur\.m2\repository\org\springframework\boot\spring-boot-autoconfigure\2.7.2\spring-boot-autoconfigure-2.7.2.jar;C:\Users\Arthur\.m2\repository\org\springframework\boot\spring-boot-starter-logging\2.7.2\spring-boot-starter-logging-2.7.2.jar;C:\Users\Arthur\.m2\repository\ch\qos\logback\logback-classic\1.2.11\logback-classic-1.2.11.jar;C:\Users\Arthur\.m2\repository\ch\qos\logback\logback-core\1.2.11\logback-core-1.2.11.jar;C:\Users\Arthur\.m2\repository\org\apache\logging\log4j\log4j-to-slf4j\2.17.2\log4j-to-slf4j-2.17.2.jar;C:\Users\Arthur\.m2\repository\org\apache\logging\log4j\log4j-api\2.17.2\log4j-api-2.17.2.jar;C:\Users\Arthur\.m2\repository\org\slf4j\jul-to-slf4j\1.7.36\jul-to-slf4j-1.7.36.jar;C:\Users\Arthur\.m2\repository\jakarta\annotation\jakarta.annotation-api\1.3.5\jakarta.annotation-api-1.3.5.jar;C:\Users\Arthur\.m2\repository\org\yaml\snakeyaml\1.30\snakeyaml-1.30.jar;C:\Users\Arthur\.m2\repository\org\springframework\boot\spring-boot-starter-json\2.7.2\spring-boot-starter-json-2.7.2.jar;C:\Users\Arthur\.m2\repository\com\fasterxml\jackson\core\jackson-databind\2.13.3\jackson-databind-2.13.3.jar;C:\Users\Arthur\.m2\repository\com\fasterxml\jackson\core\jackson-annotations\2.13.3\jackson-annotations-2.13.3.jar;C:\Users\Arthur\.m2\repository\com\fasterxml\jackson\core\jackson-core\2.13.3\jackson-core-2.13.3.jar;C:\Users\Arthur\.m2\repository\com\fasterxml\jackson\datatype\jackson-datatype-jdk8\2.13.3\jackson-datatype-jdk8-2.13.3.jar;C:\Users\Arthur\.m2\repository\com\fasterxml\jackson\datatype\jackson-datatype-jsr310\2.13.3\jackson-datatype-jsr310-2.13.3.jar;C:\Users\Arthur\.m2\repository\com\fasterxml\jackson\module\jackson-module-parameter-names\2.13.3\jackson-module-parameter-names-2.13.3.jar;C:\Users\Arthur\.m2\repository\org\springframework\boot\spring-boot-starter-tomcat\2.7.2\spring-boot-starter-tomcat-2.7.2.jar;C:\Users\Arthur\.m2\repository\org\apache\tomcat\embed\tomcat-embed-core\9.0.65\tomcat-embed-core-9.0.65.jar;C:\Users\Arthur\.m2\repository\org\apache\tomcat\embed\tomcat-embed-el\9.0.65\tomcat-embed-el-9.0.65.jar;C:\Users\Arthur\.m2\repository\org\apache\tomcat\embed\tomcat-embed-websocket\9.0.65\tomcat-embed-websocket-9.0.65.jar;C:\Users\Arthur\.m2\repository\org\springframework\spring-web\5.3.22\spring-web-5.3.22.jar;C:\Users\Arthur\.m2\repository\org\springframework\spring-webmvc\5.3.22\spring-webmvc-5.3.22.jar;C:\Users\Arthur\.m2\repository\org\springframework\spring-expression\5.3.22\spring-expression-5.3.22.jar;C:\Users\Arthur\.m2\repository\mysql\mysql-connector-java\8.0.29\mysql-connector-java-8.0.29.jar;C:\Users\Arthur\.m2\repository\jakarta\xml\bind\jakarta.xml.bind-api\2.3.3\jakarta.xml.bind-api-2.3.3.jar;C:\Users\Arthur\.m2\repository\jakarta\activation\jakarta.activation-api\1.2.2\jakarta.activation-api-1.2.2.jar;C:\Users\Arthur\.m2\repository\org\springframework\spring-core\5.3.22\spring-core-5.3.22.jar;C:\Users\Arthur\.m2\repository\org\springframework\spring-jcl\5.3.22\spring-jcl-5.3.22.jar net.CenGroup4.BookStore.BookStoreApplication

