I show several errors I encountered when I constructed Spring boot with Docker and its cause.
You'd better read this article refering my previous article How to run SpringBoot as docker container
Build Error
Unable to find a single main class from the following candidates [hello.Application, hello.Application2] -> [Help 1]
Quotation of part of error message
[INFO] --- spring-boot-maven-plugin:2.7.1:repackage (repackage) @ spring-boot-docker-complete ---
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 15.785 s
[INFO] Finished at: 2022-08-12T10:06:59Z
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.springframework.boot:spring-boot-maven-plugin:2.7.1:repackage (repackage) on project spring-boot-docker-complete: Execution repackage of goal org.springframework.boot:spring-boot-maven-plugin:2.7.1:repackage failed: Unable to find a single main class from the following candidates [hello.Application, hello.Application2] -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/PluginExecutionException
As above error message says that "Unable to find a single main class from the following candidates [hello.Application, hello.Application2] " , this cause is that there two main method in a SpringBoot project.
More precisely,
Application.java
@SpringBootApplication
@RestController
public class Application {
@RequestMapping("/")
public String home() {
return "Hello Docker World";
}
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
Application2.java
@SpringBootApplication
@RestController
public class Application2 {
@RequestMapping("/test")
public String home() {
return "Hello Docker World";
}
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.10.1:compile (default-compile) on project spring-boot-docker-complete: Compilation failure: Compilation failure:
[ERROR] /srv/gs-spring-boot-docker/complete/src/main/java/hello/TestDB.java:[10,37] package org.springframework.jdbc.core does not exist
Quotation of part of error message
[INFO] --- maven-compiler-plugin:3.10.1:compile (default-compile) @ spring-boot-docker-complete ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 3 source files to /srv/gs-spring-boot-docker/complete/target/classes
[INFO] -------------------------------------------------------------
[ERROR] COMPILATION ERROR :
[INFO] -------------------------------------------------------------
[ERROR] /srv/gs-spring-boot-docker/complete/src/main/java/hello/TestDB.java:[10,37] package org.springframework.jdbc.core does not exist
[ERROR] /srv/gs-spring-boot-docker/complete/src/main/java/hello/TestDB.java:[22,9] cannot find symbol
symbol: class JdbcTemplate
location: class hello.TestDB
[INFO] 2 errors
[INFO] -------------------------------------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 7.272 s
[INFO] Finished at: 2022-08-12T11:03:58Z
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.10.1:compile (default-compile) on project spring-boot-docker-complete: Compilation failure: Compilation failure:
[ERROR] /srv/gs-spring-boot-docker/complete/src/main/java/hello/TestDB.java:[10,37] package org.springframework.jdbc.core does not exist
[ERROR] /srv/gs-spring-boot-docker/complete/src/main/java/hello/TestDB.java:[22,9] cannot find symbol
[ERROR] symbol: class JdbcTemplate
[ERROR] location: class hello.TestDB
[ERROR] -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException
As above error message says that "package org.springframework.jdbc.core does not exist" or "cannot find symbol symbol: class JdbcTemplate location: class hello.TestDB", this cause is that although TestDB tries to use JDBC API , JDBC library doesn't exist in the SpringBoot project.
More precisely, pom.xml is as follows.
### we can not fine description about JDBC !!
### Omit
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>
</dependencies>
### Omit
Runtime Error
Invocation of init method failed; nested exception is java.lang.IllegalStateException: Ambiguous mapping. Cannot map 'application2' method
Quotation of part of error message
2022-08-12 11:25:46.849 INFO 870 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http)
2022-08-12 11:25:46.913 INFO 870 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2022-08-12 11:25:46.917 INFO 870 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.64]
2022-08-12 11:25:47.210 INFO 870 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2022-08-12 11:25:47.211 INFO 870 --- [ main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 6225 ms
2022-08-12 11:25:48.584 WARN 870 --- [ main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'requestMappingHandlerMapping' defined in class path resource [org/springframework/boot/autoconfigure/web/servlet/WebMvcAutoConfiguration$EnableWebMvcConfiguration.class]: Invocation of init method failed; nested exception is java.lang.IllegalStateException: Ambiguous mapping. Cannot map 'application2' method
hello.Application2#home()
to { [/]}: There is already 'application' bean method
hello.Application#home() mapped.
