Develop Reference

Pi4j to use java with raspberry Pi not working

I am honestly about to just give up, i've tried so many different possibilities, for multiple weeks now, almost a month, of multiple problems.
I am a new-ish programmer, especially with java, but i have a good understanding about java
I am able to create a maven project no problem, i have no problems with the structure of java itself, but i don't fully understand the pom.xml.
The file compiles just fine, but when i go to start it with java -jar (filename), i get the following output;
Exception in thread "main" java.lang.NoClassDefFoundError: com/pi4j/Pi4J
at com.pi.rasberri.Main.main(Main.java:16)
Caused by: java.lang.ClassNotFoundException: com.pi4j.Pi4J
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:641)
at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:520)
... 1 more
Heres my pom that i have figuratively almost dismembered;
(The long links)
<modelVersion>4.0.0</modelVersion>
<groupId>com.pi</groupId>
<artifactId>Rasberri</artifactId>
<version>3.6.1</version>
<packaging>jar</packaging>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>11</maven.compiler.source>
<maven.compiler.target>11</maven.compiler.target>
</properties> <dependencies>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-simple</artifactId>
<version>1.7.32</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.32</version>
</dependency>
<dependency>
<groupId>com.pi4j</groupId>
<artifactId>pi4j-core</artifactId>
<version>2.0</version>
</dependency>
<dependency>
<groupId>com.pi4j</groupId>
<artifactId>pi4j-plugin-raspberrypi</artifactId>
<version>2.0</version>
</dependency>
<dependency>
<groupId>com.pi4j</groupId>
<artifactId>pi4j-plugin-pigpio</artifactId>
<version>2.0</version>
</dependency>
</dependencies> <build>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>1.2</version> </plugin> <plugin> <groupId>org.apache.maven.plugins</groupId>
maven-jar-plugin 3.1.0
true
com.pi.rasberri.Main
lib/
true
true
com.pi.rasberri.Main
false
true
And my code, which is com.pi.rasberri.Main
package com.pi.rasberri;
import com.pi4j.Pi4J;
import com.pi4j.io.gpio.digital.DigitalOutput;
import com.pi4j.io.gpio.digital.DigitalState;
import java.util.logging.Level;
import java.util.logging.Logger;
public class Main {
private static final int PIN_LED = 6;
public static void main(String[] args) throws Exception{
var pi4j = Pi4J.newAutoContext();
int x = 0;
var ledConfig = DigitalOutput.newConfigBuilder(pi4j)
.id("led")
.name("LED Flasher")
.address(PIN_LED)
.shutdown(DigitalState.LOW)
.initial(DigitalState.LOW)
.provider("pigpio-digital-output");
var led = pi4j.create(ledConfig);
while(x != 5){
led.high();
sleep(1000);
led.low();
sleep(500);
x++;
}
}
static void sleep(int z){
try {
Thread.sleep(z);
} catch (InterruptedException ex) {
System.out.println("Thread.sleep went fucky wucky");
}
}
}
I would appreciate anything that can even direct me somewhere, because i am quite lost at this point, and of course, if i figure out the answer, i will let everyone know!
Thanks in advance
**UPDATE**
Thank you, tgdavies, the article you linked
https://stackoverflow.com/a/574650/17644313 was the answer to that
specific problem!**
Just in case anyone else has the same chain of issues as me;
But with that being said, i ran directly into another error;
[main] INFO com.pi4j.Pi4J - New auto context
[main] INFO com.pi4j.Pi4J - New context builder
[main] INFO com.pi4j.platform.impl.DefaultRuntimePlatforms - adding platform to managed platform map [id=raspberrypi; name=RaspberryPi Platform; priority=5; class=com.pi4j.plugin.raspberrypi.platform.RaspberryPiPlatform]
Exception in thread "main" com.pi4j.provider.exception.ProviderNotFoundException: Pi4J provider [pigpio-digital-output] could not be found. Please include this 'provider' JAR in the classpath.
at com.pi4j.provider.impl.DefaultRuntimeProviders.get(DefaultRuntimeProviders.java:238)
at com.pi4j.provider.impl.DefaultProviders.get(DefaultProviders.java:147)
at com.pi4j.provider.Providers.get(Providers.java:253)
at com.pi4j.context.Context.create(Context.java:316)
at com.pi4j.internal.IOCreator.create(IOCreator.java:58)
at com.pi4j.internal.IOCreator.create(IOCreator.java:96)
at com.pi4j.internal.IOCreator.create(IOCreator.java:176)
at com.pi.rasberri.Main.main(Main.java:27)
I cleaned the pom.xml a littlebit;
<dependencies>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-simple</artifactId>
<version>1.7.32</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.32</version>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>com.pi4j</groupId>
<artifactId>pi4j-core</artifactId>
<version>2.0</version>
</dependency>
<dependency>
<groupId>com.pi4j</groupId>
<artifactId>pi4j-plugin-raspberrypi</artifactId>
<version>2.0</version>
</dependency>
<dependency>
<groupId>com.pi4j</groupId>
<artifactId>pi4j-plugin-pigpio</artifactId>
<version>2.0</version>
</dependency>
</dependencies>
<build>
<plugins> <!--Package all libraries classes into one runnable jar -->
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>single</goal>
</goals>
</execution>
</executions>
<configuration>
<archive>
<manifest>
<mainClass>com.pi.rasberri.Main</mainClass>
</manifest>
</archive>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
</configuration>
</plugin>
</plugins>
</build>
</project>
At this point, i know of atleast 2 possibilities,
The code just needs to be run on the raspberry pi
I have entered the classpaths incorrectly
But i honestly dont really know as to where to start troubleshooting
I've tried a few things, one of which being to try another method of compiling the files,
but the other method just resulted in a even longer string of errors.
What should i try next?
Thanks in advance!
And thanks to anyone who has suggested troubleshooting steps thus far!
Oh, and the target is to hopefully just create a singular jar file to execute on the raspberry pi
update
I tried to run it on the Raspberri pi, and it resulted in the same error so it's not that

