java.lang.ClassCastException：java.util.ArrayList 无法转换为 java.lang.String

Question

当我运行这段代码时，它给了我异常 java.lang.ClassCastException：java.util.ArrayList 不能在 q1.list() 上转换为 java.lang.String；

Query q=session.createQuery("select categoryData FROM SearchHistoryEntity where userId=:u");
q.setInteger("u", userId);
List<String> list1=q.list();
if(list1!=null){
Query q1=session.createQuery("FROM BookEntity where category in (:names) order by bookId");
q1.setParameter("names", list1);
if(q1.list().size()>9){  
    q1.setFirstResult(1);
    q1.setMaxResults(9);
}
list=new ArrayList<BookEntity>();
list=q1.list();

这是完整的堆栈跟踪：

SEVERE: Servlet.service() for servlet [dispatcher] in context with path [/BookStore] threw        exception [Request processing failed; nested exception is java.lang.ClassCastException:     java.util.ArrayList cannot be cast to java.lang.String] with root cause
java.lang.ClassCastException: java.util.ArrayList cannot be cast to java.lang.String
at org.hibernate.type.descriptor.java.StringTypeDescriptor.unwrap(StringTypeDescriptor.java:39)
at org.hibernate.type.descriptor.sql.VarcharTypeDescriptor$1.doBind(VarcharTypeDescriptor.java:64)
at org.hibernate.type.descriptor.sql.BasicBinder.bind(BasicBinder.java:90)
at org.hibernate.type.AbstractStandardBasicType.nullSafeSet(AbstractStandardBasicType.java:286)
at org.hibernate.type.AbstractStandardBasicType.nullSafeSet(AbstractStandardBasicType.java:281)
at org.hibernate.param.NamedParameterSpecification.bind(NamedParameterSpecification.java:67)
at org.hibernate.loader.hql.QueryLoader.bindParameterValues(QueryLoader.java:613)
at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1900)
at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1861)
at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1838)
at org.hibernate.loader.Loader.doQuery(Loader.java:909)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:354)
at org.hibernate.loader.Loader.doList(Loader.java:2553)
at org.hibernate.loader.Loader.doList(Loader.java:2539)
at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2369)
at org.hibernate.loader.Loader.list(Loader.java:2364)
at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:496)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:387)
at org.hibernate.engine.query.spi.HQLQueryPlan.performList(HQLQueryPlan.java:231)
at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1264)
at org.hibernate.internal.QueryImpl.list(QueryImpl.java:103)
at com.app.dao.hib.SearchHistoryDaoImpl.categoryData(SearchHistoryDaoImpl.java:150)
at com.app.service.impl.SearchHistoryServiceImpl.recommend(SearchHistoryServiceImpl.java:62)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:98)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:262)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:95)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:207)
at $Proxy37.recommend(Unknown Source)
at com.app.controller.UserController.recommend(UserController.java:74)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:215)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:749)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:689)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:83)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:938)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:870)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:961)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:852)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:929)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1002)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:585)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)

在上面的代码中，我只是想从 SearchHistory 表中获取与特定 userId 相对应的标题列表（即查询 q），然后找到具有这些标题的书籍列表（查询 q1），但存在一些问题它不工作。 谁能帮我解决这个问题

Answer 1

这样试试

  List<String> list1= new ArrayList<String>();
  list.add(q);

Answer 2

尝试改变

q1.setParameter("names", list1);

到

q1.setParameterList("names", list1);

Answer 3

试试这个：

 For emaple we have pass data on server through api url and we pass parameter or body 
 parameter value same process is here. we will pass list in parameter in this case:

 q1.setParameterList("names", list1);

Answer 4

q1.setParameterList("names", list1);