Spring Boot - DataSource运行时错误

Question

I've been stuck on implementing MySQL using Maven and SpringBoot in Eclipse. I am trying to just run the application but it keeps showing me errors.

 2017-07-28 11:49:06.767  INFO 5296 --- [           main] io.msela.EmployeeApiDataApplication      : Starting EmployeeApiDataApplication on CTSE-MSELA with PID 5296 (C:\Users\msela\Documents\workspace-sts-3.9.0.RELEASE\mySpringDataEmployeeProject\target\classes started by msela in C:\Users\msela\Documents\workspace-sts-3.9.0.RELEASE\mySpringDataEmployeeProject)
2017-07-28 11:49:06.767  INFO 5296 --- [           main] io.msela.EmployeeApiDataApplication      : No active profile set, falling back to default profiles: default
2017-07-28 11:49:06.830  INFO 5296 --- [           main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@4718df: startup date [Fri Jul 28 11:49:06 CEST 2017]; root of context hierarchy
2017-07-28 11:49:07.970  INFO 5296 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat initialized with port(s): 8080 (http)
2017-07-28 11:49:07.983  INFO 5296 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2017-07-28 11:49:07.983  INFO 5296 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet Engine: Apache Tomcat/8.5.15
2017-07-28 11:49:08.077  INFO 5296 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2017-07-28 11:49:08.077  INFO 5296 --- [ost-startStop-1] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 1247 ms
2017-07-28 11:49:08.202  INFO 5296 --- [ost-startStop-1] o.s.b.w.servlet.ServletRegistrationBean  : Mapping servlet: 'dispatcherServlet' to [/]
2017-07-28 11:49:08.202  INFO 5296 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'characterEncodingFilter' to: [/*]
2017-07-28 11:49:08.202  INFO 5296 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
2017-07-28 11:49:08.202  INFO 5296 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'httpPutFormContentFilter' to: [/*]
2017-07-28 11:49:08.202  INFO 5296 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'requestContextFilter' to: [/*]
2017-07-28 11:49:08.233  WARN 5296 --- [           main] ationConfigEmbeddedWebApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration': Unsatisfied dependency expressed through constructor parameter 0; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSource' defined in class path resource [org/springframework/boot/autoconfigure/jdbc/DataSourceConfiguration$Tomcat.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.apache.tomcat.jdbc.pool.DataSource]: Factory method 'dataSource' threw exception; nested exception is java.lang.IllegalStateException: Cannot load driver class: com.mysql.jdbc.Driver
2017-07-28 11:49:08.233  INFO 5296 --- [           main] o.apache.catalina.core.StandardService   : Stopping service [Tomcat]
2017-07-28 11:49:08.249  INFO 5296 --- [           main] utoConfigurationReportLoggingInitializer : 

Error starting ApplicationContext. To display the auto-configuration report re-run your application with 'debug' enabled.
2017-07-28 11:49:08.265 ERROR 5296 --- [           main] o.s.boot.SpringApplication               : Application startup failed

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration': Unsatisfied dependency expressed through constructor parameter 0; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSource' defined in class path resource [org/springframework/boot/autoconfigure/jdbc/DataSourceConfiguration$Tomcat.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.apache.tomcat.jdbc.pool.DataSource]: Factory method 'dataSource' threw exception; nested exception is java.lang.IllegalStateException: Cannot load driver class: com.mysql.jdbc.Driver
    at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:749) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:189) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1193) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1095) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:513) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:372) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1173) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1067) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:513) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1078) ~[spring-context-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:857) ~[spring-context-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:543) ~[spring-context-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122) ~[spring-boot-1.5.4.RELEASE.jar:1.5.4.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:693) [spring-boot-1.5.4.RELEASE.jar:1.5.4.RELEASE]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:360) [spring-boot-1.5.4.RELEASE.jar:1.5.4.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:303) [spring-boot-1.5.4.RELEASE.jar:1.5.4.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1118) [spring-boot-1.5.4.RELEASE.jar:1.5.4.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1107) [spring-boot-1.5.4.RELEASE.jar:1.5.4.RELEASE]
    at io.msela.EmployeeApiDataApplication.main(EmployeeApiDataApplication.java:16) [classes/:na]
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSource' defined in class path resource [org/springframework/boot/autoconfigure/jdbc/DataSourceConfiguration$Tomcat.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.apache.tomcat.jdbc.pool.DataSource]: Factory method 'dataSource' threw exception; nested exception is java.lang.IllegalStateException: Cannot load driver class: com.mysql.jdbc.Driver
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:599) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1173) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1067) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:513) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:208) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1138) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1066) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:835) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:741) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    ... 28 common frames omitted
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.apache.tomcat.jdbc.pool.DataSource]: Factory method 'dataSource' threw exception; nested exception is java.lang.IllegalStateException: Cannot load driver class: com.mysql.jdbc.Driver
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:189) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:588) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    ... 41 common frames omitted
Caused by: java.lang.IllegalStateException: Cannot load driver class: com.mysql.jdbc.Driver
    at org.springframework.util.Assert.state(Assert.java:70) ~[spring-core-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.boot.autoconfigure.jdbc.DataSourceProperties.determineDriverClassName(DataSourceProperties.java:231) ~[spring-boot-autoconfigure-1.5.4.RELEASE.jar:1.5.4.RELEASE]
    at org.springframework.boot.autoconfigure.jdbc.DataSourceProperties.initializeDataSourceBuilder(DataSourceProperties.java:183) ~[spring-boot-autoconfigure-1.5.4.RELEASE.jar:1.5.4.RELEASE]
    at org.springframework.boot.autoconfigure.jdbc.DataSourceConfiguration.createDataSource(DataSourceConfiguration.java:42) ~[spring-boot-autoconfigure-1.5.4.RELEASE.jar:1.5.4.RELEASE]
    at org.springframework.boot.autoconfigure.jdbc.DataSourceConfiguration$Tomcat.dataSource(DataSourceConfiguration.java:56) ~[spring-boot-autoconfigure-1.5.4.RELEASE.jar:1.5.4.RELEASE]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_131]
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_131]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_131]
    at java.lang.reflect.Method.invoke(Unknown Source) ~[na:1.8.0_131]
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:162) ~[spring-beans-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    ... 42 common frames omitted

