DuplicateFinderMojo.java

/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.basepom.mojo.duplicatefinder;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.AbstractMap.SimpleImmutableEntry;
import java.util.Arrays;
import java.util.Collection;
import java.util.EnumSet;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.SortedSet;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;

import javax.xml.stream.XMLStreamException;

import com.google.common.base.Strings;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Maps;
import com.google.common.collect.Multimap;
import com.google.common.hash.HashFunction;
import com.google.common.hash.Hashing;
import com.google.common.io.ByteStreams;
import com.google.common.io.Closer;
import org.apache.maven.artifact.Artifact;
import org.apache.maven.artifact.DependencyResolutionRequiredException;
import org.apache.maven.artifact.versioning.InvalidVersionSpecificationException;
import org.apache.maven.artifact.versioning.OverConstrainedVersionException;
import org.apache.maven.model.Dependency;
import org.apache.maven.plugin.AbstractMojo;
import org.apache.maven.plugin.MojoExecutionException;
import org.apache.maven.plugin.MojoFailureException;
import org.apache.maven.plugins.annotations.LifecyclePhase;
import org.apache.maven.plugins.annotations.Mojo;
import org.apache.maven.plugins.annotations.Parameter;
import org.apache.maven.plugins.annotations.ResolutionScope;
import org.apache.maven.project.MavenProject;
import org.basepom.mojo.duplicatefinder.ResultCollector.ConflictResult;
import org.basepom.mojo.duplicatefinder.artifact.ArtifactFileResolver;
import org.basepom.mojo.duplicatefinder.artifact.MavenCoordinates;
import org.basepom.mojo.duplicatefinder.classpath.ClasspathDescriptor;
import org.codehaus.stax2.XMLOutputFactory2;
import org.codehaus.staxmate.SMOutputFactory;
import org.codehaus.staxmate.out.SMOutputDocument;
import org.codehaus.staxmate.out.SMOutputElement;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import static java.lang.String.format;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import static org.apache.maven.artifact.Artifact.SCOPE_COMPILE;
import static org.apache.maven.artifact.Artifact.SCOPE_PROVIDED;
import static org.apache.maven.artifact.Artifact.SCOPE_RUNTIME;
import static org.apache.maven.artifact.Artifact.SCOPE_SYSTEM;
import static org.basepom.mojo.duplicatefinder.ConflictState.CONFLICT_CONTENT_DIFFERENT;
import static org.basepom.mojo.duplicatefinder.ConflictState.CONFLICT_CONTENT_EQUAL;
import static org.basepom.mojo.duplicatefinder.ConflictType.CLASS;
import static org.basepom.mojo.duplicatefinder.ConflictType.RESOURCE;
import static org.basepom.mojo.duplicatefinder.artifact.ArtifactHelper.getOutputDirectory;
import static org.basepom.mojo.duplicatefinder.artifact.ArtifactHelper.getTestOutputDirectory;

/**
 * Finds duplicate classes/resources on the classpath.
 */
@Mojo(name = "check", requiresProject = true, threadSafe = true, defaultPhase = LifecyclePhase.VERIFY, requiresDependencyResolution = ResolutionScope.TEST)
public final class DuplicateFinderMojo extends AbstractMojo {

    private static final Logger LOG = LoggerFactory.getLogger(DuplicateFinderMojo.class);

    private static final int SAVE_FILE_VERSION = 1;

    private static final HashFunction SHA_256 = Hashing.sha256();

    private static final Set<String> COMPILE_SCOPE = ImmutableSet.of(SCOPE_COMPILE, SCOPE_PROVIDED, SCOPE_SYSTEM);
    private static final Set<String> RUNTIME_SCOPE = ImmutableSet.of(SCOPE_COMPILE, SCOPE_RUNTIME);
    private static final Set<String> TEST_SCOPE = ImmutableSet.of(); // Empty == all scopes

