What causes imported Maven project in Eclipse to use Java 1 5 instead of Java 1 6 by default and how can I ensure it doesn t

Question

I imported a Maven project and it used Java 1 5 even though I have 1 6 configured as my Eclipse default Preferences- gt Java- gt Installed JREs    When I changed the Maven project to use the 1 6 JRE it still had the build errors left over from when the project was using Java 1 5  I described these build errors earlier in  I have build errors with m2eclipse but not with maven2 on the command line - is my m2eclipse misconfigured    I m going to delete the project and try again but I want to make sure this time that it uses Java 1 6 from the start to see if this eliminates the build problems   How do I make sure the project uses Java 1 6 when I import it

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I added this to my pom xml below the project description and it worked    lt properties gt       lt maven compiler source gt 1 6 lt  maven compiler source gt       lt maven compiler target gt 1 6 lt  maven compiler target gt   lt  properties gt

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Your JRE was probably defined in run configuration  Follow these steps in Eclipse to change the build JRE    1  Right click on the project and select Run As   Run Configurations  2  From Run Configurations window  select your project build configuration on the left panel  On the right  you will see various tabs  Main  JRE  Refresh  Source      3  Click on JRE tab  you should see something like this    4  By default  Work Default JRE  The JRE you select as default under Preferences- Java- Installed JREs  will be used  If you want to use another installed JRE  tick the Alternate JRE checkbox and select your preferred JRE from the dropdown

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I wanted to add something to the answer already provided  maven-compiler-plugin by default will compile your project using Java 1 5 which is where m2e get s its information   That s why you have to explicitly declare the maven-compiler-plugin in your project with something other then 1 5  Your effective pom xml will implicitly use the default set in the maven-compiler-plugin pom xml

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To change JDK s version  you can do    1- Project   Properties  2- Go to Java Build Path  3- In Libraries  select JRE System     and click on Edit  4- Choose your appropriate version and validate

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Simplest solution in Springboot I ll give you the simplest one if you use Springboot   lt properties gt     lt java version gt 1 8 lt  java version gt   lt  properties gt   Then  right click on your Eclipse project  Maven  gt  Update project  gt  Update project configuration from pom xml That should do

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Project specific settings  One more place where this can go wrong is in the project specific settings  in Eclipse    project properties  click your project and one of the following    Alt   Enter Menu   Project   Properties right click your project   project properties  last item in the menu   click on  Java Compiler  Uncheck  Enable project specific settings   or change them all by hand     Because of client requirements we had them enabled to keep our projects in 1 6  When it was needed to upgrade to 1 7  we had a hard time because we needed to change the java version all over the place    project POM Eclipse Workspace default project specific settings executing virtual machine  1 6 was used for everything

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The m2eclipse plugin doesn t use Eclipse defaults  the m2eclipse plugin derives the settings from the POM  So if you want a Maven project to be configured to use Java 1 6 settings when imported under Eclipse  configure the maven-compiler-plugin appropriately  as I already suggested    lt plugin gt     lt groupId gt org apache maven plugins lt  groupId gt     lt artifactId gt maven-compiler-plugin lt  artifactId gt     lt version gt 2 1 lt  version gt     lt configuration gt       lt source gt 1 6 lt  source gt       lt target gt 1 6 lt  target gt     lt  configuration gt   lt  plugin gt    If your project is already imported  update the project configuration  right-click on the project then Maven V Update Project Configuration

