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example feature flag implementations
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‎spring-boot/feature-flags/pom.xml‎

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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-starter-web</artifactId>
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</dependency>
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<dependency>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-starter-jdbc</artifactId>
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</dependency>
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<dependency>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-starter-thymeleaf</artifactId>
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</dependency>
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<dependency>
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<groupId>com.h2database</groupId>
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<artifactId>h2</artifactId>
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</dependency>
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<!-- TOGGLZ -->
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<dependency>

‎spring-boot/feature-flags/src/main/java/io/reflectoring/featureflags/implementations/FeatureFlagService.java‎

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package io.reflectoring.featureflags.implementations;
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public interface FeatureFlagService {
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Boolean featureOne();
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Integer featureTwo();
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}

‎spring-boot/feature-flags/src/main/java/io/reflectoring/featureflags/implementations/code/CodeBackedFeatureFlagService.java‎

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package io.reflectoring.featureflags.implementations.code;
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import io.reflectoring.featureflags.implementations.FeatureFlagService;
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public class CodeBackedFeatureFlagService implements FeatureFlagService {
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@Override
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public Boolean featureOne() {
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return true;
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}
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@Override
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public Integer featureTwo() {
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return 42;
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}
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}

‎spring-boot/feature-flags/src/main/java/io/reflectoring/featureflags/implementations/contextsensitive/ContextSensitiveFeatureFlagService.java‎

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package io.reflectoring.featureflags.implementations.contextsensitive;
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import io.reflectoring.featureflags.implementations.FeatureFlagService;
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import io.reflectoring.featureflags.implementations.contextsensitive.Feature.RolloutStrategy;
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import io.reflectoring.featureflags.web.UserSession;
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import org.jetbrains.annotations.Nullable;
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import org.springframework.jdbc.core.JdbcTemplate;
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public class ContextSensitiveFeatureFlagService implements FeatureFlagService {
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private final JdbcTemplate jdbcTemplate;
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private final UserSession userSession;
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public ContextSensitiveFeatureFlagService(JdbcTemplate jdbcTemplate, UserSession userSession) {
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this.jdbcTemplate = jdbcTemplate;
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this.userSession = userSession;
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}
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@Override
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public Boolean featureOne() {
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Feature feature = getFeatureFromDatabase();
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if (feature == null) {
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return Boolean.FALSE;
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}
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return feature.evaluateBoolean(userSession.getUsername());
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}
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@Override
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public Integer featureTwo() {
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Feature feature = getFeatureFromDatabase();
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if (feature == null) {
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return null;
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}
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return feature.evaluateInt(userSession.getUsername());
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}
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@Nullable
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private Feature getFeatureFromDatabase() {
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return jdbcTemplate.query("select targeting, value, defaultValue, percentage from features where feature_key='FEATURE_ONE'", resultSet -> {
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if (!resultSet.next()) {
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return null;
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}
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RolloutStrategy rolloutStrategy = Enum.valueOf(RolloutStrategy.class, resultSet.getString(1));
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String value = resultSet.getString(2);
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String defaultValue = resultSet.getString(3);
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int percentage = resultSet.getInt(4);
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return new Feature(rolloutStrategy, value, defaultValue, percentage);
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});
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}
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}

‎spring-boot/feature-flags/src/main/java/io/reflectoring/featureflags/implementations/contextsensitive/Feature.java‎

