Intellij Idea doesn't work the way it was working with thymeleaf / java

I've reinstalled intellij idea and noticed some changes while working with Java / Spring MVC / thymeleaf. The exact thing that now I can't actually see if return "htmlFile"; in @Controller method exists. It was underlinning it at first, now it does not. The second thing is when I put something in Model with model.addAttribute("book", book) and trying to use "book" in html with thymeleaf it shows like "book" doesn't exists but when I run program I can see that "book" exist and I can even get it's name or whatever.
Do I need some kind of plugin installed or what?

The actual solution:

• Go to: File / Project Structure / Facets.
• Select Spring, click on plus and Add your Application context class.

My Application context class example:

package ua.yuriy.spring.config;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.core.env.Environment;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.jdbc.datasource.DriverManagerDataSource;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.annotation.EnableTransactionManagement;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.ViewResolverRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
import org.thymeleaf.spring6.SpringTemplateEngine;
import org.thymeleaf.spring6.templateresolver.SpringResourceTemplateResolver;
import org.thymeleaf.spring6.view.ThymeleafViewResolver;
import javax.sql.DataSource;
import java.util.Properties;
@Configuration
@ComponentScan("your.main.thread")
@PropertySource("classpath:hibernate.properties")
@EnableJpaRepositories("your.main.thread.repositories")
@EnableWebMvc
@EnableTransactionManagement
public class SpringConfig implements WebMvcConfigurer {
private final ApplicationContext applicationContext;
private final Environment env;
@Autowired
public SpringConfig(ApplicationContext applicationContext, Environment env) {
this.applicationContext = applicationContext;
this.env = env;
}
@Bean
public SpringResourceTemplateResolver templateResolver() {
SpringResourceTemplateResolver templateResolver = new SpringResourceTemplateResolver();
templateResolver.setApplicationContext(applicationContext);
templateResolver.setPrefix("/WEB-INF/templates/"); // You might want to change templates to views
templateResolver.setSuffix(".html");
templateResolver.setCharacterEncoding("UTF-8");
return templateResolver;
}
@Bean
public SpringTemplateEngine templateEngine() {
SpringTemplateEngine templateEngine = new SpringTemplateEngine();
templateEngine.setTemplateResolver(templateResolver());
templateEngine.setEnableSpringELCompiler(true);
return templateEngine;
}
@Override
public void configureViewResolvers(ViewResolverRegistry registry) {
ThymeleafViewResolver resolver = new ThymeleafViewResolver();
resolver.setTemplateEngine(templateEngine());
resolver.setCharacterEncoding("UTF-8");
registry.viewResolver(resolver);
}
@Bean
public DataSource dataSource() {
DriverManagerDataSource dataSource = new DriverManagerDataSource();
dataSource.setDriverClassName(env.getRequiredProperty("hibernate.driver_class"));
dataSource.setUrl(env.getRequiredProperty("hibernate.connection.url"));
dataSource.setUsername(env.getRequiredProperty("hibernate.connection.username"));
dataSource.setPassword(env.getRequiredProperty("hibernate.connection.password"));
return dataSource;
}
private Properties hibernateProperties() {
Properties properties = new Properties();
properties.put("hibernate.dialect", env.getRequiredProperty("hibernate.dialect"));
properties.put("hibernate.show_sql", env.getRequiredProperty("hibernate.show_sql"));
return properties;
}
@Bean
public LocalContainerEntityManagerFactoryBean entityManagerFactory() {
final LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
em.setDataSource(dataSource());
em.setPackagesToScan("ua.yuriy.spring.models");
final HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
em.setJpaVendorAdapter(vendorAdapter);
em.setJpaProperties(hibernateProperties());
return em;
}
@Bean
public PlatformTransactionManager transactionManager() {
JpaTransactionManager transactionManager = new JpaTransactionManager();
transactionManager.setEntityManagerFactory(entityManagerFactory().getObject());
return transactionManager;
}
}