Merge branch '2.3.x'

Closes gh-22017

spring-boot-project/spring-boot-tools/spring-boot-buildpack-platform/src/main/java/org/springframework/boot/buildpack/platform/docker/type/ImageName.java

@@ -22,8 +22,10 @@ import org.springframework.util.Assert;
  * A Docker image name of the form {@literal "docker.io/library/ubuntu"}.
  *
  * @author Phillip Webb
+ * @author Scott Frederick
  * @since 2.3.0
  * @see ImageReference
+ * @see ImageReferenceParser
  * @see #of(String)
  */
 public class ImageName {
@@ -41,11 +43,10 @@ public class ImageName {
 	private final String string;
 
 	ImageName(String domain, String name) {
-		Assert.hasText(domain, "Domain must not be empty");
 		Assert.hasText(name, "Name must not be empty");
-		this.domain = domain;
-		this.name = name;
-		this.string = domain + "/" + name;
+		this.domain = getDomainOrDefault(domain);
+		this.name = getNameWithDefaultPath(this.domain, name);
+		this.string = this.domain + "/" + this.name;
 	}
 
 	/**
@@ -100,6 +101,20 @@ public class ImageName {
 		return this.string;
 	}
 
+	private String getDomainOrDefault(String domain) {
+		if (domain == null || LEGACY_DOMAIN.equals(domain)) {
+			return DEFAULT_DOMAIN;
+		}
+		return domain;
+	}
+
+	private String getNameWithDefaultPath(String domain, String name) {
+		if (DEFAULT_DOMAIN.equals(domain) && !name.contains("/")) {
+			return OFFICIAL_REPOSITORY_NAME + "/" + name;
+		}
+		return name;
+	}
+
 	/**
 	 * Create a new {@link ImageName} from the given value. The following value forms can
 	 * be used:
@@ -112,26 +127,9 @@ public class ImageName {
 	 * @return an {@link ImageName} instance
 	 */
 	public static ImageName of(String value) {
-		String[] split = split(value);
-		return new ImageName(split[0], split[1]);
-	}
-
-	static String[] split(String value) {
 		Assert.hasText(value, "Value must not be empty");
-		String domain = DEFAULT_DOMAIN;
-		int firstSlash = value.indexOf('/');
-		if (firstSlash != -1) {
-			String firstSegment = value.substring(0, firstSlash);
-			if (firstSegment.contains(".") || firstSegment.contains(":") || "localhost".equals(firstSegment)) {
-				domain = LEGACY_DOMAIN.equals(firstSegment) ? DEFAULT_DOMAIN : firstSegment;
-				value = value.substring(firstSlash + 1);
-			}
-		}
-		if (DEFAULT_DOMAIN.equals(domain) && !value.contains("/")) {
-			value = OFFICIAL_REPOSITORY_NAME + "/" + value;
-		}
-		return new String[] { domain, value };
-
+		ImageReferenceParser parser = ImageReferenceParser.of(value);
+		return new ImageName(parser.getDomain(), parser.getName());
 	}
 
 }

spring-boot-project/spring-boot-tools/spring-boot-buildpack-platform/src/main/java/org/springframework/boot/buildpack/platform/docker/type/ImageReference.java

@@ -30,9 +30,7 @@ import org.springframework.util.ObjectUtils;
  * @author Scott Frederick
  * @since 2.3.0
  * @see ImageName
- * @see <a href=
- * "https://stackoverflow.com/questions/37861791/how-are-docker-image-names-parsed">How
- * are Docker image names parsed?</a>
+ * @see ImageReferenceParser
  */
 public final class ImageReference {
 
@@ -180,7 +178,7 @@ public final class ImageReference {
 		filename = filename.substring(0, filename.length() - 4);
 		int firstDot = filename.indexOf('.');
 		if (firstDot == -1) {
-			return ImageReference.of(filename);
+			return of(filename);
 		}
 		String name = filename.substring(0, firstDot);
 		String version = filename.substring(firstDot + 1);
@@ -226,8 +224,9 @@ public final class ImageReference {
 	 */
 	public static ImageReference of(String value) {
 		Assert.hasText(value, "Value must not be null");
-		String[] domainAndValue = ImageName.split(value);
-		return of(domainAndValue[0], domainAndValue[1]);
+		ImageReferenceParser parser = ImageReferenceParser.of(value);
+		ImageName name = new ImageName(parser.getDomain(), parser.getName());
+		return new ImageReference(name, parser.getTag(), parser.getDigest());
 	}
 
