Importer un dossier avec le src + pom dans eclipse

Avec Maven chaque projet doit produire un livrable (un jar dans ton cas), si tu as deux projets mais un seul jar à compiler il y a un problème, il faudrait probablement faire plusieurs jar.

Quant aux dépendances, avec Maven tu ne peux pas dépendre "chacun l'un de l'autre".
Si A dépend de B, alors B ne peut pas dépendre de A.
En général ça se règle avec des modules intermédiaires, en découpant A en A1 et A2, B en B1 et B2, tu pourrais avoir A1 qui dépend de A2 et B2 et en même temps B1 qui dépend de A2 et B2.
Eventuellement tu peux avoir A1 qui dépend de B1 et/ou A2 qui dépend de B2 (ou inversement, tant que ce n'est pas dans les deux sens simultanément)

Ok merci de l'info

Eclipse est parfois un peu capricieux quand on touche aux pom.xml
Je te conseilles d'éditer tes pom.xml à part et les tester en ligne de commande, avec

mvn install

Une fois que la configuration est validée, refaire un

mvn clean eclipse:eclipse

avant de rouvrir Eclipse.

Si besoin, indiques moi les erreurs Maven avec le contenu des deux pom.xml

Il n'y a pas du tout d'erreurs dans la console après l'exécution des 2 commandes, mais voilà les pom.xml :

pom.xml - Effective POM :

