是按着章学还是看必学就好，还是选学也一起看了

老师我的IDEA版本不一样，用的JDK13。问下为啥敲一些依赖无法自动提示，刚开始是红色的。

浏览器这块儿报的错怎么个意思呢

老师我上传文件 文件没有保存在我项目中的upload文件中而是在apache-tomcat-9.0.55\webapps\项目名\upload中 这个怎么解决呢

老师我这里在引入tomcat的时候 这里爆红 但是在插件里已经有tomcat插件了，我这里引进来了吗？然后在右下角有个提示，是什么作用呢？

老师，为什么我的标签会报红呀，我的jar包不是都导入了吗

版本这导不进来，刷新maven不起作用

老师，一开始的几次测试我都没commit()提交，被roll back了，直到我commit(）之后成功添加了，但，这样id的顺序就连接不上了，我的解决办法是改表结构或者用更新方法把id衔接上但是这样又很麻烦，有没有更好的解决办法？

老师我的upload输出在target里面，请问怎样设置才能在wabpp下

创建持久层接口  报错

老师，容器创建的东西不是接口的实现类吗？那为什么获取出来的是接口对象

import com.itbaizhan.mapper.UserMapper;
import com.itbaizhan.pojo.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import java.io.InputStream;
import java.util.List;

public class TestUserMapper {
   @Test
   public void testFindAll() throws Exception{
       // （1）读取核心配置文件
       InputStream is = Resources.getResourceAsStream("SqlMapConfig.xml");
       // （2）创建SqlSessionFactoryBuilder对象
       SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
       // （3）SqlSessionFactoryBuilder对象获取SqlSessionFactory对象
       SqlSessionFactory factory = builder.build(is);
       // （4）SqlSessionFactory对象获取SqlSession对象
       SqlSession session = factory.openSession();
       // （5）SqlSession对象获取代理对象
       UserMapper userMapper = session.getMapper(UserMapper.class);
       // （6）代理对象执行方法
       List<User> all = userMapper.findAll();
       all.forEach(System.out::println);
       // （7）释放资源
       session.close();
       is.close();
   }
}

D:\Software\Java\JDK\bin\java.exe -ea -Didea.test.cyclic.buffer.size=1048576 "-javaagent:D:\Software\Java\IDEA\IntelliJ IDEA 2023.1\lib\idea_rt.jar=59437:D:\Software\Java\IDEA\IntelliJ IDEA 2023.1\bin" -Dfile.encoding=UTF-8 -classpath "D:\Software\Java\IDEA\IntelliJ IDEA 2023.1\lib\idea_rt.jar;D:\Software\Java\IDEA\IntelliJ IDEA 2023.1\plugins\junit\lib\junit5-rt.jar;D:\Software\Java\IDEA\IntelliJ IDEA 2023.1\plugins\junit\lib\junit-rt.jar;E:\MavenProject\mybatiscase\mybatisDemo1\target\test-classes;E:\MavenProject\mybatiscase\mybatisDemo1\target\classes;E:\repository\org\mybatis\mybatis\3.5.7\mybatis-3.5.7.jar;E:\repository\mysql\mysql-connector-java\8.0.16\mysql-connector-java-8.0.16.jar;E:\repository\com\google\protobuf\protobuf-java\3.6.1\protobuf-java-3.6.1.jar;E:\repository\junit\junit\4.10\junit-4.10.jar;E:\repository\org\hamcrest\hamcrest-core\1.1\hamcrest-core-1.1.jar;E:\repository\log4j\log4j\1.2.12\log4j-1.2.12.jar" com.intellij.rt.junit.JUnitStarter -ideVersion5 -junit4 TestUserMapper,testFindAll
[12/03 21:44:44] 0      [           main] DEBUG ache.ibatis.logging.LogFactory  - Logging initialized using 'class org.apache.ibatis.logging.log4j.Log4jImpl' adapter.
[12/03 21:44:44] 18     [           main] DEBUG source.pooled.PooledDataSource  - PooledDataSource forcefully closed/removed all connections.
[12/03 21:44:44] 18     [           main] DEBUG source.pooled.PooledDataSource  - PooledDataSource forcefully closed/removed all connections.
[12/03 21:44:44] 18     [           main] DEBUG source.pooled.PooledDataSource  - PooledDataSource forcefully closed/removed all connections.
[12/03 21:44:44] 18     [           main] DEBUG source.pooled.PooledDataSource  - PooledDataSource forcefully closed/removed all connections.
[12/03 21:44:44] 71     [           main] DEBUG ansaction.jdbc.JdbcTransaction  - Opening JDBC Connection
Loading class `com.mysql.jdbc.Driver'. This is deprecated. The new driver class is `com.mysql.cj.jdbc.Driver'. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.