I do not have a Raspberry Pi to do final testing but I think I found a work-around.
Using this answer I managed to get 2021-10-30-raspios-bullseye-armhf-lite.img running in Docker. I built a project using your code and copied all files needed and tried to start it (mypiapp is my jar containing your main-class):
java -cp mypiapp-0.0.1-SNAPSHOT.jar:lib/pi4j-core-2.1.1.jar:lib/pi4j-library-pigpio-2.1.1.jar:lib/pi4j-plugin-pigpio-2.1.1.jar:lib/pi4j-plugin-raspberrypi-2.1.1.jar:lib/slf4j-api-1.7.32.jar:lib/slf4j-simple-1.7.32.jar com.github.fwi.mypiapp.MyPiApp
which then gave me the error:
[main] ERROR com.pi4j.library.pigpio.util.NativeLibraryLoader - Unable to load [libpi4j-pigpio.so] using path: [/lib/armhf/libpi4j-pigpio.so]
java.lang.UnsatisfiedLinkError: /tmp/libpi4j-pigpio1770932771276400506.so: libpigpio.so.1: cannot open shared object file: No such file or directory
which is a bummer. But at least there was no ProviderNotFoundException (which I also could reproduce using the "fat jar with dependencies"). The long java-command appears to prevent that exception from happening.
And I could improve the situation somewhat by running (in Raspbian)
apt install pigpio
and now the long java-command shows:
[main] WARN com.pi4j.library.pigpio.impl.PiGpioNativeImpl - PIGPIO ERROR: PI_INIT_FAILED; pigpio initialisation failed
which is to be expected when running in a Docker container. But at least the native library was found and loaded.
Now for the work-around which might solve the "fat jar" problems. We are gonna borrow some Maven setup and code from Spring. Spring can also build fat-jars and does it a bit more complicated but also better. The pom now looks like (update where needed with your project names):
<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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.6.1</version>
</parent>
<groupId>com.github.fwi</groupId>
<artifactId>mypiapp</artifactId>
<version>0.0.1-SNAPSHOT</version>
<properties>
<java.version>11</java.version>
<start.class>com.github.fwi.mypiapp.MyPiApp</start.class>
<pi4j.version>2.1.1</pi4j.version>
</properties>
<dependencies>
<dependency>
<groupId>com.pi4j</groupId>
<artifactId>pi4j-plugin-raspberrypi</artifactId>
<version>${pi4j.version}</version>
</dependency>
<dependency>
<groupId>com.pi4j</groupId>
<artifactId>pi4j-plugin-pigpio</artifactId>
<version>${pi4j.version}</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-simple</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<mainClass>${start.class}</mainClass>
<layout>ZIP</layout>
<executable>false</executable>
</configuration>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
Simply run mvn clean package to build the fat-jar. Run it using java -jar mypiapp-fat.jar In my case, it gave the exact same error as when running with the long java-command (i.e. there was no ProviderNotFoundException). So I think this could work on a real Raspberry-Pi (the apt install pigpio might still be required though).
Some notes:
the Spring parent sets some good Maven defaults and also sets good defaults for the spring-boot-maven-plugin
Java version MUST be set using the java.version property.
update start.class with the name of the class containing your main-method.
the 3 dependencies in the pom.xml will pull in all other dependencies (dependencies of dependencies)
Spring documentation references: packaging and nested-jars launcher options.