<?xml version="1.0"?>
<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <modelVersion>4.0.0</modelVersion>
  <parent>
    <groupId>org.github.paperspigot</groupId>
    <artifactId>paperspigot-parent</artifactId>
    <version>dev-SNAPSHOT</version>
  </parent>
  <groupId>org.github.paperspigot</groupId>
  <artifactId>paperspigot</artifactId>
  <version>1.7.10-R0.1-SNAPSHOT</version>
  <name>PaperSpigot</name>
  <description>Parent project for all PaperSpigot modules.</description>
  <url>https://github.com/PaperSpigot/Spigot</url>
  <scm>
    <connection>scm:svn:http://svn.sonatype.org/spice/tags/oss-parent-7/paperspigot-parent/paperspigot</connection>
    <developerConnection>scm:svn:https://svn.sonatype.org/spice/tags/oss-parent-7/paperspigot-parent/paperspigot</developerConnection>
    <url>http://svn.sonatype.org/spice/tags/oss-parent-7/paperspigot-parent/paperspigot</url>
  </scm>
  <distributionManagement>
    <repository>
      <id>md_5-releases</id>
      <url>http://repo.md-5.net/content/repositories/releases/</url>
    </repository>
    <snapshotRepository>
      <id>md_5-snapshots</id>
      <url>http://repo.md-5.net/content/repositories/snapshots/</url>
    </snapshotRepository>
  </distributionManagement>
  <properties>
    <minecraft_version>1_7_R4</minecraft_version>
    <buildtag.prefix>git-Bukkit-</buildtag.prefix>
    <buildtag.suffix></buildtag.suffix>
    <sonatypeOssDistMgmtSnapshotsUrl>https://oss.sonatype.org/content/repositories/snapshots/</sonatypeOssDistMgmtSnapshotsUrl>
    <api.version>unknown</api.version>
    <minecraft.version>1.7.10</minecraft.version>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <junit.version>4.11</junit.version>
  </properties>
  <dependencies>
    <dependency>
      <groupId>org.github.paperspigot</groupId>
      <artifactId>paperspigot-api</artifactId>
      <version>1.7.10-R0.1-SNAPSHOT</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.github.paperspigot</groupId>
      <artifactId>minecraft-server</artifactId>
      <version>1.7.10-SNAPSHOT</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>net.sf.jopt-simple</groupId>
      <artifactId>jopt-simple</artifactId>
      <version>3.2</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>jline</groupId>
      <artifactId>jline</artifactId>
      <version>2.6</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.fusesource.jansi</groupId>
      <artifactId>jansi</artifactId>
      <version>1.8</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.xerial</groupId>
      <artifactId>sqlite-jdbc</artifactId>
      <version>3.7.2</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.14</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>com.google.code.gson</groupId>
      <artifactId>gson</artifactId>
      <version>2.1</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.hamcrest</groupId>
      <artifactId>hamcrest-library</artifactId>
      <version>1.3</version>
      <scope>test</scope>
    </dependency>
  </dependencies>
  <repositories>
    <repository>
      <id>repobo-snap</id>
      <url>http://repo.bukkit.org/content/groups/public</url>
    </repository>
    <repository>
      <id>md_5-releases</id>
      <url>http://repo.md-5.net/content/repositories/releases/</url>
    </repository>
    <repository>
      <releases>
        <enabled>false</enabled>
      </releases>
      <snapshots>
        <enabled>true</enabled>
      </snapshots>
      <id>sonatype-nexus-snapshots</id>
      <name>Sonatype Nexus Snapshots</name>
      <url>https://oss.sonatype.org/content/repositories/snapshots</url>
    </repository>
    <repository>
      <snapshots>
        <enabled>false</enabled>
      </snapshots>
      <id>central</id>
      <name>Central Repository</name>
      <url>https://repo.maven.apache.org/maven2</url>
    </repository>
  </repositories>
  <pluginRepositories>
    <pluginRepository>
      <id>bukkit-plugins</id>
      <url>http://repo.bukkit.org/content/groups/public</url>
    </pluginRepository>
    <pluginRepository>
      <releases>
        <updatePolicy>never</updatePolicy>
      </releases>
      <snapshots>
        <enabled>false</enabled>
      </snapshots>
      <id>central</id>
      <name>Central Repository</name>
      <url>https://repo.maven.apache.org/maven2</url>
    </pluginRepository>
  </pluginRepositories>
  <build>
    <sourceDirectory>C:\Users\Jules\eclipse-workspace\PaperSpigot-Server\src\main\java</sourceDirectory>
    <scriptSourceDirectory>C:\Users\Jules\eclipse-workspace\PaperSpigot-Server\src\main\scripts</scriptSourceDirectory>
    <testSourceDirectory>C:\Users\Jules\eclipse-workspace\PaperSpigot-Server\src\test\java</testSourceDirectory>
    <outputDirectory>C:\Users\Jules\eclipse-workspace\PaperSpigot-Server\target\classes</outputDirectory>
    <testOutputDirectory>C:\Users\Jules\eclipse-workspace\PaperSpigot-Server\target\test-classes</testOutputDirectory>
    <defaultGoal>install</defaultGoal>
    <resources>
      <resource>
        <directory>C:\Users\Jules\eclipse-workspace\PaperSpigot-Server\src\main\resources</directory>
      </resource>
    </resources>
    <testResources>
      <testResource>