org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
### The error may exist in com/itbaizhan/mapper/UserMapper.xml
### The error may involve com.itbaizhan.mapper.UserMapper.findAll
### The error occurred while executing a query
### Cause: com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.

	at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:153)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:145)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:140)
	at org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:147)
	at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:80)
	at org.apache.ibatis.binding.MapperProxy$PlainMethodInvoker.invoke(MapperProxy.java:145)
	at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:86)
	at com.sun.proxy.$Proxy8.findAll(Unknown Source)
	at TestUserMapper.testFindAll(TestUserMapper.java:26)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:567)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:157)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater$1.execute(IdeaTestRunner.java:38)
	at com.intellij.rt.execution.junit.TestsRepeater.repeat(TestsRepeater.java:11)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:35)
	at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:232)
	at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:55)
Caused by: com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
	at com.mysql.cj.jdbc.exceptions.SQLError.createCommunicationsException(SQLError.java:174)
	at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64)
	at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:835)
	at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:455)
	at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:240)
	at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:199)
	at java.sql/java.sql.DriverManager.getConnection(DriverManager.java:677)
	at java.sql/java.sql.DriverManager.getConnection(DriverManager.java:189)
	at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.doGetConnection(UnpooledDataSource.java:224)
	at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.doGetConnection(UnpooledDataSource.java:219)
	at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.getConnection(UnpooledDataSource.java:95)
	at org.apache.ibatis.datasource.pooled.PooledDataSource.popConnection(PooledDataSource.java:432)
	at org.apache.ibatis.datasource.pooled.PooledDataSource.getConnection(PooledDataSource.java:89)
	at org.apache.ibatis.transaction.jdbc.JdbcTransaction.openConnection(JdbcTransaction.java:139)
	at org.apache.ibatis.transaction.jdbc.JdbcTransaction.getConnection(JdbcTransaction.java:61)
	at org.apache.ibatis.executor.BaseExecutor.getConnection(BaseExecutor.java:337)
	at org.apache.ibatis.executor.SimpleExecutor.prepareStatement(SimpleExecutor.java:86)
	at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:62)
	at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:325)
	at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156)
	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:109)
	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:89)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:151)
	... 32 more
Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
	at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)
	at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:481)
	at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61)
	at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:105)
	at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:151)
	at com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:167)
	at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:91)
	at com.mysql.cj.NativeSession.connect(NativeSession.java:152)
	at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:955)
	at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:825)
	... 52 more
Caused by: java.net.UnknownHostException: 不知道这样的主机。 (mybatis)
	at java.base/java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method)
	at java.base/java.net.InetAddress$PlatformNameService.lookupAllHostAddr(InetAddress.java:929)
	at java.base/java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1515)
	at java.base/java.net.InetAddress$NameServiceAddresses.get(InetAddress.java:848)
	at java.base/java.net.InetAddress.getAllByName0(InetAddress.java:1505)
	at java.base/java.net.InetAddress.getAllByName(InetAddress.java:1364)
	at java.base/java.net.InetAddress.getAllByName(InetAddress.java:1298)
	at com.mysql.cj.protocol.StandardSocketFactory.connect(StandardSocketFactory.java:132)
	at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:65)
	... 55 more


Process finished with exit code -1

老师一直报错怎么办

老师，为啥我会程序终止？？

上节课出现这样的错误为啥？重新创建还是这样的错误。