SONAR-7678 server-side stateless settings

* Settings class becomes abstract as multiple implementations
are used. Can't become an interface for binary
backward-compatibility of API

* tests should use MapSettings, an in-memory implementation
of Settings

* web server uses a thread-specific cache of settings when
processing HTTP requests

* web server does not have a cache of settings during startup,
except for the system settings loaded from sonar.properties

* Compute Engine uses a thread-specific cache of settings when
  processing a task. Cache is clear at end of task.

 * some useless methods of PersistentSettings are removed

11 files changed, 260 insertions, 223 deletions

diff --git a/sonar-plugin-api/src/main/java/org/sonar/api/batch/sensor/internal/SensorContextTester.java b/sonar-plugin-api/src/main/java/org/sonar/api/batch/sensor/internal/SensorContextTester.java
index f3971eb7fb7..fc7e4b169ad 100644
--- a/sonar-plugin-api/src/main/java/org/sonar/api/batch/sensor/internal/SensorContextTester.java
+++ b/sonar-plugin-api/src/main/java/org/sonar/api/batch/sensor/internal/SensorContextTester.java
@@ -62,6 +62,7 @@ import org.sonar.api.batch.sensor.measure.internal.DefaultMeasure;
 import org.sonar.api.batch.sensor.symbol.NewSymbolTable;
 import org.sonar.api.batch.sensor.symbol.internal.DefaultSymbolTable;
 import org.sonar.api.config.Settings;
+import org.sonar.api.config.MapSettings;
 import org.sonar.api.internal.ApiVersion;
 import org.sonar.api.internal.SonarRuntimeImpl;
 import org.sonar.api.measures.Metric;
@@ -95,7 +96,7 @@ public class SensorContextTester implements SensorContext {
   private boolean cancelled;
 
   private SensorContextTester(Path moduleBaseDir) {
-    this.settings = new Settings();
+    this.settings = new MapSettings();
     this.fs = new DefaultFileSystem(moduleBaseDir);
     this.activeRules = new ActiveRulesBuilder().build();
     this.sensorStorage = new InMemorySensorStorage();
diff --git a/sonar-plugin-api/src/main/java/org/sonar/api/config/Encryption.java b/sonar-plugin-api/src/main/java/org/sonar/api/config/Encryption.java
index f07affe4767..03d40bc4822 100644
--- a/sonar-plugin-api/src/main/java/org/sonar/api/config/Encryption.java
+++ b/sonar-plugin-api/src/main/java/org/sonar/api/config/Encryption.java
@@ -44,8 +44,8 @@ public final class Encryption {
   public Encryption(@Nullable String pathToSecretKey) {
     aesCipher = new AesCipher(pathToSecretKey);
     ciphers = ImmutableMap.of(
-        BASE64_ALGORITHM, new Base64Cipher(),
-        AES_ALGORITHM, aesCipher);
+      BASE64_ALGORITHM, new Base64Cipher(),
+      AES_ALGORITHM, aesCipher);
   }
 
   public void setPathToSecretKey(@Nullable String pathToSecretKey) {
diff --git a/sonar-plugin-api/src/main/java/org/sonar/api/config/MapSettings.java b/sonar-plugin-api/src/main/java/org/sonar/api/config/MapSettings.java
new file mode 100644
index 00000000000..d8726881e1e
--- /dev/null
+++ b/sonar-plugin-api/src/main/java/org/sonar/api/config/MapSettings.java
@@ -0,0 +1,71 @@
+/*
+ * SonarQube
+ * Copyright (C) 2009-2016 SonarSource SA
+ * mailto:contact AT sonarsource DOT com
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 3 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+package org.sonar.api.config;
+
+import com.google.common.collect.ImmutableMap;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Optional;
+
+/**
+ * In-memory map-based implementation of {@link Settings}. It must be used
+ * <b>only for unit tests</b>. This is not the implementation
+ * deployed at runtime, so non-test code must never cast
+ * {@link Settings} to {@link MapSettings}.
+ *
+ * @since 6.1
+ */
+public class MapSettings extends Settings {
+
+  private final Map<String, String> props = new HashMap<>();
+
+  public MapSettings() {
+    super(new PropertyDefinitions(), new Encryption(null));
+  }
+
+  public MapSettings(PropertyDefinitions definitions) {
+    super(definitions, new Encryption(null));
+  }
+
+  @Override
+  protected Optional<String> get(String key) {
+    return Optional.ofNullable(props.get(key));
+  }
+
+  @Override
+  protected void set(String key, String value) {
+    props.put(key, value);
+  }
+
+  @Override
+  protected void remove(String key) {
+    props.remove(key);
+  }
+
+  @Override
+  public Map<String, String> getProperties() {
+    return ImmutableMap.copyOf(props);
+  }
+
+  public MapSettings clear() {
+    props.clear();
+    return this;
+  }
+}
diff --git a/sonar-plugin-api/src/main/java/org/sonar/api/config/Settings.java b/sonar-plugin-api/src/main/java/org/sonar/api/config/Settings.java
index f2cdf1aad8d..aa3f3bdc760 100644
--- a/sonar-plugin-api/src/main/java/org/sonar/api/config/Settings.java
+++ b/sonar-plugin-api/src/main/java/org/sonar/api/config/Settings.java
@@ -22,13 +22,13 @@ package org.sonar.api.config;
 import com.google.common.base.Joiner;
 import com.google.common.base.Splitter;
 import com.google.common.base.Strings;
-import com.google.common.collect.ImmutableMap;
-import com.google.common.collect.Maps;
 import java.util.ArrayList;
 import java.util.Date;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Properties;
+import java.util.stream.Collectors;
 import javax.annotation.CheckForNull;
 import javax.annotation.Nullable;
 import org.apache.commons.lang.ArrayUtils;
@@ -38,7 +38,11 @@ import org.sonar.api.ce.ComputeEngineSide;
 import org.sonar.api.server.ServerSide;
 import org.sonar.api.utils.DateUtils;
 