    /**
     * The maven project (effective pom).
     */
    @Parameter(defaultValue = "${project}", readonly = true)
    public MavenProject project;

    /**
     * Report files that have the same sha256 has value.
     *
     * @since 1.0.6
     */
    @Parameter(defaultValue = "false", property = "duplicate-finder.printEqualFiles")
    public boolean printEqualFiles = false;

    /**
     * Fail the build if files with the same name but different content are detected.
     *
     * @since 1.0.3
     */
    @Parameter(defaultValue = "false", property = "duplicate-finder.failBuildInCaseOfDifferentContentConflict")
    public boolean failBuildInCaseOfDifferentContentConflict = false;

    /**
     * Fail the build if files with the same name and the same content are detected.
     *
     * @since 1.0.3
     */
    @Parameter(defaultValue = "false", property = "duplicate-finder.failBuildInCaseOfEqualContentConflict")
    public boolean failBuildInCaseOfEqualContentConflict = false;

    /**
     * Fail the build if any files with the same name are found.
     */
    @Parameter(defaultValue = "false", property = "duplicate-finder.failBuildInCaseOfConflict")
    public boolean failBuildInCaseOfConflict = false;

    /**
     * Use the default resource ignore list.
     */
    @Parameter(defaultValue = "true", property = "duplicate-finder.useDefaultResourceIgnoreList")
    public boolean useDefaultResourceIgnoreList = true;

    /**
     * Use the default class ignore list.
     *
     * @since 1.2.1
     */
    @Parameter(defaultValue = "true", property = "duplicate-finder.useDefaultClassIgnoreList")
    public boolean useDefaultClassIgnoreList = true;

    /**
     * Ignored resources, which are not checked for multiple occurences.
     */
    @Parameter
    public String[] ignoredResourcePatterns = new String[0];

    /**
     * Ignored classes, which are not checked for multiple occurences.
     *
     * @since 1.2.1
     */
    @Parameter
    public String[] ignoredClassPatterns = new String[0];

    /**
     * Artifacts with expected and resolved versions that are checked.
     */
    @Parameter(alias = "exceptions")
    public ConflictingDependency[] conflictingDependencies = new ConflictingDependency[0];

    /**
     * Dependencies that should not be checked at all.
     */
    @Parameter(alias = "ignoredDependencies")
    public MavenCoordinates[] ignoredDependencies = new MavenCoordinates[0];

    /**
     * Check resources and classes on the compile class path.
     */
    @Parameter(defaultValue = "true", property = "duplicate-finder.checkCompileClasspath")
    public boolean checkCompileClasspath = true;

    /**
     * Check resources and classes on the runtime class path.
     */
    @Parameter(defaultValue = "true", property = "duplicate-finder.checkRuntimeClasspath")
    public boolean checkRuntimeClasspath = true;

    /**
     * Check resources and classes on the test class path.
     */
    @Parameter(defaultValue = "true", property = "duplicate-finder.checkTestClasspath")
    public boolean checkTestClasspath = true;

    /**
     * Skips the plugin execution.
     */
    @Parameter(defaultValue = "false", property = "duplicate-finder.skip")
    public boolean skip = false;

    /**
     * Quiets the plugin (report only errors).
     *
     * @since 1.1.0
     * @deprecated Maven logging controls the log level now.
     */
    @Parameter(defaultValue = "false", property = "duplicate-finder.quiet")
    @Deprecated
    public boolean quiet = false;

    /**
     * Whether existing local directories with classes or existing artifacts are preferred.
     *
     * @since 1.1.0
     */
    @Parameter(defaultValue = "true", property = "duplicate-finder.preferLocal")
    public boolean preferLocal = true;

    /**
     * Output file for the result of the plugin.
     *
     * @since 1.1.0
     */
    @Parameter(defaultValue = "${project.build.directory}/duplicate-finder-result.xml", property = "duplicate-finder.resultFile")
    public File resultFile;

