为什么我得到一个无资格bean错误？

Question

在SpringSource论坛上尝试并等待答案的几天后，我会在这里尝试一下。 运行我的应用程序会导致此异常：

org.springframework.beans.factory.UnsatisfiedDependencyException: 
    Error creating bean with name 'loginDAOImpl': 
    Unsatisfied dependency expressed through method 'setDataSource' parameter 0: 
    No qualifying bean of type [org.apache.tomcat.dbcp.dbcp.BasicDataSource] 
    found for dependency [org.apache.tomcat.dbcp.dbcp.BasicDataSource]: 
    expected at least 1 bean which qualifies as autowire candidate for this dependency. 
Dependency annotations: {}; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.apache.tomcat.dbcp.dbcp.BasicDataSource] found for dependency [org.apache.tomcat.dbcp.dbcp.BasicDataSource]: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {} 
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredMethodElement.inject(AutowiredAnnotationBeanPostProcessor.java:648) ~[spring-beans-4.3.2.RELEASE.jar:4.3.2.RELEASE] 
at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88) ~[spring-beans-4.3.2.RELEASE.jar:4.3.2.RELEASE] 
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:349) ~[spring-beans-4.3.2.RELEASE.jar:4.3.2.RELEASE] 
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1214) ~[spring-beans-4.3.2.RELEASE.jar:4.3.2.RELEASE] 
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:543) ~[spring-beans-4.3.2.RELEASE.jar:4.3.2.RELEASE] 
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482) ~[spring-beans-4.3.2.RELEASE.jar:4.3.2.RELEASE] 
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.3.2.RELEASE.jar:4.3.2.RELEASE] 
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.3.2.RELEASE.jar:4.3.2.RELEASE] 
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.3.2.RELEASE.jar:4.3.2.RELEASE] 
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) ~[spring-beans-4.3.2.RELEASE.jar:4.3.2.RELEASE] 
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:776) ~[spring-beans-4.3.2.RELEASE.jar:4.3.2.RELEASE] 
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:866) ~[spring-context-4.3.8.RELEASE.jar:4.3.8.RELEASE] 
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:542) ~[spring-context-4.3.8.RELEASE.jar:4.3.8.RELEASE] 
at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122) ~[spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE] 
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:737) [spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE] 
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:370) [spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE] 
at org.springframework.boot.SpringApplication.run(SpringApplication.java:314) [spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE] 
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1162) [spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE] 
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1151) [spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE] 
at com.example.demo.DemoApplication.main(DemoApplication.java:10) 

下面是相关的代码

应用程序上下文：

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


<context:annotation-config/> 

<!-- Scans within the base package of the application for @Component classes to configure as beans --> 
<context:component-scan base-package="com.example.demo" /> 

<bean id="dataSource" class="org.apache.tomcat.dbcp.dbcp.BasicDataSource" 
     destroy-method="close"> 
    <property name="driverClassName" value="com.mysql.jdbc.Driver"/> 
    <property name="url" value="jdbc:mysql://localhost/atata"/> 
    <property name="username" value="user"/> 
    <property name="password" value="pass"/> 
</bean> 

<context:property-placeholder location="jdbc.properties"/> 

类LoginDAOImpl：

@Repository 
public class LoginDAOImpl implements LoginDAO { 

private JdbcTemplate jdbcTemplateObject; 

@Autowired 
public void setDataSource(BasicDataSource dataSource) { 

    this.jdbcTemplateObject = new JdbcTemplate(dataSource); 
} 
... 
} 

主：

@SpringBootApplication 
public class DemoApplication { 

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

Answer 1

一般来说， 包括与这样的问题的更多细节。 具体来说， 什么是LoginDAOImpl类包？ 什么是LoginDAOImpl类中的BasicDataSource类的导入？

起初猜测，我怀疑的BasicDataSource进口将org.apache.commons.dbcp.BasicDataSource或org.apache.tomcat.dbcp.dbcp2.BasicDataSource

这是您的数据源bean定义使用类不同。

<bean id="dataSource" class="org.apache.tomcat.dbcp.dbcp.BasicDataSource" 
    destroy-method="close"> 

可能性二：

您正在使用的数据源bean配置的用户名和密码值的格式不正确。如果用户和密码是属性值，则应使用${user}和${pass}。像这样：

<bean id="dataSource" class="org.apache.tomcat.dbcp.dbcp.BasicDataSource" 
    destroy-method="close"> 
    <property name="driverClassName" value="com.mysql.jdbc.Driver"/> 
    <property name="url" value="jdbc:mysql://localhost/atata"/> 
    <property name="username" value="${user}"/> 
    <property name="password" value="${pass}"/> 
</bean>