Error in starting application created in spring boot with JPA and mysql

Question

I was developing a simple spring boot application that fetches and inserts data to a database i created using MySql workbench. I keep getting the error below.

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2018-09-14 11:35:14.282 ERROR 11268 --- [           main] o.s.boot.SpringApplication               : Application run failed

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]: Invocation of init method failed; nested exception is org.hibernate.MappingException: class demo.fabric.Employee not found while looking for property: id
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1699) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:573) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:495) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:317) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:315) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1089) ~[spring-context-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:859) ~[spring-context-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550) ~[spring-context-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:140) ~[spring-boot-2.0.5.RELEASE.jar:2.0.5.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:780) [spring-boot-2.0.5.RELEASE.jar:2.0.5.RELEASE]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:412) [spring-boot-2.0.5.RELEASE.jar:2.0.5.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:333) [spring-boot-2.0.5.RELEASE.jar:2.0.5.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1277) [spring-boot-2.0.5.RELEASE.jar:2.0.5.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1265) [spring-boot-2.0.5.RELEASE.jar:2.0.5.RELEASE]
    at com.example.studentInfo.StudentOnlineInfoApplication.main(StudentOnlineInfoApplication.java:10) [classes/:na]
Caused by: org.hibernate.MappingException: class demo.fabric.Employee not found while looking for property: id
    at org.hibernate.internal.util.ReflectHelper.reflectedPropertyClass(ReflectHelper.java:220) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
    at org.hibernate.mapping.SimpleValue.setTypeUsingReflection(SimpleValue.java:482) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
    at org.hibernate.boot.model.source.internal.hbm.ModelBinder.bindSimpleEntityIdentifier(ModelBinder.java:726) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
    at org.hibernate.boot.model.source.internal.hbm.ModelBinder.bindEntityIdentifier(ModelBinder.java:350) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
    at org.hibernate.boot.model.source.internal.hbm.ModelBinder.bindRootEntity(ModelBinder.java:245) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
    at org.hibernate.boot.model.source.internal.hbm.ModelBinder.bindEntityHierarchy(ModelBinder.java:192) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
    at org.hibernate.boot.model.source.internal.hbm.HbmMetadataSourceProcessorImpl.processEntityHierarchies(HbmMetadataSourceProcessorImpl.java:144) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
    at org.hibernate.boot.model.process.spi.MetadataBuildingProcess$1.processEntityHierarchies(MetadataBuildingProcess.java:218) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
    at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.complete(MetadataBuildingProcess.java:265) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.metadata(EntityManagerFactoryBuilderImpl.java:861) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:888) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
    at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:57) ~[spring-orm-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:365) ~[spring-orm-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:390) ~[spring-orm-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:377) ~[spring-orm-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.afterPropertiesSet(LocalContainerEntityManagerFactoryBean.java:341) ~[spring-orm-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1758) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1695) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    ... 16 common frames omitted
Caused by: org.hibernate.boot.registry.classloading.spi.ClassLoadingException: Unable to load class [demo.fabric.Employee]
    at org.hibernate.boot.registry.classloading.internal.ClassLoaderServiceImpl.classForName(ClassLoaderServiceImpl.java:348) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
    at org.hibernate.internal.util.ReflectHelper.reflectedPropertyClass(ReflectHelper.java:216) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
    ... 33 common frames omitted
Caused by: java.lang.ClassNotFoundException: Could not load requested class : demo.fabric.Employee
    at org.hibernate.boot.registry.classloading.internal.ClassLoaderServiceImpl$AggregatedClassLoader.findClass(ClassLoaderServiceImpl.java:336) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
    at java.lang.ClassLoader.loadClass(Unknown Source) ~[na:1.8.0_161]
    at java.lang.ClassLoader.loadClass(Unknown Source) ~[na:1.8.0_161]
    at java.lang.Class.forName0(Native Method) ~[na:1.8.0_161]
    at java.lang.Class.forName(Unknown Source) ~[na:1.8.0_161]
    at org.hibernate.boot.registry.classloading.internal.ClassLoaderServiceImpl.classForName(ClassLoaderServiceImpl.java:345) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
    ... 34 common frames omitted

Below 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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.example.studentInfo</groupId>
<artifactId>studentOnlineInfo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>studentOnlineInfo</name>
<description>A web project which implements simple write and read to the database</description>
<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.0.5.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
</parent>
<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    <java.version>1.8</java.version>
</properties>
<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <scope>runtime</scope>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
</dependencies>
<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>
</project>

Here is my application.properties file

spring.datasource.url=jdbc:mysql://localhost:3306/studentInfo
spring.datasource.username=root
spring.datasource.password=Christensen001
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.jpa.show-sql=true
spring.mvc.view.prefix=/WEB-INF/jsps/
spring.mvc.view.suffix=.jsp

This is my Entity class

package com.example.studentInfo.entities;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
@Entity
@Table(name="studenData")
public class StudentInformation {
@Id
private long id;
@Column(name="sreg_num")
private String reg_num;
@Column(name="semail")
private String email;
@Column(name="sname")
private String name;
@Column(name="sage")
private int age;
@Column(name="sstate")
private String state;
@Column(name="scity")
private String city;
public long getId() {
    return id;
}
public void setId(long id) {
    this.id = id;
}
public String getReg_num() {
    return reg_num;
}
public void setReg_num(String reg_num) {
    this.reg_num = reg_num;
}
public String getEmail() {
    return email;
}
public void setEmail(String email) {
    this.email = email;
}
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}
public int getAge() {
    return age;
}
public void setAge(int age) {
    this.age = age;
}
public String getState() {
    return state;
}
public void setState(String state) {
    this.state = state;
}
public String getCity() {
    return city;
}
public void setCity(String city) {
    this.city = city;
}
public StudentInformation(long id, String reg_num, String email, String name, int age, String state, String city) {
    super();
    this.id = id;
    this.reg_num = reg_num;
    this.email = email;
    this.name = name;
    this.age = age;
    this.state = state;
    this.city = city;
}
@Override
public String toString() {
    return "StudentInformation [id=" + id + ", reg_num=" + reg_num + ", email=" + email + ", name=" + name
            + ", age=" + age + ", state=" + state + ", city=" + city + "]";
}
} </pre>

studentInfoApplication.java

package com.example.studentInfo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class StudentOnlineInfoApplication {

public static void main(String[] args) {
    SpringApplication.run(StudentOnlineInfoApplication.class, args);
}
}

How do i resolve this?

Answer 1

Update

Step 1: Likely a corrupt download. Try removing ~/.m2/respository and run mvn clean install

2. If it does not work then will recommend to create new project from SPRING INITIALIZR with all required dependencies.

3. If this not even works then will recommend to reinstall your IDE as there might be some issues in installing/caching it.

Your Entity seems fine loading as I tried with same Spring Boot configuration. so seems issue is mapping between your mysql table and entity so check you have id as primary key defined in table.

or better to use below property in application.properties to auto create your tables first time.later you can update this property to none

spring.jpa.hibernate.ddl-auto=create
spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQL57Dialect

Just a suggestion to manage id configuration like this for primary key.

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id")
private Long id;

Update

1. Remove @Autowired from StudentsController.java

2. Remove tomcat-embed-core dependencies as spring boot annotation has already embedded it.

    <dependency> <groupId>org.apache.tomcat.embed</groupId> <artifactId>tomcat-embed-core</artifactId> <scope>provided</scope> </dependency> 

3. run your code base now.