+import static java.util.Objects.requireNonNull;
+import static org.apache.commons.lang.StringUtils.trim;
+
 /**
+ *
  * Project settings on batch side, or global settings on server side. This component does not access to database, so
  * property changed via setter methods are not persisted.
  * <br>
@@ -55,7 +59,7 @@ import org.sonar.api.utils.DateUtils;
  *     defaultValue = "A default value",
  *     name = "My property"),
  * })
- * public class MyPlugin extends SonarPlugin {
+ * class MyPlugin extends SonarPlugin {
  * </code>
  * </pre>
  * then you can use:
@@ -67,8 +71,8 @@ import org.sonar.api.utils.DateUtils;
  * <li>If you are using the {@link PropertyDefinition#builder(String)} way like:
  * <pre>
  * <code>
- * public class MyPlugin extends SonarPlugin {
- *     public List getExtensions() {
+ * class MyPlugin extends SonarPlugin {
+ *     List getExtensions() {
  *       return Arrays.asList(
  *         PropertyDefinition.builder("sonar.myProp").name("My property").defaultValue("A default value").build()
  *       );
@@ -83,89 +87,130 @@ import org.sonar.api.utils.DateUtils;
  * </pre>
  * </li>
  * </ul>
- * 
+ *
+ * History - this class is abstract since 6.1.
  * @since 2.12
  */
 @ScannerSide
 @ServerSide
 @ComputeEngineSide
-public class Settings {
+public abstract class Settings {
 
-  protected Map<String, String> properties;
-  protected PropertyDefinitions definitions;
-  private Encryption encryption;
+  private final PropertyDefinitions definitions;
+  private final Encryption encryption;
 
-  public Settings() {
-    this(new PropertyDefinitions());
+  protected Settings(PropertyDefinitions definitions, Encryption encryption) {
+    this.definitions = requireNonNull(definitions);
+    this.encryption = requireNonNull(encryption);
   }
 
-  public Settings(PropertyDefinitions definitions) {
-    this.properties = Maps.newHashMap();
-    this.definitions = definitions;
-    this.encryption = new Encryption(null);
+  protected abstract Optional<String> get(String key);
+
+  protected abstract void set(String key, String value);
+
+  protected abstract void remove(String key);
+
+  /**
+   * Immutable map of the properties that have non-default values.
+   * The default values defined by {@link PropertyDefinitions} are ignored,
+   * so the returned values are not the effective values. Basically only
+   * the non-empty results of {@link #getRawString(String)} are returned.
+   * <p>
+   * Values are not decrypted if they are encrypted with a secret key.
+   * </p>
+   */
+  public abstract Map<String, String> getProperties();
+
+  // FIXME scope to be replaced by "protected" as soon as not used by JRubyFacade
+  public Encryption getEncryption() {
+    return encryption;
   }
 
   /**
-   * Clone settings. Actions are not propagated to cloned settings.
+   * The value that overrides the default value. It
+   * may be encrypted with a secret key. Use {@link #getString(String)} to get
+   * the effective and decrypted value.
    *
-   * @since 3.1
+   * @since 6.1
    */
-  public Settings(Settings other) {
-    this.properties = Maps.newHashMap(other.getProperties());
-    this.definitions = other.getDefinitions();
-    this.encryption = other.getEncryption();
+  public Optional<String> getRawString(String key) {
+    return get(definitions.validKey(requireNonNull(key)));
   }
 
-  public Encryption getEncryption() {
-    return encryption;
+  /**
+   * All the property definitions declared by core and plugins.
+   */
+  public PropertyDefinitions getDefinitions() {
+    return definitions;
   }
 
-  @CheckForNull
-  public String getDefaultValue(String key) {
-    return definitions.getDefaultValue(key);
+  /**
+   * The definition related to the specified property. It may
+   * be empty.
+   *
+   * @since 6.1
+   */
+  public Optional<PropertyDefinition> getDefinition(String key) {
+    return Optional.ofNullable(definitions.get(key));
   }
 
+  /**
+   * @return {@code true} if the property has a non-default value, else {@code false}.
+   */
   public boolean hasKey(String key) {
-    return properties.containsKey(key);
+    return getRawString(key).isPresent();
+  }
+
+  @CheckForNull
+  public String getDefaultValue(String key) {
+    return definitions.getDefaultValue(key);
   }
 
   public boolean hasDefaultValue(String key) {
     return StringUtils.isNotEmpty(getDefaultValue(key));
   }
 
+  /**
+   * The effective value of the specified property. Can return
+   * {@code null} if the property is not set and has no
+   * defined default value.
+   * <p>
+   * If the property is encrypted with a secret key,
+   * then the returned value is decrypted.
+   * </p>
+   *
+   * @throws IllegalStateException if value is encrypted but fails to be decrypted.
+   */
   @CheckForNull
   public String getString(String key) {
-    String value = getClearString(key);
-    if (value != null && encryption.isEncrypted(value)) {
+    String effectiveKey = definitions.validKey(key);
+    Optional<String> value = getRawString(effectiveKey);
+    if (!value.isPresent()) {
+      // default values cannot be encrypted, so return value as-is.
+      return getDefaultValue(effectiveKey);
+    }
+    if (encryption.isEncrypted(value.get())) {
       try {
-        value = encryption.decrypt(value);
+        return encryption.decrypt(value.get());
       } catch (Exception e) {
-        throw new IllegalStateException("Fail to decrypt the property " + key + ". Please check your secret key.", e);
+        throw new IllegalStateException("Fail to decrypt the property " + effectiveKey + ". Please check your secret key.", e);
       }
     }
-    return value;
+    return value.get();
   }
 
