java - 无法加载 JDBC 驱动程序类

Question

我正在尝试运行 tutorial 中的示例

我下载了提供的 .zip 文件并对其进行了修改(我需要连接到 PostgreSQL 而不是 mySQL)。不幸的是，我不断收到有关无法加载 JDBC 驱动程序类的错误。我查看了 Stack Overflow 上的其他主题，但提出的解决方案都不适合我。下面我列出了我尝试过的解决方案以及配置

• 我正在使用 Eclipse、Tomcat v8.0、Maven 和 Spring。 PostgreSQL 版本是 9.5.4。所以根据网页我已经下载了postgresql-9.4.1212.jar，因为我使用的是Java 1.8，Windows。
• Postgres 已添加到我的 pom.xml 文件
• 通过项目->属性->构建路径...添加到项目的PATH中
• 我无法将其添加到 WEB-INF/lib，因为我没有这样的文件夹。我是 Spring 新手，因此本教程。如果您认为这可能是解决方案，请告诉我如何将此类文件夹添加到项目中，而无需从头开始。
• 我将 .jar 文件直接添加到 tomcat/lib 和 application/lib 以及 java/jre1.8.0_77/lib/ext
• 我可以在 Eclipse 中的 JRE 系统库、Maven 依赖项和引用库中看到正确的驱动程序

我不知道该怎么办了。请帮我。

错误信息

sty 03, 2017 8:56:07 AM org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@49c2faae: startup date [Tue Jan 03 08:56:07 CET 2017]; root of context hierarchy
sty 03, 2017 8:56:07 AM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [applicationContext.xml]
sty 03, 2017 8:56:07 AM org.springframework.context.support.ClassPathXmlApplicationContext refresh
WARNING: Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'employeeDAO' defined in class path resource [applicationContext.xml]: Cannot resolve reference to bean 'dataSource' while setting bean property 'dataSource'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSource' defined in class path resource [applicationContext.xml]: Error setting property values; nested exception is org.springframework.beans.PropertyBatchUpdateException; nested PropertyAccessExceptions (1) are:
PropertyAccessException 1: org.springframework.beans.MethodInvocationException: Property 'driverClassName' threw exception; nested exception is java.lang.IllegalStateException: Could not load JDBC driver class [com.postgresql.driver]
Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'employeeDAO' defined in class path resource [applicationContext.xml]: Cannot resolve reference to bean 'dataSource' while setting bean property 'dataSource'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSource' defined in class path resource [applicationContext.xml]: Error setting property values; nested exception is org.springframework.beans.PropertyBatchUpdateException; nested PropertyAccessExceptions (1) are:
PropertyAccessException 1: org.springframework.beans.MethodInvocationException: Property 'driverClassName' threw exception; nested exception is java.lang.IllegalStateException: Could not load JDBC driver class [com.postgresql.driver]
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:359)
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:108)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1486)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1231)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:551)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:754)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:866)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:542)
    at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
    at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)
    at com.javacodegeeks.snippets.enterprise.App.main(App.java:16)
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSource' defined in class path resource [applicationContext.xml]: Error setting property values; nested exception is org.springframework.beans.PropertyBatchUpdateException; nested PropertyAccessExceptions (1) are:
PropertyAccessException 1: org.springframework.beans.MethodInvocationException: Property 'driverClassName' threw exception; nested exception is java.lang.IllegalStateException: Could not load JDBC driver class [com.postgresql.driver]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1523)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1231)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:551)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:351)
    ... 15 more
Caused by: org.springframework.beans.PropertyBatchUpdateException; nested PropertyAccessExceptions (1) are:
PropertyAccessException 1: org.springframework.beans.MethodInvocationException: Property 'driverClassName' threw exception; nested exception is java.lang.IllegalStateException: Could not load JDBC driver class [com.postgresql.driver]
    at org.springframework.beans.AbstractPropertyAccessor.setPropertyValues(AbstractPropertyAccessor.java:121)
    at org.springframework.beans.AbstractPropertyAccessor.setPropertyValues(AbstractPropertyAccessor.java:75)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1519)
    ... 23 more

pom.xml

<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.javacodegeeks.snippets.enterprise</groupId>
  <artifactId>springexample</artifactId>
  <version>0.0.1-SNAPSHOT</version>

  <dependencies>

      <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>4.3.4.RELEASE</version>
      </dependency>
      <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>4.3.4.RELEASE</version>
      </dependency>
      <dependency> 
        <groupId>org.postgresql</groupId>
        <artifactId>postgresql</artifactId>
        <version>9.4.1212</version>
      </dependency>
      <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-jdbc</artifactId>
        <version>4.3.4.RELEASE</version>
      </dependency>
  </dependencies>

  <properties>
    <org.springframework.version>3.8.3.RELEASE</org.springframework.version>
  </properties>
</project>

applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

<!--  <beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p"
    xmlns:aop="http://www.springframework.org/schema/aop" xmlns:context="http://www.springframework.org/schema/context"
    xmlns:jee="http://www.springframework.org/schema/jee" xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:task="http://www.springframework.org/schema/task"
    xsi:schemaLocation="http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.2.xsd http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.2.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd http://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task-3.2.xsd">
-->
    <bean id="employeeDAO" class="com.javacodegeeks.snippets.enterprise.dao.impl.EmployeeDAOImpl">
        <property name="dataSource" ref="dataSource" />
    </bean>

    <bean id="jdbcEmployeeDAO" class="com.javacodegeeks.snippets.enterprise.dao.impl.JDBCEmployeeDAOImpl">
        <property name="dataSource" ref="dataSource" />
    </bean>

    <bean id="dataSource"
        class="org.springframework.jdbc.datasource.DriverManagerDataSource">

        <property name="driverClassName" value="com.postgresql.driver" />
        <property name="url" value="jdbc:postgresql://localhost:5432/test" />
        <property name="username" value="postgres" />
        <property name="password" value="pass" />
    </bean>
</beans>

Answer 1

在属性定义中 = 请写入:org.postgresql.Driver 而不是 com.postgresql.driver。

在maven依赖中，可以看到“Driver”类位于org.postgresql包中。