        <directory>C:\Users\Jules\eclipse-workspace\PaperSpigot-Server\src\test\resources</directory>
      </testResource>
    </testResources>
    <directory>C:\Users\Jules\eclipse-workspace\PaperSpigot-Server\target</directory>
    <finalName>paperspigot-1.7.10-R0.1-SNAPSHOT</finalName>
    <pluginManagement>
      <plugins>
        <plugin>
          <artifactId>maven-antrun-plugin</artifactId>
          <version>1.3</version>
        </plugin>
        <plugin>
          <artifactId>maven-assembly-plugin</artifactId>
          <version>2.2-beta-5</version>
        </plugin>
        <plugin>
          <artifactId>maven-dependency-plugin</artifactId>
          <version>2.8</version>
        </plugin>
        <plugin>
          <artifactId>maven-release-plugin</artifactId>
          <version>2.1</version>
          <configuration>
            <mavenExecutorId>forked-path</mavenExecutorId>
            <useReleaseProfile>false</useReleaseProfile>
            <arguments>-Psonatype-oss-release</arguments>
          </configuration>
        </plugin>
        <plugin>
          <groupId>org.eclipse.m2e</groupId>
          <artifactId>lifecycle-mapping</artifactId>
          <version>1.0.0</version>
          <configuration>
            <lifecycleMappingMetadata>
              <pluginExecutions>
                <pluginExecution>
                  <pluginExecutionFilter>
                    <groupId>com.lukegb.mojo</groupId>
                    <artifactId>gitdescribe-maven-plugin</artifactId>
                    <versionRange>[1.3,)</versionRange>
                    <goals>
                      <goal>gitdescribe</goal>
                    </goals>
                  </pluginExecutionFilter>
                  <action>
                    <ignore></ignore>
                  </action>
                </pluginExecution>
              </pluginExecutions>
            </lifecycleMappingMetadata>
          </configuration>
        </plugin>
      </plugins>
    </pluginManagement>
    <plugins>
      <plugin>
        <artifactId>maven-enforcer-plugin</artifactId>
        <version>1.0</version>
        <executions>
          <execution>
            <id>enforce-maven</id>
            <goals>
              <goal>enforce</goal>
            </goals>
            <configuration>
              <rules>
                <requireMavenVersion>
                  <version>(,2.1.0),(2.1.0,2.2.0),(2.2.0,)</version>
                  <message>Maven 2.1.0 and 2.2.0 produce incorrect GPG signatures and checksums respectively.</message>
                </requireMavenVersion>
              </rules>
            </configuration>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <groupId>net.md-5</groupId>
        <artifactId>scriptus</artifactId>
        <version>0.2</version>
        <executions>
          <execution>
            <id>ex-paperspigot</id>
            <phase>initialize</phase>
            <goals>
              <goal>describe</goal>
            </goals>
            <configuration>
              <format>git-PaperSpigot-%s</format>
              <scmDirectory>../</scmDirectory>
              <descriptionProperty>paperspigot.desc</descriptionProperty>
            </configuration>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <artifactId>maven-jar-plugin</artifactId>
        <version>2.1</version>
        <executions>
          <execution>
            <id>default-jar</id>
            <phase>package</phase>
            <goals>
              <goal>jar</goal>
            </goals>
            <configuration>
              <archive>
                <manifestEntries>
                  <Main-Class>org.bukkit.craftbukkit.Main</Main-Class>
                  <Implementation-Title>CraftBukkit</Implementation-Title>
                  <Implementation-Version>${paperspigot.desc}</Implementation-Version>
                  <Implementation-Vendor>Bukkit Team</Implementation-Vendor>
                  <Specification-Title>Bukkit</Specification-Title>
                  <Specification-Version>unknown</Specification-Version>
                  <Specification-Vendor>Bukkit Team</Specification-Vendor>
                  <Sealed>true</Sealed>
                  <Timestamp>2018-09-01T12:37:44Z</Timestamp>
                </manifestEntries>
                <manifestSections>
                  <manifestSection>
                    <name>net/bukkit/</name>
                    <manifestEntries>
                      <Sealed>true</Sealed>
                    </manifestEntries>
                  </manifestSection>
                  <manifestSection>
                    <name>com/bukkit/</name>
                    <manifestEntries>
                      <Sealed>true</Sealed>
                    </manifestEntries>
                  </manifestSection>
                  <manifestSection>
                    <name>org/bukkit/</name>
                    <manifestEntries>
                      <Sealed>true</Sealed>
                    </manifestEntries>
                  </manifestSection>
                </manifestSections>
              </archive>
            </configuration>
          </execution>
        </executions>
        <configuration>
          <archive>
