11:12:21.924 [main] DEBUG org.apache.ibatis.logging.LogFactory - Logging initialized using 'class org.apache.ibatis.logging.slf4j.Slf4jImpl' adapter.

org.apache.ibatis.exceptions.PersistenceException:

### Error opening session.  Cause: java.lang.NullPointerException

### Cause: java.lang.NullPointerException

	at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)

	at org.apache.ibatis.session.defaults.DefaultSqlSessionFactory.openSessionFromDataSource(DefaultSqlSessionFactory.java:100)

	at org.apache.ibatis.session.defaults.DefaultSqlSessionFactory.openSession(DefaultSqlSessionFactory.java:47)

	at com.website.DB.DBAcess.getSqlSession(DBAcess.java:15)

	at com.website.controller.ProductControllerTest.insert(ProductControllerTest.java:58)

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

	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

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

	at java.lang.reflect.Method.invoke(Method.java:498)

	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.InvokeMethod.evaluate(InvokeMethod.java:17)

	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.junit.runner.JUnitCore.run(JUnitCore.java:137)

	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)

	at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)

	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)

	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

Caused by: java.lang.NullPointerException

	at org.apache.ibatis.session.defaults.DefaultSqlSessionFactory.openSessionFromDataSource(DefaultSqlSessionFactory.java:95)

	... 25 more

Process finished with exit code -1

我使用Mybatis的时候，遇到了这个报错，不明所以，后来发现是因为我没有写数据库配置的原因

<!-- 设置一个默认的连接环境信息 -->

    <environments default="mysql_developer">

        <environment id="mysql_developer">

            <!-- mybatis使用jdbc事务管理方式 -->

            <transactionManager type="JDBC"></transactionManager>

            <!-- mybatis使用连接池方式来获取连接 -->

            <dataSource type="POOLED">

                <!-- 配置与数据库交互的4个必要属性，不要直接写，单独写在一个配置文件中 -->

                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>

                <property name="url" value="jdbc:mysql://127.0.0.1:3306/shuyunquan?serverTimezone=UTC"/>

                <property name="username" value="root"/>

                <property name="password" value="123"/>

            </dataSource>

        </environment>

    </environments>

就是这个，我没配置，我在application.yml里面已经配置了数据库连接了，所以这里没有配置，同时也忘了使用properties标签去引入数据库配置。所以才导致了这个错误。