Thanks tgdavies, MadProgrammer, and khmarbaise for the answers, the fix was to create a fat jar, which is basically a jar file that contains all the dependencies in one file, example can be found in the original question/comments
UPDATE!!
Pi4j has posted instructions for the V2 fat jar on their website!
I tried it and it works perfectly now
https://pi4j.com/getting-started/minimal-example-application-fatjar/

I faced the same issue working with Raspberry P4, java 11 and pi4j v2. I solved it downloading pigpio library directly from the raspberry
sudo apt-get install pigpio
After the library was installed, the jar worked perfecrly.
Remember also to run your program with sudo if you are not root user

Maven - Executable file from a java project

I need to use maven (for a school project) to create an executable file from a single maven command. I've never used maven and tried many solutions here on stackoverlow. The solutions created a jar file, but the file never opened.
This is my project structure
src
com
project
code
swing
programm
interface
Main.class
I know this isn't maven convention, however changing it now would mean I would have to adjust the imports (as intelliJ doesn't refactor everything perfectly) for around 40 classes.
<?xml version="1.0" encoding="UTF-8"?>
<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">
<modelVersion>4.0.0</modelVersion>
<groupId>MyGroup</groupId>
<artifactId>myProgramm</artifactId>
<version>0.7-SNAPSHOT</version>
<packaging>jar</packaging>
<name>Hello World</name>
<description>Course Project</description>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<!-- https://mvnrepository.com/artifact/org.xerial/sqlite-jdbc -->
<dependency>
<groupId>org.xerial</groupId>
<artifactId>sqlite-jdbc</artifactId>
<version>3.25.2</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.junit/junit5-engine -->
<dependency>
<groupId>org.junit</groupId>
<artifactId>junit5-engine</artifactId>
<version>5.0.0-ALPHA</version>
</dependency>
</dependencies>
<build>
</build>
What do I have to put inside to make an executable file?

TimurJD's answer is correct however I would like to explain step by step what is actually happening and why.
To have a jar be executable the JVM needs to know where your main method is.
For that you need a file called META-INF/MANIFEST.MF inside the jar you create.
This file must contain a reference to the class containing your main method which is done like this:
Main-Class: com.example.ClassContainingMainMethod
There are many ways of creating said file but since you are using maven here is the plugin that will help you create this manifest file
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>3.1.1</version>
<configuration>
<archive>
<manifest>
<addClasspath>true</addClasspath>
<classpathPrefix>lib/</classpathPrefix>
<mainClass>com.my.packege.Main</mainClass>
</manifest>
</archive>
</configuration>
</plugin>
</plugins>
</build>
Once you have the plugin in your pom.xml simply run the maven install goal, either from your IDE or the command line. After you should find a folder called target in your project. That folder will contain the executable jar.
To run the jar you can call from the command line:
java -jar MyProject.jar
It should also be noted that unless you abide by the maven standard of keeping your source code in src/main/java you will have to specify your source folder explicitly.

You need to add plugin to your pom.xml file
<build>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>1.2.1</version>
<configuration>
<mainClass>com.example.Main</mainClass>
</configuration>
</plugin>
</plugins>
</build>
and to run the program: mvn clean install exec:java
... here is the link for doc http://www.mojohaus.org/exec-maven-plugin/usage.html
There are possible different solutions, depends on your requirements: https://www.baeldung.com/executable-jar-with-maven

Using maven package in Eclipse

I have Java Maven project in Eclipse. When I do maven build and set goal to package maven builds jar file with name my-project-0.0.1-SNAPSHOT.jar. I need package to be always constant name since I put it system that starts it with script. my-project.jar would be fine. How to achieve that?
How to ask maven to put all jar libraries my project is using into my-project.jar?
How to ask maven to place my-project.jar into particular folder target/ready_release. Currently maven puts jar into target folder. How to ask maven copy all libraries and configuration files project is using into this folder too.
Maybe I'm mistaking and all these jobs should be done under some other maven goal or any other operation?
pom.xml
<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">
<modelVersion>4.0.0</modelVersion>
<groupId>com.aaa.rfid.scaleandlabel</groupId>
<artifactId>my-project</artifactId>
<version>0.0.1-SNAPSHOT</version>
<organization>
<name>aaa</name>
<url>www.aaa.lt</url>
</organization>
<dependencies>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-api</artifactId>
<version>2.11.1</version>
</dependency>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-core</artifactId>
<version>2.11.1</version>
</dependency>
<dependency>
<groupId>org.scream3r</groupId>
<artifactId>jssc</artifactId>
<version>2.8.0</version>
</dependency>
</dependencies>
</project>