 	/**
@@ -261,21 +260,4 @@ public final class ImageReference {
 		return new ImageReference(name, tag, digest);
 	}
 
-	private static ImageReference of(String domain, String value) {
-		String digest = null;
-		int lastAt = value.indexOf('@');
-		if (lastAt != -1) {
-			digest = value.substring(lastAt + 1);
-			value = value.substring(0, lastAt);
-		}
-		String tag = null;
-		int firstColon = value.indexOf(':');
-		if (firstColon != -1) {
-			tag = value.substring(firstColon + 1);
-			value = value.substring(0, firstColon);
-		}
-		ImageName name = new ImageName(domain, value);
-		return new ImageReference(name, tag, digest);
-	}
-
 }

spring-boot-project/spring-boot-tools/spring-boot-buildpack-platform/src/main/java/org/springframework/boot/buildpack/platform/docker/type/ImageReferenceParser.java

+/*
+ * Copyright 2012-2020 the original author or authors.
+ *
+ * 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
+ *
+ *      https://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.springframework.boot.buildpack.platform.docker.type;
+
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * A parser for Docker image references in the form
+ * {@code [domainHost:port/][path/]name[:tag][@digest]}.
+ *
+ * @author Scott Frederick
+ * @see <a href=
+ * "https://github.com/docker/distribution/blob/master/reference/reference.go">Docker
+ * grammar reference</a>
+ * @see <a href=
+ * "https://github.com/docker/distribution/blob/master/reference/regexp.go">Docker grammar
+ * implementation</a>
+ * @see <a href=
+ * "https://stackoverflow.com/questions/37861791/how-are-docker-image-names-parsed">How
+ * are Docker image names parsed?</a>
+ */
+final class ImageReferenceParser {
+
+	private static final String DOMAIN_SEGMENT_REGEX = "(?:[a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9-]*[a-zA-Z0-9])";
+
+	private static final String DOMAIN_PORT_REGEX = "[0-9]+";
+
+	private static final String DOMAIN_REGEX = oneOf(
+			groupOf(DOMAIN_SEGMENT_REGEX, repeating("[.]", DOMAIN_SEGMENT_REGEX)),
+			groupOf(DOMAIN_SEGMENT_REGEX, "[:]", DOMAIN_PORT_REGEX),
+			groupOf(DOMAIN_SEGMENT_REGEX, repeating("[.]", DOMAIN_SEGMENT_REGEX), "[:]", DOMAIN_PORT_REGEX),
+			"localhost");
+
+	private static final String NAME_CHARS_REGEX = "[a-z0-9]+";
+
+	private static final String NAME_SEPARATOR_REGEX = "(?:[._]|__|[-]*)";
+
+	private static final String NAME_SEGMENT_REGEX = groupOf(NAME_CHARS_REGEX,
+			optional(repeating(NAME_SEPARATOR_REGEX, NAME_CHARS_REGEX)));
+
+	private static final String NAME_PATH_REGEX = groupOf(NAME_SEGMENT_REGEX,
+			optional(repeating("[/]", NAME_SEGMENT_REGEX)));
+
+	private static final String DIGEST_ALGORITHM_SEGMENT_REGEX = "[A-Za-z][A-Za-z0-9]*";
+
+	private static final String DIGEST_ALGORITHM_SEPARATOR_REGEX = "[-_+.]";
+
+	private static final String DIGEST_ALGORITHM_REGEX = groupOf(DIGEST_ALGORITHM_SEGMENT_REGEX,
+			optional(repeating(DIGEST_ALGORITHM_SEPARATOR_REGEX, DIGEST_ALGORITHM_SEGMENT_REGEX)));
+
