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fix(parameters): Correctly check for empty values in AppConfig Parameters Provider. #1982

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merged 2 commits into from
Jul 29, 2025
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fix(parameters): Correctly check for empty values in AppConfig Parameters Provider. #1982

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e24b6ed
fix(parameters): Correctly check for empty values in AppConfig Parame…
phipag Jul 29, 2025
3a45c65
fix pmd findings.
phipag Jul 29, 2025
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44 changes: 23 additions & 21 deletions ...c/main/java/software/amazon/lambda/powertools/parameters/appconfig/AppConfigProvider.java
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,8 @@

import java.util.HashMap;
import java.util.Map;

import software.amazon.awssdk.core.SdkBytes;
import software.amazon.awssdk.services.appconfigdata.AppConfigDataClient;
import software.amazon.awssdk.services.appconfigdata.model.GetLatestConfigurationRequest;
import software.amazon.awssdk.services.appconfigdata.model.GetLatestConfigurationResponse;
Expand Down Expand Up @@ -44,10 +46,10 @@ public class AppConfigProvider extends BaseProvider {
private final AppConfigDataClient client;
private final String application;
private final String environment;
private final HashMap<String, EstablishedSession> establishedSessions = new HashMap<>();
private final Map<String, EstablishedSession> establishedSessions = new HashMap<>();

AppConfigProvider(CacheManager cacheManager, TransformationManager transformationManager,
AppConfigDataClient client, String environment, String application) {
AppConfigDataClient client, String environment, String application) {
super(cacheManager, transformationManager);
this.client = client;
this.application = application;
Expand All @@ -63,7 +65,6 @@ public static AppConfigProviderBuilder builder() {
return new AppConfigProviderBuilder();
}


/**
* Retrieve the parameter value from the AppConfig parameter store.<br />
*
Expand All @@ -76,13 +77,12 @@ protected String getValue(String key) {
// so that we can the initial token. If we already have a session, we can take
// the next request token from there.
EstablishedSession establishedSession = establishedSessions.getOrDefault(key, null);
String sessionToken = establishedSession != null ?
establishedSession.nextSessionToken :
client.startConfigurationSession(StartConfigurationSessionRequest.builder()
.applicationIdentifier(this.application)
.environmentIdentifier(this.environment)
.configurationProfileIdentifier(key)
.build())
String sessionToken = establishedSession != null ? establishedSession.nextSessionToken
: client.startConfigurationSession(StartConfigurationSessionRequest.builder()
.applicationIdentifier(this.application)
.environmentIdentifier(this.environment)
.configurationProfileIdentifier(key)
.build())
.initialConfigurationToken();

// Get the configuration using the token
Expand All @@ -93,16 +93,18 @@ protected String getValue(String key) {
// Get the next session token we'll use next time we are asked for this key
String nextSessionToken = response.nextPollConfigurationToken();

// Get the value of the key. Note that AppConfig will return null if the value
// has not changed since we last asked for it in this session - in this case
// we return the value we stashed at last request.
String value = response.configuration() != null ?
response.configuration().asUtf8String() : // if we have a new value, use it
establishedSession != null ?
establishedSession.lastConfigurationValue :
// if we don't but we have a previous value, use that
null; // otherwise we've got no value

// Get the value of the key. Note that AppConfig will return an empty value if the configuration has not changed
// since we last asked for it in this session - in this case we return the value we stashed at last request.
// https://docs.aws.amazon.com/appconfig/latest/userguide/appconfig-code-samples-using-API-read-configuration.html
SdkBytes configFromApi = response.configuration();
String value;
if (configFromApi != null && configFromApi.asByteArray().length != 0) {
value = configFromApi.asUtf8String();
} else if (establishedSession != null) {
value = establishedSession.lastConfigurationValue;
} else {
value = null;
}
// Update the cache so we can get the next value later
establishedSessions.put(key, new EstablishedSession(nextSessionToken, value));

Expand All @@ -116,7 +118,7 @@ protected Map<String, String> getMultipleValues(String path) {
"Retrieving multiple parameter values is not supported with the AWS App Config Provider");
}

private static class EstablishedSession {
private static final class EstablishedSession {
private final String nextSessionToken;
private final String lastConfigurationValue;

