mysqlnontransientconnectionexception无法创建到数据库服务器的连接原因：java.lang.nullpointerexception

44u64gxh  于 2021-06-21  发布在  Mysql
关注(0)|答案(6)|浏览(359)

我有一个本地mysql社区服务器（8.0.11），运行在 127.0.0.1:3306 .
（我创建了一个数据库并为它注册了一个用户）。我可以使用以下终端查询访问数据库： ./mysql -u testuser -p 我可以访问服务器。
我使用spring和jdbc来做同样的事情，使用以下代码：

  1. private final String URL= "jdbc:mysql://127.0.0.1:3306/db_example?useSSL=false";
  2. private final String DB_USERNAME = "testuser";
  3. private final String DB_PASSWORD = "pass";
  5. public void connectAndInsertToDB() {
  6.     try {
  7.         Class.forName("com.mysql.jdbc.Driver").newInstance();
  8.     } catch (Exception e) {
  9.         System.out.println("JAVA: Class.forName() error");
  10.         e.printStackTrace();
  11.     }
  12.     try {
  14.         conn = DriverManager.getConnection(URL, DB_USERNAME, DB_PASSWORD);
  15.     } catch (SQLException e) {
  16.         System.out.println("Error in initializing a connection to MYSQL DB");
  17.         e.printStackTrace();
  19.     }
  20. }

