today in to write a project practice Mybatis framework, the dao layer by means annotations about the database operations of the abstract methods after implementation, remembered before and a classmate to write another practice projects bring Spring Boot the unit test method, because before you write is used based on Mybatis factory pattern of another way to create a test, so want to learn the Spring test method of the Boot. However, according to the project structure and configuration written by my former classmates, the following errors occurred after the configuration of my project was completed:
***************************
APPLICATION FAILED TO START
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Description:
Failed to configure a DataSource: 'url' attribute is not specified and no embedded datasource could be configured.
Reason: Failed to determine a suitable driver class
Action:
Consider the following:
If you want an embedded database (H2, HSQL or Derby), please put it on the classpath.
If you have database settings to be loaded from a particular profile you may need to activate it (no profiles are currently active).
2019-06-19 17:02:07.737 ERROR 15296 --- [ main] o.s.test.context.TestContextManager : Caught exception while allowing TestExecutionListener [org.springframework.test.context.web.ServletTestExecutionListener@3aefe5e5] to prepare test instance [com.testjob.testjob.TestJobApplicationTests@3cae7b8b]
java.lang.IllegalStateException: Failed to load ApplicationContext
at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:125) ~[spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.test.context.support.DefaultTestContext.getApplicationContext(DefaultTestContext.java:108) ~[spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.test.context.web.ServletTestExecutionListener.setUpRequestContextIfNecessary(ServletTestExecutionListener.java:190) ~[spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.test.context.web.ServletTestExecutionListener.prepareTestInstance(ServletTestExecutionListener.java:132) ~[spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:246) ~[spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTest(SpringJUnit4ClassRunner.java:227) [spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner$1.runReflectiveCall(SpringJUnit4ClassRunner.java:289) [spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) [junit-4.12.jar:4.12]
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.methodBlock(SpringJUnit4ClassRunner.java:291) [spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:246) [spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97) [spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290) [junit-4.12.jar:4.12]
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71) [junit-4.12.jar:4.12]
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288) [junit-4.12.jar:4.12]
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58) [junit-4.12.jar:4.12]
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268) [junit-4.12.jar:4.12]
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61) [spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70) [spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.junit.runners.ParentRunner.run(ParentRunner.java:363) [junit-4.12.jar:4.12]
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:190) [spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:89) [.cp/:na]
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:41) [.cp/:na]
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:541) [.cp/:na]
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:763) [.cp/:na]
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:463) [.cp/:na]
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:209) [.cp/:na]
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSource' defined in class path resource [org/springframework/boot/autoconfigure/jdbc/DataSourceConfiguration$Hikari.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.zaxxer.hikari.HikariDataSource]: Factory method 'dataSource' threw exception; nested exception is org.springframework.boot.autoconfigure.jdbc.DataSourceProperties$DataSourceBeanCreationException: Failed to determine a suitable driver class
at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:627) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:607) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1321) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1160) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:555) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:849) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:877) ~[spring-context-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:549) ~[spring-context-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:775) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:316) ~[spring-boot-2.1.4.RELEASE.jar:2.1.4.RELEASE]
at org.springframework.boot.test.context.SpringBootContextLoader.loadContext(SpringBootContextLoader.java:127) ~[spring-boot-test-2.1.4.RELEASE.jar:2.1.4.RELEASE]
at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContextInternal(DefaultCacheAwareContextLoaderDelegate.java:99) ~[spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:117) ~[spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
... 25 common frames omitted
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.zaxxer.hikari.HikariDataSource]: Factory method 'dataSource' threw exception; nested exception is org.springframework.boot.autoconfigure.jdbc.DataSourceProperties$DataSourceBeanCreationException: Failed to determine a suitable driver class
at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:622) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
... 43 common frames omitted
Caused by: org.springframework.boot.autoconfigure.jdbc.DataSourceProperties$DataSourceBeanCreationException: Failed to determine a suitable driver class
at org.springframework.boot.autoconfigure.jdbc.DataSourceProperties.determineDriverClassName(DataSourceProperties.java:236) ~[spring-boot-autoconfigure-2.1.4.RELEASE.jar:2.1.4.RELEASE]
at org.springframework.boot.autoconfigure.jdbc.DataSourceProperties.initializeDataSourceBuilder(DataSourceProperties.java:176) ~[spring-boot-autoconfigure-2.1.4.RELEASE.jar:2.1.4.RELEASE]
at org.springframework.boot.autoconfigure.jdbc.DataSourceConfiguration.createDataSource(DataSourceConfiguration.java:44) ~[spring-boot-autoconfigure-2.1.4.RELEASE.jar:2.1.4.RELEASE]
at org.springframework.boot.autoconfigure.jdbc.DataSourceConfiguration$Hikari.dataSource(DataSourceConfiguration.java:88) ~[spring-boot-autoconfigure-2.1.4.RELEASE.jar:2.1.4.RELEASE]
at org.springframework.boot.autoconfigure.jdbc.DataSourceConfiguration$Hikari$$EnhancerBySpringCGLIB$$f53fcd86.CGLIB$dataSource$0(<generated>) ~[spring-boot-autoconfigure-2.1.4.RELEASE.jar:2.1.4.RELEASE]
at org.springframework.boot.autoconfigure.jdbc.DataSourceConfiguration$Hikari$$EnhancerBySpringCGLIB$$f53fcd86$$FastClassBySpringCGLIB$$14c47932.invoke(<generated>) ~[spring-boot-autoconfigure-2.1.4.RELEASE.jar:2.1.4.RELEASE]
at org.springframework.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:244) ~[spring-core-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:363) ~[spring-context-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.boot.autoconfigure.jdbc.DataSourceConfiguration$Hikari$$EnhancerBySpringCGLIB$$f53fcd86.dataSource(<generated>) ~[spring-boot-autoconfigure-2.1.4.RELEASE.jar:2.1.4.RELEASE]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_201]