Here's my 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>io.msela</groupId>
    <artifactId>course-api-data</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>course-api-data</name>
    <description>Course API with Spring Data</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.4.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>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        </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-web</artifactId>
        </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>

And here is my app:

package io.msela;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.domain.EntityScan;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;

import io.msela.springbootstarter.employee.EmployeeRepository;
@SpringBootApplication
@ComponentScan({"io.msela"})
@EntityScan("io.msela.springbootstarter")
@EnableJpaRepositories(basePackageClasses = EmployeeRepository.class)
public class EmployeeApiDataApplication {
    public static void main(String[] args) {
        SpringApplication.run(EmployeeApiDataApplication.class, args);
    }
}

And my properties file:

spring.jpa.hibernate.ddl-auto=create-drop
spring.jpa.database-platform = org.hibernate.dialect.MySQLDialect
spring.datasource.url=jdbc:mysql://localhost:3306/db_example
spring.datasource.username=springuser
spring.datasource.password=ThePassword
spring.datasource.driver-class-name=com.mysql.jdbc.Driver

It seems like the poor thing can't initialize the DataSource. I made the project work using an internal database, but MySQL seems to be a completely different beast.

Answer 1

You don't need to specify :

spring.datasource.driver-class-name=com.mysql.jdbc.Driver

Declaring this :

spring.datasource.url=jdbc:mysql://localhost:3306/db_example

will allow Spring Boot to discover the correct driver class and to load it.

The Spring Boot documentation states :

You often won't need to specify the driver-class-name since Spring boot can deduce it for most databases from the url.

Besides, it also says :

Ie if you set spring.datasource.driver-class-name=com.mysql.jdbc.Driver then that class has to be loadable.

But the thrown exception shows that the class is not loadable :

Caused by: java.lang.IllegalStateException: Cannot load driver class: com.mysql.jdbc.Driver

So, I suppose that you have a classloading issue.

---

Here is the way which Spring Boot works to assert that the driver class is loadable :

public class DataSourceProperties {
   ...

   public String determineDriverClassName() {

     if (StringUtils.hasText(this.driverClassName)) {
        Assert.state(driverClassIsLoadable(),
                "Cannot load driver class: " + this.driverClassName);
        return this.driverClassName;
     }
   ... 

that invokes :

    ...
    private boolean driverClassIsLoadable() {
        try {
            ClassUtils.forName(this.driverClassName, null);
            return true;
        }
        catch (UnsupportedClassVersionError ex) {
            // Driver library has been compiled with a later JDK, propagate error
            throw ex;
        }
        catch (Throwable ex) {
            return false;
        }
    }
    ...
}

In your case, you enter in this catch statement :

catch (Throwable ex) {
        return false;
}

So ClassUtils.forName(this.driverClassName, null); doesn't manage to load the class and throws an exception.
The problem is that the root exception caught in the catch is shocked by Spring Boot.
So the error message is general.

If you are interested in understanding the root cause or you are using a rare DBMS that is not automatically mapped by Spring Boot to a driver class , you could run in debug mode and set a breakpoint at this statement :

ClassUtils.forName(this.driverClassName, null);

Answer 2

you must include mysql jar in your classpath before executing the application as it is throwing
"Cannot load driver class: com.mysql.jdbc.Driver" error. you can check here JDBC Driver class not found: com.mysql.jdbc.Driver