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Coverting Java project to a Maven project - can not find or load the main class

I have an old Java 1.8 project that I converted to Maven project in Eclipse.
After mvn eclipse:eclipse, the project structure changes so that Eclipse does not show packages, but a directories-like-structure. Now when I try to "Run as Java Application", Eclipse gives me a list of some weird classes to run - none of which are the Main class.
Now, if I run mvn eclipse:clean, the directory structure goes back to Package-like-view and I can choose the main class when I run the project as a Java Application, but I still get the main class not found along with error:
"Description Resource Path Location Type
The project was not built since its build path is incomplete. Cannot find the class file for java.lang.Object. Fix the build path then try building this project"
The build path should be okay after the mvn eclipse:eclipse. At least all the libraries are there and also jdk 1.8 library.
Maybe I am missing something, some kinda dependency missing from pom?
I am using Java version 1.8
My 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>myJavaApplication</groupId>
<artifactId>myJavaApplication</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>myJavaApplication</name>
<properties>
<java.version>1.8</java.version>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.target>1.8</maven.compiler.target>
<maven.compiler.source>1.8</maven.compiler.source>
</properties>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<configuration>
<archive>
<manifest>
<addClasspath>true</addClasspath>
<mainClass>my.java.application.main.Main</mainClass>
</manifest>
</archive>
</configuration>
</plugin>
</plugins>
</build>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
<dependency>
<groupId>itext</groupId>
<artifactId>itext</artifactId>
<version>1.3</version>
</dependency>
<dependency>
<groupId>commons-io</groupId>
<artifactId>commons-io</artifactId>
<version>2.4</version>
</dependency>
<dependency>
<groupId>org.codehaus.jackson</groupId>
<artifactId>jackson-mapper-asl</artifactId>
<version>1.8.5</version>
</dependency>
<dependency>
<groupId>org.codehaus.jackson</groupId>
<artifactId>jackson-core-lgpl</artifactId>
<version>1.8.5</version>
</dependency>
<dependency>
<groupId>javax.xml.bind</groupId>
<artifactId>jaxb-api</artifactId>
<version>2.3.1</version>
</dependency>
</dependencies>
</project>

spring boot maven doesn't package jsp files to "fat jar"

i'm using project structure from guides, store css & js in static folder in resources and jsp files in webapp/WEB-INF/jsp/
but when i build my spring boot application to fat jar by "maven package" task in eclipse it doesn't package all webapp folder to the jar
my project structure
click
my pom.xml
<?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 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>2.2.5.RELEASE</version>
<relativePath/>
</parent>
<groupId>ru.pa4ok</groupId>
<artifactId>csplatform</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>csplatform</name>
<description>Remote studing web service</description>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<scope>runtime</scope>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
<exclusions>
<exclusion>
<groupId>org.junit.vintage</groupId>
<artifactId>junit-vintage-engine</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.apache.tomcat.embed</groupId>
<artifactId>tomcat-embed-jasper</artifactId>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>

There is a "JSP limitation" in spring boot when done Jar packaging. In the official documentation it says as
Do not use the src/main/webapp folder if your application will be packaged as a jar. Although this folder is a common standard, it will only work with war packaging and it will be silently ignored by most build tools if you generate a jar.
For more info read here
So your webapp directory is getting ignored with fat jar packaging.
One alternate is to change the packaging to war and execute as how you execute a jar file.
Other alternate which could also work is to add the spring boot maven plugin with following.
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<version>2.2.6.RELEASE</version>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
If either of them doesn't work for you, please follow this link to more answers:

maven build succeeds, but eclipse build fails

I have an Eclipse / Maven project: The build with Maven succeeds, but Eclipse does have compile-time errors and cannot build.
My Eclipse is Neon (4.6.3) and I am using the build-in Maven and JDK 1.8
Could you help me solve the problem?
My 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>seller</groupId>
<artifactId>home.digest</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>war</packaging>
<name>home.digest Maven Webapp</name>
<!-- FIXME change it to the project's website -->
<url>http://maven.apache.org</url>
<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>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.5.8</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpcore -->
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpcore</artifactId>
<version>4.4.11</version>
</dependency>
<dependency>
<!-- jsoup HTML parser library # https://jsoup.org/ -->
<groupId>org.jsoup</groupId>
<artifactId>jsoup</artifactId>
<version>1.11.3</version>
</dependency>
</dependencies>
<build>
<finalName>home.digest</finalName>
<pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
<plugins>
<plugin>
<artifactId>maven-clean-plugin</artifactId>
<version>3.1.0</version>
</plugin>
<!-- see http://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_war_packaging -->
<plugin>
<artifactId>maven-resources-plugin</artifactId>
<version>3.0.2</version>
</plugin>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.0</version>
</plugin>
<plugin>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.22.1</version>
</plugin>
<plugin>
<artifactId>maven-war-plugin</artifactId>
<version>3.2.2</version>
</plugin>
<plugin>
<artifactId>maven-install-plugin</artifactId>
<version>2.5.2</version>
</plugin>
<plugin>
<artifactId>maven-deploy-plugin</artifactId>
<version>2.8.2</version>
</plugin>
</plugins>
</pluginManagement>
</build>
</project>
Eclipse fails to recognize the following imports in a class:
import org.apache.http.HttpEntity;
import org.apache.http.HttpHost;
import org.apache.http.protocol.HttpContext;
The Eclipse project has the following properties:

