Using Freemarker Template for generation.

pom.xml

@@ -45,6 +45,22 @@
 			<artifactId>commons-lang3</artifactId>
 			<version>3.8.1</version>
 		</dependency>
+		<dependency>
+			<groupId>org.apache.commons</groupId>
+			<artifactId>commons-text</artifactId>
+			<version>1.6</version>
+		</dependency>
+		<dependency>
+			<groupId>commons-cli</groupId>
+			<artifactId>commons-cli</artifactId>
+			<version>1.4</version>
+		</dependency>
+		<dependency>
+			<groupId>org.freemarker</groupId>
+			<artifactId>freemarker</artifactId>
+			<version>2.3.28</version>
+		</dependency>
+		
 		<!--  LOGGING  -->
 		<dependency>
 			<groupId>org.slf4j</groupId>
@@ -69,6 +85,7 @@
 			<version>${org.apache.logging.log4j}</version>
 			<scope>runtime</scope>
 		</dependency>
+		
 		<!-- TESTING -->
 		<dependency>
 			<groupId>org.hamcrest</groupId>
@@ -101,26 +118,17 @@
 			<artifactId>junit-platform-runner</artifactId>
 			<scope>test</scope>
 		</dependency>
-
-		<dependency>
-			<groupId>org.apache.commons</groupId>
-			<artifactId>commons-text</artifactId>
-			<version>1.6</version>
-		</dependency>
 		<dependency>
 			<groupId>org.mockito</groupId>
 			<artifactId>mockito-core</artifactId>
 			<version>2.24.5</version>
+			<scope>test</scope>
 		</dependency>
 		<dependency>
 			<groupId>org.mockito</groupId>
 			<artifactId>mockito-junit-jupiter</artifactId>
 			<version>2.24.5</version>
-		</dependency>
-		<dependency>
-			<groupId>commons-cli</groupId>
-			<artifactId>commons-cli</artifactId>
-			<version>1.4</version>
+			<scope>test</scope>
 		</dependency>
 	</dependencies>
 	

src/main/java/de/kreth/property2java/FreemarkerConfig.java

@@ -0,0 +1,33 @@
+package de.kreth.property2java;
+
+import java.io.File;
+import java.io.IOException;
+import java.net.URL;
+
+import freemarker.template.Configuration;
+import freemarker.template.Template;
+
+public enum FreemarkerConfig {
+
+	INSTANCE;
+
+	private final Configuration cfg;
+
+	public Template getTemplate() throws IOException {
+		return cfg.getTemplate("enum_template.tpl");
+	}
+
+	private FreemarkerConfig() {
+		cfg = new Configuration(Configuration.VERSION_2_3_28);
+		URL url = getClass().getResource("/template/enum_template.tpl");
+		try {
+			cfg.setDirectoryForTemplateLoading(new File(url.getFile()).getParentFile());
+		}
+		catch (IOException e) {
+			throw new IllegalStateException("Unable to configure freemarker", e);
+		}
+
+		cfg.setDefaultEncoding("UTF-8");
+	}
+
+}

src/main/java/de/kreth/property2java/Generator.java

@@ -3,21 +3,36 @@ package de.kreth.property2java;
 import java.io.IOException;
 import java.io.Reader;
 import java.io.Writer;
+import java.util.ArrayList;
 import java.util.Enumeration;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Properties;
 
 import de.kreth.property2java.cli.ArgumentConfiguration;
+import freemarker.template.Template;
+import freemarker.template.TemplateException;
 
 public class Generator {
 
 	private Configuration config;
 
+	private Template template;
+
 	public Generator(Configuration config) {
 		this.config = config;
+		try {
+			template = FreemarkerConfig.INSTANCE.getTemplate();
+		}
+		catch (IOException e) {
+
+			throw new IllegalStateException("Unable to load freemarker template", e);
+		}
 	}
 
-	public void start() throws IOException {
+	public void start() throws IOException, TemplateException {
 
 		for (Entry<String, Reader> entry : config.getInput().entrySet()) {
 			String fileName = entry.getKey();
@@ -28,30 +43,48 @@ public class Generator {
 		}
 	}
 
-	void generate(Properties properties, Writer out, String fileName, Configuration config) throws IOException {
+	void generate(Properties properties, Writer out, String fileName, Configuration config)
+			throws IOException, TemplateException {
+
+		Map<String, Object> root = new HashMap<>();
+		root.put("package", config.getPackage());
+		root.put("fileName", fileName);
+		root.put("classname", config.mapFilenameToClassName(fileName));
+
+		List<Entry<String, String>> entries = new ArrayList<>();
+
+		root.put("entries", entries);
 