            <manifestEntries>
              <Main-Class>org.bukkit.craftbukkit.Main</Main-Class>
              <Implementation-Title>CraftBukkit</Implementation-Title>
              <Implementation-Version>${paperspigot.desc}</Implementation-Version>
              <Implementation-Vendor>Bukkit Team</Implementation-Vendor>
              <Specification-Title>Bukkit</Specification-Title>
              <Specification-Version>unknown</Specification-Version>
              <Specification-Vendor>Bukkit Team</Specification-Vendor>
              <Sealed>true</Sealed>
              <Timestamp>2018-09-01T12:37:44Z</Timestamp>
            </manifestEntries>
            <manifestSections>
              <manifestSection>
                <name>net/bukkit/</name>
                <manifestEntries>
                  <Sealed>true</Sealed>
                </manifestEntries>
              </manifestSection>
              <manifestSection>
                <name>com/bukkit/</name>
                <manifestEntries>
                  <Sealed>true</Sealed>
                </manifestEntries>
              </manifestSection>
              <manifestSection>
                <name>org/bukkit/</name>
                <manifestEntries>
                  <Sealed>true</Sealed>
                </manifestEntries>
              </manifestSection>
            </manifestSections>
          </archive>
        </configuration>
      </plugin>
      <plugin>
        <artifactId>maven-shade-plugin</artifactId>
        <version>2.1</version>
        <executions>
          <execution>
            <phase>package</phase>
            <goals>
              <goal>shade</goal>
            </goals>
            <configuration>
              <relocations>
                <relocation>
                  <pattern>org.bouncycastle</pattern>
                  <shadedPattern>net.minecraft.v1_7_R4.org.bouncycastle</shadedPattern>
                </relocation>
                <relocation>
                  <pattern>joptsimple</pattern>
                  <shadedPattern>org.bukkit.craftbukkit.libs.joptsimple</shadedPattern>
                </relocation>
                <relocation>
                  <pattern>jline</pattern>
                  <shadedPattern>org.bukkit.craftbukkit.libs.jline</shadedPattern>
                </relocation>
                <relocation>
                  <pattern>org.ibex</pattern>
                  <shadedPattern>org.bukkit.craftbukkit.libs.org.ibex</shadedPattern>
                </relocation>
                <relocation>
                  <pattern>org.gjt</pattern>
                  <shadedPattern>org.bukkit.craftbukkit.libs.org.gjt</shadedPattern>
                </relocation>
                <relocation>
                  <pattern>com.google.gson</pattern>
                  <shadedPattern>org.bukkit.craftbukkit.libs.com.google.gson</shadedPattern>
                </relocation>
                <relocation>
                  <pattern>org.bukkit.craftbukkit</pattern>
                  <shadedPattern>org.bukkit.craftbukkit.v1_7_R4</shadedPattern>
                  <excludes>
                    <exclude>org.bukkit.craftbukkit.Main*</exclude>
                  </excludes>
                </relocation>
                <relocation>
                  <pattern>net.minecraft.server</pattern>
                  <shadedPattern>net.minecraft.server.v1_7_R4</shadedPattern>
                </relocation>
              </relocations>
            </configuration>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>2.3.2</version>
        <executions>
          <execution>
            <id>default-compile</id>
            <phase>compile</phase>
            <goals>
              <goal>compile</goal>
            </goals>
            <configuration>
              <source>1.6</source>
              <target>1.6</target>
            </configuration>
          </execution>
          <execution>
            <id>default-testCompile</id>
            <phase>test-compile</phase>
            <goals>
              <goal>testCompile</goal>
            </goals>
            <configuration>
              <source>1.6</source>
              <target>1.6</target>
            </configuration>
          </execution>
        </executions>
        <configuration>
          <source>1.6</source>
          <target>1.6</target>
        </configuration>
      </plugin>
      <plugin>
        <artifactId>maven-surefire-plugin</artifactId>
        <version>2.11</version>
        <executions>
          <execution>
            <id>default-test</id>
            <phase>test</phase>
            <goals>
              <goal>test</goal>
            </goals>
            <configuration>
              <workingDirectory>C:\Users\Jules\eclipse-workspace\PaperSpigot-Server/target/test-server</workingDirectory>
              <excludes>
                <exclude>org/bukkit/craftbukkit/updater/BukkitDLUpdaterServiceTest.java</exclude>
                <exclude>org/bukkit/craftbukkit/inventory/ItemStack*Test.java</exclude>
              </excludes>
            </configuration>
          </execution>
        </executions>
        <configuration>