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v2.7.2)

2022-07-29 22:42:16.206  INFO 24292 --- [           main] n.C.BookStore.BookStoreApplication       : Starting BookStoreApplication using Java 17.0.1 on DESKTOP-1LG3O93 with PID 24292 (C:\Users\Arthur\Documents\GitHub\BookStore\target\classes started by Arthur in C:\Users\Arthur\Documents\GitHub\BookStore)
2022-07-29 22:42:16.208  INFO 24292 --- [           main] n.C.BookStore.BookStoreApplication       : No active profile set, falling back to 1 default profile: "default"
2022-07-29 22:42:16.748  INFO 24292 --- [           main] .s.d.r.c.RepositoryConfigurationDelegate : Bootstrapping Spring Data JPA repositories in DEFAULT mode.
2022-07-29 22:42:16.814  INFO 24292 --- [           main] .s.d.r.c.RepositoryConfigurationDelegate : Finished Spring Data repository scanning in 57 ms. Found 1 JPA repository interfaces.
2022-07-29 22:42:17.407  INFO 24292 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2022-07-29 22:42:17.417  INFO 24292 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2022-07-29 22:42:17.417  INFO 24292 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.65]
2022-07-29 22:42:17.534  INFO 24292 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2022-07-29 22:42:17.534  INFO 24292 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 1285 ms
2022-07-29 22:42:17.695  INFO 24292 --- [           main] o.hibernate.jpa.internal.util.LogHelper  : HHH000204: Processing PersistenceUnitInfo [name: default]
2022-07-29 22:42:17.747  INFO 24292 --- [           main] org.hibernate.Version                    : HHH000412: Hibernate ORM core version 5.6.10.Final
2022-07-29 22:42:17.907  INFO 24292 --- [           main] o.hibernate.annotations.common.Version   : HCANN000001: Hibernate Commons Annotations {5.1.2.Final}
2022-07-29 22:42:17.999  INFO 24292 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2022-07-29 22:42:18.725  INFO 24292 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
2022-07-29 22:42:18.738  INFO 24292 --- [           main] org.hibernate.dialect.Dialect            : HHH000400: Using dialect: org.hibernate.dialect.MySQL8Dialect
Hibernate: create table book_details (id bigint not null, author varchar(255), book_code varchar(255), copies_sold bigint, description varchar(255), genre varchar(255), name varchar(255), price double precision, publisher varchar(255), year_published varchar(255), primary key (id)) engine=InnoDB
Hibernate: create table hibernate_sequence (next_val bigint) engine=InnoDB
Hibernate: insert into hibernate_sequence values ( 1 )
2022-07-29 22:42:19.653  INFO 24292 --- [           main] o.h.e.t.j.p.i.JtaPlatformInitiator       : HHH000490: Using JtaPlatform implementation: [org.hibernate.engine.transaction.jta.platform.internal.NoJtaPlatform]
2022-07-29 22:42:19.659  INFO 24292 --- [           main] j.LocalContainerEntityManagerFactoryBean : Initialized JPA EntityManagerFactory for persistence unit 'default'
2022-07-29 22:42:19.691  WARN 24292 --- [           main] JpaBaseConfiguration$JpaWebConfiguration : spring.jpa.open-in-view is enabled by default. Therefore, database queries may be performed during view rendering. Explicitly configure spring.jpa.open-in-view to disable this warning
2022-07-29 22:42:20.212  WARN 24292 --- [           main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'bookStoreRepo' defined in net.CenGroup4.BookStore.repo.BookStoreRepo defined in @EnableJpaRepositories declared on JpaRepositoriesRegistrar.EnableJpaRepositoriesConfiguration: Invocation of init method failed; nested exception is org.springframework.data.repository.query.QueryCreationException: Could not create query for public abstract java.util.Optional net.CenGroup4.BookStore.repo.BookStoreRepo.findByGenre(java.lang.String); Reason: Validation failed for query for method public abstract java.util.Optional net.CenGroup4.BookStore.repo.BookStoreRepo.findByGenre(java.lang.String)!; nested exception is java.lang.IllegalArgumentException: Validation failed for query for method public abstract java.util.Optional net.CenGroup4.BookStore.repo.BookStoreRepo.findByGenre(java.lang.String)!
2022-07-29 22:42:20.212  INFO 24292 --- [           main] j.LocalContainerEntityManagerFactoryBean : Closing JPA EntityManagerFactory for persistence unit 'default'
2022-07-29 22:42:20.213  INFO 24292 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...
2022-07-29 22:42:20.219  INFO 24292 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.
2022-07-29 22:42:20.221  INFO 24292 --- [           main] o.apache.catalina.core.StandardService   : Stopping service [Tomcat]
2022-07-29 22:42:20.230  INFO 24292 --- [           main] ConditionEvaluationReportLoggingListener : 