    /**
     * Write result to output file.
     *
     * @since 1.1.0
     */
    @Parameter(defaultValue = "true", property = "duplicate-finder.useResultFile")
    public boolean useResultFile = true;

    /**
     * Minimum occurences on the class path to be listed in the result file.
     *
     * @since 1.1.0
     */
    @Parameter(defaultValue = "2", property = "duplicate-finder.resultFileMinClasspathCount")
    public int resultFileMinClasspathCount = 2;

    /**
     * Include the boot class path in duplicate detection. This will find duplicates with the JDK
     * internal classes (e.g. the classes in rt.jar).
     *
     * @since 1.1.1
     * @deprecated Inspecting the boot classpath is no longer supported in Java 9+
     */
    @Parameter(defaultValue = "false", property = "duplicate-finder.includeBootClasspath")
    @Deprecated
    public boolean includeBootClasspath = false;

    /**
     * System property that contains the boot class path.
     *
     * @since 1.1.1
     * @deprecated Inspecting the boot classpath is no longer supported in Java 9+
     */
    @Parameter(property = "duplicate-finder.bootClasspathProperty")
    @Deprecated
    public String bootClasspathProperty = null;

    /**
     * Include POM projects in validation.
     *
     * @since 1.2.0
     */
    @Parameter(defaultValue = "false", property = "duplicate-finder.includePomProjects")
    public boolean includePomProjects = false;

    private final EnumSet<ConflictState> printState = EnumSet.of(CONFLICT_CONTENT_DIFFERENT);
    private final EnumSet<ConflictState> failState = EnumSet.noneOf(ConflictState.class);

    // called by maven
    public void setIgnoredDependencies(final Dependency[] dependencies) throws InvalidVersionSpecificationException {
        checkArgument(dependencies != null);

        this.ignoredDependencies = new MavenCoordinates[dependencies.length];
        for (int idx = 0; idx < dependencies.length; idx++) {
            this.ignoredDependencies[idx] = new MavenCoordinates(dependencies[idx]);
        }
    }

    @Override
    public void execute() throws MojoExecutionException, MojoFailureException {
        if (skip) {
            LOG.info("Skipping duplicate-finder execution!");
        } else if (!includePomProjects && "pom".equals(project.getArtifact().getType())) {
            LOG.info("Ignoring POM project!");
        } else {
            if (printEqualFiles) {
                printState.add(CONFLICT_CONTENT_EQUAL);
            }

            if (failBuildInCaseOfConflict || failBuildInCaseOfEqualContentConflict) {
                printState.add(CONFLICT_CONTENT_EQUAL);

                failState.add(CONFLICT_CONTENT_EQUAL);
                failState.add(CONFLICT_CONTENT_DIFFERENT);
            }

            if (failBuildInCaseOfDifferentContentConflict) {
                failState.add(CONFLICT_CONTENT_DIFFERENT);
            }

            if (includeBootClasspath) {
                LOG.warn("<includeBootClasspath> is no longer supported and will be ignored!");
            }
            if (bootClasspathProperty != null) {
                LOG.warn("<bootClasspathProperty> is no longer supported and will be ignored!");
            }

            if (quiet) {
                LOG.warn("<quiet> is no longer supported and will be ignored!");
            }

            try {
                // Prep conflicting dependencies
                MavenCoordinates projectCoordinates = new MavenCoordinates(project.getArtifact());

                for (ConflictingDependency conflictingDependency : conflictingDependencies) {
                    conflictingDependency.addProjectMavenCoordinates(projectCoordinates);
                }

                final ArtifactFileResolver artifactFileResolver = new ArtifactFileResolver(project, preferLocal);
                final ImmutableMap.Builder<String, Entry<ResultCollector, ClasspathDescriptor>> classpathResultBuilder = ImmutableMap.builder();

