BAEL-4209: Difference between e.getMessage() and e.getLocalizedMessage() (#10222)

* - initial commit of sample code * BAEL-4209: Moving the localized exception module into core-java-exceptions-3. * BAEL-4209: Removed the old files for localizing exception messages.
2020-11-09 12:37:47 -05:00
parent 3888cd0af1
commit 95e04696e6
6 changed files with 162 additions and 0 deletions
@@ -0,0 +1,47 @@
+package com.baeldung.exceptions.localization;
+
+import java.util.Locale;
+
+public class LocalizedException extends Exception {
+    
+    private static final long serialVersionUID = 1L;
+
+    private final String messageKey;
+    private final Locale locale;
+
+    public LocalizedException(String messageKey) {
+        this(messageKey, Locale.getDefault());
+    }
+
+    public LocalizedException(String messageKey, Locale locale) {
+        this.messageKey = messageKey;
+        this.locale = locale;
+    }
+
+    /**
+     * @return a localized message based on the messageKey provided at instantiation.
+     */
+    public String getMessage() {
+
+        /*
+         * This is a deliberate role reversal of the default implementation of getLocalizedMessage.
+         * some logging frameworks like Log4J 1 & 2 and Logback will use getMessage instead of
+         * getLocalizedMessage when logging Throwables. If we want to use these frameworks in client
+         * applications to log localized messages, then we'll need to override getMessage in a
+         * similar fashion to return the appropriate content.  Or, you can call getLocalizedMessage
+         * on your own to create the log content.
+         */
+        return getLocalizedMessage();
+    }
+
+    /**
+     * @return a localized message based on the messageKey provided at instantiation.
+     */
+    public String getLocalizedMessage() {
+
+        /*
+         * java.util.logging uses getLocalizedMessage when logging Throwables.
+         */
+        return Messages.getMessageForLocale(messageKey, locale);
+    }
+}
@@ -0,0 +1,27 @@
+package com.baeldung.exceptions.localization;
+
+import java.util.Locale;
+import java.util.ResourceBundle;
+
+public class Messages {
+
+    /**
+     * Retrieves the value for the messageKey from the locale-specific messages.properties, or from
+     * the base messages.properties for unsupported locales.
+     *
+     * @param messageKey The key for the message in the messages.properties ResourceBundle.
+     * @param locale The locale to search the message key.
+     * @return The value defined for the messageKey in the provided locale.
+     */
+    public static String getMessageForLocale(String messageKey, Locale locale) {
+
+        /*
+         * For more complex implementations, you will want a var-args parameter for MessageFormat
+         * substitutions. Then we can read the value from the bundle and pass the value with the
+         * substitutions to MessageFormat to create the final message value.
+         */
+        return ResourceBundle.getBundle("messages", locale)
+            .getString(messageKey);
+    }
+
+}
@@ -0,0 +1 @@
+message.exception = I am an exception.
@@ -0,0 +1 @@
+message.exception = Je suis une exception.