会员可以在此提问,尚新途老师有问必答

对大家有帮助的问答会被标记为“推荐”,看完课程过来浏览一下别人提的问题,会帮你学得更全面

截止目前,同学们一共提了128829个问题
YW5ynGhxZWyWaGg=2022-03-18 20:51:07

老师,为啥这里就必须try{}catch(){}??前面那个service工程就不用

相关课程:JAVA 全系列/第六阶段:项目管理与SSM框架/Maven
YW5ynGhxZWyWaGg=2022-03-18 20:37:05

image.png老师,想问下实际开发中,这个service是先定义接口,再实现这个接口的方法。还是像上面那样直接实现这个类???

相关课程:JAVA 全系列/第六阶段:项目管理与SSM框架/Maven
YW5ynGhxZWyWaGg=2022-03-17 10:48:48

image.png老师,这个版本号是自己装的数据库版本是多少就填多少吗

相关课程:JAVA 全系列/第六阶段:项目管理与SSM框架/Maven
YW5ynGhxZWyWaGg=2022-03-16 22:33:53

老师,实体类不是pojo吗?image.png


相关课程:JAVA 全系列/第六阶段:项目管理与SSM框架/Maven
YW5ynGhxZWyWaGg=2022-03-16 21:50:38

依赖有不同的版本有什么意义吗?这个有什么实际意义?

相关课程:JAVA 全系列/第六阶段:项目管理与SSM框架/Maven
YW5ynGhxZWyWaGg=2022-03-16 17:11:34

image.png这里也报错了,怎么回事?

相关课程:JAVA 全系列/第六阶段:项目管理与SSM框架/Maven
YW5ynGhxZWyWaGg=2022-03-16 17:07:14

image.png老师,为啥我会程序终止??

相关课程:JAVA 全系列/第六阶段:项目管理与SSM框架/Maven
约定>配置2022-03-16 16:30:04

maven_demo2.zip


运行测试dao方法


显示结果


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:828)

at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:448)

at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:241)

at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:198)

at java.sql.DriverManager.getConnection(DriverManager.java:664)

at java.sql.DriverManager.getConnection(DriverManager.java:247)

at com.itbaizhan.dao.StudentDao.findAll(StudentDao.java:29)

at com.itbaizhan.dao.StudentDaoTest.testFindAll(StudentDaoTest.java:12)

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.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)

at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)

at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)

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 sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)

at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)

at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)

at java.lang.reflect.Constructor.newInstance(Constructor.java:423)

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:89)

at com.mysql.cj.NativeSession.connect(NativeSession.java:120)

at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:948)

at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:818)

... 29 more

Caused by: java.net.UnknownHostException: student

at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method)

at java.net.InetAddress$2.lookupAllHostAddr(InetAddress.java:929)

at java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1324)

at java.net.InetAddress.getAllByName0(InetAddress.java:1277)

at java.net.InetAddress.getAllByName(InetAddress.java:1193)

at java.net.InetAddress.getAllByName(InetAddress.java:1127)

at com.mysql.cj.protocol.StandardSocketFactory.connect(StandardSocketFactory.java:133)

at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:63)

... 32 more



Process finished with exit code -1


相关课程:JAVA 全系列/第六阶段:项目管理与SSM框架/Maven
YW5ynGhxZWyWaGg=2022-03-16 15:56:57

image.png老师,我这里src文件都没有,咋回事?

相关课程:JAVA 全系列/第六阶段:项目管理与SSM框架/Maven
YW5ynGhxZWyWaGg=2022-03-16 10:31:45

老师,我这昨天还听着好好的,怎么今天记录全没了,咋办

相关课程:JAVA 全系列/第六阶段:项目管理与SSM框架/Mybatis
momo2022-03-15 18:50:16

老师,网盘里的源码中没有pom.xml

相关课程:JAVA 全系列/第六阶段:项目管理与SSM框架/Maven

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