Extract ExitCodeGenerators class

Extract exit code logic from SpringApplication to a new
`ExitCodeGenerators` class so that it can be reused.

Fixes gh-4757

spring-boot/src/main/java/org/springframework/boot/ExitCodeGenerators.java

@@ -0,0 +1,83 @@
+/*
+ * 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.springframework.boot;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.List;
+
+import org.springframework.util.Assert;
+
+/**
+ * Maintains a collection of {@link ExitCodeGenerator} instances and allows the final exit
+ * code to be calculated.
+ *
+ * @author Dave Syer
+ * @author Phillip Webb
+ * @since 1.3.1
+ * @see #getExitCode()
+ * @see ExitCodeGenerator
+ */
+public class ExitCodeGenerators implements Iterable<ExitCodeGenerator> {
+
+	private List<ExitCodeGenerator> generators = new ArrayList<ExitCodeGenerator>();
+
+	public void addAll(ExitCodeGenerator... generators) {
+		Assert.notNull(generators, "Generators must not be null");
+		addAll(Arrays.asList(generators));
+	}
+
+	public void addAll(Iterable<? extends ExitCodeGenerator> generators) {
+		Assert.notNull(generators, "Generators must not be null");
+		for (ExitCodeGenerator generator : generators) {
+			add(generator);
+		}
+	}
+
+	public void add(ExitCodeGenerator generator) {
+		Assert.notNull(generator, "Generator must not be null");
+		this.generators.add(generator);
+	}
+
+	@Override
+	public Iterator<ExitCodeGenerator> iterator() {
+		return this.generators.iterator();
+	}
+
+	/**
+	 * Get the final exit code that should be returned based on all contained generators.
+	 * @return the final exit code.
+	 */
+	public int getExitCode() {
+		int exitCode = 0;
+		for (ExitCodeGenerator generator : this.generators) {
+			try {
+				int value = generator.getExitCode();
+				if (value > 0 && value > exitCode || value < 0 && value < exitCode) {
+					exitCode = value;
+				}
+			}
+			catch (Exception ex) {
+				exitCode = (exitCode == 0 ? 1 : exitCode);
+				ex.printStackTrace();
+			}
+		}
+		return exitCode;
+	}
+
+}

spring-boot/src/main/java/org/springframework/boot/SpringApplication.java

@@ -1143,11 +1143,12 @@ public class SpringApplication {
 		int exitCode = 0;
 		try {
 			try {
-				List<ExitCodeGenerator> generators = new ArrayList<ExitCodeGenerator>();
-				generators.addAll(Arrays.asList(exitCodeGenerators));
-				generators
-						.addAll(context.getBeansOfType(ExitCodeGenerator.class).values());
-				exitCode = getExitCode(generators);
+				ExitCodeGenerators generators = new ExitCodeGenerators();
+				Collection<ExitCodeGenerator> beans = context
+						.getBeansOfType(ExitCodeGenerator.class).values();
+				generators.addAll(exitCodeGenerators);
+				generators.addAll(beans);
+				exitCode = generators.getExitCode();
 			}
 			finally {
 				close(context);
@@ -1161,23 +1162,6 @@ public class SpringApplication {
 		return exitCode;
 	}
 
-	private static int getExitCode(List<ExitCodeGenerator> exitCodeGenerators) {
-		int exitCode = 0;
-		for (ExitCodeGenerator exitCodeGenerator : exitCodeGenerators) {
-			try {
-				int value = exitCodeGenerator.getExitCode();
-				if (value > 0 && value > exitCode || value < 0 && value < exitCode) {
-					exitCode = value;
-				}
-			}
-			catch (Exception ex) {
-				exitCode = (exitCode == 0 ? 1 : exitCode);
-				ex.printStackTrace();
-			}
-		}
-		return exitCode;
-	}
-
 	private static void close(ApplicationContext context) {
 		if (context instanceof ConfigurableApplicationContext) {
 			ConfigurableApplicationContext closable = (ConfigurableApplicationContext) context;

spring-boot/src/test/java/org/springframework/boot/ExitCodeGeneratorsTests.java

@@ -0,0 +1,93 @@
+/*
+ * 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.springframework.boot;
+
+import java.util.List;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+
+import static org.hamcrest.Matchers.equalTo;
+import static org.junit.Assert.assertThat;
+import static org.mockito.BDDMockito.given;
+import static org.mockito.Mockito.mock;
+
+/**
+ * Tests for {@link ExitCodeGenerators}.
+ *
+ * @author Phillip Webb
+ */
+public class ExitCodeGeneratorsTests {
+
+	@Rule
+	public ExpectedException thrown = ExpectedException.none();
+
+	@Test
+	public void addAllWhenGeneratorsIsNullShouldThrowException() throws Exception {
+		this.thrown.expect(IllegalArgumentException.class);
+		this.thrown.expectMessage("Generators must not be null");
+		List<ExitCodeGenerator> generators = null;
+		new ExitCodeGenerators().addAll(generators);
+	}
+
+	@Test
+	public void addWhenGeneratorIsNullShouldThrowException() throws Exception {
+		this.thrown.expect(IllegalArgumentException.class);
+		this.thrown.expectMessage("Generator must not be null");
+		new ExitCodeGenerators().add(null);
+	}
+
+	@Test
+	public void getExitCodeWhenNoGeneratorsShouldReturnZero() throws Exception {
+		assertThat(new ExitCodeGenerators().getExitCode(), equalTo(0));
+	}
+
+	@Test
+	public void getExitCodeWhenGeneratorThrowsShouldReturnOne() throws Exception {
+		ExitCodeGenerator generator = mock(ExitCodeGenerator.class);
+		given(generator.getExitCode()).willThrow(new IllegalStateException());
+		ExitCodeGenerators generators = new ExitCodeGenerators();
+		generators.add(generator);
+		assertThat(generators.getExitCode(), equalTo(1));
+	}
+
+	@Test
+	public void getExitCodeWhenAllNegativeShouldReturnLowestValue() throws Exception {
+		ExitCodeGenerators generators = new ExitCodeGenerators();
+		generators.add(mockGenerator(-1));
+		generators.add(mockGenerator(-3));
+		generators.add(mockGenerator(-2));
+		assertThat(generators.getExitCode(), equalTo(-3));
+	}
+
+	@Test
+	public void getExitCodeWhenAllPositiveShouldReturnHighestValue() throws Exception {
+		ExitCodeGenerators generators = new ExitCodeGenerators();
+		generators.add(mockGenerator(1));
+		generators.add(mockGenerator(3));
+		generators.add(mockGenerator(2));
+		assertThat(generators.getExitCode(), equalTo(3));
+	}
+
+	private ExitCodeGenerator mockGenerator(int exitCode) {
+		ExitCodeGenerator generator = mock(ExitCodeGenerator.class);
+		given(generator.getExitCode()).willReturn(exitCode);
+		return generator;
+	}
+
+}