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2022-07-29 22:42:20.251 ERROR 24292 --- [           main] o.s.boot.SpringApplication               : Application run failed

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'bookStoreRepo' defined in net.CenGroup4.BookStore.repo.BookStoreRepo defined in @EnableJpaRepositories declared on JpaRepositoriesRegistrar.EnableJpaRepositoriesConfiguration: Invocation of init method failed; nested exception is org.springframework.data.repository.query.QueryCreationException: Could not create query for public abstract java.util.Optional net.CenGroup4.BookStore.repo.BookStoreRepo.findByGenre(java.lang.String); Reason: Validation failed for query for method public abstract java.util.Optional net.CenGroup4.BookStore.repo.BookStoreRepo.findByGenre(java.lang.String)!; nested exception is java.lang.IllegalArgumentException: Validation failed for query for method public abstract java.util.Optional net.CenGroup4.BookStore.repo.BookStoreRepo.findByGenre(java.lang.String)!
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1804) ~[spring-beans-5.3.22.jar:5.3.22]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:620) ~[spring-beans-5.3.22.jar:5.3.22]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:542) ~[spring-beans-5.3.22.jar:5.3.22]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335) ~[spring-beans-5.3.22.jar:5.3.22]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-5.3.22.jar:5.3.22]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333) ~[spring-beans-5.3.22.jar:5.3.22]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208) ~[spring-beans-5.3.22.jar:5.3.22]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:936) ~[spring-beans-5.3.22.jar:5.3.22]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:918) ~[spring-context-5.3.22.jar:5.3.22]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:583) ~[spring-context-5.3.22.jar:5.3.22]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:147) ~[spring-boot-2.7.2.jar:2.7.2]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:734) ~[spring-boot-2.7.2.jar:2.7.2]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:408) ~[spring-boot-2.7.2.jar:2.7.2]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:308) ~[spring-boot-2.7.2.jar:2.7.2]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1306) ~[spring-boot-2.7.2.jar:2.7.2]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1295) ~[spring-boot-2.7.2.jar:2.7.2]
    at net.CenGroup4.BookStore.BookStoreApplication.main(BookStoreApplication.java:16) ~[classes/:na]
Caused by: org.springframework.data.repository.query.QueryCreationException: Could not create query for public abstract java.util.Optional net.CenGroup4.BookStore.repo.BookStoreRepo.findByGenre(java.lang.String); Reason: Validation failed for query for method public abstract java.util.Optional net.CenGroup4.BookStore.repo.BookStoreRepo.findByGenre(java.lang.String)!; nested exception is java.lang.IllegalArgumentException: Validation failed for query for method public abstract java.util.Optional net.CenGroup4.BookStore.repo.BookStoreRepo.findByGenre(java.lang.String)!
    at org.springframework.data.repository.query.QueryCreationException.create(QueryCreationException.java:101) ~[spring-data-commons-2.7.2.jar:2.7.2]
    at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.lookupQuery(QueryExecutorMethodInterceptor.java:107) ~[spring-data-commons-2.7.2.jar:2.7.2]
    at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.lambda$mapMethodsToQuery$1(QueryExecutorMethodInterceptor.java:95) ~[spring-data-commons-2.7.2.jar:2.7.2]
    at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:197) ~[na:na]
    at java.base/java.util.Iterator.forEachRemaining(Iterator.java:133) ~[na:na]
    at java.base/java.util.Collections$UnmodifiableCollection$1.forEachRemaining(Collections.java:1061) ~[na:na]
    at java.base/java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1845) ~[na:na]
    at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509) ~[na:na]
    at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499) ~[na:na]
    at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:921) ~[na:na]
    at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[na:na]
    at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:682) ~[na:na]
    at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.mapMethodsToQuery(QueryExecutorMethodInterceptor.java:97) ~[spring-data-commons-2.7.2.jar:2.7.2]
    at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.lambda$new$0(QueryExecutorMethodInterceptor.java:87) ~[spring-data-commons-2.7.2.jar:2.7.2]
    at java.base/java.util.Optional.map(Optional.java:260) ~[na:na]