但是我得到了以下错误：

  1. com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database server.
  2. 23:03:28,603 ERROR [stderr] (default task-3)    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
  3. 23:03:28,603 ERROR [stderr] (default task-3)    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
  4. 23:03:28,604 ERROR [stderr] (default task-3)    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
  5. 23:03:28,607 ERROR [stderr] (default task-3)    at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
  6. 23:03:28,608 ERROR [stderr] (default task-3)    at com.mysql.jdbc.Util.handleNewInstance(Util.java:404)
  7. 23:03:28,608 ERROR [stderr] (default task-3)    at com.mysql.jdbc.Util.getInstance(Util.java:387)
  8. 23:03:28,608 ERROR [stderr] (default task-3)    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:917)
  9. 23:03:28,609 ERROR [stderr] (default task-3)    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:896)
  10. 23:03:28,609 ERROR [stderr] (default task-3)    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:885)
  11. 23:03:28,609 ERROR [stderr] (default task-3)    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:860)
  12. 23:03:28,610 ERROR [stderr] (default task-3)    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2332)
  13. 23:03:28,611 ERROR [stderr] (default task-3)    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2085)
  14. 23:03:28,611 ERROR [stderr] (default task-3)    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:795)
  15. 23:03:28,611 ERROR [stderr] (default task-3)    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:44)
  16. 23:03:28,611 ERROR [stderr] (default task-3)    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
  17. 23:03:28,612 ERROR [stderr] (default task-3)    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
  18. 23:03:28,612 ERROR [stderr] (default task-3)    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
  19. 23:03:28,612 ERROR [stderr] (default task-3)    at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
  20. 23:03:28,612 ERROR [stderr] (default task-3)    at com.mysql.jdbc.Util.handleNewInstance(Util.java:404)
  21. 23:03:28,613 ERROR [stderr] (default task-3)    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:400)
  22. 23:03:28,613 ERROR [stderr] (default task-3)    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:327)
  23. 23:03:28,613 ERROR [stderr] (default task-3)    at java.sql.DriverManager.getConnection(DriverManager.java:664)
  24. 23:03:28,613 ERROR [stderr] (default task-3)    at java.sql.DriverManager.getConnection(DriverManager.java:247)
  25. 23:03:28,613 ERROR [stderr] (default task-3)    at com.voice4.spring.security.config.core.Inventory.connectAndInsertToDB(Inventory.java:41)
  26. 23:03:28,614 ERROR [stderr] (default task-3)    at com.voice4.spring.security.config.core.KomalController.indexPage(KomalController.java:36)
  27. 23:03:28,614 ERROR [stderr] (default task-3)    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  28. 23:03:28,614 ERROR [stderr] (default task-3)    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
  29. 23:03:28,614 ERROR [stderr] (default task-3)    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  30. 23:03:28,614 ERROR [stderr] (default task-3)    at java.lang.reflect.Method.invoke(Method.java:497)
  31. 23:03:28,615 ERROR [stderr] (default task-3)    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221)
  32. 23:03:28,615 ERROR [stderr] (default task-3)    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136)
  33. 23:03:28,615 ERROR [stderr] (default task-3)    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:114)
  34. 23:03:28,616 ERROR [stderr] (default task-3)    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
  35. 23:03:28,616 ERROR [stderr] (default task-3)    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
  36. 23:03:28,616 ERROR [stderr] (default task-3)    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
  37. 23:03:28,616 ERROR [stderr] (default task-3)    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963)
  38. 23:03:28,617 ERROR [stderr] (default task-3)    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897)
  39. 23:03:28,617 ERROR [stderr] (default task-3)    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
  40. 23:03:28,617 ERROR [stderr] (default task-3)    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
  41. 23:03:28,617 ERROR [stderr] (default task-3)    at javax.servlet.http.HttpServlet.service(HttpServlet.java:687)
  42. 23:03:28,618 ERROR [stderr] (default task-3)    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
  43. 23:03:28,618 ERROR [stderr] (default task-3)    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
  44. 23:03:28,618 ERROR [stderr] (default task-3)    at io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:85)
  45. 23:03:28,619 ERROR [stderr] (default task-3)    at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:129)
  46. 23:03:28,619 ERROR [stderr] (default task-3)    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:317)
  47. 23:03:28,620 ERROR [stderr] (default task-3)    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:127)
  48. 23:03:28,621 ERROR [stderr] (default task-3)    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:91)
  49. 23:03:28,621 ERROR [stderr] (default task-3)    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
  50. 23:03:28,622 ERROR [stderr] (default task-3)    at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:115)
  51. 23:03:28,622 ERROR [stderr] (default task-3)    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
  52. 23:03:28,622 ERROR [stderr] (default task-3)    at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:137)
  53. 23:03:28,623 ERROR [stderr] (default task-3)    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
  54. 23:03:28,623 ERROR [stderr] (default task-3)    at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:111)
  55. 23:03:28,624 ERROR [stderr] (default task-3)    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
  56. 23:03:28,624 ERROR [stderr] (default task-3)    at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:169)
  57. 23:03:28,625 ERROR [stderr] (default task-3)    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
  58. 23:03:28,625 ERROR [stderr] (default task-3)    at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:63)
  59. 23:03:28,625 ERROR [stderr] (default task-3)    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
  60. 23:03:28,625 ERROR [stderr] (default task-3)    at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:200)
  61. 23:03:28,625 ERROR [stderr] (default task-3)    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
  62. 23:03:28,626 ERROR [stderr] (default task-3)    at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:121)
  63. 23:03:28,626 ERROR [stderr] (default task-3)    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
  64. 23:03:28,626 ERROR [stderr] (default task-3)    at org.springframework.security.web.csrf.CsrfFilter.doFilterInternal(CsrfFilter.java:100)
  65. 23:03:28,626 ERROR [stderr] (default task-3)    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
  66. 23:03:28,627 ERROR [stderr] (default task-3)    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
  67. 23:03:28,627 ERROR [stderr] (default task-3)    at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:66)
  68. 23:03:28,627 ERROR [stderr] (default task-3)    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
  69. 23:03:28,627 ERROR [stderr] (default task-3)    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
  70. 23:03:28,627 ERROR [stderr] (default task-3)    at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:105)
  71. 23:03:28,627 ERROR [stderr] (default task-3)    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
