Improve substitutions

ChangeLog.md

@@ -1,5 +1,11 @@
 # Change Log
 
+## 3.0.6
+
+- Support default values in substitutions: ${some.property:-default.value}
+- Support system properties and environment variables in substitutions: ${sys:some.property} and ${env:some.property}
+- Support nested substitutions for default values: ${env:some.property:-${sys:some.property:-default.value}}
+
 ## 3.0.5
 
 - Support SLF4J 2.0.+.

README.md

@@ -13,8 +13,8 @@ Highly efficient garbage-free logging framework for Java 8+.
 Add the following dependencies to your project:
 
 ```gradle
-implementation 'com.epam.deltix:gflog-api:3.0.5'
-runtimeOnly    'com.epam.deltix:gflog-core:3.0.5'
+implementation 'com.epam.deltix:gflog-api:3.0.6'
+runtimeOnly    'com.epam.deltix:gflog-core:3.0.6'
 ```
 
 Use the following sample to log a message:

gflog-core/src/main/java/com/epam/deltix/gflog/core/util/PropertyUtil.java

@@ -9,9 +9,6 @@
 
 public final class PropertyUtil {
 
-    private static final String SUBSTITUTION_START = "${";
-    private static final char SUBSTITUTION_END = '}';
-
     private PropertyUtil() {
     }
 
@@ -161,43 +158,6 @@ public static Duration toDuration(final String value) {
     }
 
     public static String substitute(final String value, final Properties properties) {
-        if (value.contains(SUBSTITUTION_START)) {
-            final StringBuilder builder = new StringBuilder();
-
-            final int length = value.length();
-            int i = 0;
-
-            while (true) {
-                final int j = value.indexOf(SUBSTITUTION_START, i);
-                if (j == -1) {
-                    break;
-                }
-
-                final int k = j + SUBSTITUTION_START.length();
-                final int m = value.indexOf(SUBSTITUTION_END, k);
-                if (m == -1) {
-                    break;
-                }
-
-                if (i < j) {
-                    builder.append(value, i, j);
-                }
-
-                final String name = value.substring(k, m);
-                final String substitution = properties.getProperty(name, "");
-
-                builder.append(substitution);
-                i = m + 1;
-            }
-
-            if (i < length) {
-                builder.append(value, i, length);
-            }
-
-            return builder.toString();
-        }
-
-        return value;
+        return new StringSubstitution(properties, System.getProperties(), System.getenv()).substitute(value);
     }
-
 }

gflog-core/src/main/java/com/epam/deltix/gflog/core/util/StringSubstitution.java

@@ -0,0 +1,118 @@
+package com.epam.deltix.gflog.core.util;
+
+import java.util.Map;
+import java.util.Properties;
+
+
+public final class StringSubstitution {
+
+    private static final String SYSTEM_PROPERTY_PREFIX = "sys:";
+    private static final String ENVIRONMENT_VARIABLE_PREFIX = "env:";
+
+    private final Properties defaultProperties;
+    private final Properties systemProperties;
+    private final Map<String, String> environmentVariables;
+
+    public StringSubstitution(final Properties defaultProperties,
+                              final Properties systemProperties,
+                              final Map<String, String> environmentVariables) {
+        this.defaultProperties = defaultProperties;
+        this.systemProperties = systemProperties;
+        this.environmentVariables = environmentVariables;
+    }
+
+    public String substitute(final String text) {
+        final StringBuilder builder = new StringBuilder();
+
+        for (int index = 0; index < text.length(); ) {
+            final int position = text.indexOf("${", index);
+
+            if (position < 0) {
+                builder.append(text, index, text.length());
+                break;
+            }
+
+            builder.append(text, index, position);
+            index = substitute(text, position, builder);
+        }
+
+        return builder.toString();
+    }
+
+    private int substitute(final String source, int index, final StringBuilder target) {
+        final int end = source.length();
+        final int start = index;
+
+        index += 2;
+
+        while (index < end) {
+            char c = source.charAt(index);
+
+            if (c == '}') {
+                final String key = source.substring(start + 2, index);
+                final String value = lookup(key);
+
+                if (value == null) {
+                    target.append("${").append(key).append(":#UNRESOLVED#").append("}");
+                } else {
+                    target.append(value);
+                }
+
+                return index + 1;
+            }
+
+            if (c == ':' && index + 1 < end && source.charAt(index + 1) == '-') {
+                final String key = source.substring(start + 2, index);
+                final String value = lookup(key);
+
+                final int length = target.length();
+                final int mid = index + 2;
+
+                index = mid;
+
+                while (index < end) {
+                    c = source.charAt(index);
+
+                    if (c == '}') {
+                        if (value != null) {
+                            target.setLength(length);
+                            target.append(value);
+                        }
+
+                        return index + 1;
+                    }
+
+                    if (c == '$' && index + 1 < end && source.charAt(index + 1) == '{') {
+                        index = substitute(source, index, target);
+                        continue;
+                    }
+
+                    target.append(c);
+                    index++;
+                }
+
+                target.insert(length, source, start, mid);
+                return end;
+            }
+
+            index++;
+        }
+
+        target.append(source, start, end);
+        return index;
+    }
+
+    private String lookup(final String key) {
+        if (key.startsWith(SYSTEM_PROPERTY_PREFIX)) {
+            final String propertyKey = key.substring(SYSTEM_PROPERTY_PREFIX.length());
+            return systemProperties.getProperty(propertyKey);
+        }
+
+        if (key.startsWith(ENVIRONMENT_VARIABLE_PREFIX)) {
+            final String environmentKey = key.substring(ENVIRONMENT_VARIABLE_PREFIX.length());
+            return environmentVariables.get(environmentKey);
+        }
+
+        return defaultProperties.getProperty(key);
+    }
+}