Expand Down
84 changes: 43 additions & 41 deletions ...st/java/software/amazon/lambda/powertools/parameters/appconfig/AppConfigProviderTest.java
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -14,9 +14,9 @@

package software.amazon.lambda.powertools.parameters.appconfig;

import static org.assertj.core.api.Assertions.assertThat;
import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
import static org.assertj.core.api.Assertions.assertThatRuntimeException;
import static org.assertj.core.api.Assertions.assertThat;
import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
import static org.mockito.MockitoAnnotations.openMocks;
import static software.amazon.lambda.powertools.parameters.transform.Transformer.json;
Expand All @@ -27,6 +27,7 @@
import org.mockito.Captor;
import org.mockito.Mock;
import org.mockito.Mockito;

import software.amazon.awssdk.core.SdkBytes;
import software.amazon.awssdk.services.appconfigdata.AppConfigDataClient;
import software.amazon.awssdk.services.appconfigdata.model.GetLatestConfigurationRequest;
Expand All @@ -36,11 +37,11 @@
import software.amazon.lambda.powertools.parameters.cache.CacheManager;
import software.amazon.lambda.powertools.parameters.transform.TransformationManager;

public class AppConfigProviderTest {
class AppConfigProviderTest {

private final String environmentName = "test";
private final String applicationName = "fakeApp";
private final String defaultTestKey = "key1";
private static final String ENVIRONMENT_NAME = "test";
private static final String DEFAULT_TEST_KEY = "key1";
private static final String APPLICATION_NAME = "fakeApp";

@Mock
AppConfigDataClient client;
Expand All @@ -53,27 +54,26 @@ public class AppConfigProviderTest {
private AppConfigProvider provider;

@BeforeEach
public void init() {
void init() {
openMocks(this);

provider = AppConfigProvider.builder()
.withClient(client)
.withApplication(applicationName)
.withEnvironment(environmentName)
.withApplication(APPLICATION_NAME)
.withEnvironment(ENVIRONMENT_NAME)
.withCacheManager(new CacheManager())
.withTransformationManager(new TransformationManager())
.build();
}


/**
* Tests repeated calls to the AppConfigProvider for the same key behave correctly. This is more complicated than
* it seems, as the service itself will return no-data if the value of a property remains unchanged since the
* start of a session. This means the provider must cache the result and return it again if it gets no data, but
* subsequent calls should once again return the new data.
*/
@Test
public void getValueRetrievesValue() {
void getValueRetrievesValue() {
// Arrange
StartConfigurationSessionResponse firstSession = StartConfigurationSessionResponse.builder()
.initialConfigurationToken("token1")
Expand All @@ -92,24 +92,32 @@ public void getValueRetrievesValue() {
GetLatestConfigurationResponse thirdResponse = GetLatestConfigurationResponse.builder()
.nextPollConfigurationToken("token4")
.build();
// Forth response returns empty, which means the provider should yield the previous value again
GetLatestConfigurationResponse forthResponse = GetLatestConfigurationResponse.builder()
.nextPollConfigurationToken("token5")
.configuration(SdkBytes.fromUtf8String(""))
.build();
Mockito.when(client.startConfigurationSession(startSessionRequestCaptor.capture()))
.thenReturn(firstSession);
Mockito.when(client.getLatestConfiguration(getLatestConfigurationRequestCaptor.capture()))
.thenReturn(firstResponse, secondResponse, thirdResponse);
.thenReturn(firstResponse, secondResponse, thirdResponse, forthResponse);

// Act
String returnedValue1 = provider.getValue(defaultTestKey);
String returnedValue2 = provider.getValue(defaultTestKey);
String returnedValue3 = provider.getValue(defaultTestKey);
String returnedValue1 = provider.getValue(DEFAULT_TEST_KEY);
String returnedValue2 = provider.getValue(DEFAULT_TEST_KEY);
String returnedValue3 = provider.getValue(DEFAULT_TEST_KEY);
String returnedValue4 = provider.getValue(DEFAULT_TEST_KEY);

