DefaultLogger: make log level static (read it once) (Azure#27193)

* cache missing env value and neven re-read it

Author: Liudmila Molkova

sdk/core/azure-core/src/main/java/com/azure/core/implementation/logging/DefaultLogger.java

@@ -67,9 +67,8 @@ public DefaultLogger(String className) {
             classPath = className;
         }
         this.classPath = classPath;
-        int configuredLogLevel =
-            LogLevel.fromString(Configuration.getGlobalConfiguration().get(Configuration.PROPERTY_AZURE_LOG_LEVEL))
-                .getLogLevel();
+        int configuredLogLevel = LogLevel.fromString(Configuration.getGlobalConfiguration().get(Configuration.PROPERTY_AZURE_LOG_LEVEL))
+            .getLogLevel();
 
         isTraceEnabled = LogLevel.VERBOSE.getLogLevel() > configuredLogLevel;
         isDebugEnabled = LogLevel.VERBOSE.getLogLevel() >= configuredLogLevel;

sdk/core/azure-core/src/main/java/com/azure/core/util/Configuration.java

@@ -3,6 +3,7 @@
 
 package com.azure.core.util;
 
+import java.util.Optional;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 import java.util.function.Function;
@@ -214,7 +215,7 @@ public class Configuration implements Cloneable {
     @SuppressWarnings("StaticInitializerReferencesSubClass")
     public static final Configuration NONE = new NoopConfiguration();
 
-    private final ConcurrentMap<String, String> configurations;
+    private final ConcurrentMap<String, Optional<String>> configurations;
 
     /**
      * Constructs a configuration containing the known Azure properties constants.
@@ -224,7 +225,7 @@ public Configuration() {
         loadBaseConfiguration(this);
     }
 
-    private Configuration(ConcurrentMap<String, String> configurations) {
+    private Configuration(ConcurrentMap<String, Optional<String>> configurations) {
         this.configurations = new ConcurrentHashMap<>(configurations);
     }
 
@@ -300,18 +301,15 @@ public <T> T get(String name, Function<String, T> converter) {
      * variable, in that order, if found, otherwise null.
      */
     private String getOrLoad(String name) {
-        String value = configurations.get(name);
-        if (value != null) {
-            return value;
+        Optional<String> cached = configurations.get(name);
+        if (cached != null) {
+            return cached.orElse(null);
         }
 
-        value = load(name);
-        if (value != null) {
-            configurations.put(name, value);
-            return value;
-        }
+        String value = load(name);
+        configurations.put(name, Optional.ofNullable(value));
 
-        return null;
+        return value;
     }
 
     /*
@@ -350,7 +348,7 @@ String loadFromProperties(String name) {
      * @return The updated Configuration object.
      */
     public Configuration put(String name, String value) {
-        configurations.put(name, value);
+        configurations.put(name, Optional.of(value));
         return this;
     }
 
@@ -363,7 +361,8 @@ public Configuration put(String name, String value) {
      * @return The configuration if it previously existed, otherwise null.
      */
     public String remove(String name) {
-        return configurations.remove(name);
+        Optional<String> value = configurations.remove(name);
+        return (value != null && value.isPresent()) ? value.get() : null;
     }
 
     /**
@@ -376,7 +375,8 @@ public String remove(String name) {
      * @return True if the configuration exists, otherwise false.
      */
     public boolean contains(String name) {
-        return configurations.containsKey(name);
+        Optional<String> value = configurations.get(name);
+        return value != null && value.isPresent();
     }
 
     /**

sdk/core/azure-core/src/test/java/com/azure/core/util/ConfigurationTests.java

@@ -12,6 +12,7 @@
 
 import static com.azure.core.util.Configuration.PROPERTY_AZURE_TRACING_DISABLED;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.mockito.Mockito.spy;
@@ -57,6 +58,7 @@ public void environmentConfigurationFound() {
     public void configurationNotFound() {
         Configuration configuration = new Configuration();
         assertNull(configuration.get(MY_CONFIGURATION));
+        assertFalse(configuration.contains(MY_CONFIGURATION));
     }
 
     /**