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why maven-compiler-plugin exclude disable

<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<excludes>
<exclude>**/Application.java</exclude>
</excludes>
</configuration>
</plugin>
this is my pom.xml , maven-compiler-plugin.version is 3.8.1 .
but i see the Applciation.class still in my jar package by maven

You are looking at the wrong location. From what I see in the screenshot, you've found some Application file from the External Libraries. What the maven-compiler-plugin does is to generate the target folder. That's where the class file should be excluded from. Check the existence of the file class under:
target/classes/...
And don't forget to run mvn clean install before (with emphasis on clean - this will wipe out your target folder)

In a project, I had to do a similar thing, due I need to exclude the module-info.java. I resolved using this configuration:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<executions>
<execution>
<id>default-compile</id>
<configuration>
<excludes>
<exclude>**/module-info.java</exclude>
</excludes>
</configuration>
</execution>
</executions>
</plugin>
If you want the entire project you can get it from GitHub. I hope this helps.

Maven How to show warnings of codes when compiling

I'm using maven to build a new project. There are some warnings in my codes which are underlined by yellow line. I wish maven could report these warnings in console. How can I accomplish that? Can I just add some parameters in the command such as mvn -XXX clean compile?

<showDeprecation>
Sets whether to show source locations where deprecated APIs are used.
Default value is: false
User property is: maven.compiler.showDeprecation
<showWarnings>
Set to true to show compilation warnings.
Default value is: false
User property is: maven.compiler.showWarnings
-- Maven Doku
As simple as mvn clean install -Dmaven.compiler.showDeprecation=true -Dmaven.compiler.showWarnings=true all in one line.
You could even remove the =true part because, when you add a maven parameter with -D it automatically sets its value to true, if not set to something else.

With maven 3.3.9, using the maven-compiler-plugin and Java 1.8, you need a <configuration> section like the following:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.0</version>
<executions>
<execution>
<id>compile</id>
<phase>compile</phase>
<goals>
<goal>compile</goal>
</goals>
</execution>
<execution>
<id>testCompile</id>
<phase>test-compile</phase>
<goals>
<goal>testCompile</goal>
</goals>
</execution>
</executions>
<configuration>
<compilerArgument>-Xlint:all</compilerArgument>
<showWarnings>true</showWarnings>
<showDeprecation>true</showDeprecation>
</configuration>
</plugin>
I got this answer from here when none of the above worked for me: http://frequal.com/java/EnableWarningsInMaven.html

I am guessing you are using the compiler plugin. Have you tried this?

Use the maven compiler plugin in your pom.xml:
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<configuration>
<skipTests>false</skipTests>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<compilerArgument>-Xlint:all</compilerArgument>
</configuration>
</plugin>
</plugins>
</build>

To get to see detailed logs in maven you can use the command line option
-X, --debug Produce execution debug output
e.g this can be used as
mvn clean install -X
Also if what you want to get in the logs is the compiler warnings (The value of the local variable a is not used). You can try modifying your project's pom.xml with the following -
...
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.6.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
<showWarnings>true</showWarnings>
</configuration>
</plugin>
... other plugins
</plugins>
</build>

How to set custom version of jdk in maven?

I am new in Maven.
I work in Windows and when I try to do the next instructions mvn clean install in folder with pom.xml file it throw me errors like this:
CLASS_NAME.java error: diamond operator is not supported in -source 1.5
[ERROR] (use -source 7 or higher to enable diamond operator)
As I can understand from the message it occurs because maven use jdk version 1.5 (Actually I even didn't install it). In maven settings folder I found toolchains.xml file. If I understood right, it is possible to set custom version of jdk for user using this file. So I add this code to my pom.xml file
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-toolchains-plugin</artifactId>
<version>1.1</version>
<configuration>
<toolchains>
<jdk>
<version>[1.8]</version>
</jdk>
</toolchains>
</configuration>
<executions>
<execution>
<goals>
<goal>toolchain</goal>
</goals>
</execution>
</executions>
</plugin>
and this to toolchains.xml
<toolchain>
<type>jdk</type>
<provides>
<version>1.8</version>
<vendor>sun</vendor>
</provides>
<configuration>
<jdkHome>C:/Program Files/Java/jdk1.8.0_45</jdkHome>
</configuration>
</toolchain>
If somebody know can you tell me how to fix this? I will appreciate any help, idea or explanation.
P.S. JAVA_HOME is C:\Program Files\Java\jdk1.8.0_45

