How do I tell Spring Boot which main class to use for the executable jar

Question

Execution default of goal  org springframework boot spring-boot-maven-plugin 1 0 1 RELEASE repackage  failed   Unable to find a single main class from the following candidates   My project has more than one class with a main method  How do I tell the Spring Boot Maven plugin which of the classes it should use as the main class

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If you are using Grade  it is possible to apply the  application  plugin rather than the  java  plugin  This allows specifying the main class as below without using any Spring Boot Gradle plugin tasks  plugins     id  org springframework boot  version  2 3 3 RELEASE    id  io spring dependency-management  version  1 0 10 RELEASE    id  application    application     mainClassName    com example ExampleApplication     As a nice benefit  one is able to run the application using gradle run with the classpath automatically configured by Gradle  The plugin also packages the application as a TAR and or ZIP including operating system specific start scripts

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If you re using spring-boot-starter-parent in your pom  you simply add the following to your pom    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  plugin gt       lt  plugins gt   lt  build gt    Then do your mvn package   See this Spring docs page   A very important aspect here is to mention that the directory structure has to be src main java nameofyourpackage

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For those using Gradle  instead of Maven   referencing here       The main class can also be configured explicitly using the task   s mainClassName property    bootJar       mainClassName    com example ExampleApplication         Alternatively  the main class name can be configured project-wide using the mainClassName property of the Spring Boot DSL    springBoot       mainClassName    com example ExampleApplication

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Add your start class in your pom    lt properties gt       lt  -- The main class to start by executing java -jar -- gt       lt start-class gt com mycorp starter HelloWorldApplication lt  start-class gt   lt  properties gt    or    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 configuration gt                   lt mainClass gt com mycorp starter HelloWorldApplication lt  mainClass gt           lt  configuration gt       lt  plugin gt   lt  plugins gt   lt  build gt

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I had renamed my project and it was still finding the old Application class on the build path  I removed it in the  build  folder and all was fine

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Have seen this issue with Java 1 9 and SpringBoot 1 5 x  when main-class is not specified explicitly   With Java 1 8  it is able to find main-class without explicit property and  mvn package  works fine

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I tried the following code in pom xml and it worked for me   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 configuration gt               lt mainClass gt myPackage HelloWorld lt  mainClass gt            lt  configuration gt       lt  plugin gt       lt plugin gt           lt artifactId gt maven-compiler-plugin lt  artifactId gt           lt configuration gt               lt fork gt true lt  fork gt               lt executable gt D  jdk1 8 bin javaw exe lt  executable gt           lt  configuration gt       lt  plugin gt   lt  plugins gt

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For those using Gradle  instead of Maven     springBoot       mainClass    com example Main

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If you do NOT use the spring-boot-starter-parent pom  then from the Spring documentation    lt plugin gt       lt groupId gt org springframework boot lt  groupId gt       lt artifactId gt spring-boot-maven-plugin lt  artifactId gt       lt version gt 1 1 3 RELEASE lt  version gt       lt configuration gt           lt mainClass gt my package MyStartClass lt  mainClass gt           lt layout gt ZIP lt  layout gt       lt  configuration 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

User · Answer

Since Spring Boot 1 5  you can complete ignore the error-prone string literal in pom or build gradle  The repackaging tool  via maven or gradle plugin  will pick the one annotated with  SpringBootApplication for you   Refer to this issue for detail  https   github com spring-projects spring-boot issues 6496

[java] How do I tell Spring Boot which main class to use for the executable jar?

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