          <workingDirectory>C:\Users\Jules\eclipse-workspace\PaperSpigot-Server/target/test-server</workingDirectory>
          <excludes>
            <exclude>org/bukkit/craftbukkit/updater/BukkitDLUpdaterServiceTest.java</exclude>
            <exclude>org/bukkit/craftbukkit/inventory/ItemStack*Test.java</exclude>
          </excludes>
        </configuration>
      </plugin>
      <plugin>
        <artifactId>maven-resources-plugin</artifactId>
        <version>2.4.3</version>
        <executions>
          <execution>
            <id>default-testResources</id>
            <phase>process-test-resources</phase>
            <goals>
              <goal>testResources</goal>
            </goals>
          </execution>
          <execution>
            <id>default-resources</id>
            <phase>process-resources</phase>
            <goals>
              <goal>resources</goal>
            </goals>
          </execution>
          <execution>
            <id>maps-file</id>
            <phase>package</phase>
            <goals>
              <goal>copy-resources</goal>
            </goals>
            <configuration>
              <outputDirectory>C:\Users\Jules\eclipse-workspace\PaperSpigot-Server/target</outputDirectory>
              <resources>
                <resource>
                  <directory>C:\Users\Jules\eclipse-workspace\PaperSpigot-Server</directory>
                  <filtering>true</filtering>
                  <includes>
                    <include>maps.yml</include>
                  </includes>
                </resource>
              </resources>
            </configuration>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <groupId>com.wolvereness</groupId>
        <artifactId>overmapped</artifactId>
        <version>0.0.2</version>
        <executions>
          <execution>
            <phase>package</phase>
            <goals>
              <goal>map</goal>
            </goals>
            <configuration>
              <maps>C:\Users\Jules\eclipse-workspace\PaperSpigot-Server/target/maps.yml</maps>
              <input>C:\Users\Jules\eclipse-workspace\PaperSpigot-Server/target/paperspigot-1.7.10-R0.1-SNAPSHOT.jar</input>
              <original>C:\Users\Jules\eclipse-workspace\PaperSpigot-Server/target/unmapped-paperspigot-1.7.10-R0.1-SNAPSHOT.jar</original>
            </configuration>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <artifactId>maven-clean-plugin</artifactId>
        <version>2.5</version>
        <executions>
          <execution>
            <id>default-clean</id>
            <phase>clean</phase>
            <goals>
              <goal>clean</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <artifactId>maven-install-plugin</artifactId>
        <version>2.4</version>
        <executions>
          <execution>
            <id>default-install</id>
            <phase>install</phase>
            <goals>
              <goal>install</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <artifactId>maven-deploy-plugin</artifactId>
        <version>2.7</version>
        <executions>
          <execution>
            <id>default-deploy</id>
            <phase>deploy</phase>
            <goals>
              <goal>deploy</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <artifactId>maven-site-plugin</artifactId>
        <version>3.3</version>
        <executions>
          <execution>
            <id>default-site</id>
            <phase>site</phase>
            <goals>
              <goal>site</goal>
            </goals>
            <configuration>
              <outputDirectory>C:\Users\Jules\eclipse-workspace\PaperSpigot-Server\target\site</outputDirectory>
              <reportPlugins>
                <reportPlugin>
                  <groupId>org.apache.maven.plugins</groupId>
                  <artifactId>maven-project-info-reports-plugin</artifactId>
                </reportPlugin>
              </reportPlugins>
            </configuration>
          </execution>
          <execution>
            <id>default-deploy</id>
            <phase>site-deploy</phase>
            <goals>
              <goal>deploy</goal>
            </goals>
            <configuration>
              <outputDirectory>C:\Users\Jules\eclipse-workspace\PaperSpigot-Server\target\site</outputDirectory>
              <reportPlugins>
                <reportPlugin>
                  <groupId>org.apache.maven.plugins</groupId>
                  <artifactId>maven-project-info-reports-plugin</artifactId>
                </reportPlugin>
              </reportPlugins>
            </configuration>
          </execution>
        </executions>
        <configuration>
          <outputDirectory>C:\Users\Jules\eclipse-workspace\PaperSpigot-Server\target\site</outputDirectory>
          <reportPlugins>
            <reportPlugin>
              <groupId>org.apache.maven.plugins</groupId>
              <artifactId>maven-project-info-reports-plugin</artifactId>
            </reportPlugin>
          </reportPlugins>
        </configuration>
      </plugin>
    </plugins>
  </build>
  <reporting>
    <outputDirectory>C:\Users\Jules\eclipse-workspace\PaperSpigot-Server\target\site</outputDirectory>
  </reporting>
</project>