 		@SuppressWarnings("unchecked")
 		Enumeration<String> propertyNames = (Enumeration<String>) properties.propertyNames();
-		String packageName = config.getPackage();
-		if (packageName != null && !packageName.isBlank()) {
-			out.write("package ");
-			out.write(packageName);
-			out.write(";\n\n");
-		}
-		out.write("public interface ");
-		out.write(config.mapFilenameToClassName(fileName));
-		out.write(" {\n");
+
 		while (propertyNames.hasMoreElements()) {
-			String key = propertyNames.nextElement();
-			out.write(
-					"\tpublic static String " + key.toUpperCase().replaceAll("[\\.-]", "_") + " = \"" + key + "\";\n");
+			final String propertyKeyString = propertyNames.nextElement();
+			final String propertyValue = properties.getProperty(propertyKeyString);
+
+			Entry<String, String> entry = new Entry<String, String>() {
+
+				@Override
+				public String getKey() {
+					return propertyKeyString.toUpperCase().replaceAll("[\\.-]", "_");
+				}
+
+				@Override
+				public String getValue() {
+					return propertyValue;
+				}
+
+				@Override
+				public String setValue(String value) {
+					throw new UnsupportedOperationException("Set Value not supported!");
+				}
+			};
+			entries.add(entry);
 		}
-		out.write(" }\n");
-		out.flush();
-		out.close();
+		template.process(root, out);
 	}
 
-	public static void main(String[] args) throws IOException {
+	public static void main(String[] args) throws IOException, TemplateException {
 		Generator generator = new Generator(ArgumentConfiguration.parse(args));
 		generator.start();
 	}

src/main/resources/template/enum_template.tpl

@@ -0,0 +1,44 @@
+<#if package??>package ${package};
+
+</#if>import java.util.Properties;
+import java.util.ResourceBundle;
+import java.util.function.UnaryOperator;
+
+/**
+ * Property key from ${fileName}
+ */
+public enum ${classname} {
+
+<#list entries as entry>
+	/**
+	 * "${entry.value}"
+	 */
+	${entry.key} ("${entry.value}")<#sep>,
+</#sep>
+</#list>;
+
+	private final String value;
+
+	private ${classname} (String value) {
+		this.value = value;
+	}
+
+	/**
+	 * Represented Key in property File.
+	 * @return key
+	 */
+	public String getValue() {
+		return value;
+	}
+
+	/**
+	 * Resolves the value for this key from the parameter function.
+	 * <p>
+	 * e.g. <code>${classname}.getString(resBundle::getString)</code>
+	 * @param resourceFunction {@link Properties#getProperty(String)} or {@link ResourceBundle#getString(String)}
+	 * @return
+	 */
+	public String getString(UnaryOperator<String> resourceFunction) {
+		return resourceFunction.apply(value);
+	}
+}

src/test/java/de/kreth/property2java/ConfigurationTest.java

@@ -33,12 +33,14 @@ class ConfigurationTest {
 
 	@Test
 	void testPathMapping() {
+		when(config.mapFilenameToClassName(anyString())).thenCallRealMethod();
 		String className = config.mapFilenameToClassName("application.properties");
 		assertEquals("Application_Properties", className);
 	}
 
 	@Test
 	void testPathMappingLocalized() {
+		when(config.mapFilenameToClassName(anyString())).thenCallRealMethod();
 		String className = config.mapFilenameToClassName("application_de_DE.properties");
 		assertEquals("Application_Properties", className);
 		className = config.mapFilenameToClassName("application_en_US.properties");

src/test/java/de/kreth/property2java/GeneratorTests.java

@@ -27,6 +27,8 @@ import org.hamcrest.Matchers;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
+import freemarker.template.TemplateException;
+
 class GeneratorTests {
 
 	private String path = "application.properties";
@@ -48,9 +50,10 @@ class GeneratorTests {
 	}
 
 	@Test
-	void testClassDefinition() throws IOException {
+	void testClassDefinition() throws IOException, TemplateException {
 
 		when(config.getPackage()).thenReturn("de.kreth.property2java");
+		when(config.mapFilenameToClassName(anyString())).thenCallRealMethod();
 
 		StringWriter out = new StringWriter();
 		when(config.outWriter(anyString())).thenReturn(out);
@@ -68,7 +71,7 @@ class GeneratorTests {
 			if (line.trim().startsWith("package")) {
 				linePackage = line;
 			}
-			else if (line.trim().startsWith("public interface")) {
+			else if (line.trim().startsWith("public enum")) {
 				lineClass = line;
 			}
 			if (line.contains("{")) {
@@ -89,12 +92,12 @@ class GeneratorTests {
 				Matchers.stringContainsInOrder(Arrays.asList("package", "de.kreth.property2java", ";")));
 
 		assertThat(lineClass,
-				Matchers.stringContainsInOrder(Arrays.asList("public", "interface", "Application_Properties")));
+				Matchers.stringContainsInOrder(Arrays.asList("public", "enum", "Application_Properties")));
 
 	}
 
 	@Test
-	void testOneInputGeneratesOneOutput() throws IOException {
+	void testOneInputGeneratesOneOutput() throws IOException, TemplateException {
 
 		Writer out = mock(Writer.class);
 		Writer nonOut = mock(Writer.class);
@@ -106,7 +109,7 @@ class GeneratorTests {
 	}
 
 	@Test
-	void testKeys() throws IOException {
+	void testKeys() throws IOException, TemplateException {
 
 		StringWriter out = new StringWriter();
 		when(config.outWriter(anyString())).thenReturn(out);