2022-08-12 11:25:48.601 INFO 870 --- [ main] o.apache.catalina.core.StandardService : Stopping service [Tomcat]
2022-08-12 11:25:48.658 INFO 870 --- [ main] ConditionEvaluationReportLoggingListener :
Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2022-08-12 11:25:48.767 ERROR 870 --- [ main] o.s.boot.SpringApplication : Application run failed
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'requestMappingHandlerMapping' defined in class path resource [org/springframework/boot/autoconfigure/web/servlet/WebMvcAutoConfiguration$EnableWebMvcConfiguration.class]: Invocation of init method failed; nested exception is java.lang.IllegalStateException: Ambiguous mapping. Cannot map 'application2' method
hello.Application2#home()
to { [/]}: There is already 'application' bean method
hello.Application#home() mapped.
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1804) ~[spring-beans-5.3.21.jar!/:5.3.21]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:620) ~[spring-beans-5.3.21.jar!/:5.3.21]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:542) ~[spring-beans-5.3.21.jar!/:5.3.21]
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335) ~[spring-beans-5.3.21.jar!/:5.3.21]
This cause when there are two same Request mapping , in Application.java and in Application2.java.
More precisely,
Application.java
@SpringBootApplication
@RestController
public class Application {
@RequestMapping("/")
public String home() {
return "Hello Docker World";
}
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
Application2.java
@SpringBootApplication
@RestController
public class Application2 {
@RequestMapping("/")
public String home() {
return "Hello Docker World";
}
}
com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure
Quotation of part of error message
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) ~[mysql-connector-java-8.0.29.jar!/:8.0.29]
at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64) ~[mysql-connector-java-8.0.29.jar!/:8.0.29]
at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:828) ~[mysql-connector-java-8.0.29.jar!/:8.0.29]
at com.mysql.cj.jdbc.ConnectionImpl.(ConnectionImpl.java:448) ~[mysql-connector-java-8.0.29.jar!/:8.0.29]
at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:241) ~[mysql-connector-java-8.0.29.jar!/:8.0.29]
at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:198) ~[mysql-connector-java-8.0.29.jar!/:8.0.29]
at com.zaxxer.hikari.util.DriverDataSource.getConnection(DriverDataSource.java:138) ~[HikariCP-4.0.3.jar!/:na]
at com.zaxxer.hikari.pool.PoolBase.newConnection(PoolBase.java:364) ~[HikariCP-4.0.3.jar!/:na]
at com.zaxxer.hikari.pool.PoolBase.newPoolEntry(PoolBase.java:206) ~[HikariCP-4.0.3.jar!/:na]
/////
Caused by: java.net.UnknownHostException: any: Name or service not known
at java.base/java.net.Inet4AddressImpl.lookupAllHostAddr(Native Method) ~[na:na]
at java.base/java.net.InetAddress$PlatformNameService.lookupAllHostAddr(InetAddress.java:929) ~[na:na]
at java.base/java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1529) ~[na:na]
at java.base/java.net.InetAddress$NameServiceAddresses.get(InetAddress.java:848) ~[na:na]
at java.base/java.net.InetAddress.getAllByName0(InetAddress.java:1519) ~[na:na]
The message in above Error ,"The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server." , enable us to guesss that the destination we suppose to send is wrong.
Practically , checking the application.yml , the host name of database server is wrong.
application.yml
server:
port: 8080
#TODO: figure out why I need this here and in bootstrap.yml
spring:
application:
name: testLatticeApp
datasource:
url: jdbc:mysql://any:3306/sample?useLegacyDatetimeCode=false&serverTimezone=Asia/Tokyo #"any" is wrong. According to docker-compose.yml , it should be db.
username: root
password: root
driver-class-name: com.mysql.cj.jdbc.Driver
ribbon:
ServerListRefreshInterval: 1000
endpoints:
health:
sensitive: false
restart:
enabled: true
shutdown:
enabled: true
