Introduce ConfigurableEnvironment#addActiveProfile

Provides a convenient mechanism for activating an additional profile
while preserving those that are already active, as opposed to
calling #setActiveProfiles with the contents of #getActiveProfiles plus
the new profile.

Issue: SPR-8548

Author: cbeams

org.springframework.core/src/main/java/org/springframework/core/env/AbstractEnvironment.java

@@ -188,8 +188,16 @@ protected Set<String> doGetActiveProfiles() {
 	}
 
 	public void setActiveProfiles(String... profiles) {
+		Assert.notNull(profiles, "Profile array must not be null");
 		this.activeProfiles.clear();
-		this.activeProfiles.addAll(Arrays.asList(profiles));
+		for (String profile : profiles) {
+			this.addActiveProfile(profile);
+		}
+	}
+
+	public void addActiveProfile(String profile) {
+		this.validateProfile(profile);
+		this.activeProfiles.add(profile);
 	}
 
 	public String[] getDefaultProfiles() {
@@ -226,6 +234,7 @@ protected Set<String> doGetDefaultProfiles() {
 	 * @see #getReservedDefaultProfiles()
 	 */
 	public void setDefaultProfiles(String... profiles) {
+		Assert.notNull(profiles, "Profile array must not be null");
 		this.defaultProfiles.clear();
 		for (String profile : profiles) {
 			this.validateProfile(profile);
@@ -255,6 +264,7 @@ public boolean acceptsProfiles(String... profiles) {
 	 * <p>Subclasses may override to impose further restrictions on profile syntax.
 	 * @throws IllegalArgumentException if the profile is null, empty or whitespace-only
 	 * @see #acceptsProfiles
+	 * @see #addActiveProfile
 	 * @see #setDefaultProfiles
 	 */
 	protected void validateProfile(String profile) {

org.springframework.core/src/main/java/org/springframework/core/env/ConfigurableEnvironment.java

@@ -19,9 +19,9 @@
 import java.util.Map;
 
 /**
- * Configuration interface to be implemented by most if not all {@link Environment
- * Environments}. Provides facilities for setting active and default profiles as well
- * as accessing the {@linkplain #getPropertySources() property sources}.
+ * Configuration interface to be implemented by most if not all {@link Environment} types.
+ * Provides facilities for setting active and default profiles as well
+ * as accessing underlying {@linkplain #getPropertySources() property sources}.
  *
  * @author Chris Beams
  * @since 3.1
@@ -35,15 +35,24 @@ public interface ConfigurableEnvironment extends Environment, ConfigurableProper
 	 * evaluated during container bootstrap to determine whether bean definitions
 	 * should be registered with the container.
 	 * <p>Any existing active profiles will be replaced with the given arguments; call
-	 * with zero arguments to clear the current set of active profiles.
+	 * with zero arguments to clear the current set of active profiles. Use
+	 * {@link #addActiveProfile} to add a profile while preserving the existing set.
 	 *
+	 * @see #addActiveProfile
 	 * @see #setDefaultProfiles
 	 * @see org.springframework.context.annotation.Profile
 	 * @see AbstractEnvironment#ACTIVE_PROFILES_PROPERTY_NAME
 	 * @throws IllegalArgumentException if any profile is null, empty or whitespace-only
 	 */
 	void setActiveProfiles(String... profiles);
 
+	/**
+	 * Add a profile to the current set of active profiles.
+	 * @see #setActiveProfiles
+	 * @throws IllegalArgumentException if the profile is null, empty or whitespace-only
+	 */
+	void addActiveProfile(String profile);
+
 	/**
 	 * Specify the set of profiles to be made active by default if no other profiles
 	 * are explicitly made active through {@link #setActiveProfiles}.

org.springframework.core/src/test/java/org/springframework/core/env/EnvironmentTests.java

@@ -120,6 +120,21 @@ public void setDefaultProfiles_withEmptyProfile() {
 		environment.setDefaultProfiles("");
 	}
 
+	@Test
+	public void addActiveProfile() {
+		assertThat(environment.getActiveProfiles().length, is(0));
+		environment.setActiveProfiles("local", "embedded");
+		assertThat(Arrays.asList(environment.getActiveProfiles()), hasItems("local", "embedded"));
+		assertThat(environment.getActiveProfiles().length, is(2));
+		environment.addActiveProfile("p1");
+		assertThat(Arrays.asList(environment.getActiveProfiles()), hasItems("p1"));
+		assertThat(environment.getActiveProfiles().length, is(3));
+		environment.addActiveProfile("p2");
+		environment.addActiveProfile("p3");
+		assertThat(Arrays.asList(environment.getActiveProfiles()), hasItems("p2", "p3"));
+		assertThat(environment.getActiveProfiles().length, is(5));
+	}
+
 	@Test
 	public void reservedDefaultProfile() {
 		assertThat(environment.getDefaultProfiles(), equalTo(new String[]{RESERVED_DEFAULT_PROFILE_NAME}));