The problem was, that the jar file was corrupt:
[ERROR] error reading C:\Users\User.m2\repository\org\apache\httpcomponents\httpcore\4.4.11\httpcore-4.4.11.jar; invalid LOC header (bad signature)
I solved the problem by replacing the dependency
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpcore</artifactId>
<version>4.4.11</version>
</dependency>
by the dependency on an earlier version:
4.4.10

Hello
First of all, You should check to contain the apache jar file your maven local folder. Some version folder have in your local maven folder. But doesn't have jar file.
OR
this line code add to your pom.xml file.
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.5.6</version>
</dependency>

Spring Boot application is not executable

I am migrating my old Spring setup to Spring Boot 1.5.1.RELEASE.
I'm failing to get an executable .jar, I followed countless examples but my jar fails to become an executable.
It's a multi-module setup so here is my parent pom.xml
<?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/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.xyz</groupId>
<artifactId>xyz</artifactId>
<name>xyz</name>
<version>1.0.0</version>
<packaging>pom</packaging>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.1.RELEASE</version>
</parent>
<properties>
<java.version>1.8</java.version>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<commons.version>3.5</commons.version>
<guava.version>21.0</guava.version>
</properties>
<modules>
<module>mainApp</module>
<module>module1</module>
<module>module2</module>
..........
</modules>
<dependencyManagement>
<dependencies>
<!-- Spring boot -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<!-- commons -->
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.5</version>
</dependency>
<!-- google guava -->
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>${guava.version}</version>
</dependency>
<!-- Test -->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
</dependencyManagement>
</project>
This is the pom of the mainApp, it is the module that has Application.java which holds main method.
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<artifactId>xyz</artifactId>
<groupId>com.xyz</groupId>
<version>1.0.0</version>
</parent>
<artifactId>mainApp</artifactId>
<groupId>com.xyz.mainApp</groupId>
<packaging>jar</packaging>
<name>mainApp</name>
<dependencies>
<!-- Spring Boot -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!-- Spring Security OAuth2-->
<dependency>
<groupId>org.springframework.security.oauth</groupId>
<artifactId>spring-security-oauth2</artifactId>
</dependency>
<!-- xyz dependencies -->
<dependency>
<groupId>com.xyz.module3</groupId>
<artifactId>module3</artifactId>
<version>${project.version}</version>
</dependency>
<dependency>
<groupId>com.xyz.module2</groupId>
<artifactId>module2</artifactId>
<version>${project.version}</version>
</dependency>
</dependencies>
<build>
<pluginManagement>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<executable>true</executable>
</configuration>
</plugin>
</plugins>
</pluginManagement>
<finalName>xyz</finalName>
</build>
</project>
Things that work:
So things work okay when I do mvn clean install in the folder of parent pom.xml and then run mvn spring-boot:run in the mainApp folder
Things that fail:
when I execute java -jar mainApp/target/xyz.jar I get an error like:
no main manifest attribute, in mainApp/target/xyz.jar
if I attempt to run the jar like ./mainApp/target/xyz.jar, well I can't as the file is not an executable, my macOS Sierra terminal shows this for file permissions:
-rw-r--r-- 1 userXYZ staff 37641156 Feb 1 13:14 xyz.jar
If I manually change the permissions to -rwxr--r-- and attempt to run the file I get this gibberish:
/xyz.jar: line 1: PK: command not found
./xyz.jar: line 2: syntax error near unexpected token `)'
./xyz.jar: line 2: ?iAJ META-INF?iAJMETA-INF/MANIFEST.MFu??J?0??y?y??,??nW*???Jb3?F?LI?????qa?n?3???)Mp5&V????ñ^IQ?????ޱ?.#??`?$?{<??7?m6?j܀?W????'????γڎ9?>????RT?͡?V??
G??
3iR?G4???dә?A(̀?z?ϖV]ٷ??T??O>?^??0wy?u?^??S]?iG?2?"???i?$?'