gflog-core/src/test/java/com/epam/deltix/gflog/core/util/StringSubstitutionTest.java

@@ -0,0 +1,83 @@
+package com.epam.deltix.gflog.core.util;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.Properties;
+
+public class StringSubstitutionTest {
+
+    @Test
+    public void testDefaults() {
+        final Properties defaults = new Properties();
+        defaults.put("a", "A");
+        defaults.put("b", "B");
+        defaults.put("c", "C");
+
+        final Properties systems = new Properties();
+        final Map<String, String> environments = new HashMap<>();
+        final StringSubstitution substitution = new StringSubstitution(defaults, systems, environments);
+        final Map<String, String> mapping = new LinkedHashMap<>();
+
+        mapping.put("12345", "12345");
+        mapping.put("${a} ${b} ${c}", "A B C");
+        mapping.put("${a:-10} ${b:-${c:-100500}}", "A B");
+        mapping.put("${missing:-5} + ${missing:-10}", "5 + 10");
+        mapping.put("${missing:-${a}}", "A");
+        mapping.put("${missing:-${missing2:-${b}}}", "B");
+        mapping.put("${missing:-${missing2:-${missing3:-${c}}}}", "C");
+        mapping.put("${a:-5", "${a:-5");
+        mapping.put(" ${a:-${b} ", " ${a:-B ");
+        mapping.put(" ${a:-${b:-${c ", " ${a:-${b:-${c ");
+        mapping.put(" ${a:-${b:-${c} ", " ${a:-${b:-C ");
+        mapping.put(" ${a:-${b:-${c}} ", " ${a:-B ");
+        mapping.put("${missing}", "${missing:#UNRESOLVED#}");
+        mapping.put("${missing:-1 ${a} 2 ${missing2} 3}", "1 A 2 ${missing2:#UNRESOLVED#} 3");
+        mapping.put("${missing:-}", "");
+
+        for (final Map.Entry<String, String> entry : mapping.entrySet()) {
+            final String text = entry.getKey();
+            final String expected = entry.getValue();
+            final String actual = substitution.substitute(text);
+
+            Assert.assertEquals(expected, actual);
+        }
+    }
+
+    @Test
+    public void testEnvironmentAndSystemSubstitution() {
+        final Properties defaults = new Properties();
+        defaults.put("a", "1");
+        defaults.put("b", "2");
+        defaults.put("c", "3");
+
+        final Properties systems = new Properties();
+        systems.put("a", "4");
+        systems.put("b", "5");
+        systems.put("c", "6");
+
+        final Map<String, String> environments = new HashMap<>();
+        environments.put("a", "7");
+        environments.put("b", "8");
+        environments.put("c", "9");
+
+        final StringSubstitution substitution = new StringSubstitution(defaults, systems, environments);
+        final Map<String, String> mapping = new LinkedHashMap<>();
+
+        mapping.put("${a} ${sys:a} ${env:a}", "1 4 7");
+        mapping.put("${missing:-${b}} ${missing:-${sys:b}} ${missing:-${env:b}}", "2 5 8");
+        mapping.put("${sys:missing:-${b}} ${sys:missing:-${sys:b}} ${sys:missing:-${env:b}}", "2 5 8");
+        mapping.put("${env:missing:-${b}} ${env:missing:-${sys:b}} ${env:missing:-${env:b}}", "2 5 8");
+
+        for (final Map.Entry<String, String> entry : mapping.entrySet()) {
+            final String text = entry.getKey();
+            final String expected = entry.getValue();
+            final String actual = substitution.substitute(text);
+
+            Assert.assertEquals(expected, actual);
+        }
+    }
+}