   /**
-   * Does not decrypt value.
+   * Effective value as boolean. It is {@code false} if {@link #getString(String)}
+   * does not return {@code "true"}, even if it's not a boolean representation.
+   * @return {@code true} if the effective value is {@code "true"}, else {@code false}.
    */
-  @CheckForNull
-  protected String getClearString(String key) {
-    doOnGetProperties(key);
-    String validKey = definitions.validKey(key);
-    String value = properties.get(validKey);
-    if (value == null) {
-      value = getDefaultValue(validKey);
-    }
-    return value;
-  }
-
   public boolean getBoolean(String key) {
     String value = getString(key);
     return StringUtils.isNotEmpty(value) && Boolean.parseBoolean(value);
   }
 
   /**
+   * Effective value as int.
    * @return the value as int. If the property does not exist and has no default value, then 0 is returned.
    */
   public int getInt(String key) {
@@ -239,8 +284,8 @@ public class Settings {
    * </ul>
    */
   public String[] getStringArray(String key) {
-    PropertyDefinition property = getDefinitions().get(key);
-    if ((null != property) && (property.multiValues())) {
+    Optional<PropertyDefinition> def = getDefinition(key);
+    if ((def.isPresent()) && (def.get().multiValues())) {
       String value = getString(key);
       if (value == null) {
         return ArrayUtils.EMPTY_STRING_ARRAY;
@@ -271,7 +316,7 @@ public class Settings {
   }
 
   /**
-   * Value is splitted and trimmed.
+   * Value is split and trimmed.
    */
   public String[] getStringArrayBySeparator(String key, String separator) {
     String value = getString(key);
@@ -279,36 +324,27 @@ public class Settings {
       String[] strings = StringUtils.splitByWholeSeparator(value, separator);
       String[] result = new String[strings.length];
       for (int index = 0; index < strings.length; index++) {
-        result[index] = StringUtils.trim(strings[index]);
+        result[index] = trim(strings[index]);
       }
       return result;
     }
     return ArrayUtils.EMPTY_STRING_ARRAY;
   }
 
-  public List<String> getKeysStartingWith(String prefix) {
-    List<String> result = new ArrayList<>();
-    for (String key : properties.keySet()) {
-      if (StringUtils.startsWith(key, prefix)) {
-        result.add(key);
-      }
-    }
-    return result;
-  }
-
-  public Settings appendProperty(String key, String value) {
-    String newValue = properties.get(definitions.validKey(key));
-    if (StringUtils.isEmpty(newValue)) {
-      newValue = StringUtils.trim(value);
+  public Settings appendProperty(String key, @Nullable String value) {
+    Optional<String> existingValue = getRawString(definitions.validKey(key));
+    String newValue;
+    if (!existingValue.isPresent()) {
+      newValue = trim(value);
     } else {
-      newValue += "," + StringUtils.trim(value);
+      newValue = existingValue.get() + "," + trim(value);
     }
     return setProperty(key, newValue);
   }
 
   public Settings setProperty(String key, @Nullable String[] values) {
-    PropertyDefinition property = getDefinitions().get(key);
-    if ((null == property) || (!property.multiValues())) {
+    Optional<PropertyDefinition> def = getDefinition(key);
+    if (!def.isPresent() || (!def.get().multiValues())) {
       throw new IllegalStateException("Fail to set multiple values on a single value property " + key);
     }
 
@@ -324,7 +360,7 @@ public class Settings {
       }
 
       String escapedValue = Joiner.on(',').join(escaped);
-      text = StringUtils.trim(escapedValue);
+      text = trim(escapedValue);
     }
     return setProperty(key, text);
   }
@@ -332,11 +368,10 @@ public class Settings {
   public Settings setProperty(String key, @Nullable String value) {
     String validKey = definitions.validKey(key);
     if (value == null) {
-      properties.remove(validKey);
-      doOnRemoveProperty(validKey);
+      removeProperty(validKey);
+
     } else {
-      properties.put(validKey, StringUtils.trim(value));
-      doOnSetProperty(validKey, value);
+      set(validKey, trim(value));
     }
     return this;
   }
@@ -379,11 +414,6 @@ public class Settings {
     return this;
   }
 
-  public Settings setProperties(Map<String, String> props) {
-    clear();
-    return addProperties(props);
-  }
-
   public Settings setProperty(String key, @Nullable Date date, boolean includeTime) {
     if (date == null) {
       return removeProperty(key);
@@ -392,48 +422,14 @@ public class Settings {
   }
 
   public Settings removeProperty(String key) {
-    return setProperty(key, (String) null);
-  }
-
-  public Settings clear() {
-    properties.clear();
-    doOnClearProperties();
+    remove(key);
     return this;
   }
 
-  /**
-   *
-   * @return immutable copy of properties. Encrypted values are kept and not decrypted.
-   */
-  public Map<String, String> getProperties() {
-    return ImmutableMap.copyOf(properties);
-  }
-
-  public PropertyDefinitions getDefinitions() {
-    return definitions;
-  }
-
-  /**
-   * Create empty settings. Definition of available properties is loaded from the given annotated class.
-   * This method is usually used by unit tests.
-   */
-  public static Settings createForComponent(Object component) {
-    return new Settings(new PropertyDefinitions(component));
-  }
-
-  protected void doOnSetProperty(String key, @Nullable String value) {
-    // can be overridden
-  }
-
-  protected void doOnRemoveProperty(String key) {
-    // can be overridden
-  }
-
-  protected void doOnClearProperties() {
-    // can be overridden
+  public List<String> getKeysStartingWith(String prefix) {
+    return getProperties().keySet().stream()
+      .filter(key -> StringUtils.startsWith(key, prefix))
+      .collect(Collectors.toList());
   }
 