+	private static final String DIGEST_VALUE_REGEX = "[0-9A-Fa-f]{32,}";
+
+	private static final String DIGEST_REGEX = groupOf(DIGEST_ALGORITHM_REGEX, "[:]", DIGEST_VALUE_REGEX);
+
+	private static final String TAG_REGEX = "[\\w][\\w.-]{0,127}";
+
+	private static final String DOMAIN_CAPTURE_GROUP = "domain";
+
+	private static final String NAME_CAPTURE_GROUP = "name";
+
+	private static final String TAG_CAPTURE_GROUP = "tag";
+
+	private static final String DIGEST_CAPTURE_GROUP = "digest";
+
+	private static final Pattern REFERENCE_REGEX_PATTERN = patternOf(anchored(
+			optional(captureOf(DOMAIN_CAPTURE_GROUP, DOMAIN_REGEX), "[/]"),
+			captureOf(NAME_CAPTURE_GROUP, NAME_PATH_REGEX), optional("[:]", captureOf(TAG_CAPTURE_GROUP, TAG_REGEX)),
+			optional("[@]", captureOf(DIGEST_CAPTURE_GROUP, DIGEST_REGEX))));
+
+	private final String domain;
+
+	private final String name;
+
+	private final String tag;
+
+	private final String digest;
+
+	private ImageReferenceParser(String domain, String name, String tag, String digest) {
+		this.domain = domain;
+		this.name = name;
+		this.tag = tag;
+		this.digest = digest;
+	}
+
+	String getDomain() {
+		return this.domain;
+	}
+
+	String getName() {
+		return this.name;
+	}
+
+	String getTag() {
+		return this.tag;
+	}
+
+	String getDigest() {
+		return this.digest;
+	}
+
+	static ImageReferenceParser of(String reference) {
+		Matcher matcher = REFERENCE_REGEX_PATTERN.matcher(reference);
+		if (!matcher.matches()) {
+			throw new IllegalArgumentException("Unable to parse image reference \"" + reference + "\". "
+					+ "Image reference must be in the form \"[domainHost:port/][path/]name[:tag][@digest]\", "
+					+ "with \"path\" and \"name\" containing only [a-z0-9][.][_][-]");
+		}
+		return new ImageReferenceParser(matcher.group(DOMAIN_CAPTURE_GROUP), matcher.group(NAME_CAPTURE_GROUP),
+				matcher.group(TAG_CAPTURE_GROUP), matcher.group(DIGEST_CAPTURE_GROUP));
+	}
+
+	private static Pattern patternOf(String... expressions) {
+		return Pattern.compile(join(expressions));
+	}
+
+	private static String groupOf(String... expressions) {
+		return "(?:" + join(expressions) + ')';
+	}
+
+	private static String captureOf(String groupName, String... expressions) {
+		return "(?<" + groupName + ">" + join(expressions) + ')';
+	}
+
+	private static String oneOf(String... expressions) {
+		return groupOf(String.join("|", expressions));
+	}
+
+	private static String optional(String... expressions) {
+		return groupOf(join(expressions)) + '?';
+	}
+
+	private static String repeating(String... expressions) {
+		return groupOf(join(expressions)) + '+';
+	}
+
+	private static String anchored(String... expressions) {
+		return '^' + join(expressions) + '$';
+	}
+
+	private static String join(String... expressions) {
+		return String.join("", expressions);
+	}
+
+}

spring-boot-project/spring-boot-tools/spring-boot-buildpack-platform/src/test/java/org/springframework/boot/buildpack/platform/build/BuildRequestTests.java