    at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.<init>(QueryExecutorMethodInterceptor.java:87) ~[spring-data-commons-2.7.2.jar:2.7.2]
    at org.springframework.data.repository.core.support.RepositoryFactorySupport.getRepository(RepositoryFactorySupport.java:365) ~[spring-data-commons-2.7.2.jar:2.7.2]
    at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.lambda$afterPropertiesSet$5(RepositoryFactoryBeanSupport.java:323) ~[spring-data-commons-2.7.2.jar:2.7.2]
    at org.springframework.data.util.Lazy.getNullable(Lazy.java:231) ~[spring-data-commons-2.7.2.jar:2.7.2]
    at org.springframework.data.util.Lazy.get(Lazy.java:115) ~[spring-data-commons-2.7.2.jar:2.7.2]
    at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.afterPropertiesSet(RepositoryFactoryBeanSupport.java:329) ~[spring-data-commons-2.7.2.jar:2.7.2]
    at org.springframework.data.jpa.repository.support.JpaRepositoryFactoryBean.afterPropertiesSet(JpaRepositoryFactoryBean.java:144) ~[spring-data-jpa-2.7.2.jar:2.7.2]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1863) ~[spring-beans-5.3.22.jar:5.3.22]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1800) ~[spring-beans-5.3.22.jar:5.3.22]
    ... 16 common frames omitted
Caused by: java.lang.IllegalArgumentException: Validation failed for query for method public abstract java.util.Optional net.CenGroup4.BookStore.repo.BookStoreRepo.findByGenre(java.lang.String)!
    at org.springframework.data.jpa.repository.query.SimpleJpaQuery.validateQuery(SimpleJpaQuery.java:96) ~[spring-data-jpa-2.7.2.jar:2.7.2]
    at org.springframework.data.jpa.repository.query.SimpleJpaQuery.<init>(SimpleJpaQuery.java:66) ~[spring-data-jpa-2.7.2.jar:2.7.2]
    at org.springframework.data.jpa.repository.query.JpaQueryFactory.fromMethodWithQueryString(JpaQueryFactory.java:51) ~[spring-data-jpa-2.7.2.jar:2.7.2]
    at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$DeclaredQueryLookupStrategy.resolveQuery(JpaQueryLookupStrategy.java:169) ~[spring-data-jpa-2.7.2.jar:2.7.2]
    at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$CreateIfNotFoundQueryLookupStrategy.resolveQuery(JpaQueryLookupStrategy.java:253) ~[spring-data-jpa-2.7.2.jar:2.7.2]
    at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$AbstractQueryLookupStrategy.resolveQuery(JpaQueryLookupStrategy.java:93) ~[spring-data-jpa-2.7.2.jar:2.7.2]
    at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.lookupQuery(QueryExecutorMethodInterceptor.java:103) ~[spring-data-commons-2.7.2.jar:2.7.2]
    ... 38 common frames omitted
Caused by: java.lang.IllegalArgumentException: org.hibernate.QueryException: unexpected char: '{' [{'genre': ?0}]
    at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:138) ~[hibernate-core-5.6.10.Final.jar:5.6.10.Final]
    at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:181) ~[hibernate-core-5.6.10.Final.jar:5.6.10.Final]
    at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:188) ~[hibernate-core-5.6.10.Final.jar:5.6.10.Final]
    at org.hibernate.internal.AbstractSharedSessionContract.createQuery(AbstractSharedSessionContract.java:757) ~[hibernate-core-5.6.10.Final.jar:5.6.10.Final]
    at org.hibernate.internal.AbstractSharedSessionContract.createQuery(AbstractSharedSessionContract.java:114) ~[hibernate-core-5.6.10.Final.jar:5.6.10.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.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:362) ~[spring-orm-5.3.22.jar:5.3.22]
    at jdk.proxy2/jdk.proxy2.$Proxy95.createQuery(Unknown Source) ~[na:na]
    at org.springframework.data.jpa.repository.query.SimpleJpaQuery.validateQuery(SimpleJpaQuery.java:90) ~[spring-data-jpa-2.7.2.jar:2.7.2]
    ... 44 common frames omitted
Caused by: org.hibernate.QueryException: unexpected char: '{' [{'genre': ?0}]
    at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:236) ~[hibernate-core-5.6.10.Final.jar:5.6.10.Final]
    at org.hibernate.hql.internal.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:144) ~[hibernate-core-5.6.10.Final.jar:5.6.10.Final]
    at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:113) ~[hibernate-core-5.6.10.Final.jar:5.6.10.Final]
    at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:73) ~[hibernate-core-5.6.10.Final.jar:5.6.10.Final]
    at org.hibernate.engine.query.spi.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:162) ~[hibernate-core-5.6.10.Final.jar:5.6.10.Final]
    at org.hibernate.internal.AbstractSharedSessionContract.getQueryPlan(AbstractSharedSessionContract.java:636) ~[hibernate-core-5.6.10.Final.jar:5.6.10.Final]
    at org.hibernate.internal.AbstractSharedSessionContract.createQuery(AbstractSharedSessionContract.java:748) ~[hibernate-core-5.6.10.Final.jar:5.6.10.Final]
    ... 52 common frames omitted