-  protected void doOnGetProperties(String key) {
-    // can be overridden
-  }
 }
diff --git a/sonar-plugin-api/src/test/java/org/sonar/api/batch/bootstrap/ProjectBuilderTest.java b/sonar-plugin-api/src/test/java/org/sonar/api/batch/bootstrap/ProjectBuilderTest.java
index 6fbf0bdfdc7..5bb9adc01eb 100644
--- a/sonar-plugin-api/src/test/java/org/sonar/api/batch/bootstrap/ProjectBuilderTest.java
+++ b/sonar-plugin-api/src/test/java/org/sonar/api/batch/bootstrap/ProjectBuilderTest.java
@@ -19,17 +19,15 @@
  */
 package org.sonar.api.batch.bootstrap;
 
+import java.io.File;
 import org.junit.Test;
 import org.sonar.api.batch.bootstrap.internal.ProjectBuilderContext;
 import org.sonar.api.config.Settings;
+import org.sonar.api.config.MapSettings;
 
 import static org.assertj.core.api.Assertions.assertThat;
-
-import java.io.File;
-
 import static org.hamcrest.core.Is.is;
 import static org.junit.Assert.assertThat;
-import static org.junit.matchers.JUnitMatchers.hasItem;
 
 public class ProjectBuilderTest {
 
@@ -38,7 +36,7 @@ public class ProjectBuilderTest {
     // this reactor is created and provided by Sonar
     final ProjectReactor projectReactor = new ProjectReactor(ProjectDefinition.create());
 
-    ProjectBuilder builder = new ProjectBuilderSample(new Settings());
+    ProjectBuilder builder = new ProjectBuilderSample(new MapSettings());
     builder.build(new ProjectBuilderContext(projectReactor));
 
     assertThat(projectReactor.getProjects().size(), is(2));
diff --git a/sonar-plugin-api/src/test/java/org/sonar/api/batch/sensor/cpd/internal/DefaultCpdTokensTest.java b/sonar-plugin-api/src/test/java/org/sonar/api/batch/sensor/cpd/internal/DefaultCpdTokensTest.java
index 96310b70977..c5772e3b349 100644
--- a/sonar-plugin-api/src/test/java/org/sonar/api/batch/sensor/cpd/internal/DefaultCpdTokensTest.java
+++ b/sonar-plugin-api/src/test/java/org/sonar/api/batch/sensor/cpd/internal/DefaultCpdTokensTest.java
@@ -23,6 +23,7 @@ import org.junit.Test;
 import org.sonar.api.batch.fs.internal.DefaultInputFile;
 import org.sonar.api.batch.sensor.internal.SensorStorage;
 import org.sonar.api.config.Settings;
+import org.sonar.api.config.MapSettings;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.fail;
@@ -42,7 +43,7 @@ public class DefaultCpdTokensTest {
   @Test
   public void save_no_tokens() {
     SensorStorage sensorStorage = mock(SensorStorage.class);
-    DefaultCpdTokens tokens = new DefaultCpdTokens(new Settings(), sensorStorage)
+    DefaultCpdTokens tokens = new DefaultCpdTokens(new MapSettings(), sensorStorage)
       .onFile(INPUT_FILE);
 
     tokens.save();
@@ -55,7 +56,7 @@ public class DefaultCpdTokensTest {
   @Test
   public void save_one_token() {
     SensorStorage sensorStorage = mock(SensorStorage.class);
-    DefaultCpdTokens tokens = new DefaultCpdTokens(new Settings(), sensorStorage)
+    DefaultCpdTokens tokens = new DefaultCpdTokens(new MapSettings(), sensorStorage)
       .onFile(INPUT_FILE)
       .addToken(INPUT_FILE.newRange(1, 2, 1, 5), "foo");
 
@@ -69,7 +70,7 @@ public class DefaultCpdTokensTest {
   @Test
   public void handle_exclusions_by_pattern() {
     SensorStorage sensorStorage = mock(SensorStorage.class);
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     settings.setProperty("sonar.cpd.exclusions", "src/Foo.java,another");
     DefaultCpdTokens tokens = new DefaultCpdTokens(settings, sensorStorage)
       .onFile(INPUT_FILE)
@@ -85,7 +86,7 @@ public class DefaultCpdTokensTest {
   @Test
   public void save_many_tokens() {
     SensorStorage sensorStorage = mock(SensorStorage.class);
-    DefaultCpdTokens tokens = new DefaultCpdTokens(new Settings(), sensorStorage)
+    DefaultCpdTokens tokens = new DefaultCpdTokens(new MapSettings(), sensorStorage)
       .onFile(INPUT_FILE)
       .addToken(INPUT_FILE.newRange(1, 2, 1, 5), "foo")
       .addToken(INPUT_FILE.newRange(1, 6, 1, 10), "bar")
@@ -106,7 +107,7 @@ public class DefaultCpdTokensTest {
   @Test
   public void basic_validation() {
     SensorStorage sensorStorage = mock(SensorStorage.class);
-    DefaultCpdTokens tokens = new DefaultCpdTokens(new Settings(), sensorStorage);
+    DefaultCpdTokens tokens = new DefaultCpdTokens(new MapSettings(), sensorStorage);
     try {
       tokens.save();
       fail("Expected exception");
@@ -136,7 +137,7 @@ public class DefaultCpdTokensTest {
   @Test
   public void validate_tokens_order() {
     SensorStorage sensorStorage = mock(SensorStorage.class);
-    DefaultCpdTokens tokens = new DefaultCpdTokens(new Settings(), sensorStorage)
+    DefaultCpdTokens tokens = new DefaultCpdTokens(new MapSettings(), sensorStorage)
       .onFile(INPUT_FILE)
       .addToken(INPUT_FILE.newRange(1, 6, 1, 10), "bar");
 
