Add FileEncodingApplicationContextInitializer

Looks for spring.mandatory_file_encoding and matches it against
System.getProperty("file.encoding").

Fixes gh-46

spring-boot/src/main/java/org/springframework/boot/context/initializer/FileEncodingApplicationContextInitializer.java

@@ -0,0 +1,74 @@
+/*
+ * Copyright 2012-2013 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.context.initializer;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.springframework.boot.bind.RelaxedPropertyResolver;
+import org.springframework.context.ApplicationContextInitializer;
+import org.springframework.context.ConfigurableApplicationContext;
+
+/**
+ * An {@link ApplicationContextInitializer} halts application startup if the system file
+ * encoding does not match an expected value set in the environment. By default has no
+ * effect, but if you set <code>spring.mandatory_file_encoding</code> (or some camelCase
+ * or UPPERCASE variant of that) to the name of a character encoding (e.g. "UTF-8") then
+ * this initializer throws an exception when the <code>file.encoding</code> System
+ * property does not equal it.
+ * 
+ * <p>
+ * The System property <code>file.encoding</code> is normally set by the JVM in response
+ * to the <code>LANG</code> or <code>LC_ALL</code> environment variables. It is used
+ * (along with other platform-dependent variables keyed off those environment variables)
+ * to encode JVM arguments as well as file names and paths. In most cases you can override
+ * the file encoding System property on the command line (with standard JVM features), but
+ * also consider setting the <code>LANG</code> environment variable to an explicit
+ * character-encoding value (e.g. "en_GB.UTF-8").
+ * 
+ * @author Dave Syer
+ */
+public class FileEncodingApplicationContextInitializer implements
+		ApplicationContextInitializer<ConfigurableApplicationContext> {
+
+	private static Log logger = LogFactory
+			.getLog(FileEncodingApplicationContextInitializer.class);
+
+	@Override
+	public void initialize(final ConfigurableApplicationContext context) {
+		RelaxedPropertyResolver resolver = new RelaxedPropertyResolver(
+				context.getEnvironment(), "spring.");
+		if (resolver.containsProperty("mandatoryFileEncoding")) {
+			final String encoding = System.getProperty("file.encoding");
+			final String desired = resolver.getProperty("mandatoryFileEncoding");
+			if (encoding != null && !desired.equalsIgnoreCase(encoding)) {
+				logger.error("System property 'file.encoding' is currently '" + encoding
+						+ "'. It should be '" + desired
+						+ "' (as defined in 'spring.mandatoryFileEncoding').");
+				logger.error("Environment variable LANG is '" + System.getenv("LANG")
+						+ "'. You could use a locale setting that matches encoding='"
+						+ desired + "'.");
+				logger.error("Environment variable LC_ALL is '" + System.getenv("LC_ALL")
+						+ "'. You could use a locale setting that matches encoding='"
+						+ desired + "'.");
+				throw new IllegalStateException(
+						"The Java Virtual Machine has not "
+								+ " been configured to use the desired default character encoding ("
+								+ desired + ").");
+			}
+		}
+	}
+};

spring-boot/src/main/resources/META-INF/spring.factories

@@ -1,6 +1,7 @@
 # Application Context Initializers
 org.springframework.context.ApplicationContextInitializer=\
 org.springframework.boot.context.initializer.ConfigFileApplicationContextInitializer,\
+org.springframework.boot.context.initializer.FileEncodingApplicationContextInitializer,\
 org.springframework.boot.context.initializer.ContextIdApplicationContextInitializer,\
 org.springframework.boot.context.initializer.EnvironmentDelegateApplicationContextInitializer,\
 org.springframework.boot.context.initializer.LoggingApplicationContextInitializer,\

spring-boot/src/test/java/org/springframework/boot/context/initializer/FileEncodingApplicationContextInitializerTests.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2012-2013 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.context.initializer;
+
+import org.junit.Assume;
+import org.junit.Before;
+import org.junit.Test;
+import org.springframework.boot.TestUtils;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.context.support.StaticApplicationContext;
+
+/**
+ * @author Dave Syer
+ */
+public class FileEncodingApplicationContextInitializerTests {
+
+	private FileEncodingApplicationContextInitializer initializer = new FileEncodingApplicationContextInitializer();
+	private ConfigurableApplicationContext context;
+
+	@Before
+	public void init() {
+		this.context = new StaticApplicationContext();
+	}
+
+	@Test(expected = IllegalStateException.class)
+	public void testIllegalState() {
+		TestUtils.addEnviroment(this.context, "spring.mandatory_file_encoding:FOO");
+		this.initializer.initialize(this.context);
+	}
+
+	@Test
+	public void testSunnyDayNothingMandated() {
+		this.initializer.initialize(this.context);
+	}
+
+	@Test
+	public void testSunnyDayMandated() {
+		Assume.assumeNotNull(System.getProperty("file.encoding"));
+		TestUtils.addEnviroment(this.context,
+				"spring.mandatory_file_encoding:" + System.getProperty("file.encoding"));
+		this.initializer.initialize(this.context);
+	}
+
+}