You can specify the name of the package by configuring the jar plugin:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>3.1.0</version>
<configuration>
<finalName>ready_release/my-project</finalName>
</configuration>
</plugin>
This will create the jar file at <project-root>/target/ready_release/jar-name.jar and every subsequent build will overwrite it.

java executing maven project outside IDE [duplicate]

This question already has answers here:
How can I create an executable/runnable JAR with dependencies using Maven?
(33 answers)
Closed 6 years ago.
i might have completely missundestood how maven works, but i have the following issue.
i created an application with maven in netbeans. it runs in netbeans fine, but when i make Clean and Build it just compiles my source files, and the maven dependendencies are not in the jar file, so cannot run in command window.
this is my pom file. it has build section, the dependencies are in the classpath of mainfest.mf
<?xml version="1.0" encoding="UTF-8"?>
<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">
<modelVersion>4.0.0</modelVersion>
<groupId>com.ibh</groupId>
<artifactId>SafePassword</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>jar</packaging>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>2.4</version>
<configuration>
<archive>
<manifest>
<addClasspath>true</addClasspath>
<mainClass>com.ibh.safepassword.TestMain</mainClass>
</manifest>
</archive>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
</configuration>
</plugin>
</plugins>
</build>
<dependencies>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-entitymanager</artifactId>
<version>4.3.1.Final</version>
</dependency>
<dependency>
<groupId>org.hibernate.javax.persistence</groupId>
<artifactId>hibernate-jpa-2.1-api</artifactId>
<version>1.0.0.Final</version>
</dependency>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<version>1.4.192</version>
<type>jar</type>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-validator</artifactId>
<version>4.2.0.Final</version>
<type>jar</type>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-validator-annotation-processor</artifactId>
<version>4.2.0.Final</version>
<type>jar</type>
</dependency>
</dependencies>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
</properties>
i came from c# world, thought maven is similar than NuGet which is playing the game only in DEV phase, but at compile time everything is there ...
what is missing? how to execute the jar file to have the other dependencies in place and so the app can run?
thanks for your hints!
EDIT
i don't agree that this question is fully duplicated to the one you're referring to.
as i can read these many solutions maven is quite complicated, there is no ONE solution for every issue

By default Maven builds a jar that is basically a library - it doesn't contain its dependencies. If you want to include dependencies, making a runnable application, you have two main options:
Bundle everything in that one jar using some plugin that allows it, such as maven-shade-plugin. You can then run this jar.
Create a distribution bundle with your jar and all dependencies:
Use packaging that is designed to be a distribution, such as war or ear - if one of them matches your intent
Otherwise use generic bundling plugin, such as standard maven-assembly-plugin or even more advanced appassembler-maven-plugin

Building a maven project for deployment

Hello all I'm pretty new to using maven to build Java project so I'm sure the solution to my problem will be quite easy. I have installed the Eclipse Maven plugin and created a maven project. I now wish to package this project and distribute it as a runnable jar file. However when I run
mvn package
and then try to run the jar file I get the following error:
Exception in thread "main" java.lang.NoClassDefFoundError: main/Formatter
The pom for this particular file looks like so:
<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">
<modelVersion>4.0.0</modelVersion>
<groupId>GROUP</groupId>
<artifactId>pcap.csv.xml</artifactId>
<version>0.0.1-SNAPSHOT</version>
<dependencies>
<dependency>
<groupId>net.sf.opencsv</groupId>
<artifactId>opencsv</artifactId>
<version>2.0</version>
</dependency>
</dependencies>
</project>
Any help would be greatly appreciated.

You need to specify the main class in the jar plugin:
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<configuration>
<archive>
<manifest>
<addClasspath>true</addClasspath>
<mainClass>main.Formatter</mainClass>
</manifest>
</archive>
</configuration>
</plugin>
</plugins>
</build>
If you want to distribute a single jar you need to use a single-jarifier (fatjar, jarjar, onejar, etc.)