diff --git a/sonar-plugin-api/src/test/java/org/sonar/api/batch/sensor/internal/SensorContextTesterTest.java b/sonar-plugin-api/src/test/java/org/sonar/api/batch/sensor/internal/SensorContextTesterTest.java
index 79f96f23e55..807d8663773 100644
--- a/sonar-plugin-api/src/test/java/org/sonar/api/batch/sensor/internal/SensorContextTesterTest.java
+++ b/sonar-plugin-api/src/test/java/org/sonar/api/batch/sensor/internal/SensorContextTesterTest.java
@@ -42,6 +42,7 @@ import org.sonar.api.batch.sensor.highlighting.TypeOfText;
 import org.sonar.api.batch.sensor.issue.NewIssue;
 import org.sonar.api.batch.sensor.symbol.NewSymbolTable;
 import org.sonar.api.config.Settings;
+import org.sonar.api.config.MapSettings;
 import org.sonar.api.measures.CoreMetrics;
 import org.sonar.api.rule.RuleKey;
 import org.sonar.api.utils.SonarException;
@@ -69,7 +70,7 @@ public class SensorContextTesterTest {
 
   @Test
   public void testSettings() {
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     settings.setProperty("foo", "bar");
     tester.setSettings(settings);
     assertThat(tester.settings().getString("foo")).isEqualTo("bar");
diff --git a/sonar-plugin-api/src/test/java/org/sonar/api/config/EmailSettingsTest.java b/sonar-plugin-api/src/test/java/org/sonar/api/config/EmailSettingsTest.java
index 4f326137891..2c395c980ca 100644
--- a/sonar-plugin-api/src/test/java/org/sonar/api/config/EmailSettingsTest.java
+++ b/sonar-plugin-api/src/test/java/org/sonar/api/config/EmailSettingsTest.java
@@ -19,31 +19,24 @@
  */
 package org.sonar.api.config;
 
-import org.junit.Before;
 import org.junit.Test;
 import org.sonar.api.CoreProperties;
-import org.sonar.api.config.EmailSettings;
-import org.sonar.api.config.Settings;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
 public class EmailSettingsTest {
-  EmailSettings emailSettings;
 
-  @Before
-  public void setUp() {
-    emailSettings = new EmailSettings(new Settings());
-  }
+  private EmailSettings underTest = new EmailSettings(new MapSettings());
 
   @Test
   public void should_return_default_values() {
-    assertThat(emailSettings.getSmtpHost()).isEqualTo("");
-    assertThat(emailSettings.getSmtpPort()).isEqualTo(25);
-    assertThat(emailSettings.getSmtpUsername()).isEmpty();
-    assertThat(emailSettings.getSmtpPassword()).isEmpty();
-    assertThat(emailSettings.getSecureConnection()).isEmpty();
-    assertThat(emailSettings.getFrom()).isEqualTo("noreply@nowhere");
-    assertThat(emailSettings.getPrefix()).isEqualTo("[SONARQUBE]");
-    assertThat(emailSettings.getServerBaseURL()).isEqualTo(CoreProperties.SERVER_BASE_URL_DEFAULT_VALUE);
+    assertThat(underTest.getSmtpHost()).isEqualTo("");
+    assertThat(underTest.getSmtpPort()).isEqualTo(25);
+    assertThat(underTest.getSmtpUsername()).isEmpty();
+    assertThat(underTest.getSmtpPassword()).isEmpty();
+    assertThat(underTest.getSecureConnection()).isEmpty();
+    assertThat(underTest.getFrom()).isEqualTo("noreply@nowhere");
+    assertThat(underTest.getPrefix()).isEqualTo("[SONARQUBE]");
+    assertThat(underTest.getServerBaseURL()).isEqualTo(CoreProperties.SERVER_BASE_URL_DEFAULT_VALUE);
   }
 }
diff --git a/sonar-plugin-api/src/test/java/org/sonar/api/config/SettingsTest.java b/sonar-plugin-api/src/test/java/org/sonar/api/config/MapSettingsTest.java
index 58822cadb7f..e4ba990c7ef 100644
--- a/sonar-plugin-api/src/test/java/org/sonar/api/config/SettingsTest.java
+++ b/sonar-plugin-api/src/test/java/org/sonar/api/config/MapSettingsTest.java
@@ -19,7 +19,7 @@
  */
 package org.sonar.api.config;
 
-import com.google.common.collect.ImmutableMap;
+import java.util.Date;
 import org.assertj.core.data.Offset;
 import org.junit.Before;
 import org.junit.Rule;
@@ -30,11 +30,9 @@ import org.sonar.api.Property;
 import org.sonar.api.PropertyType;
 import org.sonar.api.utils.DateUtils;
 
-import java.util.Date;
-
 import static org.assertj.core.api.Assertions.assertThat;
 
-public class SettingsTest {
+public class MapSettingsTest {
 
   private PropertyDefinitions definitions;
 
@@ -52,7 +50,7 @@ public class SettingsTest {
     @Property(key = "newKeyWithDefaultValue", name = "New key with default value", deprecatedKey = "oldKeyWithDefaultValue", defaultValue = "default_value"),
     @Property(key = "new_multi_values", name = "New multi values", defaultValue = "1,2,3", multiValues = true, deprecatedKey = "old_multi_values")
   })
-  static class Init {
+  private static class Init {
   }
 
   @Rule
@@ -66,13 +64,13 @@ public class SettingsTest {
 
   @Test
   public void default_values_should_be_loaded_from_definitions() {
-    Settings settings = new Settings(definitions);
+    Settings settings = new MapSettings(definitions);
     assertThat(settings.getDefaultValue("hello")).isEqualTo("world");
   }
 