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_201]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_201]
at java.lang.reflect.Method.invoke(Unknown Source) ~[na:1.8.0_201]
at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
... 44 common frames omitted
and then started looking for the cause of the error and found this:
Reason: Failed to determine a suitable driver class
translates as
原因：无法确定合适的驱动程序类
then started to find out why the problem occurred. According to others’ blog, it was caused by the introduction of extra jar packages in the pom.xml file configuration. It was because the application didn’t use the DataSource, but mybatis spring-boot-starter was introduced into the DataSource in the pom.xml
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>2.0.1</version>
</dependency>
The
dependency is either annotated or the code associated with spring boot’s auto-initializing DataSource is disabled in one of two ways:
//在启动类的@SpringBootApplication加上
@SpringBootApplication(exclude = { DataSourceAutoConfiguration.class, DataSourceTransactionManagerAutoConfiguration.class })
or add:
in the application.properties file
spring.autoconfigure.exclude=org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration,org.springframework.boot.autoconfigure.jdbc.DataSourceTransactionManagerAutoConfiguration
then re-run, the result is an error, so feel mybatis – config. XML file database connection configuration has a problem, and according to practice writing before the factory pattern to create SQL connection test, to be able to insert data to the database, the database connection information and dao layer write no problem, then continue to look for solutions and spent the whole morning, also did not solve the problem, finally find wrote this unit test students to see the project I wrote something wrong, and then took a look, You can’t change the name of the configuration file application.properties under SRC /main/resources, because you always named the configuration file jdbc.properties, but when you use the unit test that comes with Spring Boot, you can’t directly recognize the file once the file name is changed, so rerun the test class after changing the name. The “Failed to determine a suitable driver class” error is gone and a new error appears:
2019-06-19 17:16:05.131 ERROR 15688 --- [ main] o.s.test.context.TestContextManager : Caught exception while allowing TestExecutionListener [org.springframework.boot.test.autoconfigure.SpringBootDependencyInjectionTestExecutionListener@2f7c2f4f] to prepare test instance [com.testjob.testjob.TestJobApplicationTests@2133661d]
org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'com.testjob.testjob.TestJobApplicationTests': Unsatisfied dependency expressed through field 'admindao'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.shop_demo.dao.AdminDAO' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:596) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:90) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:374) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1411) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireBeanProperties(AbstractAutowireCapableBeanFactory.java:391) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.injectDependencies(DependencyInjectionTestExecutionListener.java:119) ~[spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.prepareTestInstance(DependencyInjectionTestExecutionListener.java:83) ~[spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.boot.test.autoconfigure.SpringBootDependencyInjectionTestExecutionListener.prepareTestInstance(SpringBootDependencyInjectionTestExecutionListener.java:44) ~[spring-boot-test-autoconfigure-2.1.4.RELEASE.jar:2.1.4.RELEASE]
at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:246) ~[spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTest(SpringJUnit4ClassRunner.java:227) [spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner$1.runReflectiveCall(SpringJUnit4ClassRunner.java:289) [spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) [junit-4.12.jar:4.12]
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.methodBlock(SpringJUnit4ClassRunner.java:291) [spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:246) [spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97) [spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290) [junit-4.12.jar:4.12]
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71) [junit-4.12.jar:4.12]
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288) [junit-4.12.jar:4.12]
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58) [junit-4.12.jar:4.12]
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268) [junit-4.12.jar:4.12]
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61) [spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70) [spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.junit.runners.ParentRunner.run(ParentRunner.java:363) [junit-4.12.jar:4.12]
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:190) [spring-test-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:89) [.cp/:na]
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:41) [.cp/:na]
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:541) [.cp/:na]
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:763) [.cp/:na]
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:463) [.cp/:na]
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:209) [.cp/:na]
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.shop_demo.dao.AdminDAO' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoMatchingBeanFound(DefaultListableBeanFactory.java:1654) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1213) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1167) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:593) ~[spring-beans-5.1.6.RELEASE.jar:5.1.6.RELEASE]
... 29 common frames omitted
from which we find:
No qualifying bean of type 'com.shop_demo.dao.AdminDAO' available
no qualified bean of ‘com.shop_demo.dao.admindao’ type is available, that is, ‘com.shop_demo.dao.admindao’ class cannot be found. Then, according to the prompts of my classmates, add annotations in the startup class automatically generated by the project to scan other file packages
package com.testjob.testjob;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.ServletComponentScan;
import org.springframework.context.annotation.ComponentScan;
@MapperScan("com.shop_demo.dao")
@ServletComponentScan("com.shop_demo.servlet")
@ComponentScan({"com.shop_demo.serviceImpl","com.shop_demo.controller", "com.shop_demo.model",
"com.shop_demo.util"})
/*上面三个注解用于扫描其他包*/
@SpringBootApplication
public class TestJobApplication {
public static void main(String[] args) {
SpringApplication.run(TestJobApplication.class, args);
}
}
after adding the annotation, run again, and the database inserted the data successfully.
the above three annotations explain:
@MapperScan：通过使用@MapperScan可以指定要扫描的Mapper类的包的路径
@ServletComponentScan：使用@ServletComponentScan注解后，Servlet、Filter、Listener可以直接通过@WebServlet、
@WebFilter、@WebListener注解自动注册，无需其他代码
@ComponentScan：@ComponentScan主要就是定义扫描的路径并从中找出标识了需要装配的类自动装配到spring的bean容器中
PS: still too little is known about annotations and mybatis and the SpringBoot framework.
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