Simplify contract of LayoutFactory

It's simpler if the build tools just use a factory if one is provided
otherwise derive the layout from its type.

Author: Dave Syer

spring-boot-docs/src/main/asciidoc/build-tool-plugins.adoc

@@ -481,11 +481,11 @@ The following configuration options are available:
 
 |`layout`
 |The `LayoutType` of archive, corresponding to how the dependencies are laid out inside
- (defaults to a guess based on the archive type).
+ (defaults to a guess based on the archive type). See 
+<<build-tool-plugins-gradle-configuration-layouts,available layouts for more details>>.
 
 |`layoutFactory`
-|A factory for the actual `Layout` derived from the `LayoutType`. See 
-<<build-tool-plugins-gradle-configuration-layouts,available layouts for more details>>.
+|A factory for the actual `Layout` derived from the `LayoutType`. If the factory is provided then the layout is ignored.
 
 |`requiresUnpack`
 |A list of dependencies (in the form "`groupId:artifactId`" that must be unpacked from

spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/SpringBootPluginExtension.java

@@ -154,10 +154,17 @@ public SpringBootPluginExtension(Project project) {
 	 * @return the Layout to use or null if not explicitly set
 	 */
 	public Layout convertLayout(File file) {
-		if (this.layout == null) {
-			this.layout = LayoutType.forFile(file);
+		Layout result;
+		if (this.layoutFactory != null) {
+			result = this.layoutFactory.getLayout();
 		}
-		return this.layoutFactory.getLayout(this.layout);
+		else if (this.layout == null) {
+			result = Layouts.forFile(file);
+		}
+		else {
+			result = Layouts.forType(this.layout);
+		}
+		return result;
 	}
 
 	public String getMainClass() {

spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/DefaultLayoutFactory.java

@@ -24,6 +24,6 @@
  */
 public interface LayoutFactory {
 
-	Layout getLayout(LayoutType type);
+	Layout getLayout();
 
 }

spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/LayoutFactory.java

@@ -50,7 +50,27 @@ private Layouts() {
 	 * @return a {@link Layout}
 	 */
 	public static Layout forFile(File file) {
-		return Layouts.getDefaultLayoutFactory().getLayout(LayoutType.forFile(file));
+		return forType(LayoutType.forFile(file));
+	}
+
+	/**
+	 * Return a layout for the given type.
+	 * @param type the layout type
+	 * @return a {@link Layout}
+	 */
+	public static Layout forType(LayoutType type) {
+		switch (type) {
+		case JAR:
+			return new Layouts.Jar();
+		case WAR:
+			return new Layouts.War();
+		case ZIP:
+			return new Layouts.Expanded();
+		case MODULE:
+			return new Layouts.Module();
+		default:
+			return new Layouts.None();
+		}
 	}
 
 	/**
@@ -65,7 +85,7 @@ public static LayoutFactory getDefaultLayoutFactory() {
 		if (factories.size() == 1) {
 			return factories.get(0);
 		}
-		return new DefaultLayoutFactory();
+		return null;
 	}
 
 	/**

spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/Layouts.java

@@ -42,6 +42,7 @@
 
 import org.springframework.boot.loader.tools.DefaultLaunchScript;
 import org.springframework.boot.loader.tools.LaunchScript;
+import org.springframework.boot.loader.tools.Layout;
 import org.springframework.boot.loader.tools.LayoutFactory;
 import org.springframework.boot.loader.tools.LayoutType;
 import org.springframework.boot.loader.tools.Layouts;
@@ -234,12 +235,19 @@ private File getTargetFile() {
 	private Repackager getRepackager(File source) {
 		Repackager repackager = new LoggingRepackager(source, getLog());
 		repackager.setMainClass(this.mainClass);
-		if (this.layout == null) {
-			this.layout = LayoutType.forFile(source);
+		Layout forUse;
+		if (this.layoutFactory != null) {
+			forUse = this.layoutFactory.getLayout();
 		}
-		getLog().info("Layout: " + this.layout);
+		else if (this.layout == null) {
+			forUse = Layouts.forFile(source);
+		}
+		else {
+			forUse = Layouts.forType(this.layout);
+		}
+		getLog().info("Layout: " + forUse.getClass());
 		try {
-			repackager.setLayout(this.layoutFactory.getLayout(this.layout));
+			repackager.setLayout(forUse);
 		}
 		catch (Exception e) {
 			throw new IllegalStateException("Cannot create layout", e);