   @Test
   public void set_property_int() {
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     settings.setProperty("foo", 123);
     assertThat(settings.getInt("foo")).isEqualTo(123);
     assertThat(settings.getString("foo")).isEqualTo("123");
@@ -81,7 +79,7 @@ public class SettingsTest {
 
   @Test
   public void default_number_values_are_zero() {
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     assertThat(settings.getInt("foo")).isEqualTo(0);
     assertThat(settings.getLong("foo")).isEqualTo(0L);
   }
@@ -90,41 +88,34 @@ public class SettingsTest {
   public void getInt_value_must_be_valid() {
     thrown.expect(NumberFormatException.class);
 
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     settings.setProperty("foo", "not a number");
     settings.getInt("foo");
   }
 
   @Test
   public void all_values_should_be_trimmed_set_property() {
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     settings.setProperty("foo", "   FOO ");
     assertThat(settings.getString("foo")).isEqualTo("FOO");
   }
 
   @Test
-  public void all_values_should_be_trimmed_set_properties() {
-    Settings settings = new Settings();
-    settings.setProperties(ImmutableMap.of("foo", "  FOO "));
-    assertThat(settings.getString("foo")).isEqualTo("FOO");
-  }
-
-  @Test
   public void test_get_default_value() {
-    Settings settings = new Settings(definitions);
+    Settings settings = new MapSettings(definitions);
     assertThat(settings.getDefaultValue("unknown")).isNull();
   }
 
   @Test
   public void test_get_string() {
-    Settings settings = new Settings(definitions);
+    Settings settings = new MapSettings(definitions);
     settings.setProperty("hello", "Russia");
     assertThat(settings.getString("hello")).isEqualTo("Russia");
   }
 
   @Test
   public void setProperty_date() {
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     Date date = DateUtils.parseDateTime("2010-05-18T15:50:45+0100");
     settings.setProperty("aDate", date);
     settings.setProperty("aDateTime", date, true);
@@ -135,7 +126,7 @@ public class SettingsTest {
 
   @Test
   public void test_get_date() {
-    Settings settings = new Settings(definitions);
+    Settings settings = new MapSettings(definitions);
     assertThat(settings.getDate("unknown")).isNull();
     assertThat(settings.getDate("date").getDate()).isEqualTo(18);
     assertThat(settings.getDate("date").getMonth()).isEqualTo(4);
@@ -143,13 +134,13 @@ public class SettingsTest {
 
   @Test
   public void test_get_date_not_found() {
-    Settings settings = new Settings(definitions);
+    Settings settings = new MapSettings(definitions);
     assertThat(settings.getDate("unknown")).isNull();
   }
 
   @Test
   public void test_get_datetime() {
-    Settings settings = new Settings(definitions);
+    Settings settings = new MapSettings(definitions);
     assertThat(settings.getDateTime("unknown")).isNull();
     assertThat(settings.getDateTime("datetime").getDate()).isEqualTo(18);
     assertThat(settings.getDateTime("datetime").getMonth()).isEqualTo(4);
@@ -158,7 +149,7 @@ public class SettingsTest {
 
   @Test
   public void test_get_double() {
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     settings.setProperty("from_double", 3.14159);
     settings.setProperty("from_string", "3.14159");
     assertThat(settings.getDouble("from_double")).isEqualTo(3.14159, Offset.offset(0.00001));
@@ -168,7 +159,7 @@ public class SettingsTest {
 
   @Test
   public void test_get_float() {
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     settings.setProperty("from_float", 3.14159f);
     settings.setProperty("from_string", "3.14159");
     assertThat(settings.getDouble("from_float")).isEqualTo(3.14159f, Offset.offset(0.00001));
@@ -178,7 +169,7 @@ public class SettingsTest {
 
   @Test
   public void test_get_bad_float() {
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     settings.setProperty("foo", "bar");
 
     thrown.expect(IllegalStateException.class);
@@ -188,7 +179,7 @@ public class SettingsTest {
 
   @Test
   public void test_get_bad_double() {
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     settings.setProperty("foo", "bar");
 
     thrown.expect(IllegalStateException.class);
@@ -198,28 +189,28 @@ public class SettingsTest {
 
   @Test
   public void testSetNullFloat() {
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     settings.setProperty("foo", (Float) null);
     assertThat(settings.getFloat("foo")).isNull();
   }
 
   @Test
   public void testSetNullDouble() {
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     settings.setProperty("foo", (Double) null);
     assertThat(settings.getDouble("foo")).isNull();
   }
 
   @Test
   public void getStringArray() {
-    Settings settings = new Settings(definitions);
+    Settings settings = new MapSettings(definitions);
     String[] array = settings.getStringArray("array");
     assertThat(array).isEqualTo(new String[] {"one", "two", "three"});
   }
 
   @Test
   public void setStringArray() {
-    Settings settings = new Settings(definitions);
+    Settings settings = new MapSettings(definitions);
     settings.setProperty("multi_values", new String[] {"A", "B"});
     String[] array = settings.getStringArray("multi_values");
     assertThat(array).isEqualTo(new String[] {"A", "B"});
@@ -227,7 +218,7 @@ public class SettingsTest {
 
   @Test
   public void setStringArrayTrimValues() {
-    Settings settings = new Settings(definitions);
+    Settings settings = new MapSettings(definitions);
     settings.setProperty("multi_values", new String[] {" A ", " B "});
     String[] array = settings.getStringArray("multi_values");
     assertThat(array).isEqualTo(new String[] {"A", "B"});
@@ -235,7 +226,7 @@ public class SettingsTest {
 