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Here is the root cause of java 1 5      Also note that at present the default source setting is 1 5 and the default target setting is 1 5  independently of the JDK you run Maven with  If you want to change these defaults  you should set source and target    Reference   Apache Mavem Compiler Plugin  Following are the details   Plain pom xml        lt  xml version  1 0  encoding  UTF-8   gt       lt project xmlns  http   maven apache org POM 4 0 0               xmlns xsi  http   www w3 org 2001 XMLSchema-instance               xsi schemaLocation  http   maven apache org POM 4 0 0               http   maven apache org xsd maven-4 0 0 xsd  gt           lt modelVersion gt 4 0 0 lt  modelVersion gt        lt groupId gt com pluralsight lt  groupId gt       lt artifactId gt spring sample lt  artifactId gt       lt version gt 1 0-SNAPSHOT lt  version gt    lt  project gt    Following plugin is taken from an expanded POM version Effective POM    This can be get by this command from the command line C  mvn help effective-pom I just put here a small snippet instead of an entire pom        lt plugin gt       lt artifactId gt maven-compiler-plugin lt  artifactId gt       lt version gt 3 1 lt  version gt       lt executions gt         lt execution gt           lt id gt default-compile lt  id gt           lt phase gt compile lt  phase gt           lt goals gt             lt goal gt compile lt  goal gt           lt  goals gt         lt  execution gt         lt execution gt           lt id gt default-testCompile lt  id gt           lt phase gt test-compile lt  phase gt           lt goals gt             lt goal gt testCompile lt  goal gt           lt  goals gt         lt  execution gt       lt  executions gt     lt  plugin gt    Even here you don t see where is the java version defined  lets dig more     Download the plugin  Apache Maven Compiler Plugin    3 1 as its available in jar and open it in any file compression tool like 7-zip  Traverse the jar and findout      plugin xml   file inside folder      maven-compiler-plugin-3 1 jar META-INF maven    Now you will see the following section in the file          lt configuration gt       lt basedir implementation  java io File  default-value    basedir    gt       lt buildDirectory implementation  java io File  default-value    project build directory    gt       lt classpathElements implementation  java util List  default-value    project testClasspathElements    gt       lt compileSourceRoots implementation  java util List  default-value    project testCompileSourceRoots    gt       lt compilerId implementation  java lang String  default-value  javac  gt   maven compiler compilerId  lt  compilerId gt       lt compilerReuseStrategy implementation  java lang String  default-value    reuseCreated   gt   maven compiler compilerReuseStrategy  lt  compilerReuseStrategy gt       lt compilerVersion implementation  java lang String  gt   maven compiler compilerVersion  lt  compilerVersion gt       lt debug implementation  boolean  default-value  true  gt   maven compiler debug  lt  debug gt       lt debuglevel implementation  java lang String  gt   maven compiler debuglevel  lt  debuglevel gt       lt encoding implementation  java lang String  default-value    project build sourceEncoding   gt   encoding  lt  encoding gt       lt executable implementation  java lang String  gt   maven compiler executable  lt  executable gt       lt failOnError implementation  boolean  default-value  true  gt   maven compiler failOnError  lt  failOnError gt       lt forceJavacCompilerUse implementation  boolean  default-value  false  gt   maven compiler forceJavacCompilerUse  lt  forceJavacCompilerUse gt       lt fork implementation  boolean  default-value  false  gt   maven compiler fork  lt  fork gt       lt generatedTestSourcesDirectory implementation  java io File  default-value    project build directory  generated-test-sources test-annotations   gt       lt maxmem implementation  java lang String  gt   maven compiler maxmem  lt  maxmem gt       lt meminitial implementation  java lang String  gt   maven compiler meminitial  lt  meminitial gt       lt mojoExecution implementation  org apache maven plugin MojoExecution  gt   mojoExecution  lt  mojoExecution gt       lt optimize implementation  boolean  default-value  false  gt   maven compiler optimize  lt  optimize gt       lt outputDirectory implementation  java io File  default-value    project build testOutputDirectory    gt       lt showDeprecation implementation  boolean  default-value  false  gt   maven compiler showDeprecation  lt  showDeprecation gt       lt showWarnings implementation  boolean  default-value  false  gt   maven compiler showWarnings  lt  showWarnings gt       lt skip implementation  boolean  gt   maven test skip  lt  skip gt       lt skipMultiThreadWarning implementation  boolean  default-value  false  gt   maven compiler skipMultiThreadWarning  lt  skipMultiThreadWarning gt       lt source implementation  java lang String  default-value  1 5  gt   maven compiler source  lt  source gt       lt staleMillis implementation  int  default-value  0  gt   lastModGranularityMs  lt  staleMillis gt       lt target implementation  java lang String  default-value  1 5  gt   maven compiler target  lt  target gt       lt testSource implementation  java lang String  gt   maven compiler testSource  lt  testSource gt       lt testTarget implementation  java lang String  gt   maven compiler testTarget  lt  testTarget gt       lt useIncrementalCompilation implementation  boolean  default-value  true  gt   maven compiler useIncrementalCompilation  lt  useIncrementalCompilation gt       lt verbose implementation  boolean  default-value  false  gt   maven compiler verbose  lt  verbose gt       lt mavenSession implementation  org apache maven execution MavenSession  default-value    session    gt       lt session implementation  org apache maven execution MavenSession  default-value    session    gt     lt  configuration gt    Look at the above code and find out the following 2 lines       lt source implementation  java lang String  default-value  1 5  gt   maven compiler source  lt  source gt       lt target implementation  java lang String  default-value  1 5  gt   maven compiler target  lt  target gt    Good luck