                if (checkCompileClasspath) {
                    LOG.info("Checking compile classpath");
                    final ResultCollector resultCollector = new ResultCollector(printState, failState);
                    final ClasspathDescriptor classpathDescriptor = checkClasspath(resultCollector, artifactFileResolver, COMPILE_SCOPE,
                            getOutputDirectory(project));
                    classpathResultBuilder.put("compile", new SimpleImmutableEntry<>(resultCollector, classpathDescriptor));
                }

                if (checkRuntimeClasspath) {
                    LOG.info("Checking runtime classpath");
                    final ResultCollector resultCollector = new ResultCollector(printState, failState);
                    final ClasspathDescriptor classpathDescriptor = checkClasspath(resultCollector, artifactFileResolver, RUNTIME_SCOPE,
                            getOutputDirectory(project));
                    classpathResultBuilder.put("runtime", new SimpleImmutableEntry<>(resultCollector, classpathDescriptor));
                }

                if (checkTestClasspath) {
                    LOG.info("Checking test classpath");
                    final ResultCollector resultCollector = new ResultCollector(printState, failState);
                    final ClasspathDescriptor classpathDescriptor = checkClasspath(resultCollector,
                            artifactFileResolver,
                            TEST_SCOPE,
                            getOutputDirectory(project),
                            getTestOutputDirectory(project));
                    classpathResultBuilder.put("test", new SimpleImmutableEntry<>(resultCollector, classpathDescriptor));
                }

                final ImmutableMap<String, Entry<ResultCollector, ClasspathDescriptor>> classpathResults = classpathResultBuilder.build();

                if (useResultFile) {
                    checkState(resultFile != null, "resultFile must be set if useResultFile is true");
                    writeResultFile(resultFile, classpathResults);
                }

                boolean failed = false;

                for (Map.Entry<String, Entry<ResultCollector, ClasspathDescriptor>> classpathEntry : classpathResults.entrySet()) {
                    String classpathName = classpathEntry.getKey();
                    ResultCollector resultCollector = classpathEntry.getValue().getKey();

                    for (final ConflictState state : printState) {
                        for (final ConflictType type : ConflictType.values()) {
                            if (resultCollector.hasConflictsFor(type, state)) {
                                final Map<String, Collection<ConflictResult>> results = resultCollector.getResults(type, state);
                                for (final Map.Entry<String, Collection<ConflictResult>> entry : results.entrySet()) {
                                    final String artifactNames = entry.getKey();
                                    final Collection<ConflictResult> conflictResults = entry.getValue();

                                    LOG.warn(format("Found duplicate %s %s in [%s]:", state.getHint(), type.getType(), artifactNames));
                                    for (final ConflictResult conflictResult : conflictResults) {
                                        LOG.warn(format("  %s", conflictResult.getName()));
                                    }
                                }
                            }
                        }
                    }

                    failed |= resultCollector.isFailed();

                    if (resultCollector.isFailed()) {
                        LOG.warn(format("Found duplicate classes/resources in %s classpath.", classpathName));
                    }
                }

                if (failed) {
                    throw new MojoExecutionException("Found duplicate classes/resources!");
                }
            } catch (final DependencyResolutionRequiredException e) {
                throw new MojoFailureException("Could not resolve dependencies", e);
            } catch (final InvalidVersionSpecificationException e) {
                throw new MojoFailureException("Invalid version specified", e);
            } catch (final OverConstrainedVersionException e) {
                throw new MojoFailureException("Version too constrained", e);
            } catch (final IOException e) {
                throw new MojoExecutionException("While loading artifacts", e);
            }
        }
    }

    private ImmutableSet<String> getIgnoredResourcePatterns() {
        ImmutableSet.Builder<String> builder = ImmutableSet.builder();
        builder.add(ignoredResourcePatterns);

        return builder.build();
    }

    private ImmutableSet<String> getIgnoredClassPatterns() {
        ImmutableSet.Builder<String> builder = ImmutableSet.builder();
        builder.add(ignoredClassPatterns);