   @Test
   public void setStringArrayEscapeCommas() {
-    Settings settings = new Settings(definitions);
+    Settings settings = new MapSettings(definitions);
     settings.setProperty("multi_values", new String[] {"A,B", "C,D"});
     String[] array = settings.getStringArray("multi_values");
     assertThat(array).isEqualTo(new String[] {"A,B", "C,D"});
@@ -243,7 +234,7 @@ public class SettingsTest {
 
   @Test
   public void setStringArrayWithEmptyValues() {
-    Settings settings = new Settings(definitions);
+    Settings settings = new MapSettings(definitions);
     settings.setProperty("multi_values", new String[] {"A,B", "", "C,D"});
     String[] array = settings.getStringArray("multi_values");
     assertThat(array).isEqualTo(new String[] {"A,B", "", "C,D"});
@@ -251,7 +242,7 @@ public class SettingsTest {
 
   @Test
   public void setStringArrayWithNullValues() {
-    Settings settings = new Settings(definitions);
+    Settings settings = new MapSettings(definitions);
     settings.setProperty("multi_values", new String[] {"A,B", null, "C,D"});
     String[] array = settings.getStringArray("multi_values");
     assertThat(array).isEqualTo(new String[] {"A,B", "", "C,D"});
@@ -259,20 +250,20 @@ public class SettingsTest {
 
   @Test(expected = IllegalStateException.class)
   public void shouldFailToSetArrayValueOnSingleValueProperty() {
-    Settings settings = new Settings(definitions);
+    Settings settings = new MapSettings(definitions);
     settings.setProperty("array", new String[] {"A", "B", "C"});
   }
 
   @Test
   public void getStringArray_no_value() {
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     String[] array = settings.getStringArray("array");
     assertThat(array).isEmpty();
   }
 
   @Test
   public void shouldTrimArray() {
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     settings.setProperty("foo", "  one,  two, three  ");
     String[] array = settings.getStringArray("foo");
     assertThat(array).isEqualTo(new String[] {"one", "two", "three"});
@@ -280,7 +271,7 @@ public class SettingsTest {
 
   @Test
   public void shouldKeepEmptyValuesWhenSplitting() {
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     settings.setProperty("foo", "  one,  , two");
     String[] array = settings.getStringArray("foo");
     assertThat(array).isEqualTo(new String[] {"one", "", "two"});
@@ -288,13 +279,13 @@ public class SettingsTest {
 
   @Test
   public void testDefaultValueOfGetString() {
-    Settings settings = new Settings(definitions);
+    Settings settings = new MapSettings(definitions);
     assertThat(settings.getString("hello")).isEqualTo("world");
   }
 
   @Test
   public void set_property_boolean() {
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     settings.setProperty("foo", true);
     settings.setProperty("bar", false);
     assertThat(settings.getBoolean("foo")).isTrue();
@@ -305,7 +296,7 @@ public class SettingsTest {
 
   @Test
   public void ignore_case_of_boolean_values() {
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     settings.setProperty("foo", "true");
     settings.setProperty("bar", "TRUE");
     // labels in UI
@@ -318,7 +309,7 @@ public class SettingsTest {
 
   @Test
   public void get_boolean() {
-    Settings settings = new Settings(definitions);
+    Settings settings = new MapSettings(definitions);
     assertThat(settings.getBoolean("boolean")).isTrue();
     assertThat(settings.getBoolean("falseboolean")).isFalse();
     assertThat(settings.getBoolean("unknown")).isFalse();
@@ -327,7 +318,8 @@ public class SettingsTest {
 
   @Test
   public void shouldCreateByIntrospectingComponent() {
-    Settings settings = Settings.createForComponent(MyComponent.class);
+    Settings settings = new MapSettings();
+    settings.getDefinitions().addComponent(MyComponent.class);
 
     // property definition has been loaded, ie for default value
     assertThat(settings.getDefaultValue("foo")).isEqualTo("bar");
@@ -339,38 +331,20 @@ public class SettingsTest {
   }
 
   @Test
-  public void cloneSettings() {
-    Settings target = new Settings(definitions).setProperty("foo", "bar");
-    Settings settings = new Settings(target);
-
-    assertThat(settings.getString("foo")).isEqualTo("bar");
-    assertThat(settings.getDefinitions()).isSameAs(definitions);
-
-    // do not propagate changes
-    settings.setProperty("foo", "changed");
-    settings.setProperty("new", "value");
-
-    assertThat(settings.getString("foo")).isEqualTo("changed");
-    assertThat(settings.getString("new")).isEqualTo("value");
-    assertThat(target.getString("foo")).isEqualTo("bar");
-    assertThat(target.getString("new")).isNull();
-  }
-
-  @Test
   public void getStringLines_no_value() {
-    assertThat(new Settings().getStringLines("foo")).hasSize(0);
+    assertThat(new MapSettings().getStringLines("foo")).hasSize(0);
   }
 
   @Test
   public void getStringLines_single_line() {
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     settings.setProperty("foo", "the line");
     assertThat(settings.getStringLines("foo")).isEqualTo(new String[] {"the line"});
   }
 
   @Test
   public void getStringLines_linux() {
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     settings.setProperty("foo", "one\ntwo");
     assertThat(settings.getStringLines("foo")).isEqualTo(new String[] {"one", "two"});
 
@@ -380,7 +354,7 @@ public class SettingsTest {
 
   @Test
   public void getStringLines_windows() {
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     settings.setProperty("foo", "one\r\ntwo");
     assertThat(settings.getStringLines("foo")).isEqualTo(new String[] {"one", "two"});
 
@@ -390,14 +364,14 @@ public class SettingsTest {
 
   @Test
   public void getStringLines_mix() {
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     settings.setProperty("foo", "one\r\ntwo\nthree");
     assertThat(settings.getStringLines("foo")).isEqualTo(new String[] {"one", "two", "three"});
   }
 
