Dependency on the plugin via Maven

Hello.
I'm making a project that uses two dependencies (except Spigot): JDA and my plugin.
The problem is that if I connect my plugin via Maven, then when accessing any method of its class (for example, the same getInstance of any class), it returns null.
I could connect his jar directly to the project, but you can't connect JDA like that, and I need to use both.

How to solve this problem?

Example of a class from a plugin:

Code:

public class DatabaseEditor {

    static Connection connection;
    public static DatabaseEditor instance;

    public DatabaseEditor(Connection con) {
        connection = con;
        QChat.getInstance().getLogger().info("DB Connected");
        String query = "CREATE TABLE IF NOT EXISTS 'users' (" +
                "'username' TEXT NOT NULL UNIQUE, " +
                "'chat' TEXT NOT NULL " +
                ")";
        try {
            Statement statement = connection.createStatement();
            statement.executeUpdate(query);
            String query_delete = "DELETE FROM users";
            statement.executeUpdate(query_delete);
            statement.close();
            QChat.getInstance().getLogger().info("DB Table created.");
        } catch (SQLException e) {
            e.printStackTrace();
        }
        instance = this;
    }

    public static void selectChat(Player player, Chat chat) {
        String name = player.getName();
        String query = String.format("INSERT INTO users VALUES('%s', '%s')", name, chat.getName());
        String query_delete = String.format("DELETE FROM 'users' WHERE username='%s'", name);
        try {
            Statement statement = connection.createStatement();
            statement.executeUpdate(query_delete);
            statement.executeUpdate(query);
            statement.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public static String getSelectedChat(Player player) {
        String name = player.getName();
        String query = "SELECT chat FROM users WHERE username = '" + name + "'";
        String result = "none";
        try {
            Statement statement = connection.createStatement();
            ResultSet rs = statement.executeQuery(query);
            while(rs.next()) {
                result = rs.getString("chat");
            }
            statement.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return result;
    }

    public static DatabaseEditor getInstance() {
        return instance;
    }

}

Code for accessing the plugin

Code:

if(DatabaseEditor.getSelectedChat(event.getPlayer()).equals(ChatGlobal.getInstance().getName())) {

Error in the console

Code:

[16:55:30 ERROR]: Could not pass event AsyncPlayerChatEvent to (название плагина) v1.0                                        java.lang.NullPointerException: Cannot invoke "java.sql.Connection.createStatement()" because "quietw.qchat.Database.DatabaseEditor.connection" is null

ps: spigot version - 1.18, tried with spigot and paper both

add:

"API" pom.xml:

Code:

<?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>quietw</groupId> <artifactId>qchat</artifactId> <version>1.3.3</version> <packaging>jar</packaging> <name>QChat</name> <properties> <java.version>1.8</java.version> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> </properties> <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <version>3.8.1</version> <configuration> <source>${java.version}</source> <target>${java.version}</target> </configuration> </plugin> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-shade-plugin</artifactId> <version>3.2.4</version> <executions> <execution> <phase>package</phase> <goals> <goal>shade</goal> </goals> <configuration> <createDependencyReducedPom>false</createDependencyReducedPom> </configuration> </execution> </executions> </plugin> </plugins> <resources> <resource> <directory>src/main/resources</directory> <filtering>true</filtering> </resource> </resources> </build> <repositories> <repository> <id>spigotmc-repo</id> <url>https://hub.spigotmc.org/nexus/content/repositories/snapshots/</url> </repository> <repository> <id>sonatype</id> <url>https://oss.sonatype.org/content/groups/public/</url> </repository> </repositories> <dependencies> <dependency> <groupId>org.spigotmc</groupId> <artifactId>spigot-api</artifactId> <version>1.18-R0.1-SNAPSHOT</version> <scope>provided</scope> </dependency> </dependencies></project>

Plugin pom.xml:

Code:

<?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>iqw</groupId>
    <artifactId>discordlogin</artifactId>
    <version>1.0</version>
    <packaging>jar</packaging>

    <name>DiscordLogin</name>

    <properties>
        <java.version>1.8</java.version>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.1</version>
                <configuration>
                    <source>${java.version}</source>
                    <target>${java.version}</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>3.2.4</version>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                        <configuration>
                            <createDependencyReducedPom>false</createDependencyReducedPom>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>

    <repositories>
        <repository>
            <id>spigotmc-repo</id>
            <url>https://hub.spigotmc.org/nexus/content/repositories/snapshots/</url>
        </repository>
        <repository>
            <id>sonatype</id>
            <url>https://oss.sonatype.org/content/groups/public/</url>
        </repository>
    </repositories>

    <dependencies>
        <dependency>
            <groupId>org.spigotmc</groupId>
            <artifactId>spigot-api</artifactId>
            <version>1.18-R0.1-SNAPSHOT</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>net.dv8tion</groupId>
            <artifactId>JDA</artifactId>
            <version>5.0.0-alpha.1</version>
        </dependency>
        <dependency>
            <groupId>quietw</groupId>
            <artifactId>qchat</artifactId>
            <version>1.3.3</version>
        </dependency>
    </dependencies>
</project>

EDIT by Moderator: merged posts, please use the edit button instead of double posting.

 

Your problem is with the dependency itself and not with Maven, otherwise you would get NoSuchMethod or something similar.

 

And how I can fix it? (Dependency was created by me so I can edit it)