Try configuring the maven-compiler-plugin instead of the maven-toolchains-plugin in your pom.xml.
<project>
[...]
<build>
[...]
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.5.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
</plugins>
[...]
</build>
[...]
</project>
Source

Weblogic 11g Maven deploy Issue

I am trying to deploy a war file on Weblogic 11g server using Maven (weblogic-maven-plugin) v 10.3.4
But I am getting below error on running mvn wls:deploy
Cannot find MW_HOME at location.....C:\work_maven\springmvc\Oracle\Software. You must define the middlewareHome parameter for the Maven goal.
I have installed weblogic at C:\bea11g
I also have MW_HOME set to above weblogic path.
My project's pom.xml build looks like this:
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.0.2</version>
<configuration>
<source>1.6</source>
<target>1.6</target>
</configuration>
</plugin>
<plugin>
<groupId>com.oracle.weblogic</groupId>
<artifactId>weblogic-maven-plugin</artifactId>
<version>10.3.4</version>
<configuration>
<middlewareHome>C:\bea11g</middlewareHome>
<adminurl>t3://localhost:7001</adminurl>
<user>weblogic</user>
<password>weblogic1</password>
<upload>true</upload>
<action>deploy</action>
<remote>false</remote>
<verbose>true</verbose>
<source>
${project.build.directory}/${project.build.finalName}.${project.packaging}
</source>
<name>${project.build.finalName}</name>
</configuration>
<executions>
<execution>
<phase>install</phase>
<goals>
<goal>deploy</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
Any help is greatly appreciated.
Thanks.

MW_HOME should be set to C:\bea11g, the directory where you installed WebLogic.
However, it looks like it is set to C:\work_maven\springmvc\Ora cle\Software.
Double check your environment variable setup and retry.
[Edit]
See here for reference:
http://docs.oracle.com/cd/E24329_01/web.1211/e24368/maven.htm
It looks like you need to set weblogicHome rather than middlewareHome in your plugin configuration.

It looks like something was wrong with the weblogic-maven-plugin installation and configuration.
I followed the link http://docs.oracle.com/cd/E21764_01/web.1111/e13702/maven_deployer.htm and now it is working fine.

Maven project dependency against JDK version

I have projects that need to be build with a specific version of the JDK.
The problem isn't in the source and target parameters but in the jars of the runtime used during compilation.
In some cases I get a compilation error if I try to compile with the wrong JDK, but sometimes the build is successful and I get runtime errors when using the jars.
For example in eclipse I have the ability to establish the execution enviroment for the project in the .classpath file.
Is there a way to handle such situation in maven?
What I would like to have is the ability to handle JRE dependency like other dependencies of the project in the POM file.
UPDATE:
The accepted solution was the best one when I asked this question, so I won't change it. Meanwhile a new solution to this kind of problems has been introduced: Maven Toolchain. Follow the link for further details.

I've found this article:
http://maven.apache.org/plugins/maven-compiler-plugin/examples/compile-using-different-jdk.html
<project>
[...]
<build>
[...]
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.1</version>
<configuration>
<verbose>true</verbose>
<fork>true</fork>
<executable>${JAVA_1_4_HOME}/bin/javac</executable>
<compilerVersion>1.3</compilerVersion>
</configuration>
</plugin>
</plugins>
[...]
</build>
[...]
</project>

I have projects that need to be build with a specific version of the JDK.
You can use the Maven Enforcer plugin to enforce the use of a particular version of the JDK:
<project>
[...]
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-enforcer-plugin</artifactId>
<executions>
<execution>
<id>enforce-versions</id>
<goals>
<goal>enforce</goal>
</goals>
<configuration>
<rules>
<requireJavaVersion>
<version>1.5</version>
</requireJavaVersion>
</rules>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
[...]
</project>
But I'm not sure I really understood the question. If this is not what you want, maybe you could declare your JDK specific dependencies in profiles and use an activation trigger based on the JDK version. For example:
<profiles>
<profile>
<activation>
<jdk>1.5</jdk>
</activation>
...
</profile>
</profiles>
This configuration will trigger the profile when the JDK's version starts with "1.5".

I believe that this can be solved with following plugin in your pom:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.1</version>
<configuration>
<source>1.6</source>
<target>1.6</target>
</configuration>
</plugin>
Here you target version 1.6 , or write your own version