   @Test
   public void getKeysStartingWith() {
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     settings.setProperty("sonar.jdbc.url", "foo");
     settings.setProperty("sonar.jdbc.username", "bar");
     settings.setProperty("sonar.security", "admin");
@@ -409,7 +383,7 @@ public class SettingsTest {
 
   @Test
   public void should_fallback_deprecated_key_to_default_value_of_new_key() {
-    Settings settings = new Settings(definitions);
+    Settings settings = new MapSettings(definitions);
 
     assertThat(settings.getString("newKeyWithDefaultValue")).isEqualTo("default_value");
     assertThat(settings.getString("oldKeyWithDefaultValue")).isEqualTo("default_value");
@@ -417,7 +391,7 @@ public class SettingsTest {
 
   @Test
   public void should_fallback_deprecated_key_to_new_key() {
-    Settings settings = new Settings(definitions);
+    Settings settings = new MapSettings(definitions);
     settings.setProperty("newKey", "value of newKey");
 
     assertThat(settings.getString("newKey")).isEqualTo("value of newKey");
@@ -427,7 +401,7 @@ public class SettingsTest {
   @Test
   public void should_load_value_of_deprecated_key() {
     // it's used for example when deprecated settings are set through command-line
-    Settings settings = new Settings(definitions);
+    Settings settings = new MapSettings(definitions);
     settings.setProperty("oldKey", "value of oldKey");
 
     assertThat(settings.getString("newKey")).isEqualTo("value of oldKey");
@@ -436,7 +410,7 @@ public class SettingsTest {
 
   @Test
   public void should_load_values_of_deprecated_key() {
-    Settings settings = new Settings(definitions);
+    Settings settings = new MapSettings(definitions);
     settings.setProperty("oldKey", "a,b");
 
     assertThat(settings.getStringArray("newKey")).containsOnly("a", "b");
@@ -445,7 +419,7 @@ public class SettingsTest {
 
   @Test
   public void should_support_deprecated_props_with_multi_values() {
-    Settings settings = new Settings(definitions);
+    Settings settings = new MapSettings(definitions);
     settings.setProperty("new_multi_values", new String[] {" A ", " B "});
     assertThat(settings.getStringArray("new_multi_values")).isEqualTo(new String[] {"A", "B"});
     assertThat(settings.getStringArray("old_multi_values")).isEqualTo(new String[] {"A", "B"});
diff --git a/sonar-plugin-api/src/test/java/org/sonar/api/scan/filesystem/FileExclusionsTest.java b/sonar-plugin-api/src/test/java/org/sonar/api/scan/filesystem/FileExclusionsTest.java
index dd01bd616b8..373631daff8 100644
--- a/sonar-plugin-api/src/test/java/org/sonar/api/scan/filesystem/FileExclusionsTest.java
+++ b/sonar-plugin-api/src/test/java/org/sonar/api/scan/filesystem/FileExclusionsTest.java
@@ -22,13 +22,14 @@ package org.sonar.api.scan.filesystem;
 import org.junit.Test;
 import org.sonar.api.CoreProperties;
 import org.sonar.api.config.Settings;
+import org.sonar.api.config.MapSettings;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
 public class FileExclusionsTest {
   @Test
   public void ignore_inclusion_of_world() {
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     settings.setProperty(CoreProperties.PROJECT_INCLUSIONS_PROPERTY, "**/*");
     settings.setProperty(CoreProperties.PROJECT_TEST_INCLUSIONS_PROPERTY, "**/*");
     assertThat(new FileExclusions(settings).sourceInclusions()).isEmpty();
@@ -37,7 +38,7 @@ public class FileExclusionsTest {
 
   @Test
   public void load_inclusions() {
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     settings.setProperty(CoreProperties.PROJECT_INCLUSIONS_PROPERTY, "**/*Foo.java");
     settings.setProperty(CoreProperties.PROJECT_TEST_INCLUSIONS_PROPERTY, "**/*FooTest.java");
     FileExclusions moduleExclusions = new FileExclusions(settings);
@@ -48,7 +49,7 @@ public class FileExclusionsTest {
 
   @Test
   public void load_exclusions() {
-    Settings settings = new Settings();
+    Settings settings = new MapSettings();
     settings.setProperty(CoreProperties.PROJECT_EXCLUSIONS_PROPERTY, "**/*Foo.java");
     settings.setProperty(CoreProperties.PROJECT_TEST_EXCLUSIONS_PROPERTY, "**/*FooTest.java");
     FileExclusions moduleExclusions = new FileExclusions(settings);
diff --git a/sonar-plugin-api/src/test/java/org/sonar/api/utils/DurationsTest.java b/sonar-plugin-api/src/test/java/org/sonar/api/utils/DurationsTest.java
index cbda72dc5f7..409da22f751 100644
--- a/sonar-plugin-api/src/test/java/org/sonar/api/utils/DurationsTest.java
+++ b/sonar-plugin-api/src/test/java/org/sonar/api/utils/DurationsTest.java
@@ -26,6 +26,7 @@ import org.mockito.Mock;
 import org.mockito.runners.MockitoJUnitRunner;
 import org.sonar.api.CoreProperties;
 import org.sonar.api.config.Settings;
+import org.sonar.api.config.MapSettings;
 import org.sonar.api.i18n.I18n;
 
 import java.util.Locale;
@@ -54,7 +55,7 @@ public class DurationsTest {
 
   @Before
   public void setUp() {
-    settings = new Settings();
+    settings = new MapSettings();
     settings.setProperty(CoreProperties.HOURS_IN_DAY, HOURS_IN_DAY);
     durations = new Durations(settings, i18n);
   }