Unable to start embedded Tomcat when building Spring application

Question

I'm trying to start a Spring application using Intellij and I get the error below. I tried with putting the Tomcat dependency in pom.xml but this didn't work (I also later found out that this was not needed).

org.springframework.context.ApplicationContextException: Unable to start web server; nested exception is org.springframework.boot.web.server.WebServerException: Unable to start embedded Tomcat
Caused by: org.springframework.boot.web.server.WebServerException: Unable to start embedded Tomcat
Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'securityConfig': Unsatisfied dependency expressed through field 'customUserDetailsService'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'customUserDetailsService': Unsatisfied dependency expressed through field 'userRepository'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userRepository': Cannot create inner bean '(inner bean)#65d6ef78' of type [org.springframework.orm.jpa.SharedEntityManagerCreator] while setting bean property 'entityManager'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name '(inner bean)#65d6ef78': Cannot resolve reference to bean 'entityManagerFactory' while setting constructor argument; nested exception is 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 javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory
Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'customUserDetailsService': Unsatisfied dependency expressed through field 'userRepository'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userRepository': Cannot create inner bean '(inner bean)#65d6ef78' of type [org.springframework.orm.jpa.SharedEntityManagerCreator] while setting bean property 'entityManager'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name '(inner bean)#65d6ef78': Cannot resolve reference to bean 'entityManagerFactory' while setting constructor argument; nested exception is 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 javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory

Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userRepository': Cannot create inner bean '(inner bean)#65d6ef78' of type [org.springframework.orm.jpa.SharedEntityManagerCreator] while setting bean property 'entityManager'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name '(inner bean)#65d6ef78': Cannot resolve reference to bean 'entityManagerFactory' while setting constructor argument; nested exception is 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 javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name '(inner bean)#65d6ef78': Cannot resolve reference to bean 'entityManagerFactory' while setting constructor argument; nested exception is 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 javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory
Caused by: 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 javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory
Caused by: javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory
Caused by: org.hibernate.MappingException: Could not get constructor for org.hibernate.persister.entity.SingleTableEntityPersister
Caused by: org.hibernate.HibernateException: Unable to instantiate default tuplizer
Caused by: java.lang.reflect.InvocationTargetException: null
Caused by: java.lang.NullPointerException: Cannot invoke "java.lang.reflect.AccessibleObject.setAccessible(boolean)" because "ao" is null

The application should work fine because it already works on a colleague's PC so I'm not quite sure why I'm getting this error. I've tried several fixes that I came across here on SO but none of them worked. Here's my pom.xml :

<?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</groupId>
    <artifactId>middleman</artifactId>
    <version>2.0.9</version>
    <packaging>jar</packaging>

    <name>middleman</name>
    <description>Middleman application</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.0.RELEASE</version>
        <relativePath /> 
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
        <jjwt.version>0.9.0</jjwt.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>com.github.greengerong</groupId>
            <artifactId>prerender-java</artifactId>
            <version>1.6.4</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-security</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>com.microsoft.sqlserver</groupId>
            <artifactId>sqljdbc4</artifactId>
            <version>4.0</version>
        </dependency>

        <dependency>
            <groupId>org.postgresql</groupId>
            <artifactId>postgresql</artifactId>
            <version>42.2.6</version>
        </dependency>


        <!-- For Working with Json Web Tokens (JWT) -->
        <dependency>
            <groupId>io.jsonwebtoken</groupId>
            <artifactId>jjwt</artifactId>
            <version>${jjwt.version}</version>
        </dependency>

        <!-- For Java 8 Date/Time Support -->
        <dependency>
            <groupId>com.fasterxml.jackson.datatype</groupId>
            <artifactId>jackson-datatype-jsr310</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework.security</groupId>
            <artifactId>spring-security-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger2</artifactId>
            <version>2.9.2</version>
        </dependency>
        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger-ui</artifactId>
            <version>2.9.2</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-mail</artifactId>
        </dependency>

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

Answer 1

Looking at the exception, it's more of the bean configuration issue. Please check if the bean definition is correct and all the relevant bean dependencies are created properly.

Error creating bean with name 'securityConfig' --> Unsatisfied dependency expressed through field 'customUserDetailsService'

Answer 2

Based on the logs, there is an issue with the bean creation of UserRepository. There is null pointer exception on something named ao , not sure what it is, but it is causing the issue.

Answer 3

I hit the same issue (where Tomcat worked fine on another laptop with the same code but failed locally), and was getting the same error. Finally traced the problem to the version of Java - my new laptop was running Java 15 - but the other laptop was still running Java 8. Installing openjdk8 and running Tomcat with that fixed the error.

Your pom.xml is specifying Java 8 too - and as Hibernate pokes around in a lot of the Java internals (byte assist etc), I suspect that there is a compatibility issue with the version of Hibernate and JDK.

This answer to a similar question may lead you to the right compatibility upgrades for Hibernate: https://stackoverflow.com/a/65422258