        return builder.build();
    }

    /**
     * Checks the maven classpath for a given set of scopes whether it contains duplicates. In addition to the
     * artifacts on the classpath, one or more additional project folders are added.
     */
    private ClasspathDescriptor checkClasspath(final ResultCollector resultCollector,
            final ArtifactFileResolver artifactFileResolver,
            final Set<String> scopes,
            final File... projectFolders)
            throws MojoExecutionException, InvalidVersionSpecificationException, OverConstrainedVersionException, DependencyResolutionRequiredException {

        // Map of files to artifacts. Depending on the type of build, referenced projects in a multi-module build
        // may be local folders in the project instead of repo jar references.
        final Multimap<File, Artifact> fileToArtifactMap = artifactFileResolver.resolveArtifactsForScopes(scopes);

        final ClasspathDescriptor classpathDescriptor = ClasspathDescriptor.createClasspathDescriptor(project,
                fileToArtifactMap,
                getIgnoredResourcePatterns(),
                getIgnoredClassPatterns(),
                Arrays.asList(ignoredDependencies),
                useDefaultResourceIgnoreList,
                useDefaultClassIgnoreList,
                projectFolders);

        // Now a scope specific classpath descriptor (scope relevant artifacts and project folders) and the global artifact resolver
        // are primed. Run conflict resolution for classes and resources.
        checkForDuplicates(CLASS, resultCollector, classpathDescriptor, artifactFileResolver);
        checkForDuplicates(RESOURCE, resultCollector, classpathDescriptor, artifactFileResolver);
        return classpathDescriptor;
    }

    private void checkForDuplicates(final ConflictType type, final ResultCollector resultCollector, final ClasspathDescriptor classpathDescriptor,
            final ArtifactFileResolver artifactFileResolver)
            throws OverConstrainedVersionException {
        // only look at entries with a size > 1.
        final Map<String, Collection<File>> filteredMap = ImmutableMap.copyOf(Maps.filterEntries(classpathDescriptor.getClasspathElementLocations(type),
                entry -> {
                    checkNotNull(entry, "entry is null");
                    checkState(entry.getValue() != null, "Entry '%s' is invalid", entry);

                    return entry.getValue().size() > 1;
                }));

        for (final Map.Entry<String, Collection<File>> entry : filteredMap.entrySet()) {
            final String name = entry.getKey();
            final Collection<File> elements = entry.getValue();

            // Map which contains a printable name for the conflicting entry (which is either the printable name for an artifact or
            // a folder name for a project folder) as keys and a classpath element as value.
            final SortedSet<ClasspathElement> conflictingClasspathElements = artifactFileResolver.getClasspathElementsForElements(elements);

            ImmutableSet.Builder<Artifact> artifactBuilder = ImmutableSet.builder();

            for (ClasspathElement conflictingClasspathElement : conflictingClasspathElements) {
                if (conflictingClasspathElement.hasArtifact()) {
                    artifactBuilder.add(conflictingClasspathElement.getArtifact());
                } else if (conflictingClasspathElement.isLocalFolder()) {
                    artifactBuilder.add(project.getArtifact());
                }
            }

            final boolean excepted = isExcepted(type, name, artifactBuilder.build());
            final ConflictState conflictState = DuplicateFinderMojo.determineConflictState(type, name, elements);

            resultCollector.addConflict(type, name, conflictingClasspathElements, excepted, conflictState);
        }
    }

