Antlr4 with maven sample project

Question

I haven a Maven project using Antlr4.5 with the following structure:

src/main/antlr4/ArrayInit.g4
src/main/java/Test.java
pom.xml

Test.java:

import org.antlr.v4.runtime.*;
import org.antlr.v4.runtime.tree.*;
public class Test {
    public static void main(String[] args) throws Exception {
        ANTLRInputStream input = new ANTLRInputStream(System.in);
        ArrayInitLexer lexer = new ArrayInitLexer(input);
        CommonTokenStream tokens = new CommonTokenStream(lexer);
        ArrayInitParser parser = new ArrayInitParser(tokens);
        ParseTree tree = parser.init(); // begin parsing at init rule
        System.out.println(tree.toStringTree(parser)); // print LISP-style tree
    }
}

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/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>antlrtest</groupId>
    <artifactId>app1</artifactId>
    <version>1.0-SNAPSHOT</version>

    <build>
        <plugins>
            <plugin>
                <groupId>org.antlr</groupId>
                <artifactId>antlr4-maven-plugin</artifactId>
                <version>4.5</version>
                <executions>
                    <execution>
                        <id>antlr</id>
                        <goals>
                            <goal>antlr4</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

    <dependencies>
        <dependency>
            <groupId>org.antlr</groupId>
            <artifactId>antlr4-runtime</artifactId>
            <version>4.5</version>
        </dependency>
        <dependency>
            <groupId>org.antlr</groupId>
            <artifactId>antlr4-maven-plugin</artifactId>
            <version>4.5</version>
            <type>maven-plugin</type>
        </dependency>
    </dependencies>

</project>

Compiling with

mvn package 

is successful and the antlr generated sources and corresponding classes are created in target/classes.

However running the generated jar with

java -cp target/app1-1.0-SNAPSHOT.jar Test

has the following error as result:

Error: A JNI error has occurred, please check your installation and 

try again
Exception in thread "main" java.lang.NoClassDefFoundError: org/antlr/v4/runtime/CharStream
    at java.lang.Class.getDeclaredMethods0(Native Method)
    at java.lang.Class.privateGetDeclaredMethods(Class.java:2701)
    at java.lang.Class.privateGetMethodRecursive(Class.java:3048)
    at java.lang.Class.getMethod0(Class.java:3018)
    at java.lang.Class.getMethod(Class.java:1784)
    at sun.launcher.LauncherHelper.validateMainClass(LauncherHelper.java:544)
    at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:526)
Caused by: java.lang.ClassNotFoundException: org.antlr.v4.runtime.CharStream
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 7 more

What did I miss?

Answer 1

Seems like ANTLR is not included into the jar. One has to add it via classpath or tell Maven to include its dependencies by putting them into the jar file.

Include dependencies with assembly plugin:

        <plugin>
            <artifactId>maven-assembly-plugin</artifactId>
            <configuration>
                <archive>
                    <manifest>
                        <mainClass>Test</mainClass>
                    </manifest>
                </archive>
                <descriptorRefs>
                    <descriptorRef>jar-with-dependencies</descriptorRef>
                </descriptorRefs>
            </configuration>
            <executions>
                <execution>
                    <id>make-assembly</id> <!-- this is used for inheritance merges -->
                    <phase>package</phase> <!-- bind to the packaging phase -->
                    <goals>
                        <goal>single</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>

Afterwards it can be compiled using

mvn clean package

or

mvn clean compile assembly:single 

It can be executed using

java -jar target/app1-1.0-SNAPSHOT-jar-with-dependencies.jar