Improve dependency order in generated build

Closes gh-601

initializr-generator/src/main/java/io/spring/initializr/generator/ProjectGenerator.java

@@ -689,10 +689,38 @@ public class ProjectGenerator {
 	private static List<Dependency> filterDependencies(List<Dependency> dependencies,
 			String scope) {
 		return dependencies.stream().filter(dep -> scope.equals(dep.getScope()))
-				.sorted(Comparator.comparing(MetadataElement::getId))
+				.sorted(DependencyComparator.INSTANCE)
 				.collect(Collectors.toList());
 	}
 
+	private static class DependencyComparator implements Comparator<Dependency> {
+
+		private static final DependencyComparator INSTANCE = new DependencyComparator();
+
+		@Override
+		public int compare(Dependency o1, Dependency o2) {
+			if (isSpringBootDependency(o1) && isSpringBootDependency(o2)) {
+				return o1.getArtifactId().compareTo(o2.getArtifactId());
+			}
+			if (isSpringBootDependency(o1)) {
+				return -1;
+			}
+			if (isSpringBootDependency(o2)) {
+				return 1;
+			}
+			int group = o1.getGroupId().compareTo(o2.getGroupId());
+			if (group != 0) {
+				return group;
+			}
+			return o1.getArtifactId().compareTo(o2.getArtifactId());
+		}
+
+		private boolean isSpringBootDependency(Dependency dependency) {
+			return dependency.getGroupId().startsWith("org.springframework.boot");
+		}
+
+	}
+
 	private static class Imports {
 
 		private final List<String> statements = new ArrayList<>();

initializr-generator/src/test/java/io/spring/initializr/generator/ProjectGeneratorTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -34,8 +34,7 @@ import org.springframework.context.annotation.ComponentScan;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.io.ClassPathResource;
 
-import static org.hamcrest.CoreMatchers.containsString;
-import static org.junit.Assert.assertThat;
+import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.Assert.fail;
 
 /**
@@ -817,6 +816,23 @@ public class ProjectGeneratorTests extends AbstractProjectGeneratorTests {
 				.equalsTo(new ClassPathResource("project/gradle/gitignore.gen"));
 	}
 
+	@Test
+	public void dependencyOrderSpringBootTakesPrecedence() {
+		Dependency depOne = Dependency.withId("one", "org.acme", "first", "1.2.3");
+		Dependency depTwo = Dependency.withId("two", "com.example", "second", "1.2.3");
+		InitializrMetadata metadata = InitializrMetadataTestBuilder.withDefaults()
+				.addDependencyGroup("core", "web", "security", "data-jpa")
+				.addDependencyGroup("sample", depOne, depTwo).build();
+		applyMetadata(metadata);
+		ProjectRequest request = createProjectRequest("one", "web", "two", "data-jpa");
+		assertThat(generateGradleBuild(request).getGradleBuild())
+				.containsSequence(
+						"compile('org.springframework.boot:spring-boot-starter-data-jpa')",
+						"compile('org.springframework.boot:spring-boot-starter-web')",
+						"compile('com.example:second:1.2.3')",
+						"compile('org.acme:first:1.2.3')");
+	}
+
 	@Test
 	public void invalidProjectTypeMavenPom() {
 		ProjectRequest request = createProjectRequest("web");
@@ -843,7 +859,7 @@ public class ProjectGeneratorTests extends AbstractProjectGeneratorTests {
 			fail("Should have failed to generate project");
 		}
 		catch (InvalidProjectRequestException ex) {
-			assertThat(ex.getMessage(), containsString("foo-bar"));
+			assertThat(ex.getMessage()).contains("foo-bar");
 			verifyProjectFailedEventFor(request, ex);
 		}
 	}
@@ -857,7 +873,7 @@ public class ProjectGeneratorTests extends AbstractProjectGeneratorTests {
 			fail("Should have failed to generate project");
 		}
 		catch (InvalidProjectRequestException ex) {
-			assertThat(ex.getMessage(), containsString("foo-bar"));
+			assertThat(ex.getMessage()).contains("foo-bar");
 			verifyProjectFailedEventFor(request, ex);
 		}
 	}
@@ -871,7 +887,7 @@ public class ProjectGeneratorTests extends AbstractProjectGeneratorTests {
 			fail("Should have failed to generate project");
 		}
 		catch (InvalidProjectRequestException ex) {
-			assertThat(ex.getMessage(), containsString("foo-bar"));
+			assertThat(ex.getMessage()).contains("foo-bar");
 			verifyProjectFailedEventFor(request, ex);
 		}
 	}
@@ -885,7 +901,7 @@ public class ProjectGeneratorTests extends AbstractProjectGeneratorTests {
 			fail("Should have failed to generate project");
 		}
 		catch (InvalidProjectRequestException ex) {
-			assertThat(ex.getMessage(), containsString("foo-bar"));
+			assertThat(ex.getMessage()).contains("foo-bar");
 			verifyProjectFailedEventFor(request, ex);
 		}
 	}

initializr-generator/src/test/java/io/spring/initializr/test/generator/GradleBuildAssert.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -77,4 +77,9 @@ public class GradleBuildAssert {
 				content.contains(expression));
 		return this;
 	}
+
+	public String getGradleBuild() {
+		return this.content;
+	}
+
 }