    /**
     * Detects class/resource differences via SHA256 hash comparison.
     */
    private static ConflictState determineConflictState(final ConflictType type, final String name, final Iterable<File> elements) {
        File firstFile = null;
        String firstSHA256 = null;

        final String resourcePath = type == ConflictType.CLASS ? name.replace('.', '/') + ".class" : name;

        for (final File element : elements) {
            try {
                final String newSHA256 = getSHA256HexOfElement(element, resourcePath);

                if (firstSHA256 == null) {
                    // save sha256 hash from the first element
                    firstSHA256 = newSHA256;
                    firstFile = element;
                } else if (!newSHA256.equals(firstSHA256)) {
                    LOG.debug(format("Found different SHA256 hashes for elements %s in file %s and %s", resourcePath, firstFile, element));
                    return ConflictState.CONFLICT_CONTENT_DIFFERENT;
                }
            } catch (final IOException ex) {
                LOG.warn(format("Could not read content from file %s!", element), ex);
            }
        }

        return ConflictState.CONFLICT_CONTENT_EQUAL;
    }

    /**
     * Calculates the SHA256 Hash of a class in a file.
     *
     * @param file         the archive contains the class
     * @param resourcePath the name of the class
     * @return the MD% Hash as Hex-Value
     * @throws IOException if any error occurs on reading class in archive
     */
    private static String getSHA256HexOfElement(final File file, final String resourcePath) throws IOException {

        try (Closer closer = Closer.create()) {
            InputStream in;

            if (file.isDirectory()) {
                final File resourceFile = new File(file, resourcePath);
                in = closer.register(new BufferedInputStream(new FileInputStream(resourceFile)));
            } else {
                final ZipFile zip = new ZipFile(file);

                closer.register(zip::close);

                final ZipEntry zipEntry = zip.getEntry(resourcePath);

                if (zipEntry == null) {
                    throw new IOException(format("Could not find %s in archive %s", resourcePath, file));
                }

                in = zip.getInputStream(zipEntry);
            }

            return SHA_256.newHasher().putBytes(ByteStreams.toByteArray(in)).hash().toString();
        }
    }

    private boolean isExcepted(final ConflictType type, final String name, final Set<Artifact> artifacts)
            throws OverConstrainedVersionException {
        final ImmutableSet.Builder<ConflictingDependency> conflictBuilder = ImmutableSet.builder();
        checkState(conflictingDependencies != null, "conflictingDependencies is null");

        // Find all exception definitions from the configuration that match these artifacts.
        for (final ConflictingDependency conflictingDependency : conflictingDependencies) {
            if (conflictingDependency.isForArtifacts(artifacts)) {
                conflictBuilder.add(conflictingDependency);
            }
        }

        // If any of the possible candidates covers this class or resource, then the conflict is excepted.
        for (final ConflictingDependency conflictingDependency : conflictBuilder.build()) {
            if (type == ConflictType.CLASS && conflictingDependency.containsClass(name)) {
                return true;
            } else if (type == ConflictType.RESOURCE && conflictingDependency.containsResource(name)) {
                return true;
            }
        }
        return false;
    }

    private void writeResultFile(File resultFile, ImmutableMap<String, Entry<ResultCollector, ClasspathDescriptor>> results)
            throws MojoExecutionException, InvalidVersionSpecificationException, OverConstrainedVersionException {
        File parent = resultFile.getParentFile();
        if (!parent.exists()) {
            if (!parent.mkdirs()) {
                throw new MojoExecutionException("Could not create parent folders for " + parent.getAbsolutePath());
            }
        }
        if (!parent.isDirectory() || !parent.canWrite()) {
            throw new MojoExecutionException("Can not create result file in " + parent.getAbsolutePath());
        }

        try {
            SMOutputFactory factory = new SMOutputFactory(XMLOutputFactory2.newFactory());
            SMOutputDocument resultDocument = factory.createOutputDocument(resultFile);
            resultDocument.setIndentation("\n" + Strings.repeat(" ", 64), 1, 4);

            SMOutputElement rootElement = resultDocument.addElement("duplicate-finder-result");
            XMLWriterUtils.addAttribute(rootElement, "version", SAVE_FILE_VERSION);

            XMLWriterUtils.addProjectInformation(rootElement, project);

            addConfiguration(rootElement);