// Assert
assertThat(returnedValue1).isEqualTo(firstResponse.configuration().asUtf8String());
assertThat(returnedValue2).isEqualTo(secondResponse.configuration().asUtf8String());
assertThat(returnedValue3).isEqualTo(secondResponse.configuration()
.asUtf8String()); // Third response is mocked to return null and should re-use previous value
assertThat(startSessionRequestCaptor.getValue().applicationIdentifier()).isEqualTo(applicationName);
assertThat(startSessionRequestCaptor.getValue().environmentIdentifier()).isEqualTo(environmentName);
assertThat(startSessionRequestCaptor.getValue().configurationProfileIdentifier()).isEqualTo(defaultTestKey);
assertThat(returnedValue4).isEqualTo(secondResponse.configuration()
.asUtf8String()); // Forth response is mocked to return empty and should re-use previous value
assertThat(startSessionRequestCaptor.getValue().applicationIdentifier()).isEqualTo(APPLICATION_NAME);
assertThat(startSessionRequestCaptor.getValue().environmentIdentifier()).isEqualTo(ENVIRONMENT_NAME);
assertThat(startSessionRequestCaptor.getValue().configurationProfileIdentifier()).isEqualTo(DEFAULT_TEST_KEY);
assertThat(getLatestConfigurationRequestCaptor.getAllValues().get(0).configurationToken()).isEqualTo(
firstSession.initialConfigurationToken());
assertThat(getLatestConfigurationRequestCaptor.getAllValues().get(1).configurationToken()).isEqualTo(
Expand All @@ -119,8 +127,7 @@ public void getValueRetrievesValue() {
}

@Test
public void getValueNoValueExists() {

void getValueNoValueExists() {
// Arrange
StartConfigurationSessionResponse session = StartConfigurationSessionResponse.builder()
.initialConfigurationToken("token1")
Expand All @@ -134,19 +141,18 @@ public void getValueNoValueExists() {
.thenReturn(response);

// Act
String returnedValue = provider.getValue(defaultTestKey);

String returnedValue = provider.getValue(DEFAULT_TEST_KEY);

// Assert
assertThat(returnedValue).isEqualTo(null);
assertThat(returnedValue).isNull();
}

/**
* If we mix requests for different keys together through the same provider, retrieval should
* work as expected. This means two separate configuration sessions should be established with AppConfig.
*/
@Test
public void multipleKeysRetrievalWorks() {
void multipleKeysRetrievalWorks() {
// Arrange
String param1Key = "key1";
StartConfigurationSessionResponse param1Session = StartConfigurationSessionResponse.builder()
Expand Down Expand Up @@ -184,49 +190,45 @@ public void multipleKeysRetrievalWorks() {
param1Session.initialConfigurationToken());
assertThat(getLatestConfigurationRequestCaptor.getAllValues().get(1).configurationToken()).isEqualTo(
param2Session.initialConfigurationToken());

}

@Test
public void getMultipleValuesThrowsException() {

void getMultipleValuesThrowsException() {
// Act & Assert
assertThatRuntimeException().isThrownBy(() -> provider.getMultipleValues("path"))
.withMessage("Retrieving multiple parameter values is not supported with the AWS App Config Provider");
}

@Test
public void testAppConfigProviderBuilderMissingEnvironment_throwsException() {

void testAppConfigProviderBuilderMissingEnvironment_throwsException() {
// Act & Assert
assertThatIllegalStateException().isThrownBy(() -> AppConfigProvider.builder()
.withCacheManager(new CacheManager())
.withApplication(applicationName)
.withClient(client)
.build())
.withCacheManager(new CacheManager())
.withApplication(APPLICATION_NAME)
.withClient(client)
.build())
.withMessage("No environment provided; please provide one");
}

@Test
public void testAppConfigProviderBuilderMissingApplication_throwsException() {

void testAppConfigProviderBuilderMissingApplication_throwsException() {
// Act & Assert
assertThatIllegalStateException().isThrownBy(() -> AppConfigProvider.builder()
.withCacheManager(new CacheManager())
.withEnvironment(environmentName)
.withClient(client)
.build())
.withCacheManager(new CacheManager())
.withEnvironment(ENVIRONMENT_NAME)
.withClient(client)
.build())
.withMessage("No application provided; please provide one");
}
@Test
public void testAppConfigProvider_withoutParameter_shouldHaveDefaultTransformationManager() {

@Test
void testAppConfigProvider_withoutParameter_shouldHaveDefaultTransformationManager() {
// Act
AppConfigProvider appConfigProvider = AppConfigProvider.builder()
.withEnvironment("test")
.withApplication("app")
.build();
// Assert
assertDoesNotThrow(()->appConfigProvider.withTransformation(json));
assertDoesNotThrow(() -> appConfigProvider.withTransformation(json));
}
}
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