pom.xml - 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>org.github.paperspigot</groupId>
  <artifactId>paperspigot</artifactId>
  <packaging>jar</packaging>
  <version>1.7.10-R0.1-SNAPSHOT</version>
  <name>PaperSpigot</name>
  <url>https://github.com/PaperSpigot/Spigot</url>
 
  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <api.version>unknown</api.version>
    <junit.version>4.11</junit.version>
    <minecraft.version>1.7.10</minecraft.version>
    <minecraft_version>1_7_R4</minecraft_version>
    <buildtag.prefix>git-Bukkit-</buildtag.prefix>
    <buildtag.suffix></buildtag.suffix>
  </properties>
 
  <parent>
    <groupId>org.github.paperspigot</groupId>
    <artifactId>paperspigot-parent</artifactId>
    <version>dev-SNAPSHOT</version>
    <relativePath>../pom.xml</relativePath>
  </parent>
 
  <repositories>
    <repository>
      <id>repobo-snap</id>
      <url>http://repo.bukkit.org/content/groups/public</url>
    </repository>
  </repositories>
 
  <pluginRepositories>
    <pluginRepository>
      <id>bukkit-plugins</id>
      <url>http://repo.bukkit.org/content/groups/public</url>
    </pluginRepository>
  </pluginRepositories>
 
  <dependencies>
    <dependency>
      <groupId>org.github.paperspigot</groupId>
      <artifactId>paperspigot-api</artifactId>
      <version>${project.version}</version>
      <type>jar</type>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.github.paperspigot</groupId>
      <artifactId>minecraft-server</artifactId>
      <version>${minecraft.version}-SNAPSHOT</version>
      <type>jar</type>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>net.sf.jopt-simple</groupId>
      <artifactId>jopt-simple</artifactId>
      <version>3.2</version>
      <type>jar</type>
      <scope>compile</scope>
    </dependency>
    <!-- jline and jansi versions must be kept in sync -->
    <dependency>
      <groupId>jline</groupId>
      <artifactId>jline</artifactId>
      <version>2.6</version>
      <type>jar</type>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.fusesource.jansi</groupId>
      <artifactId>jansi</artifactId>
      <version>1.8</version>
      <type>jar</type>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.xerial</groupId>
      <artifactId>sqlite-jdbc</artifactId>
      <version>3.7.2</version>
      <type>jar</type>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.14</version>
      <type>jar</type>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>com.google.code.gson</groupId>
      <artifactId>gson</artifactId>
      <version>2.1</version>
    </dependency>
    <!-- testing -->
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>${junit.version}</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.hamcrest</groupId>
      <artifactId>hamcrest-library</artifactId>
      <version>1.3</version>
      <scope>test</scope>
    </dependency>
  </dependencies>
 
