Spring Boot - DataSource運行時錯誤

Question

我一直堅持在Eclipse中使用Maven和SpringBoot實現MySQL。我試圖運行該應用程序，但它不斷顯示我的錯誤。

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 

這裏是我的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> 

這裏是我的應用程序：

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); 
    } 
} 

我的屬性文件：

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 

這似乎是可憐的東西能不初始化數據源。我使用內部數據庫使項目工作，但MySQL似乎是一個完全不同的野獸。

Answer 1

你並不需要指定：

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

此聲明：

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

將使春季啓動發現正確的驅動程序類，並加載它。

The Spring Boot documentation狀態：

你往往不需要指定驅動程序類名，因爲春季 啓動可以推斷出它從URL大多數數據庫。

此外，它也說：

即如果你設置了 spring.datasource.driver-class-name = com.mysql.jdbc.Driver，那麼 類必須是可加載的。

但拋出的異常顯示出類不加載：

致：java.lang.IllegalStateException：無法加載驅動程序類： com.mysql.jdbc.Driver

所以，我想你有一個類加載問題。

---

這裏是一個春天引導工作斷言，驅動程序類是可加載的方式：

public class DataSourceProperties { 
    ... 

    public String determineDriverClassName() { 

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

調用：

... 
    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; 
     } 
    } 
    ... 
} 

在你的情況，你在這個catch進入聲明：

catch (Throwable ex) { 
     return false; 
} 

因此ClassUtils.forName(this.driverClassName, null);無法加載類並引發異常。
問題是Spring Boot引起了catch中捕獲的根異常。
所以錯誤信息是一般的。

如果您有興趣瞭解的根本原因或您使用的是沒有自動春天引導映射到一個驅動程序類難得的DBMS，你可以在調試模式下運行，並在這個語句上設置斷點：

ClassUtils.forName(this.driverClassName, null); 

Answer 2

必須包括在類路徑中的MySQL罐子執行應用程序之前，因爲它拋出
「無法加載驅動程序類：com.mysql.jdbc.Driver」的錯誤。你可以在這裏查看JDBC Driver class not found: com.mysql.jdbc.Driver