refactor: Extract messages to the properties bundle

server/src/main/java/com/microsoft/java/bs/core/Launcher.java

@@ -7,6 +7,7 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import com.microsoft.java.bs.core.i18n.MessageUtils;
 import com.microsoft.java.bs.core.internal.managers.BuildTargetManager;
 import com.microsoft.java.bs.core.internal.server.GradleBuildServer;
 import com.microsoft.java.bs.core.internal.services.BuildTargetService;
@@ -18,7 +19,7 @@
  * Main entry point for the BSP server.
  */
 public class Launcher {
-  
+
   /**
    * The property name for the build server storage location.
    */
@@ -54,7 +55,7 @@ private static org.eclipse.lsp4j.jsonrpc.Launcher<BuildClient> createLauncher()
 
   private static void checkRequiredProperties() {
     if (System.getProperty(PROP_BUILD_SERVER_STORAGE) == null) {
-      throw new IllegalStateException("The property 'buildServerStorage' is not set");
+      throw new IllegalStateException(MessageUtils.get("error.serverStorageMissing"));
     }
   }
 

server/src/main/java/com/microsoft/java/bs/core/i18n/MessageUtils.java

@@ -0,0 +1,26 @@
+package com.microsoft.java.bs.core.i18n;
+
+import java.util.Locale;
+import java.util.ResourceBundle;
+
+/**
+ * Utils to get the messages from properties file.
+ */
+public class MessageUtils {
+  private static ResourceBundle messages;
+
+  static {
+    // By default, use the system default locale
+    messages = ResourceBundle.getBundle("messages");
+  }
+
+  public static void setLocale(Locale locale) {
+    messages = ResourceBundle.getBundle("messages", locale);
+  }
+
+  public static String get(String key) {
+    return messages.getString(key);
+  }
+
+  private MessageUtils() {}
+}

server/src/main/java/com/microsoft/java/bs/core/internal/gradle/GradleApiConnector.java

@@ -13,6 +13,7 @@
 import org.gradle.tooling.ModelBuilder;
 import org.gradle.tooling.ProjectConnection;
 
+import com.microsoft.java.bs.core.i18n.MessageUtils;
 import com.microsoft.java.bs.gradle.model.GradleSourceSets;
 
 /**
@@ -83,7 +84,7 @@ private File copyPluginJarFile() {
         Files.write(pluginJarFile.toPath(), pluginJarBytes);
       }
     } catch (IOException | NoSuchAlgorithmException e) {
-      throw new IllegalStateException("Failed to get plugin jar.", e);
+      throw new IllegalStateException(MessageUtils.get("error.pluginMissing"), e);
     }
     return pluginJarFile;
   }
@@ -116,7 +117,7 @@ classpath files('%s')
       }
       return initScriptFile;
     } catch (IOException | NoSuchAlgorithmException e) {
-      throw new IllegalStateException("Failed to get init.script", e);
+      throw new IllegalStateException(MessageUtils.get("error.initScriptMissing"), e);
     }
   }
 

server/src/main/java/com/microsoft/java/bs/core/internal/services/BuildTargetService.java

@@ -8,6 +8,7 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import com.microsoft.java.bs.core.i18n.MessageUtils;
 import com.microsoft.java.bs.core.internal.managers.BuildTargetManager;
 import com.microsoft.java.bs.core.internal.model.GradleBuildTarget;
 import com.microsoft.java.bs.gradle.model.GradleSourceSet;
@@ -61,8 +62,7 @@ public SourcesResult getBuildTargetSources(SourcesParams params) {
     for (BuildTargetIdentifier btId : params.getTargets()) {
       GradleBuildTarget target = buildTargetManager.getGradleBuildTarget(btId);
       if (target == null) {
-        logger.warn("Skip sources collection for the build target: {}"
-            + "because it cannot be found in the cache.", btId.getUri());
+        logger.warn(MessageUtils.get("warning.skipBuildTargetSources"), btId.getUri());
         continue;
       }
 
@@ -90,8 +90,7 @@ public ResourcesResult getBuildTargetResources(ResourcesParams params) {
     for (BuildTargetIdentifier btId : params.getTargets()) {
       GradleBuildTarget target = buildTargetManager.getGradleBuildTarget(btId);
       if (target == null) {
-        logger.warn("Skip resources collection for the build target: {}"
-            + "because it cannot be found in the cache.", btId.getUri());
+        logger.warn(MessageUtils.get("warning.skipBuildTargetResources"), btId.getUri());
         continue;
       }
 
@@ -114,8 +113,7 @@ public OutputPathsResult getBuildTargetOutputPaths(OutputPathsParams params) {
     for (BuildTargetIdentifier btId : params.getTargets()) {
       GradleBuildTarget target = buildTargetManager.getGradleBuildTarget(btId);
       if (target == null) {
-        logger.warn("Skip output collection for the build target: {}"
-            + "because it cannot be found in the cache.", btId.getUri());
+        logger.warn(MessageUtils.get("warning.skipBuildTargetOutputPaths"), btId.getUri());
         continue;
       }
 

server/src/main/resources/messages.properties

@@ -0,0 +1,7 @@
+error.serverStorageMissing=The property 'buildServerStorage' is not set.
+error.pluginMissing=Failed to get plugin jar.
+error.initScriptMissing=Failed to get init.script.
+
+warning.skipBuildTargetSources=Skip sources collection for the build target: {} because it cannot be found in the cache.
+warning.skipBuildTargetResources=Skip resources collection for the build target: {} because it cannot be found in the cache.
+warning.skipBuildTargetOutputPaths=Skip output paths collection for the build target: {} because it cannot be found in the cache.

server/src/test/java/com/microsoft/java/bs/core/i18n/MessageUtilsTest.java

@@ -0,0 +1,21 @@
+package com.microsoft.java.bs.core.i18n;
+
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+import java.util.Locale;
+
+import org.junit.jupiter.api.Test;
+
+class MessageUtilsTest {
+  @Test
+  void testGet() {
+    assertNotNull(MessageUtils.get("error.serverStorageMissing"));
+  }
+
+  @Test
+  void testSetLocale() {
+    MessageUtils.setLocale(new Locale("zh", "CN"));
+    assertNotNull(MessageUtils.get("error.serverStorageMissing"));
+  }
+
+}