  72. 23:03:28,628 ERROR [stderr] (default task-3)    at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:56)
  73. 23:03:28,628 ERROR [stderr] (default task-3)    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
  74. 23:03:28,628 ERROR [stderr] (default task-3)    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
  75. 23:03:28,628 ERROR [stderr] (default task-3)    at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:214)
  76. 23:03:28,628 ERROR [stderr] (default task-3)    at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:177)
  77. 23:03:28,629 ERROR [stderr] (default task-3)    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346)
  78. 23:03:28,629 ERROR [stderr] (default task-3)    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:262)
  79. 23:03:28,629 ERROR [stderr] (default task-3)    at io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:61)
  80. 23:03:28,629 ERROR [stderr] (default task-3)    at io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:131)
  81. 23:03:28,629 ERROR [stderr] (default task-3)    at io.undertow.servlet.handlers.FilterHandler.handleRequest(FilterHandler.java:84)
  82. 23:03:28,630 ERROR [stderr] (default task-3)    at io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:62)
  83. 23:03:28,630 ERROR [stderr] (default task-3)    at io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36)
  84. 23:03:28,630 ERROR [stderr] (default task-3)    at org.wildfly.extension.undertow.security.SecurityContextAssociationHandler.handleRequest(SecurityContextAssociationHandler.java:78)
  85. 23:03:28,630 ERROR [stderr] (default task-3)    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
  86. 23:03:28,630 ERROR [stderr] (default task-3)    at io.undertow.servlet.handlers.security.SSLInformationAssociationHandler.handleRequest(SSLInformationAssociationHandler.java:131)
  87. 23:03:28,631 ERROR [stderr] (default task-3)    at io.undertow.servlet.handlers.security.ServletAuthenticationCallHandler.handleRequest(ServletAuthenticationCallHandler.java:57)
  88. 23:03:28,631 ERROR [stderr] (default task-3)    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
  89. 23:03:28,631 ERROR [stderr] (default task-3)    at io.undertow.security.handlers.AbstractConfidentialityHandler.handleRequest(AbstractConfidentialityHandler.java:46)
  90. 23:03:28,631 ERROR [stderr] (default task-3)    at io.undertow.servlet.handlers.security.ServletConfidentialityConstraintHandler.handleRequest(ServletConfidentialityConstraintHandler.java:64)
  91. 23:03:28,632 ERROR [stderr] (default task-3)    at io.undertow.security.handlers.AuthenticationMechanismsHandler.handleRequest(AuthenticationMechanismsHandler.java:60)
  92. 23:03:28,632 ERROR [stderr] (default task-3)    at io.undertow.servlet.handlers.security.CachedAuthenticatedSessionHandler.handleRequest(CachedAuthenticatedSessionHandler.java:77)
  93. 23:03:28,633 ERROR [stderr] (default task-3)    at io.undertow.security.handlers.NotificationReceiverHandler.handleRequest(NotificationReceiverHandler.java:50)
  94. 23:03:28,633 ERROR [stderr] (default task-3)    at io.undertow.security.handlers.AbstractSecurityContextAssociationHandler.handleRequest(AbstractSecurityContextAssociationHandler.java:43)
  95. 23:03:28,633 ERROR [stderr] (default task-3)    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
  96. 23:03:28,634 ERROR [stderr] (default task-3)    at org.wildfly.extension.undertow.security.jacc.JACCContextIdHandler.handleRequest(JACCContextIdHandler.java:61)
  97. 23:03:28,634 ERROR [stderr] (default task-3)    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
  98. 23:03:28,634 ERROR [stderr] (default task-3)    at org.wildfly.extension.undertow.deployment.GlobalRequestControllerHandler.handleRequest(GlobalRequestControllerHandler.java:68)
  99. 23:03:28,634 ERROR [stderr] (default task-3)    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
  100. 23:03:28,635 ERROR [stderr] (default task-3)    at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:292)
  101. 23:03:28,635 ERROR [stderr] (default task-3)    at io.undertow.servlet.handlers.ServletInitialHandler.access$100(ServletInitialHandler.java:81)
  102. 23:03:28,636 ERROR [stderr] (default task-3)    at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:138)
  103. 23:03:28,636 ERROR [stderr] (default task-3)    at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:135)
  104. 23:03:28,636 ERROR [stderr] (default task-3)    at io.undertow.servlet.core.ServletRequestContextThreadSetupAction$1.call(ServletRequestContextThreadSetupAction.java:48)
  105. 23:03:28,636 ERROR [stderr] (default task-3)    at io.undertow.servlet.core.ContextClassLoaderSetupAction$1.call(ContextClassLoaderSetupAction.java:43)
  106. 23:03:28,637 ERROR [stderr] (default task-3)    at org.wildfly.extension.undertow.security.SecurityContextThreadSetupAction.lambda$create$0(SecurityContextThreadSetupAction.java:105)
  107. 23:03:28,637 ERROR [stderr] (default task-3)    at org.wildfly.extension.undertow.security.SecurityContextThreadSetupAction$$Lambda$887/252834873.call(Unknown Source)
  108. 23:03:28,638 ERROR [stderr] (default task-3)    at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1508)
  109. 23:03:28,639 ERROR [stderr] (default task-3)    at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction$$Lambda$888/1261718761.call(Unknown Source)
  110. 23:03:28,639 ERROR [stderr] (default task-3)    at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1508)
  111. 23:03:28,639 ERROR [stderr] (default task-3)    at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction$$Lambda$888/1261718761.call(Unknown Source)
  112. 23:03:28,640 ERROR [stderr] (default task-3)    at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1508)
  113. 23:03:28,640 ERROR [stderr] (default task-3)    at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction$$Lambda$888/1261718761.call(Unknown Source)
  114. 23:03:28,640 ERROR [stderr] (default task-3)    at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1508)
  115. 23:03:28,641 ERROR [stderr] (default task-3)    at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction$$Lambda$888/1261718761.call(Unknown Source)
  116. 23:03:28,641 ERROR [stderr] (default task-3)    at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:272)
  117. 23:03:28,641 ERROR [stderr] (default task-3)    at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:81)
  118. 23:03:28,642 ERROR [stderr] (default task-3)    at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:104)
  119. 23:03:28,642 ERROR [stderr] (default task-3)    at io.undertow.server.Connectors.executeRootHandler(Connectors.java:326)
  120. 23:03:28,642 ERROR [stderr] (default task-3)    at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:812)
  121. 23:03:28,642 ERROR [stderr] (default task-3)    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
  122. 23:03:28,643 ERROR [stderr] (default task-3)    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
  123. 23:03:28,643 ERROR [stderr] (default task-3)    at java.lang.Thread.run(Thread.java:745)
  124. 23:03:28,644 ERROR [stderr] (default task-3) Caused by: java.lang.NullPointerException
  125. 23:03:28,644 ERROR [stderr] (default task-3)    at com.mysql.jdbc.ConnectionImpl.getServerCharset(ConnectionImpl.java:3005)
  126. 23:03:28,644 ERROR [stderr] (default task-3)    at com.mysql.jdbc.MysqlIO.sendConnectionAttributes(MysqlIO.java:1916)
  127. 23:03:28,644 ERROR [stderr] (default task-3)    at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:1845)
  128. 23:03:28,645 ERROR [stderr] (default task-3)    at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1215)
  129. 23:03:28,645 ERROR [stderr] (default task-3)    at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2255)
  130. 23:03:28,645 ERROR [stderr] (default task-3)    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2286)
  131. 23:03:28,645 ERROR [stderr] (default task-3)    ... 111 more

