错误解决记录（持续更新）

注意事项

1、版本一定要匹配

2、jar包建在WEB-INF

错误记录

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错误一：在IDEA连接不了数据库

最简单的解决方法是在连接后面添加 allowPublicKeyRetrieval=true

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错误二：当我使用单元测试检查我的数据库插入方法时出现的错误

	二月 23, 2021 5:57:19 下午 com.alibaba.druid.pool.DruidDataSource error
严重: {dataSource-1} init error
java.sql.SQLException: com.mysql.cj.jdbc.Driver
	at com.alibaba.druid.util.JdbcUtils.createDriver(JdbcUtils.java:625)
	at com.alibaba.druid.pool.DruidDataSource.init(DruidDataSource.java:897)
	at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java:1376)
	at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java:1372)
	at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java:109)
	at com.dyx.util.DruidUtil.getConnection(DruidUtil.java:31)
	at com.dyx.dao.impl.UserDaoImpl.addUser(UserDaoImpl.java:12)
	at com.dyx.test.DBTest.TestAddUser(DBTest.java:17)
	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:44)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:76)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:157)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.junit.IdeaTestRunner$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: java.lang.ClassNotFoundException: com.mysql.cj.jdbc.Driver
	at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Class.java:264)
	at com.alibaba.druid.util.JdbcUtils.createDriver(JdbcUtils.java:623)
	... 28 more

java.sql.SQLException: com.mysql.cj.jdbc.Driver
	at com.alibaba.druid.util.JdbcUtils.createDriver(JdbcUtils.java:625)
	at com.alibaba.druid.pool.DruidDataSource.init(DruidDataSource.java:897)
	at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java:1376)
	at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java:1372)
	at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java:109)
	at com.dyx.util.DruidUtil.getConnection(DruidUtil.java:31)
	at com.dyx.dao.impl.UserDaoImpl.addUser(UserDaoImpl.java:12)
	at com.dyx.test.DBTest.TestAddUser(DBTest.java:17)
	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:44)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
false
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:76)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:157)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.junit.IdeaTestRunner$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: java.lang.ClassNotFoundException: com.mysql.cj.jdbc.Driver
	at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Class.java:264)
	at com.alibaba.druid.util.JdbcUtils.createDriver(JdbcUtils.java:623)
	... 28 more

Process finished with exit code 0

我列举一下以上发生的错误

java.sql.SQLException: com.mysql.cj.jdbc.Driver

Caused by: java.lang.ClassNotFoundException: com.mysql.cj.jdbc.Driver

java.sql.SQLException: com.mysql.cj.jdbc.Driver

Caused by: java.lang.ClassNotFoundException: com.mysql.cj.jdbc.Driver

我们发现com.mysql.cj.jdbc.Driver都是mysql的jar包问题，后来我回想着我导入的jar是5.1.37版本，与我的mysql数据库的版本（我的是8.0）不匹配。

我把8.0版本的jar包导入后解决了问题

注意：写的方法的时候没有检查数据库的数据是否重复，所以使用同一查询语句的时候会报一个重复不能使用

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