Process finished with exit code 1

BookStoreRepo

package net.CenGroup4.BookStore.repo;

import net.CenGroup4.BookStore.model.BookDetails;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;

import java.util.List;
import java.util.Optional;

public interface  BookStoreRepo extends JpaRepository<BookDetails, String> {


   void deleteBookDetailsId(Long id);

   Optional <BookDetails> findBookDetails(Long id);

   @Query("{'id': ?0}")
   Optional<BookDetails> findById(Long id);

   @Query("{'genre': ?0}")
   Optional<List<BookDetails>> findByGenre(String genre);

}

BookStoreService

package net.CenGroup4.BookStore.service;

import net.CenGroup4.BookStore.exception.BookNotFoundException;
import net.CenGroup4.BookStore.model.BookDetails;
import net.CenGroup4.BookStore.repo.BookStoreRepo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Sort;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;

import java.util.ArrayList;
import java.util.List;
import java.util.UUID;

@Service
public class BookStoreService
{

    private final BookStoreRepo bookStoreRepo;

    @Autowired
    public BookStoreService(BookStoreRepo bookStoreRepo)
    {
        this.bookStoreRepo = bookStoreRepo;
    }
/*
    Basic book functions

    Add book
    find all books
    update book details
    find book by id
    delete book

 */

    //Add book
    public BookDetails addBookDetails(BookDetails details)
    {
        details.setBookCode(UUID.randomUUID().toString());
        return bookStoreRepo.save(details);
    }

