Spring Boot Program cannot find main class

Question

I have a program which runs as a Spring boot App in eclipse  The program was running fine  Then i did the following   Right click on project -   Run As -  Maven Test    This was accidental  When i then tried to run the program as a spring boot app again  it threw the following error below      Error  Could not find or load main class com bt collab alu api webapp Application  How do i point the application back to my main class   Thanks

User · Answer

Encountered the same issue and was able to fix it by the following the steps listed below    File -  Invalidate Cache and Restart File -  New -  Project from existing source Select the pom xml file just  not the whole project directory  to load the project  Project will be setup automatically

User · Answer

Even I faced the same issue  later I found that it happened because the maven build operation was not happening properly in my environment  Please check it in your case also

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In case if someone is using Gradle for the build then fix will be by adding the following lines in build gradle file  apply plugin   application   mainClassName    com example demo DemoApplication

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In my case the following helped   Added the following section in pom     lt plugins gt       lt plugin gt               lt groupId gt org springframework boot lt  groupId gt               lt artifactId gt spring-boot-maven-plugin lt  artifactId gt               lt configuration gt                   lt executable gt true lt  executable gt               lt  configuration gt       lt  plugin gt     lt  plugins gt    Ran it using maven3 and it worked

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I am new in spring boot and using STS with maven build  I did all the things mentioned above but won t work for me  I noticed two problems in problem window of STS  There was a missing jar file on the path  C  Users UserName m2 repository com jayway jsonpath json-path 2 2 0   I did following  the way is not strongly suggested but worked for me   1  I deleted  m2 folder from the path location  2  Restarted STS  3  Right Click on project folder -  maven -  update project -  checked  Force update of snapshots releases  -  Click Ok   Maven updated its dependencies and the problem is solved

User · Answer

I ran into same error  although i was using gradle build  Delegating  IDE build run actions to Gradle is solved my problem   Intellij  Settings -  Build  Execution  Deployment -  Build Tools -  Gradle -  Runner

User · Answer

There are good answers here  but maybe this one will also help somebody  For me it happened just after i deleted  idea  with IntelliJ   and reimported the project  then this issue started  i tried to run mvn compile  just via IDE Maven toolbar   once i fixed few compilation errors  issue disappeared

User · Answer

This happened to me after i updated the pom  Added some dependencies    The following step helped me to avoid this error  right click on the project  gt  maven  gt  update project

User · Answer

deleting old jars from  m2 and updating maven project should be primary step  In most of the cases it resolves the issue The reason for this issue is mostly corrupted old jars

User · Answer

If you re using Spring Boot and the above suggestions don t work  you might want to look at the Eclipse Problems view  available at Window -  Show View -  Problems    For example  you can get the same error  Error  Could not find or load main class groupId Application  if one of your jar files is corrupted  Eclipse will complain that it can t find the Applications class  even though the bad jar is the root cause    The Problems view  however  will identify the bad jar for you   At any rate  I had to manually go to my local mvn repo  in  m2  and manually delete the corrupted jar  and update it  right click on the project in the Package Explorer   Maven --  Update Project    -  OK  assuming that the correct project is check-marked

User · Answer

I was facing the same problem  I have deleted the target folder and run maven install  it worked

User · Answer

I had similar kind of problem while I was adding spring security dependency to my project   then I deleted my target folder and used maven update again   It s worked for me

User · Answer

Use spring-boot run command to start spring boot application   Precondition  1  Add following property to pom xml   lt property gt       lt start-class gt com package name YourApplicationMainClass lt  start-class gt   lt  property gt    2  Build your project  Then configure maven command with spring-boot run   Navigation   Right Click Project   Run As   Run Configuration      Add new Maven Configuration with command spring-boot run

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I had the same problem  Try this    Right Click the project -  Maven -  Update Project  Then Re-run the project  Hope it work for you too

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I have used spring 1 5 3 RELEASE version and given pom dependencies like        lt parent gt           lt groupId gt org springframework boot lt  groupId gt           lt artifactId gt spring-boot-starter-parent lt  artifactId gt           lt version gt 1 5 3 RELEASE lt  version gt       lt  parent gt        lt dependencies gt           lt dependency gt               lt groupId gt org springframework boot lt  groupId gt               lt artifactId gt spring-boot-starter-web lt  artifactId gt           lt  dependency gt      lt  dependencies gt    And my main class was    SpringBootApplication public class SpringAppStarter         public static void main String   args             SpringApplication run SpringAppStarter class  args              But still while execution of main class I was getting       Could not find or load main class     with my class name    I could see that class was available in the class path and I was using STS IDE   I was not getting reason for the issue then I tried manual build through maven with   mvn clean install   Still problem was there then i realize that my project has two libraries   Reference Library  Maven Library    What I did  I have created another mavenRepo folder and build it again and refresh my project  After that it worked and I saw that Maven Library was deleted from project class path   Issues was while execution it was getting multiple version so it was not able to find proper class to execute my application   Other Solution listed in this page also resolves the issue but if you are doing mistake in    Annotating class  pom entry  jar version etc     Hope this may resolve problem if somebody get this issue

