I am using Spring and hibernate in a recent project and can't get around a class cast exception whenever I use stream() on a list of entities. I am not sure if it is an issue with spring, or if it is somehow related to hibernate interacting with spring. I am new with spring and hibernate so I'm not sure if there is something basic I am missing. Here is the error I am getting:
java.lang.ClassCastException: com.w2e.model.Session cannot be cast to com.w2e.model.Session
at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193) ~[na:1.8.0_71]
at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1374) ~[na:1.8.0_71]
at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481) ~[na:1.8.0_71]
at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471) ~[na:1.8.0_71]
at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708) ~[na:1.8.0_71]
at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[na:1.8.0_71]
at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499) ~[na:1.8.0_71]
at com.w2e.services.SessionService.get(SessionService.java:30) ~[classes/:na]
at com.w2e.controllers.CourseResource.getSession(CourseResource.java:24) ~[classes/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_71]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_71]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_71]
at java.lang.reflect.Method.invoke(Method.java:497) ~[na:1.8.0_71]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190) ~[spring-web-5.2.4.RELEASE.jar:5.2.4.RELEASE]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) ~[spring-web-5.2.4.RELEASE.jar:5.2.4.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106) ~[spring-webmvc-5.2.4.RELEASE.jar:5.2.4.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:879) ~[spring-webmvc-5.2.4.RELEASE.jar:5.2.4.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:793) ~[spring-webmvc-5.2.4.RELEASE.jar:5.2.4.RELEASE]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.2.4.RELEASE.jar:5.2.4.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040) ~[spring-webmvc-5.2.4.RELEASE.jar:5.2.4.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943) ~[spring-webmvc-5.2.4.RELEASE.jar:5.2.4.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.2.4.RELEASE.jar:5.2.4.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) ~[spring-webmvc-5.2.4.RELEASE.jar:5.2.4.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:634) ~[tomcat-embed-core-9.0.31.jar:9.0.31]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.2.4.RELEASE.jar:5.2.4.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) ~[tomcat-embed-core-9.0.31.jar:9.0.31]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.31.jar:9.0.31]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.31.jar:9.0.31]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.31.jar:9.0.31]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.31.jar:9.0.31]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.31.jar:9.0.31]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.2.4.RELEASE.jar:5.2.4.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.4.RELEASE.jar:5.2.4.RELEASE
Here is my pom.xml file:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.2.5.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.in28minutes.fullstack.springboot.maven.crud</groupId>
<artifactId>spring-boot-fullstack-crud-full-stack-with-maven</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>spring-boot-fullstack-crud-full-stack-with-maven</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
<spring-version>5.1.3.RELEASE</spring-version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-beans</artifactId>
<version>5.2.2.RELEASE</version>
</dependency>
<dependency>
<groupId>com.google.maps</groupId>
<artifactId>google-maps-services</artifactId>
<version>0.11.0</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-simple</artifactId>
<version>1.7.25</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.13</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.hibernate/hibernate-core -->
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>5.3.7.Final</version>
</dependency>
<dependency>
<groupId>org.liquibase</groupId>
<artifactId>liquibase-core</artifactId>
<version>3.4.1</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
<plugin>
<groupId>org.liquibase</groupId>
<artifactId>liquibase-maven-plugin</artifactId>
<version>3.4.1</version>
<configuration>
<propertyFile>src/main/resources/liquibase.properties</propertyFile>
</configuration>
<dependencies>
<dependency>
<groupId>org.liquibase.ext</groupId>
<artifactId>liquibase-hibernate4</artifactId>
<version>3.5</version>
</dependency>
<dependency>
<groupId>org.springframework.data</groupId>
<artifactId>spring-data-jpa</artifactId>
<version>1.7.3.RELEASE</version>
</dependency>
</dependencies>
</plugin>
</plugins>
</build>
</project>
I am using the following entity:
package com.w2e.model;
import javax.persistence.*;
@Entity
@Table(name = "session")
public class Session{
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id")
private Long id;
@Column(name = "completions")
private int completions;
public Session(int completions){
this.completions=completions;
}
//For Hybernate
public Session(){}
public int getCompletions() {
return completions;
}
public void setCompletions(int completions) {
this.completions = completions;
}
public Long getId() {
return id;
}
}
Here is my service:
package com.w2e.services;
import com.w2e.model.Session;
import com.w2e.repository.SessionRepository;
import org.springframework.stereotype.Service;
import java.util.List;
import java.util.stream.Collectors;
import static java.util.Objects.requireNonNull;
@Service
public class SessionService {
private final SessionRepository sessionRepository;
public SessionService(SessionRepository sessionRepository) {
this.sessionRepository = requireNonNull(sessionRepository);
}
public List<Long> get(){
return sessionRepository.get().stream().map(Session::getId).collect(Collectors.toList());
}
}
the repository:
package com.w2e.repository;
import com.w2e.model.Session;
import org.hibernate.HibernateException;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.springframework.stereotype.Repository;
import java.util.ArrayList;
import java.util.List;
@Repository
public class SessionRepository{
private final SessionFactory factory;
public SessionRepository(SessionFactory factory) {
this.factory=factory;
}
public List<Session> get() {
org.hibernate.Session session = factory.openSession();
Transaction tx = null;
List<Session> e = new ArrayList<>();
try {
tx = session.beginTransaction();
String query = "FROM Session";
e.addAll(session.createQuery(query, Session.class).getResultList());
} catch (HibernateException exp) {
if (tx!=null) tx.rollback();
exp.printStackTrace();
} finally {
session.close();
}
return e;
}
}
The rest controller:
package com.w2e.controllers;
import com.w2e.services.SessionService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.CrossOrigin;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;
import java.util.List;
@CrossOrigin(origins = { "http://localhost:3000", "http://localhost:4200", "http://localhost:8081" })
@RestController
public class CourseResource {
@Autowired
private SessionService sessionService;
@GetMapping("/session")
public List<Long> getSession(@PathVariable long id) {
return sessionService.get();
}
}
I initialize hibernate and spring using:
@SpringBootApplication
public class SpringBootFullstackCrudFullStackWithMavenApplication {
public static SessionFactory factory;
public static void main(String[] args) {
try {
Configuration config = new Configuration()
.addAnnotatedClass(Session.class)
.configure("hibernate.cfg.xml");
factory = config.buildSessionFactory();
} catch (Throwable ex) {
System.err.println("Failed to create sessionFactory object." + ex);
throw new ExceptionInInitializerError(ex);
}
SpringApplication.run(SpringBootFullstackCrudFullStackWithMavenApplication.class, args);
}
}