  <!-- This builds a completely 'ready to start' jar with all dependencies inside -->
  <build>
    <defaultGoal>install</defaultGoal>
    <plugins>
      <plugin>
        <groupId>net.md-5</groupId>
        <artifactId>scriptus</artifactId>
        <version>0.2</version>
        <executions>
          <execution>
            <id>ex-paperspigot</id>
            <configuration>
              <format>git-PaperSpigot-%s</format>
              <scmDirectory>../</scmDirectory>
              <descriptionProperty>paperspigot.desc</descriptionProperty>
            </configuration>
            <phase>initialize</phase>
            <goals>
              <goal>describe</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-jar-plugin</artifactId>
        <version>2.1</version>
        <configuration>
          <archive>
            <manifestEntries>
              <Main-Class>org.bukkit.craftbukkit.Main</Main-Class>
              <Implementation-Title>CraftBukkit</Implementation-Title>
              <Implementation-Version>${paperspigot.desc}</Implementation-Version>
              <Implementation-Vendor>Bukkit Team</Implementation-Vendor>
              <Specification-Title>Bukkit</Specification-Title>
              <Specification-Version>${api.version}</Specification-Version>
              <Specification-Vendor>Bukkit Team</Specification-Vendor>
              <Sealed>true</Sealed>
              <Timestamp>${maven.build.timestamp}</Timestamp>
            </manifestEntries>
            <manifestSections>
              <manifestSection>
                <name>net/bukkit/</name>
                <manifestEntries>
                  <Sealed>true</Sealed>
                </manifestEntries>
              </manifestSection>
              <manifestSection>
                <name>com/bukkit/</name>
                <manifestEntries>
                  <Sealed>true</Sealed>
                </manifestEntries>
              </manifestSection>
              <manifestSection>
                <name>org/bukkit/</name>
                <manifestEntries>
                  <Sealed>true</Sealed>
                </manifestEntries>
              </manifestSection>
            </manifestSections>
          </archive>
        </configuration>
      </plugin>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-shade-plugin</artifactId>
        <version>2.1</version>
        <executions>
          <execution>
            <phase>package</phase>
            <goals>
              <goal>shade</goal>
            </goals>
            <configuration>
              <relocations>
                <relocation>
                  <pattern>org.bouncycastle</pattern>
                  <shadedPattern>net.minecraft.v${minecraft_version}.org.bouncycastle</shadedPattern>
                </relocation>
                <relocation>
                  <pattern>joptsimple</pattern>
                  <shadedPattern>org.bukkit.craftbukkit.libs.joptsimple</shadedPattern>
                </relocation>
                <relocation>
                  <pattern>jline</pattern>
                  <shadedPattern>org.bukkit.craftbukkit.libs.jline</shadedPattern>
                </relocation>
                <relocation>
                  <pattern>org.ibex</pattern>
                  <shadedPattern>org.bukkit.craftbukkit.libs.org.ibex</shadedPattern>
                </relocation>
                <relocation>
                  <pattern>org.gjt</pattern>
                  <shadedPattern>org.bukkit.craftbukkit.libs.org.gjt</shadedPattern>
                </relocation>
                <relocation>
                  <pattern>com.google.gson</pattern>
                  <shadedPattern>org.bukkit.craftbukkit.libs.com.google.gson</shadedPattern>
                </relocation>
                <!-- These contain native libraries, and cannot be properly relocated
               <relocation>
                 <pattern>org.fusesource</pattern>
                 <shadedPattern>org.bukkit.craftbukkit.libs.${project.dependencies[4].version}.org.fusesource</shadedPattern>
               </relocation>
               <relocation>
                 <pattern>org.sqlite</pattern>
                 <shadedPattern>org.bukkit.craftbukkit.libs.${project.dependencies[5].version}.org.sqlite</shadedPattern>
               </relocation>
               <relocation>
                 <pattern>com.mysql</pattern>
                 <shadedPattern>org.bukkit.craftbukkit.libs.${project.dependencies[6].version}.com.mysql</shadedPattern>
               </relocation>
               !-->
                <relocation>
                    <pattern>org.bukkit.craftbukkit</pattern>
                    <shadedPattern>org.bukkit.craftbukkit.v${minecraft_version}</shadedPattern>
                    <excludes>
                        <exclude>org.bukkit.craftbukkit.Main*</exclude>
                    </excludes>
                </relocation>
                <relocation>
                    <pattern>net.minecraft.server</pattern>
                    <shadedPattern>net.minecraft.server.v${minecraft_version}</shadedPattern>
                </relocation>
              </relocations>
            </configuration>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>2.3.2</version>
        <configuration>
          <source>1.6</source>
          <target>1.6</target>
        </configuration>
      </plugin>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-surefire-plugin</artifactId>
        <version>2.11</version>
        <configuration>
          <workingDirectory>${basedir}/target/test-server</workingDirectory>
            <excludes>
              <exclude>org/bukkit/craftbukkit/updater/BukkitDLUpdaterServiceTest.java</exclude>
              <exclude>org/bukkit/craftbukkit/inventory/ItemStack*Test.java</exclude>
            </excludes>
        </configuration>
      </plugin>
      <plugin>
        <artifactId>maven-resources-plugin</artifactId>
        <version>2.4.3</version>
        <executions>
          <execution>
            <id>maps-file</id>
            <phase>package</phase>
            <goals>
              <goal>copy-resources</goal>
            </goals>
            <configuration>
              <outputDirectory>${basedir}/target</outputDirectory>
              <resources>
                <resource>
                  <directory>${basedir}</directory>
                  <filtering>true</filtering>
                  <includes>
                    <include>maps.yml</include>
                  </includes>
                </resource>
              </resources>
            </configuration>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <groupId>com.wolvereness</groupId>
        <artifactId>overmapped</artifactId>
        <version>0.0.2</version>
        <executions>
          <execution>
            <phase>package</phase>
            <goals>
              <goal>map</goal>
            </goals>
            <configuration>
              <maps>${basedir}/target/maps.yml</maps>
              <input>${basedir}/target/${project.artifactId}-${project.version}.jar</input>
              <original>${basedir}/target/unmapped-${project.artifactId}-${project.version}.jar</original>
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins>
    <pluginManagement>
      <plugins>
        <!--This plugin's configuration is used to store Eclipse m2e settings only. It has no influence on the Maven build itself.-->
        <plugin>
          <groupId>org.eclipse.m2e</groupId>
          <artifactId>lifecycle-mapping</artifactId>
          <version>1.0.0</version>
          <configuration>
            <lifecycleMappingMetadata>
              <pluginExecutions>
                <pluginExecution>
                  <pluginExecutionFilter>
                    <groupId>com.lukegb.mojo</groupId>
                    <artifactId>
                      gitdescribe-maven-plugin
                    </artifactId>
                    <versionRange>[1.3,)</versionRange>
                    <goals>
                      <goal>gitdescribe</goal>
                    </goals>
                  </pluginExecutionFilter>
                  <action>
                    <ignore></ignore>
                  </action>
                </pluginExecution>
              </pluginExecutions>
            </lifecycleMappingMetadata>
          </configuration>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>
</project>