@@ -100,9 +100,9 @@ public class BuildRequestTests {
 	@Test
 	void withBuilderWhenHasDigestUpdatesBuilder() throws IOException {
 		BuildRequest request = BuildRequest.forJarFile(writeTestJarFile("my-app-0.0.1.jar")).withBuilder(ImageReference
-				.of("spring/builder:@sha256:6e9f67fa63b0323e9a1e587fd71c561ba48a034504fb804fd26fd8800039835d"));
+				.of("spring/builder@sha256:6e9f67fa63b0323e9a1e587fd71c561ba48a034504fb804fd26fd8800039835d"));
 		assertThat(request.getBuilder().toString()).isEqualTo(
-				"docker.io/spring/builder:@sha256:6e9f67fa63b0323e9a1e587fd71c561ba48a034504fb804fd26fd8800039835d");
+				"docker.io/spring/builder@sha256:6e9f67fa63b0323e9a1e587fd71c561ba48a034504fb804fd26fd8800039835d");
 	}
 
 	@Test
@@ -115,9 +115,9 @@ public class BuildRequestTests {
 	@Test
 	void withRunImageWhenHasDigestUpdatesRunImage() throws IOException {
 		BuildRequest request = BuildRequest.forJarFile(writeTestJarFile("my-app-0.0.1.jar")).withRunImage(ImageReference
-				.of("example.com/custom/run-image:@sha256:6e9f67fa63b0323e9a1e587fd71c561ba48a034504fb804fd26fd8800039835d"));
+				.of("example.com/custom/run-image@sha256:6e9f67fa63b0323e9a1e587fd71c561ba48a034504fb804fd26fd8800039835d"));
 		assertThat(request.getRunImage().toString()).isEqualTo(
-				"example.com/custom/run-image:@sha256:6e9f67fa63b0323e9a1e587fd71c561ba48a034504fb804fd26fd8800039835d");
+				"example.com/custom/run-image@sha256:6e9f67fa63b0323e9a1e587fd71c561ba48a034504fb804fd26fd8800039835d");
 	}
 
 	@Test

spring-boot-project/spring-boot-tools/spring-boot-buildpack-platform/src/test/java/org/springframework/boot/buildpack/platform/build/BuilderTests.java

@@ -115,7 +115,7 @@ class BuilderTests {
 		given(docker.image().pull(eq(ImageReference.of(BuildRequest.DEFAULT_BUILDER_IMAGE_NAME)), any()))
 				.willAnswer(withPulledImage(builderImage));
 		given(docker.image().pull(eq(ImageReference.of(
-				"docker.io/cloudfoundry/run:@sha256:6e9f67fa63b0323e9a1e587fd71c561ba48a034504fb804fd26fd8800039835d")),
+				"docker.io/cloudfoundry/run@sha256:6e9f67fa63b0323e9a1e587fd71c561ba48a034504fb804fd26fd8800039835d")),
 				any())).willAnswer(withPulledImage(runImage));
 		Builder builder = new Builder(BuildLog.to(out), docker);
 		BuildRequest request = getTestRequest();

spring-boot-project/spring-boot-tools/spring-boot-buildpack-platform/src/test/java/org/springframework/boot/buildpack/platform/docker/type/ImageNameTests.java

@@ -25,6 +25,7 @@ import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException
  * Tests for {@link ImageName}.
  *
  * @author Phillip Webb
+ * @author Scott Frederick
  */
 class ImageNameTests {
 
@@ -99,11 +100,13 @@ class ImageNameTests {
 	void hashCodeAndEquals() {
 		ImageName n1 = ImageName.of("ubuntu");
 		ImageName n2 = ImageName.of("library/ubuntu");
-		ImageName n3 = ImageName.of("docker.io/library/ubuntu");
-		ImageName n4 = ImageName.of("index.docker.io/library/ubuntu");
-		ImageName n5 = ImageName.of("alpine");
-		assertThat(n1.hashCode()).isEqualTo(n2.hashCode()).isEqualTo(n3.hashCode()).isEqualTo(n4.hashCode());
-		assertThat(n1).isEqualTo(n1).isEqualTo(n2).isEqualTo(n3).isEqualTo(n4).isNotEqualTo(n5);
+		ImageName n3 = ImageName.of("docker.io/ubuntu");
+		ImageName n4 = ImageName.of("docker.io/library/ubuntu");
+		ImageName n5 = ImageName.of("index.docker.io/library/ubuntu");
+		ImageName n6 = ImageName.of("alpine");
+		assertThat(n1.hashCode()).isEqualTo(n2.hashCode()).isEqualTo(n3.hashCode()).isEqualTo(n4.hashCode())
+				.isEqualTo(n5.hashCode());
+		assertThat(n1).isEqualTo(n1).isEqualTo(n2).isEqualTo(n3).isEqualTo(n4).isNotEqualTo(n6);
 	}
 
