Add the capability to render file fragments into config.xml

hivemq-edge/src/main/java/com/hivemq/configuration/reader/ConfigFileReaderWriter.java

@@ -26,6 +26,7 @@
 import com.hivemq.configuration.entity.listener.UDPListenerEntity;
 import com.hivemq.configuration.entity.listener.WebsocketListenerEntity;
 import com.hivemq.exceptions.UnrecoverableException;
+import com.hivemq.util.FileFragmentUtil;
 import org.jetbrains.annotations.NotNull;
 import com.hivemq.util.EnvVarUtil;
 import org.apache.commons.io.FileUtils;
@@ -266,6 +267,7 @@ public void writeConfigToXML(final @NotNull Writer writer) {
                 //replace environment variable placeholders
                 String configFileContent = new String(Files.readAllBytes(configFile.toPath()), StandardCharsets.UTF_8);
                 configFileContent = EnvVarUtil.replaceEnvironmentVariablePlaceholders(configFileContent);
+                configFileContent = FileFragmentUtil.replaceFragmentPlaceHolders(configFileContent);
                 final ByteArrayInputStream is =
                         new ByteArrayInputStream(configFileContent.getBytes(StandardCharsets.UTF_8));
                 final StreamSource streamSource = new StreamSource(is);

hivemq-edge/src/main/java/com/hivemq/util/EnvVarUtil.java

@@ -21,7 +21,6 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import javax.inject.Singleton;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -30,7 +29,6 @@
  *
  * @author Christoph Schäbel
  */
-@Singleton
 public class EnvVarUtil {
 
     private static final Logger log = LoggerFactory.getLogger(EnvVarUtil.class);
@@ -55,7 +53,7 @@ public class EnvVarUtil {
     }
 
     /**
-     * Replaces placeholders like '${VAR_NAME}' and '${ENV:VAR_NAME}' with the according environment variables.
+     * Replaces placeholders like '${ENV:VAR_NAME}' with the according environment variables.
      *
      * @param text the text which contains placeholders (or not)
      * @return the text with all the placeholders replaced

hivemq-edge/src/main/java/com/hivemq/util/FileFragmentUtil.java

@@ -0,0 +1,84 @@
+package com.hivemq.util;
+
+import com.hivemq.exceptions.UnrecoverableException;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+public class FileFragmentUtil {
+    private static final Logger log = LoggerFactory.getLogger(EnvVarUtil.class);
+
+    private static final @NotNull String FRAGMENT_VAR_PATTERN = "\\$\\{FRAGMENT:(.*)}";
+
+    /**
+     * Load a file fragment
+     *
+     * @param path the path where the fragment is located
+     * @return return the content of the fragment
+     */
+    public static @Nullable String getFragment(final @NotNull String path) {
+        try {
+            return Files.readString(Path.of(path), StandardCharsets.UTF_8);
+        } catch (IOException e) {
+            log.error("Unable to load fragment from {}", path, e);
+        }
+        return null;
+    }
+
+    /**
+     * Replaces fragment markers like '${FRAGMENT:VAR_NAME}' with the according fragment loaded from the filesystem.
+     *
+     * @param text the text which contains placeholders (or not)
+     * @return the text with all the placeholders replaced
+     * @throws UnrecoverableException if a fragment used in a placeholder can't be loaded
+     */
+    public static @NotNull String replaceFragmentPlaceHolders(final @NotNull String text) {
+
+        final StringBuffer resultString = new StringBuffer();
+
+        final Matcher matcher = Pattern.compile(FRAGMENT_VAR_PATTERN)
+                .matcher(text);
+
+        while (matcher.find()) {
+
+            if (matcher.groupCount() < 1) {
+                //this should never happen as we declared 1 groups in the ENV_VAR_PATTERN
+                log.warn("Found unexpected fragment variable placeholder in config.xml");
+                matcher.appendReplacement(resultString, "");
+                continue;
+            }
+
+            final String fragmentPath = matcher.group(1);
+
+            final String replacement = getFragment(fragmentPath);
+
+            if (replacement == null) {
+                log.error("Fragment {} for HiveMQ config.xml can't be loaded.", fragmentPath);
+                throw new UnrecoverableException(false);
+            }
+
+            //sets replacement for this match
+            matcher.appendReplacement(resultString, escapeReplacement(replacement));
+
+        }
+
+        //adds everything except the replacements to the string buffer
+        matcher.appendTail(resultString);
+
+        return resultString.toString();
+    }
+
+    private static @NotNull String escapeReplacement(final @NotNull String replacement) {
+        return replacement
+                .replace("\\", "\\\\")
+                .replace("$", "\\$");
+    }
+}

hivemq-edge/src/test/java/com/hivemq/util/EnvVarUtilTest.java

@@ -80,12 +80,12 @@ public void test_replaceEnvironmentVariablePlaceholders() throws Exception {
         setTempEnvVars(Map.of("VALUE1", "value$1", "VALUE2", "2", "VALUE3", "value-_/!\"\\'3!§%&/()=?`*,;.:[]|{}"));
 
         final String testString =
-                "<test1><test2 id=\"VALUE1\"><test3>${ENV:VALUE1}</test3><test4>${ENV:VALUE2}</test4><test5>${ENV:VALUE3}</test5></test2></test1>";
+                "<test1><test2 id=\"VALUE1\"><test3>${ENV:VALUE1}${FRAGMENT:FRAGGY}</test3><test4>${ENV:VALUE2}</test4><test5>${ENV:VALUE3}</test5></test2></test1>";
 
         final String result = EnvVarUtil.replaceEnvironmentVariablePlaceholders(testString);
 
         final String expected =
-                "<test1><test2 id=\"VALUE1\"><test3>value$1</test3><test4>2</test4><test5>value-_/!\"\\'3!§%&/()=?`*,;.:[]|{}</test5></test2></test1>";
+                "<test1><test2 id=\"VALUE1\"><test3>value$1${FRAGMENT:FRAGGY}</test3><test4>2</test4><test5>value-_/!\"\\'3!§%&/()=?`*,;.:[]|{}</test5></test2></test1>";
 
         assertEquals(expected, result);
     }

hivemq-edge/src/test/java/com/hivemq/util/FileFragmentUtilTest.java

@@ -0,0 +1,22 @@
+package com.hivemq.util;
+
+import org.junit.jupiter.api.Test;
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class FileFragmentUtilTest {
+
+    @Test
+    public void testRender() throws Exception {
+        final Path fragment = Files.createTempFile("fragment", ".xml");
+
+        Files.writeString(fragment, "THE FRAGMENT");
+        final String fragmented = "<hallo>${FRAGMENT:" + fragment.toFile() + "}</hallo>";
+        final String resolved = FileFragmentUtil.replaceFragmentPlaceHolders(fragmented);
+
+        assertThat(resolved).isEqualTo("<hallo>THE FRAGMENT</hallo>");
+    }
+}