在错误消息的底部，我得到了一个提示，它是由空指针异常引起的，但是我就是不知道在我的查询/代码中什么可以是空的？任何东西都可以完美地与终端一起工作，只是与jdbc不同。

Javamysqljdbcspring-data-jpa

6条答案

按热度按时间
puruo6ea

puruo6ea1#

我也面临着同样的问题，我所做的只是更新到 mysql-connector-java-8.0.11 以前是 mysql-connector-java-5.1.38 .
改变

  1. Class.forName("com.mysql.jdbc.Driver");

至

  1. Class.forName("com.mysql.cj.jdbc.Driver");

使用mysql-8.0.17.0

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9bfwbjaz

9bfwbjaz2#

您的程序上有哪个版本的mysql connector java？我在我的电脑上运行了你的代码，没有问题。但是我把mysql connector java改成了5.1.26版本，我得到了同样的错误。您使用的是mysql 8.0.11，因此可以尝试使用mysql connector java8.0.11。
顺便说一下 URL ，在版本8中应该这样写

  1. String URL= "jdbc:mysql://127.0.0.1:3306/db_example?useUnicode=true&characterEncoding=UTF-8&zeroDateTimeBehavior=CONVERT_TO_NULL&serverTimezone=GMT";
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ztyzrc3y

ztyzrc3y3#

我试着使用mysql-connector-java-8.0.11，但是没有解决我的问题解决问题的方法是在我下载了“mysql-connector-java-8.0.11”之后，我将它添加到我的项目所在的文件夹中，然后我将整个文件夹（包括src文件夹）添加为外部库，由于某种原因解决了问题

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u3r8eeie

u3r8eeie4#

我更新了mysql版本，现在可以工作了：

  1. <dependency>
  2.     <groupId>mysql</groupId>
  3.     <artifactId>mysql-connector-java</artifactId>
  4.     <version>8.0.22</version>
  5. </dependency>
赞(0）分享  回复(0）举报  2021-06-21
p4tfgftt

p4tfgftt5#

就springboot应用程序而言，如果您的项目包含多个模块，每个模块都有单独的 pom.xml 然后确保所有文件都具有与mysql服务器兼容的相同版本的mysql connector。

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j13ufse2

j13ufse26#

不幸的是，如果你的设备使用的是旧版本的android ie.v6。上述方法行不通。jdbc驱动程序v8+与旧版本的android不兼容。

赞(0）分享  回复(0）举报  2021-06-21
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