The problem is not how the plugin is configured, but where the plugin is configured.
I have wrapped my plugins with <pluginManagement>, which was causing all the problems, when i removed it all was resolved and worked perfectly

update your build block in pom.xml with following, make sure you are using using Maven 3.2 (or better):
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<version>1.5.1.RELEASE</version>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>

the main class entry is missing in the jar manifesto.
Please modify the boot maven plugin as below:
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<mainClass>${start-class}</mainClass>
<layout>ZIP</layout>
</configuration>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
</plugin>
Plugin info

dependencies.dependency.version' is missing error

I am trying to create a bundle using apache maven. When I run mvn clean install command it is giving the below error:
dependencies.dependency.version' is missing for
javax.servlet:servlet-api.jar
I have placed that ‘servlet-api.jar’ inside resource folder of my project
Could any anyone please tell where should I place that jar file?
UPDATE:
Here is my 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/maven-v4_0_0.xsd">
<parent>
<artifactId>felix-parent</artifactId>
<groupId>org.apache.felix</groupId>
<version>2.1</version>
<relativePath>../pom/pom.xml</relativePath>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>maven-bundle-plugin</artifactId>
<version>2.4.1-SNAPSHOT</version>
<packaging>maven-plugin</packaging>
<name>Maven Bundle Plugin</name>
<description>
Provides a maven plugin that supports creating an OSGi bundle
from the contents of the compilation classpath along with its
resources and dependencies. Plus a zillion other features.
The plugin uses the Bnd tool (http://www.aqute.biz/Code/Bnd)
</description>
<scm>
<connection>scm:svn:http://svn.apache.org/repos/asf/felix/trunk/bundleplugin</connection>
<developerConnection>scm:svn:https://svn.apache.org/repos/asf/felix/trunk/bundleplugin</developerConnection>
<url>http://svn.apache.org/repos/asf/felix/trunk/bundleplugin</url>
</scm>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.5</source>
<target>1.5</target>
</configuration>
</plugin>
</plugins>
</build>
<dependencies>
<!-- Provided APIs -->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>servlet-api</artifactId>
</dependency>
</dependencies>
<reporting>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-plugin-plugin</artifactId>
<version>3.2</version>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-changes-plugin</artifactId>
<version>2.9</version>
<configuration>
<component>12311143</component>
<versionPrefix>maven-bundle-plugin-</versionPrefix>
<statusIds>Resolved,Closed</statusIds>
<maxEntries>1000</maxEntries>
<issueManagementSystems>
<issueManagementSystem>JIRA</issueManagementSystem>
</issueManagementSystems>
<useJql>true</useJql>
</configuration>
</plugin>
</plugins>
</reporting>
</project>
Thanks
Anderson

You haven't added the version tag in dependency.
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>servlet-api</artifactId>
<version>1.0.0</version> //Add the version.
</dependency>

I had this same error for a slightly different reason.
My project uses dependency management (has 2 <dependencyManagement> sections for some reason) and has many modules and sub-modules.
Top level pom had:
<dependencyManagement>
<dependency>
<groupId>org.apache.spark</groupId>
<artifactId>spark-core_2.10</artifactId>
<version>${spark.version}</version>
</dependency>
</dependencyManagement>
Sub-level pom had
<dependencyManagement>
<dependency>
<groupId>org.apache.spark</groupId>
<artifactId>spark-core_2.10</artifactId>
<scope>provided</scope>
</dependency>
</dependencyManagement>
Leaf pom had
<dependency>
<groupId>org.apache.spark</groupId>
<artifactId>spark-core_2.10</artifactId>
</dependency>
To fix it I removed the <dependencyManagement> section from the mid-level pom and changed the leaf pom to have
<dependency>
<groupId>org.apache.spark</groupId>
<artifactId>spark-core_2.10</artifactId>
<scope>provided</scope>
</dependency>

The message is quite clear: inside the dependencies element of your pom, you have a dependency element with the artefact javax.servlet:servlet-api.jar. And inside this dependency element, there must be a version element, but you didn't provide it.
<dependencies>
<!-- Provided APIs -->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>servlet-api</artifactId>
<!-- missing version here: -->
<version>3.0</version>
</dependency>
</dependencies>
Note that 3.0 is just an example. Provide the right version.