User · Answer

I also got this error  was not having any clue  I could see the class and jars in Target folder  I later installed Maven 3 5  switched my local repo from C drive to other drive through conf settings xml of Maven  It worked perfectly fine after that  I think having local repo in C drive was main issue  Even though repo was having full access

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I tried all the above solution  but didn t worked for me   Finally was able to resolve it with a simple fix    on STS   Run Configuration   open your Spring Boot App   Open your configuration   Follow the steps    In Spring boot Tab  check your Main class and profile   Then go to classpath tab  In the bottom you will see two checkboxes one is  Exclude Test Code  Check this if you do not want to run test classes  and other   Use Temporary Jar file to specify classpath   this is necessary     Save your configuration and run

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I know this is pretty late answer  But it might still help some new learners   The Following example is only for springboot with NETBEANS  I had to do the following steps   Step 1  Follow  Mariuszs answer    Step 2  Right click on project -  Properties -  RUN  Make sure the Main Class field is has the correct starter class else Click browse and select from the available classes    Step 3  Click OK-  OK  Thant is all  Thank you

User · Answer

Have a look under  Run -  Run Configurations     in Eclipse  You should delete the new one which you created by mistake  you should still have the existing one    I suspect it has created a new run configuration for the  Run as Maven Test  and you are now always starting this one

User · Answer

I got the same error in the  quot Spring Tool Suite quot  software  In my case  I have Java 8 installed and I created a project of Java 11  And when I run the project I got the same error  like  quot  can not find main class  quot   Then I created a project in Java 8 and the problem resolved

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Error Could not load or find main class  Project Spring Boot Tool STS    Resolve Steps      Run the project      See in problems tab  it will show the corrupted error       Delete that particular jar corrupted jar  in  m2 folder      Update project       Run successfully

User · Answer

If you came across the      error could not find or load main class in maven project   do this it worked for me  Reason for the error  The reason for this error is the jar file or dependency to run a maven project is not installed correctly   Solution for the error  Go to the project folder  eg  D  office OIA-service-app  in the address bar of computer type command cmd and press enter  In the command prompt type command mvn clean install make sure you have the internet connection

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I was having the same problem just delete  m2 folder folder from your local repositry Hope it will work

User · Answer

Main class is configurable in pom xml   lt properties gt       lt start-class gt com bt collab alu api webapp Application lt  start-class gt   lt  properties gt

User · Answer

start-class doesn t work for me  I fixed it by adding build plugins to pom xml  and executions is necessary   lt build gt       lt plugins gt           lt plugin gt               lt groupId gt org springframework boot lt  groupId gt               lt artifactId gt spring-boot-maven-plugin lt  artifactId gt               lt executions gt                   lt execution gt                       lt goals gt                           lt goal gt repackage lt  goal gt                       lt  goals gt                   lt  execution gt               lt  executions gt           lt  plugin gt       lt  plugins gt   lt  build gt

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Intellij   close Intellij remove all files related to Intellij   idea folder and   iml files  open the project in Intellij as if it was the first time  using open recent won t work  id needs to be done via file -  open

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If your project packaging type war you could not start  I was using maven assembly plugin with this configuration    lt build gt       lt plugins gt           lt plugin gt               lt artifactId gt maven-assembly-plugin lt  artifactId gt               lt version gt 3 0 0 lt  version gt  lt  -- NO-MVN-MAN-VER  -- gt               lt configuration gt                   lt descriptors gt                       lt descriptor gt assembly xml lt  descriptor gt                   lt  descriptors gt                   lt descriptorRefs gt                       lt descriptorRef gt jar-with-dependencies lt  descriptorRef gt                   lt  descriptorRefs gt                   lt archive gt                       lt manifest gt                           lt mainClass gt com ttech VideoUploaderApplication lt  mainClass gt                       lt  manifest gt                   lt  archive gt               lt  configuration gt               lt executions gt                   lt execution gt                       lt id gt make-assembly lt  id gt   lt  -- this is used for inheritance merges -- gt                       lt phase gt package lt  phase gt   lt  -- bind to the packaging phase -- gt                       lt goals gt                           lt goal gt single lt  goal gt                       lt  goals gt                   lt  execution gt               lt  executions gt           lt  plugin gt       lt  plugins gt   lt  build gt    and my packaging tpe was war i got cannot find main class exception bu i changed packaging to jar it worked    lt groupId gt com ttect lt  groupId gt   lt artifactId gt VideoUploadListener lt  artifactId gt   lt version gt 1 0 0 lt  version gt   lt packaging gt   jar   lt  packaging gt

[java] Spring Boot Program cannot find main class

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