Dear professor,

When I want to save an item with either text or url content, it gives me this error even that I put this "@RequestParam(required = false) MultipartFile uploadedFile" in my post method controller:

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is org.springframework.dao.InvalidDataAccessApiUsageException: org.hibernate.TransientObjectException: object is an unsaved transient instance - save the transient instance before merging: csns.model.core.File; nested exception is java.lang.IllegalStateException: org.hibernate.TransientObjectException: object is an unsaved transient instance - save the transient instance before merging: csns.model.core.File org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:656) org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:560) javax.servlet.http.HttpServlet.service(HttpServlet.java:641) javax.servlet.http.HttpServlet.service(HttpServlet.java:722) org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:368) org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:109) org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:83) org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380) org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:97) org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380) csns.security.filter.RequestLoggingFilter.doFilterInternal(RequestLoggingFilter.java:37) org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76) org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380) org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:100) org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380) org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:78) org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380) org.springframework.security.web.authentication.rememberme.RememberMeAuthenticationFilter.doFilter(RememberMeAuthenticationFilter.java:119) org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380) org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:54) org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380) org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:35) org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380) org.springframework.security.web.authentication.www.BasicAuthenticationFilter.doFilter(BasicAuthenticationFilter.java:177) org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380) org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:187) org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380) org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:105) org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380) org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:79) org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380) org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:169) org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:237) org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:167) org.springframework.orm.jpa.support.OpenEntityManagerInViewFilter.doFilterInternal(OpenEntityManagerInViewFilter.java:113) org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)

How can I fix this problem?