 }

spring-boot-project/spring-boot-tools/spring-boot-buildpack-platform/src/test/java/org/springframework/boot/buildpack/platform/docker/type/ImageReferenceParserTests.java

+/*
+ * Copyright 2012-2020 the original author or authors.
+ *
+ * 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
+ *
+ *      https://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.springframework.boot.buildpack.platform.docker.type;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+
+/**
+ * Tests for {@link ImageReferenceParser}.
+ *
+ * @author Scott Frederick
+ */
+class ImageReferenceParserTests {
+
+	@Test
+	void unableToParseWithUppercaseInName() {
+		assertThatIllegalArgumentException().isThrownBy(() -> ImageReferenceParser.of("Test"))
+				.withMessageContaining("Test");
+	}
+
+	@Test
+	void parsesName() {
+		ImageReferenceParser parser = ImageReferenceParser.of("ubuntu");
+		assertThat(parser.getDomain()).isNull();
+		assertThat(parser.getName()).isEqualTo("ubuntu");
+		assertThat(parser.getTag()).isNull();
+		assertThat(parser.getDigest()).isNull();
+	}
+
+	@Test
+	void parsesNameWithPath() {
+		ImageReferenceParser parser = ImageReferenceParser.of("library/ubuntu");
+		assertThat(parser.getDomain()).isNull();
+		assertThat(parser.getName()).isEqualTo("library/ubuntu");
+		assertThat(parser.getTag()).isNull();
+		assertThat(parser.getDigest()).isNull();
+	}
+
+	@Test
+	void parsesNameWithLongPath() {
+		ImageReferenceParser parser = ImageReferenceParser.of("path1/path2/path3/ubuntu");
+		assertThat(parser.getDomain()).isNull();
+		assertThat(parser.getName()).isEqualTo("path1/path2/path3/ubuntu");
+		assertThat(parser.getTag()).isNull();
+		assertThat(parser.getDigest()).isNull();
+	}
+
+	@Test
+	void parsesDomainAndNameWithPath() {
+		ImageReferenceParser parser = ImageReferenceParser.of("repo.example.com/library/ubuntu");
+		assertThat(parser.getDomain()).isEqualTo("repo.example.com");
+		assertThat(parser.getName()).isEqualTo("library/ubuntu");
+		assertThat(parser.getTag()).isNull();
+		assertThat(parser.getDigest()).isNull();
+	}
+
+	@Test
+	void parsesDomainWithPortAndNameWithPath() {
+		ImageReferenceParser parser = ImageReferenceParser.of("repo.example.com:8080/library/ubuntu");
+		assertThat(parser.getDomain()).isEqualTo("repo.example.com:8080");
+		assertThat(parser.getName()).isEqualTo("library/ubuntu");
+		assertThat(parser.getTag()).isNull();
+		assertThat(parser.getDigest()).isNull();
+	}
+
+	@Test
+	void parsesSimpleDomainWithPortAndName() {
+		ImageReferenceParser parser = ImageReferenceParser.of("repo:8080/ubuntu");
+		assertThat(parser.getDomain()).isEqualTo("repo:8080");
+		assertThat(parser.getName()).isEqualTo("ubuntu");
+		assertThat(parser.getTag()).isNull();
+		assertThat(parser.getDigest()).isNull();
+	}
+
+	@Test
+	void parsesSimpleDomainWithPortAndNameWithPath() {
+		ImageReferenceParser parser = ImageReferenceParser.of("repo:8080/library/ubuntu");
+		assertThat(parser.getDomain()).isEqualTo("repo:8080");
+		assertThat(parser.getName()).isEqualTo("library/ubuntu");
+		assertThat(parser.getTag()).isNull();
+		assertThat(parser.getDigest()).isNull();
+	}
+
+	@Test
+	void parsesLocalhostDomainAndName() {