            SMOutputElement resultsElement = rootElement.addElement("results");
            for (Map.Entry<String, Entry<ResultCollector, ClasspathDescriptor>> entry : results.entrySet()) {
                SMOutputElement resultElement = resultsElement.addElement("result");
                XMLWriterUtils.addAttribute(resultElement, "name", entry.getKey());
                XMLWriterUtils.addResultCollector(resultElement, entry.getValue().getKey());
                XMLWriterUtils.addClasspathDescriptor(resultElement, resultFileMinClasspathCount, entry.getValue().getValue());
            }

            resultDocument.closeRootAndWriter();
        } catch (XMLStreamException e) {
            throw new MojoExecutionException("While writing result file", e);
        }
    }

    private void addConfiguration(SMOutputElement rootElement)
            throws XMLStreamException {
        SMOutputElement prefs = XMLWriterUtils.addElement(rootElement, "configuration", null);
        // Simple configuration options
        XMLWriterUtils.addAttribute(prefs, "skip", skip);
        XMLWriterUtils.addAttribute(prefs, "checkCompileClasspath", checkCompileClasspath);
        XMLWriterUtils.addAttribute(prefs, "checkRuntimeClasspath", checkRuntimeClasspath);
        XMLWriterUtils.addAttribute(prefs, "checkTestClasspath", checkTestClasspath);
        XMLWriterUtils.addAttribute(prefs, "failBuildInCaseOfDifferentContentConflict", failBuildInCaseOfDifferentContentConflict);
        XMLWriterUtils.addAttribute(prefs, "failBuildInCaseOfEqualContentConflict", failBuildInCaseOfEqualContentConflict);
        XMLWriterUtils.addAttribute(prefs, "failBuildInCaseOfConflict", failBuildInCaseOfConflict);
        XMLWriterUtils.addAttribute(prefs, "printEqualFiles", printEqualFiles);
        XMLWriterUtils.addAttribute(prefs, "preferLocal", preferLocal);
        XMLWriterUtils.addAttribute(prefs, "includePomProjects", includePomProjects);
        // Ignoring Dependencies and resources
        XMLWriterUtils.addAttribute(prefs, "useDefaultResourceIgnoreList", useDefaultResourceIgnoreList);
        XMLWriterUtils.addAttribute(prefs, "useDefaultClassIgnoreList", useDefaultClassIgnoreList);
        // Result file options
        XMLWriterUtils.addAttribute(prefs, "useResultFile", useResultFile);
        XMLWriterUtils.addAttribute(prefs, "resultFileMinClasspathCount", resultFileMinClasspathCount);
        XMLWriterUtils.addAttribute(prefs, "resultFile", resultFile.getAbsolutePath());

        SMOutputElement ignoredResourcesElement = prefs.addElement("ignoredResourcePatterns");
        for (String ignoredResource : getIgnoredResourcePatterns()) {
            XMLWriterUtils.addElement(ignoredResourcesElement, "ignoredResourcePattern", ignoredResource);
        }

        SMOutputElement ignoredClassElement = prefs.addElement("ignoredClassPatterns");
        for (String ignoredClass : getIgnoredClassPatterns()) {
            XMLWriterUtils.addElement(ignoredClassElement, "ignoredClassPattern", ignoredClass);
        }

        SMOutputElement conflictingDependenciesElement = prefs.addElement("conflictingDependencies");
        for (ConflictingDependency conflictingDependency : conflictingDependencies) {
            XMLWriterUtils.addConflictingDependency(conflictingDependenciesElement, "conflictingDependency", conflictingDependency);
        }

        SMOutputElement ignoredDependenciesElement = prefs.addElement("ignoredDependencies");
        for (MavenCoordinates ignoredDependency : ignoredDependencies) {
            XMLWriterUtils.addMavenCoordinate(ignoredDependenciesElement, "dependency", ignoredDependency);
        }
    }
}