Create output directory if necessary

If the `repackage` goal defines an output directory that does not exist,
the maven plugin now creates it.

Closes gh-3136

spring-boot-tools/spring-boot-maven-plugin/src/it/jar-create-dir/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>
+	<groupId>org.springframework.boot.maven.it</groupId>
+	<artifactId>jar-create-dir</artifactId>
+	<version>0.0.1.BUILD-SNAPSHOT</version>
+	<properties>
+		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+	</properties>
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>@project.groupId@</groupId>
+				<artifactId>@project.artifactId@</artifactId>
+				<version>@project.version@</version>
+				<executions>
+					<execution>
+						<goals>
+							<goal>repackage</goal>
+						</goals>
+						<configuration>
+							<outputDirectory>${project.build.directory}/foo</outputDirectory>
+							<classifier>foo</classifier>
+						</configuration>
+					</execution>
+				</executions>
+			</plugin>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-jar-plugin</artifactId>
+				<version>2.4</version>
+				<configuration>
+					<archive>
+						<manifest>
+							<mainClass>some.random.Main</mainClass>
+						</manifest>
+						<manifestEntries>
+							<Not-Used>Foo</Not-Used>
+						</manifestEntries>
+					</archive>
+				</configuration>
+			</plugin>
+		</plugins>
+	</build>
+	<dependencies>
+		<dependency>
+			<groupId>org.springframework</groupId>
+			<artifactId>spring-context</artifactId>
+			<version>@spring.version@</version>
+		</dependency>
+		<dependency>
+			<groupId>javax.servlet</groupId>
+			<artifactId>javax.servlet-api</artifactId>
+			<version>@servlet-api.version@</version>
+			<scope>provided</scope>
+		</dependency>
+	</dependencies>
+</project>

spring-boot-tools/spring-boot-maven-plugin/src/it/jar-create-dir/src/main/java/org/test/SampleApplication.java

+/*
+ * Copyright 2012-2015 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
+ *
+ *      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.test;
+
+public class SampleApplication {
+
+	public static void main(String[] args) {
+	}
+
+}

spring-boot-tools/spring-boot-maven-plugin/src/it/jar-create-dir/verify.groovy

+import java.io.*;
+import org.springframework.boot.maven.*;
+
+Verify.verifyJar(
+	new File( basedir, "target/foo/jar-create-dir-0.0.1.BUILD-SNAPSHOT-foo.jar" ), "some.random.Main"
+);
+

spring-boot-tools/spring-boot-maven-plugin/src/main/java/org/springframework/boot/maven/RepackageMojo.java

@@ -186,6 +186,11 @@ public class RepackageMojo extends AbstractDependencyFilterMojo {
 		if (classifier.length() > 0 && !classifier.startsWith("-")) {
 			classifier = "-" + classifier;
 		}
+
+		if (!this.outputDirectory.exists()) {
+			this.outputDirectory.mkdirs();
+		}
+
 		return new File(this.outputDirectory, this.finalName + classifier + "."
 				+ this.project.getArtifact().getArtifactHandler().getExtension());
 	}