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In case anyone s wondering why Eclipse still puts a J2SE-1 5 library on the Java Build Path in a Maven project even if a Java version  gt   9 is specified by the maven compiler release property  as of October 2020  that is Eclipse version 2020-09 including Maven version 3 6 3   Maven by default uses version 3 1 of the Maven compiler plugin  while the release property has been introduced only in version 3 6  So don t forget to include a current version of the Maven compiler plugin in your pom xml when using the release property   lt properties gt       lt maven compiler release gt 15 lt  maven compiler release gt   lt  properties gt    lt build gt       lt plugins gt           lt plugin gt               lt groupId gt org apache maven plugins lt  groupId gt               lt artifactId gt maven-compiler-plugin lt  artifactId gt               lt version gt 3 8 1 lt  version gt           lt  plugin gt       lt  plugins gt   lt  build gt   Or alternatively but possibly less prominent  specify the Java version directly in the plugin configuration   lt build gt       lt plugins gt           lt plugin gt               lt groupId gt org apache maven plugins lt  groupId gt               lt artifactId gt maven-compiler-plugin lt  artifactId gt               lt version gt 3 8 1 lt  version gt               lt configuration gt                   lt release gt 15 lt  release gt               lt  configuration gt           lt  plugin gt       lt  plugins gt   lt  build gt   This picks up Line s comment on the accepted answer which  had I seen it earlier  would have saved me another hour of searching

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If you want to make sure that newly created projects or imported projects in Eclipse use another default java version than Java 1 5  you can change the configuration in the maven-compiler-plugin    Go to the folder  m2 repository org apache maven plugins maven-compiler-plugin 3 1  Open maven-compiler-plugin-3 1 jar with a zip program  Go to META-INF maven and open the plugin xml In the following lines   lt source implementation  java lang String  default-value  1 5  gt   maven compiler source  lt  source gt   lt target implementation  java lang String  default-value  1 5  gt   maven compiler target  lt  target gt  change the default-value to 1 6 or 1 8 or whatever you like  Save the file and make sure it is written back to the zip file    From now on all new Maven projects use the java version you specified   Information is from the following blog post  https   sandocean wordpress com 2019 03 22 directly-generating-maven-projects-in-eclipse-with-java-version-newer-than-1-5

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lt project gt        lt  --     -- gt        lt build gt           lt plugins gt               lt plugin gt                   lt groupId gt org apache maven plugins lt  groupId gt                   lt artifactId gt maven-compiler-plugin lt  artifactId gt                   lt version gt 3 2 lt  version gt                   lt configuration gt                       lt source gt 1 8 lt  source gt                       lt target gt 1 8 lt  target gt                   lt  configuration gt               lt  plugin gt           lt  plugins gt       lt  build gt    lt  project gt

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I found that my issue was someone committed the file  project and  classpath that had references to Java1 5 as the default JRE      lt classpathentry kind  con  path  org eclipse jdt launching JRE CONTAINER org eclipse jdt internal debug ui launcher StandardVMType J2SE-1 5  gt       lt attributes gt           lt attribute name  owner project facets  value  java   gt       lt  attributes gt   lt  classpathentry gt    By closing the project  removing the files  and then re-importing as a Maven project  I was able to properly set the project to use workspace JRE or the relevant jdk without it reverting back to 1 5    Thus  avoid checking into your SVN the  project and  classpath files  Hope this helps others

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One more possible reason if you are using Tycho and Maven to build bundles  that you have wrong execution environment  Bundle-RequiredExecutionEnvironment  in the manifest file  manifest mf  defined  For example   Manifest-Version  1 0 Bundle-ManifestVersion  2 Bundle-Name  Engine Plug-in Bundle-SymbolicName  com foo bar Bundle-Version  4 6 5 qualifier Bundle-Activator  com foo bar Activator Bundle-Vendor  Foobar Technologies Ltd  Require-Bundle  org eclipse core runtime   org jdom bundle-version  1 0 0    org apache commons codec bundle-version  1 3 0    bcprov-ext bundle-version  1 47 0  Bundle-RequiredExecutionEnvironment  JavaSE-1 5 Export-Package          Import-Package            In my case everything else was ok  The compiler plugins  normal maven and tycho as well  were set correctly  still m2 generated old compliance level because of the manifest  I thought I share the experience

[java] What causes imported Maven project in Eclipse to use Java 1.5 instead of Java 1.6 by default and how can I ensure it doesn't?

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