正在学习 IoC
使用的 jdk 版本为 jdk 17
依赖为：
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>6.0.6</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>6.0.9</version>
</dependency>
<dependency>
<groupId>org.junit.jupiter</groupId>
<artifactId>junit-jupiter-api</artifactId>
<version>5.9.2</version>
</dependency>
</dependencies>
报错内容如下：
7月 14, 2023 9:04:39 下午 org.springframework.context.support.AbstractApplicationContext refresh
警告: Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'user' defined in class path resource [bean.xml]: No bean class specified on bean definition
Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'user' defined in class path resource [bean.xml]: No bean class specified on bean definition
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1314)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1199)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:560)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:520)
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:326)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:324)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:200)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:973)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:941)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:608)
at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:144)
at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:85)
at com.study.spring6.iocxml.UserTest.main(UserTest.java:8)
Caused by: java.lang.IllegalStateException: No bean class specified on bean definition
at org.springframework.beans.factory.support.AbstractBeanDefinition.getBeanClass(AbstractBeanDefinition.java:428)
at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:74)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1308)
... 13 more
报错文件配置：
<bean id="user" name="com.study.spring6.iocxml.User"/>
搜了一下出现 bug 的原因：https://stackoverflow.com/questions/20544963/java-lang-illegalstateexception-no-bean-class-specified-on-bean-definition
A bean definition essentially is a recipe for creating one or more objects. The container looks at the recipe for a named bean when asked, and uses the configuration metadata encapsulated by that bean definition to create (or acquire) an actual object.
If you use XML-based configuration metadata, you specify the type (or class) of object that is to be instantiated in the class attribute of the element. This class attribute, which internally is a Class property on a BeanDefinition instance, is usually mandatory.
机翻一下：
bean 定义本质上是创建一个或多个对象的配方。当被请求时，容器会查看命名 bean 的配方，并使用该 bean 定义封装的配置元数据来创建（或获取）实际对象。
如果您使用基于 XML 的配置元数据，您可以在元素的 class 属性中指定要实例化的对象类型（或类）。该 class 属性在内部是 BeanDefinition 实例的 Class 属性，通常是强制性的。
分析原因：
没有配置 class
解决：
添加上 class 属性
<bean id="user" class="com.study.spring6.iocxml.User"/>