Ok je me perds facilement avec tout ça mais voilà d'où j'ai clone le repo : https://github.com/IPVP-MC/Paper-1.7 et en lisant le readme.md et en exécutant tout on obtient toutes les sources (notamment les dépendances qui n'existent plus). Désolé mais je trouve ça plutôt compliqué...

En effet c'est compliqué, car ce qui est proposé c'est de la bidouille sur de la bidouille...

Ceci étant dit, en suivant les différentes étapes indiquées sur le site (git clone, git submodule update --init, ./applyPatches.sh, mvn clean install) et en rajoutant la procédure que j'ai indiqué (mvn eclipse:eclipse) on a bien un projet complet que tu peux importer dans Eclipse.

Il y a effectivement des erreurs affichées par Eclipse au niveau des pom.xml mais ce sont des faux positifs.
Tant que Maven arrive à builder le projet (en ligne de commandes) c'est le plus important, Eclipse ne sert qu'à éditer le code et à ce niveau là il n'y a pas d'erreur.

Remarque : il y a 6 fichiers pom.xml quand tu ne m'en indiquais qu'un seul (deux fois le même)

Normalement ce problème de compilation tu aurais du l'avoir aussi avant de modifier le code...

Tu as l'air d'être sous Windows 10, que je ne connais pas trop, mais normalement il faudrait mettre le JDK en tête du PATH, en particulier avant les autres JRE, parce que là tu as 4 entrées dans le PATH qui pointent vers Java, il doit prendre la première mais ce n'est pas un JDK...

Je te conseilles de supprimer les 4 entrées de Java et d'ajouter le JAVA_HOME en tête.
En invites de commande si tu tapes

mvn --version

tu devrais obtenir ce résultat :

Java version: 1.8.0_181, vendor: Oracle Corporation, runtime: C:\Program Files\Java\jdk1.8.0_181\jre

Comme tu peux le voir j'ai fait exactement ce que tu m'as dit et j'ai exactement la même erreur, je ne comprends pas pourquoi... :

Le résultat de la commande

mvn --version

semble plutôt bon pourtant.
Dans ton image tu sembles modifier la variable système Path (en bas), que contient la variable utilisateur Path (en haut) ? Si elle contient d'autres références à Java il faudrait aussi les supprimer.

Il n'y a pas de références à Java, je ne comprends pas...

C'est bizarre le "path de maven" dans eclipse pointe vers le jre : https://prnt.sc/kswgxo
Un moyen de le modifier peut-être ou je dois essayer de réinstaller maven ?