会报出如下错误

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.mybatis.spring.mapper.MapperScannerConfigurer#0' defined in class path resource [spring/applicationContext.xml]: Initialization of bean failed; nested exception is org.springframework.beans.ConversionNotSupportedException: Failed to convert property value of type 'org.apache.ibatis.session.defaults.DefaultSqlSessionFactory' to required type 'java.lang.String' for property 'sqlSessionFactoryBeanName'; nested exception is java.lang.IllegalStateException: Cannot convert value of type [org.apache.ibatis.session.defaults.DefaultSqlSessionFactory] to required type [java.lang.String] for property 'sqlSessionFactoryBeanName': no matching editors or conversion strategy found

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:547)

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:475)

at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:304)

at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:228)

at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:300)

at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:200)

at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:116)

at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:609)

at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:464)

at org.springframework.context.support.ClassPathXmlApplicationContext.(ClassPathXmlApplicationContext.java:139)

at org.springframework.context.support.ClassPathXmlApplicationContext.(ClassPathXmlApplicationContext.java:83)

at com.atguigu.junit.test.UserMapperTest.setUp(UserMapperTest.java:31)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

at java.lang.reflect.Method.invoke(Method.java:601)

at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)

at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)

at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)

at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:24)

at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)

at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)

at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)

at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)

at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)

at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)

at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)

at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)

at org.junit.runners.ParentRunner.run(ParentRunner.java:363)

at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)

at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)

at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)

at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)

at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)

at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)

Caused by: org.springframework.beans.ConversionNotSupportedException: Failed to convert property value of type 'org.apache.ibatis.session.defaults.DefaultSqlSessionFactory' to required type 'java.lang.String' for property 'sqlSessionFactoryBeanName'; nested exception is java.lang.IllegalStateException: Cannot convert value of type [org.apache.ibatis.session.defaults.DefaultSqlSessionFactory] to required type [java.lang.String] for property 'sqlSessionFactoryBeanName': no matching editors or conversion strategy found

at org.springframework.beans.BeanWrapperImpl.convertIfNecessary(BeanWrapperImpl.java:474)

at org.springframework.beans.BeanWrapperImpl.convertForProperty(BeanWrapperImpl.java:511)

at org.springframework.beans.BeanWrapperImpl.convertForProperty(BeanWrapperImpl.java:505)

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.convertForProperty(AbstractAutowireCapableBeanFactory.java:1502)

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1461)

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1197)

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:537)

... 34 more

Caused by: java.lang.IllegalStateException: Cannot convert value of type [org.apache.ibatis.session.defaults.DefaultSqlSessionFactory] to required type [java.lang.String] for property 'sqlSessionFactoryBeanName': no matching editors or conversion strategy found

at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:267)

at org.springframework.beans.BeanWrapperImpl.convertIfNecessary(BeanWrapperImpl.java:459)

... 40 more

原因：因为MapperScannerConigurer实际是在解析加载bean定义阶段的，这个时候要是设置sqlSessionFactory的话，会导致提前初始化一些类，这个时候，PropertyPlaceholderConfigurer还没来得及替换定义中的变量，导致把表达式当作字符串复制了。

解决办法：

第一种方式：

修改

property name="sqlSessionFactory" ref="sqlSessionFactory"

为

property name="sqlSessionFactoryBeanName" value="sqlSessionFactory"

原理：使用sqlSessionFactoryBeanName注入，不会立即初始化sqlSessionFactory, 所以不会引发提前初始化问题。

第二种：直接删掉

注意：在没有配置这一行时，必须配置一个以sqlSessionFactory命名的org.mybatis.spring.SqlSessionFactoryBean。