+		ImageReferenceParser parser = ImageReferenceParser.of("localhost/ubuntu");
+		assertThat(parser.getDomain()).isEqualTo("localhost");
+		assertThat(parser.getName()).isEqualTo("ubuntu");
+		assertThat(parser.getTag()).isNull();
+		assertThat(parser.getDigest()).isNull();
+	}
+
+	@Test
+	void parsesLocalhostDomainAndNameWithPath() {
+		ImageReferenceParser parser = ImageReferenceParser.of("localhost/library/ubuntu");
+		assertThat(parser.getDomain()).isEqualTo("localhost");
+		assertThat(parser.getName()).isEqualTo("library/ubuntu");
+		assertThat(parser.getTag()).isNull();
+		assertThat(parser.getDigest()).isNull();
+	}
+
+	@Test
+	void parsesNameAndTag() {
+		ImageReferenceParser parser = ImageReferenceParser.of("ubuntu:v1");
+		assertThat(parser.getDomain()).isNull();
+		assertThat(parser.getName()).isEqualTo("ubuntu");
+		assertThat(parser.getTag()).isEqualTo("v1");
+		assertThat(parser.getDigest()).isNull();
+	}
+
+	@Test
+	void parsesNameAndDigest() {
+		ImageReferenceParser parser = ImageReferenceParser
+				.of("ubuntu@sha256:47bfdb88c3ae13e488167607973b7688f69d9e8c142c2045af343ec199649c09");
+		assertThat(parser.getDomain()).isNull();
+		assertThat(parser.getName()).isEqualTo("ubuntu");
+		assertThat(parser.getTag()).isNull();
+		assertThat(parser.getDigest())
+				.isEqualTo("sha256:47bfdb88c3ae13e488167607973b7688f69d9e8c142c2045af343ec199649c09");
+	}
+
+	@Test
+	void parsesReferenceWithTag() {
+		ImageReferenceParser parser = ImageReferenceParser.of("repo.example.com:8080/library/ubuntu:v1");
+		assertThat(parser.getDomain()).isEqualTo("repo.example.com:8080");
+		assertThat(parser.getName()).isEqualTo("library/ubuntu");
+		assertThat(parser.getTag()).isEqualTo("v1");
+		assertThat(parser.getDigest()).isNull();
+	}
+
+	@Test
+	void parsesReferenceWithDigest() {
+		ImageReferenceParser parser = ImageReferenceParser.of(
+				"repo.example.com:8080/library/ubuntu@sha256:47bfdb88c3ae13e488167607973b7688f69d9e8c142c2045af343ec199649c09");
+		assertThat(parser.getDomain()).isEqualTo("repo.example.com:8080");
+		assertThat(parser.getName()).isEqualTo("library/ubuntu");
+		assertThat(parser.getTag()).isNull();
+		assertThat(parser.getDigest())
+				.isEqualTo("sha256:47bfdb88c3ae13e488167607973b7688f69d9e8c142c2045af343ec199649c09");
+	}
+
+}

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/tasks/bundling/BootBuildImageIntegrationTests.java

@@ -135,6 +135,16 @@ class BootBuildImageIntegrationTests {
 		assertThat(result.getOutput()).containsPattern("Builder lifecycle '.*' failed with status code");
 	}
 
+	@TestTemplate
+	void failsWithInvalidImageName() {
+		writeMainClass();
+		writeLongNameResource();
+		BuildResult result = this.gradleBuild.buildAndFail("bootBuildImage", "--imageName=example/Invalid-Image-Name");
+		assertThat(result.task(":bootBuildImage").getOutcome()).isEqualTo(TaskOutcome.FAILED);
+		assertThat(result.getOutput()).containsPattern("Unable to parse image reference")
+				.containsPattern("example/Invalid-Image-Name");
+	}
+
 	private void writeMainClass() {
 		File examplePackage = new File(this.gradleBuild.getProjectDir(), "src/main/java/example");
 		examplePackage.mkdirs();