    //find all books
    public List<BookDetails> findALLBooks()
    {
        return bookStoreRepo.findAll();
    }

    //update book details
    public BookDetails updateBookDetails(BookDetails details)
    {
        return bookStoreRepo.save(details);
    }


    public BookDetails findBookDetails(Long id)
    {
        return ((BookStoreRepo) bookStoreRepo).findBookDetails(id).orElseThrow(() -> new BookNotFoundException("Book was not found " + id));
    }

    public void deleteBookDetails(Long id){
        ((BookStoreRepo) bookStoreRepo).deleteBookDetailsId(id);
    }


    /*
    -Retrieve List of Books by Genre

    -Retrieve List of Top Sellers (Top 10 books that have sold the most copied)

    -Retrieve List of Books for a particular rating and higher

    -Retrieve List of X Books at a time where X is an integer from a given position in the overall recordset.


*/


    //Retrieve List of Books by Genre
    public List<BookDetails> getBookByGenre(String genre) {
        return ((BookStoreRepo) bookStoreRepo).findByGenre(genre).orElseThrow(() -> new BookNotFoundException("Genre was not found " + genre));

    }


    //Retrieve List of Top Sellers (Top 10 books that have sold the most copied)
    public List<BookDetails> tenMostSold()
    {

        List<BookDetails> allBooks = ((JpaRepository<BookDetails, String>) bookStoreRepo).findAll(Sort.by(Sort.Direction.DESC, "numsold"));
        List<BookDetails> subsetBooks = allBooks.subList(0,10);
        return subsetBooks;
    }


    //Retrieve List of Books for a particular rating and higher
    public List<BookDetails> getBooksWithAvgRatingHigherThan(float value) {

        List<BookDetails> allBooks = findALLBooks();

        // List of all books which average rating was higher than parameter
        List<BookDetails> bookMatches = new ArrayList<BookDetails>();

        for (BookDetails book : allBooks) {
            if (bookAvgValue(book.getId()) >= value) {
                bookMatches.add(book);
            }
        }

        return bookMatches;
    }


    private float bookAvgValue(Long bookID) {

        // Set the server installation/config, do not hard coded
        String uri = "http://localhost:8080/api/rating/avg/";
        uri += bookID;

        RestTemplate restTemplate = new RestTemplate();
        return restTemplate.getForObject(uri, float.class);
    }


    //Retrieve List of X Books at a time where X is an integer from a given position in the overall recordset.
    public List<BookDetails> getSubset(int quantity, int position) {

        List<BookDetails> allBooks = findALLBooks();

        if (position >= allBooks.size()) {
            throw new RuntimeException("This starting position exceeds the size of the collection");
        }

        List<BookDetails> subSet = new ArrayList<BookDetails>();

        for (int i = position; (i < allBooks.size()) && quantity > 0;  i++) {
            subSet.add(allBooks.get(i));
            --quantity;
        }

        return subSet;
    }


}

Answer 1

The error message is clear

Caused by: org.springframework.data.repository.query.QueryCreationException: Could not create query for public abstract java.util.Optional net.CenGroup4.BookStore.repo.BookStoreRepo.findByGenre(java.lang.String); Reason: Validation failed for query for method public abstract java.util.Optional net.CenGroup4.BookStore.repo.BookStoreRepo.findByGenre(java.lang.String)!; nested exception is java.lang.IllegalArgumentException: Validation failed for query for method public abstract java.util.Optional net.CenGroup4.BookStore.repo.BookStoreRepo.findByGenre(java.lang.String)!

Further in the stacktrace it specifies the exact cause

Caused by: org.hibernate.QueryException: unexpected char: '{' [{'genre': ?0}]

The @Query annotation will support JPQL-based queries by default unless you set nativeQuery param to true for SQL-based Queries. What you have written is neither of the two.

You are most likely looking for something like this instead. Also you don't need to wrap a List<> with an Optional as it will just return an empty list if there are no results.

@Query("select bd from BookDetails bd where genre = :genre")
List<BookDetails> findByGenre(String genre);