PoC for fetching the Java source code of an artifact from a maven repository

GetMethodSourceDemo.java

package demo;

import com.github.javaparser.JavaParser;
import com.github.javaparser.ast.CompilationUnit;
import com.github.javaparser.ast.body.MethodDeclaration;
import org.eclipse.aether.DefaultRepositorySystemSession;
import org.eclipse.aether.RepositorySystem;
import org.eclipse.aether.RepositorySystemSession;
import org.eclipse.aether.artifact.Artifact;
import org.eclipse.aether.artifact.DefaultArtifact;
import org.eclipse.aether.repository.LocalRepository;
import org.eclipse.aether.repository.RemoteRepository;
import org.eclipse.aether.resolution.ArtifactRequest;
import org.eclipse.aether.resolution.ArtifactResolutionException;
import org.eclipse.aether.resolution.ArtifactResult;
import org.eclipse.aether.supplier.RepositorySystemSupplier;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardCopyOption;
import java.util.Collections;
import java.util.Optional;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;

public class GetMethodSourceDemo {

    static class MavenResolver {

        private static RepositorySystem newRepositorySystem() {
            return new RepositorySystemSupplier().get();
        }
        
        public static RepositorySystemSession newRepositorySystemSession(RepositorySystem system) {
            DefaultRepositorySystemSession session = new DefaultRepositorySystemSession();
            session.setLocalRepositoryManager(system.newLocalRepositoryManager(session, new LocalRepository("target/local-repo")));
            return session;
        }

        public static File resolveArtifact(String groupId, String artifactId, String version) throws ArtifactResolutionException {
            RepositorySystem system = newRepositorySystem();
            RepositorySystemSession session = newRepositorySystemSession(system);

            Artifact artifact = new DefaultArtifact(groupId, artifactId, "sources", "jar", version);
            ArtifactRequest request = new ArtifactRequest();
            request.setArtifact(artifact);
            request.setRepositories(Collections.singletonList(new RemoteRepository.Builder("central", "default", "https://repo.maven.apache.org/maven2/").build()));

            ArtifactResult result = system.resolveArtifact(session, request);
            return result.getArtifact().getFile();
        }
    }

    static class SourceExtractor {
        public static String readSourceFile(File jarFile, String className) throws IOException {
            try (JarFile jar = new JarFile(jarFile)) {
                String entryName = className.replace('.', '/') + ".java";
                JarEntry entry = jar.getJarEntry(entryName);
                if (entry != null) {
                    try (InputStream input = jar.getInputStream(entry)) {
                        Path tempFile = Files.createTempFile("source-", ".java");
                        Files.copy(input, tempFile, StandardCopyOption.REPLACE_EXISTING);
                        return new String(Files.readAllBytes(tempFile), StandardCharsets.UTF_8);
                    }
                } else {
                    throw new IOException("Source file for class " + className + " not found in JAR");
                }
            }
        }
    }

    static class MethodExtractor {
        public static String getMethodSource(String sourceCode, String methodName) {
            CompilationUnit cu = new JavaParser().parse(sourceCode).getResult().orElseThrow();
            Optional<MethodDeclaration> method = cu.findAll(MethodDeclaration.class).stream().filter(m -> m.getNameAsString().equals(methodName)).findFirst();
            return method.map(MethodDeclaration::toString).orElse(null);
        }
    }

    public static void main(String[] args) throws Exception {
        File sourceFile = MavenResolver.resolveArtifact("org.springframework", "spring-core", "6.1.10");
        String sourceCode = SourceExtractor.readSourceFile(sourceFile, "org.springframework.util.Assert");
        String methodSource = MethodExtractor.getMethodSource(sourceCode, "assignableCheckFailed");
        System.out.println("Method source: \n" + methodSource);
    }

}

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>
    <parent>
        <groupId>com.github.thomasdarimont.training</groupId>
        <artifactId>java-workbench</artifactId>
        <version>1.0-SNAPSHOT</version>
    </parent>

    <groupId>org.example</groupId>
    <artifactId>lib-maven-aether</artifactId>


    <properties>
        <java.version>22</java.version>
        <java.release>22</java.release>
        <maven-aether.version>1.1.0</maven-aether.version>
        <javaparser.version>3.26.0</javaparser.version>
        <maven-resolver.version>1.9.20</maven-resolver.version>
    </properties>

    <dependencies>

        <dependency>
            <groupId>org.apache.maven.resolver</groupId>
            <artifactId>maven-resolver-api</artifactId>
            <version>${maven-resolver.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.maven.resolver</groupId>
            <artifactId>maven-resolver-spi</artifactId>
            <version>${maven-resolver.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.maven.resolver</groupId>
            <artifactId>maven-resolver-supplier</artifactId>
            <version>${maven-resolver.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.maven.resolver</groupId>
            <artifactId>maven-resolver-util</artifactId>
            <version>${maven-resolver.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.maven.resolver</groupId>
            <artifactId>maven-resolver-impl</artifactId>
            <version>${maven-resolver.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.maven.resolver</groupId>
            <artifactId>maven-resolver-connector-basic</artifactId>
            <version>${maven-resolver.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.maven.resolver</groupId>
            <artifactId>maven-resolver-transport-http</artifactId>
            <version>${maven-resolver.version}</version>
        </dependency>

        <dependency>
            <groupId>org.apache.maven.resolver</groupId>
            <artifactId>maven-resolver-transport-file</artifactId>
            <version>1.9.13</version>
        </dependency>

        <dependency>
            <groupId>com.github.javaparser</groupId>
            <artifactId>javaparser-core</artifactId>
            <version>${javaparser.version}</version>
        </dependency>
    </dependencies>


</project>