Allow the SpringApplication class used by the CLI to be configured

This commit adds support to the CLI for launching a custom
SpringApplication implementation. The class that is launched can be
configured using the spring.application.class.name System property
or the SPRING_APPLICATION_CLASS_NAME environment variable with the
former taking priority.

Closes gh-2030

spring-boot-cli/src/main/java/org/springframework/boot/cli/app/SpringApplicationLauncher.java

@@ -22,21 +22,26 @@ import java.util.HashMap;
 import java.util.Map;
 
 /**
- * A launcher for {@code SpringApplication}. Uses reflection to allow the launching code
+ * A launcher for {@code SpringApplication} or a {@code SpringApplication} subclass. The
- * to exist in a separate ClassLoader from the application code.
+ * class that is used can be configured using the System property
+ * {@code spring.application.class.name} or the {@code SPRING_APPLICATION_CLASS_NAME}
+ * environment variable. Uses reflection to allow the launching code to exist in a
+ * separate ClassLoader from the application code.
  *
  * @author Andy Wilkinson
  * @since 1.2.0
+ * @see System#getProperty(String)
+ * @see System#getenv(String)
  */
 public class SpringApplicationLauncher {
 
-	private static final String SPRING_APPLICATION_CLASS = "org.springframework.boot.SpringApplication";
+	private static final String DEFAULT_SPRING_APPLICATION_CLASS = "org.springframework.boot.SpringApplication";
 
 	private final ClassLoader classLoader;
 
 	/**
-	 * Creates a new launcher that will use the given {@code classLoader} to load
+	 * Creates a new launcher that will use the given {@code classLoader} to load the
-	 * {@code SpringApplication}.
+	 * configured {@code SpringApplication} class.
 	 * @param classLoader the {@code ClassLoader} to use
 	 */
 	public SpringApplicationLauncher(ClassLoader classLoader) {
@@ -54,7 +59,8 @@ public class SpringApplicationLauncher {
 	public Object launch(Object[] sources, String[] args) throws Exception {
 		Map<String, Object> defaultProperties = new HashMap<String, Object>();
 		defaultProperties.put("spring.groovy.template.check-template-location", "false");
-		Class<?> applicationClass = this.classLoader.loadClass(SPRING_APPLICATION_CLASS);
+		Class<?> applicationClass = this.classLoader
+				.loadClass(getSpringApplicationClassName());
 		Constructor<?> constructor = applicationClass.getConstructor(Object[].class);
 		Object application = constructor.newInstance((Object) sources);
 		applicationClass.getMethod("setDefaultProperties", Map.class).invoke(application,
@@ -63,4 +69,19 @@ public class SpringApplicationLauncher {
 		return method.invoke(application, (Object) args);
 	}
 
+	private String getSpringApplicationClassName() {
+		String className = System.getProperty("spring.application.class.name");
+		if (className == null) {
+			className = getEnvironmentVariable("SPRING_APPLICATION_CLASS_NAME");
+		}
+		if (className == null) {
+			className = DEFAULT_SPRING_APPLICATION_CLASS;
+		}
+		return className;
+	}
+
+	protected String getEnvironmentVariable(String name) {
+		return System.getenv(name);
+	}
+
 }

spring-boot-cli/src/test/java/org/springframework/boot/cli/app/SpringApplicationLauncherTests.java

@@ -0,0 +1,162 @@
+/*
+ * Copyright 2012-2014 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.springframework.boot.cli.app;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.junit.After;
+import org.junit.Test;
+
+import static org.hamcrest.Matchers.contains;
+import static org.hamcrest.Matchers.equalTo;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * Tests for {@link SpringApplicationLauncher}
+ *
+ * @author Andy Wilkinson
+ */
+public class SpringApplicationLauncherTests {
+
+	private Map<String, String> env = new HashMap<String, String>();
+
+	@After
+	public void cleanUp() {
+		System.clearProperty("spring.application.class.name");
+	}
+
+	@Test
+	public void defaultLaunch() throws Exception {
+		assertThat(launch(), contains("org.springframework.boot.SpringApplication"));
+	}
+
+	@Test
+	public void launchWithClassConfiguredBySystemProperty() {
+		System.setProperty("spring.application.class.name",
+				"system.property.SpringApplication");
+		assertThat(launch(), contains("system.property.SpringApplication"));
+	}
+
+	@Test
+	public void launchWithClassConfiguredByEnvironmentVariable() {
+		this.env.put("SPRING_APPLICATION_CLASS_NAME",
+				"environment.variable.SpringApplication");
+		assertThat(launch(), contains("environment.variable.SpringApplication"));
+	}
+
+	@Test
+	public void systemPropertyOverridesEnvironmentVariable() {
+		System.setProperty("spring.application.class.name",
+				"system.property.SpringApplication");
+		this.env.put("SPRING_APPLICATION_CLASS_NAME",
+				"environment.variable.SpringApplication");
+		assertThat(launch(), contains("system.property.SpringApplication"));
+
+	}
+
+	@Test
+	public void sourcesDefaultPropertiesAndArgsAreUsedToLaunch() throws Exception {
+		System.setProperty("spring.application.class.name",
+				TestSpringApplication.class.getName());
+
+		Object[] sources = new Object[0];
+		String[] args = new String[0];
+		new SpringApplicationLauncher(getClass().getClassLoader()).launch(sources, args);
+
+		assertTrue(sources == TestSpringApplication.sources);
+		assertTrue(args == TestSpringApplication.args);
+
+		Map<String, String> defaultProperties = TestSpringApplication.defaultProperties;
+		assertThat(defaultProperties.size(), equalTo(1));
+		assertThat(
+				defaultProperties.get("spring.groovy.template.check-template-location"),
+				equalTo("false"));
+	}
+
+	private List<String> launch() {
+		TestClassLoader classLoader = new TestClassLoader(getClass().getClassLoader());
+		try {
+			new TestSpringApplicationLauncher(classLoader).launch(new Object[0],
+					new String[0]);
+		}
+		catch (Exception e) {
+			// SpringApplication isn't on the classpath, but we can still check that
+			// the launcher tried to use the right class
+		}
+		return classLoader.classes;
+	}
+
+	private static class TestClassLoader extends ClassLoader {
+
+		private List<String> classes = new ArrayList<String>();
+
+		public TestClassLoader(ClassLoader parent) {
+			super(parent);
+		}
+
+		@Override
+		protected Class<?> findClass(String name) throws ClassNotFoundException {
+			this.classes.add(name);
+			return super.findClass(name);
+		}
+
+	}
+
+	@SuppressWarnings("unused")
+	private static class TestSpringApplication {
+
+		private static Object[] sources;
+
+		private static Map<String, String> defaultProperties;
+
+		private static String[] args;
+
+		public TestSpringApplication(Object[] sources) {
+			TestSpringApplication.sources = sources;
+		}
+
+		public void setDefaultProperties(Map<String, String> defaultProperties) {
+			TestSpringApplication.defaultProperties = defaultProperties;
+		}
+
+		public void run(String[] args) {
+			TestSpringApplication.args = args;
+		}
+	}
+
+	private class TestSpringApplicationLauncher extends SpringApplicationLauncher {
+
+		public TestSpringApplicationLauncher(ClassLoader classLoader) {
+			super(classLoader);
+		}
+
+		@Override
+		protected String getEnvironmentVariable(String name) {
+			String variable = SpringApplicationLauncherTests.this.env.get(name);
+			if (variable == null) {
+				variable = super.getEnvironmentVariable(name);
+			}
+			return variable;
+		}
+
+	}
+
+}