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package io.reflectoring.featureflags.implementations.contextsensitive;
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import java.nio.charset.StandardCharsets;
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import java.security.MessageDigest;
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import java.security.NoSuchAlgorithmException;
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import java.util.Arrays;
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public class Feature {
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public enum RolloutStrategy {
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GLOBAL,
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PERCENTAGE;
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}
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private final RolloutStrategy rolloutStrategy;
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private final int percentage;
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private final String value;
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private final String defaultValue;
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public Feature(RolloutStrategy rolloutStrategy, String value, String defaultValue, int percentage) {
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this.rolloutStrategy = rolloutStrategy;
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this.percentage = percentage;
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this.value = value;
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this.defaultValue = defaultValue;
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}
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public boolean evaluateBoolean(String userId) {
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switch (this.rolloutStrategy) {
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case GLOBAL:
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return this.getBooleanValue();
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case PERCENTAGE:
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if (percentageHashCode(userId) <= this.percentage) {
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return this.getBooleanValue();
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} else {
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return this.getBooleanDefaultValue();
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}
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}
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return this.getBooleanDefaultValue();
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}
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public Integer evaluateInt(String userId) {
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switch (this.rolloutStrategy) {
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case GLOBAL:
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return this.getIntValue();
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case PERCENTAGE:
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if (percentageHashCode(userId) <= this.percentage) {
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return this.getIntValue();
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} else {
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return this.getIntDefaultValue();
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}
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}
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return this.getIntDefaultValue();
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}
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double percentageHashCode(String text) {
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try {
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MessageDigest digest = MessageDigest.getInstance("SHA-256");
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byte[] encodedhash = digest.digest(
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text.getBytes(StandardCharsets.UTF_8));
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double INTEGER_RANGE = 1L << 32;
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return (((long) Arrays.hashCode(encodedhash) - Integer.MIN_VALUE) / INTEGER_RANGE) * 100;
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} catch (NoSuchAlgorithmException e) {
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throw new IllegalStateException(e);
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}
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}
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public RolloutStrategy getTargeting() {
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return rolloutStrategy;
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}
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public int getPercentage() {
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return percentage;
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}
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public int getIntValue() {
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return Integer.parseInt(this.value);
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}
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public int getIntDefaultValue() {
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return Integer.parseInt(this.defaultValue);
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}
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public boolean getBooleanValue() {
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return Boolean.parseBoolean(this.value);
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}
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public boolean getBooleanDefaultValue() {
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return Boolean.parseBoolean(this.defaultValue);
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}
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public String getStringValue() {
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return value;
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}
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public String getDefaultValue() {
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return defaultValue;
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}
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}

‎spring-boot/feature-flags/src/main/java/io/reflectoring/featureflags/implementations/database/DatabaseBackedFeatureFlagService.java‎

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package io.reflectoring.featureflags.implementations.database;
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import io.reflectoring.featureflags.implementations.FeatureFlagService;
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import org.springframework.jdbc.core.JdbcTemplate;
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public class DatabaseBackedFeatureFlagService implements FeatureFlagService {
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private JdbcTemplate jdbcTemplate;
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@Override
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public Boolean featureOne() {
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return jdbcTemplate.query("select value from features where feature_key='FEATURE_ONE'", resultSet -> {
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if(!resultSet.next()){
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return false;
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}
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boolean value = Boolean.parseBoolean(resultSet.getString(1));
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return value ? Boolean.TRUE : Boolean.FALSE;
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});
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}
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@Override
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public Integer featureTwo() {
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return jdbcTemplate.query("select value from features where feature_key='FEATURE_TWO'", resultSet -> {
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if(!resultSet.next()){
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return null;
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}
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return Integer.valueOf(resultSet.getString(1));
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});
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}
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}

‎spring-boot/feature-flags/src/main/java/io/reflectoring/featureflags/implementations/launchdarkly/LaunchDarklyFeatureFlagService.java‎

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package io.reflectoring.featureflags.implementations.launchdarkly;
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import com.launchdarkly.sdk.LDUser;
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import com.launchdarkly.sdk.server.LDClient;
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import io.reflectoring.featureflags.implementations.FeatureFlagService;
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import io.reflectoring.featureflags.web.UserSession;
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public class LaunchDarklyFeatureFlagService implements FeatureFlagService {
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private final LDClient launchdarklyClient;
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private final UserSession userSession;
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public LaunchDarklyFeatureFlagService(LDClient launchdarklyClient, UserSession userSession) {
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this.launchdarklyClient = launchdarklyClient;
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this.userSession = userSession;
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}
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@Override
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public Boolean featureOne() {
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return launchdarklyClient.boolVariation("feature-one", getLaunchdarklyUserFromSession(), false);
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}
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@Override
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public Integer featureTwo() {
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return launchdarklyClient.intVariation("feature-two", getLaunchdarklyUserFromSession(), 0);
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}
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private LDUser getLaunchdarklyUserFromSession() {
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return new LDUser.Builder(userSession.getUsername())
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.build();
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}
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}

‎spring-boot/feature-flags/src/main/java/io/reflectoring/featureflags/implementations/properties/FeatureProperties.java‎

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package io.reflectoring.featureflags.implementations.properties;
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import org.springframework.boot.context.properties.ConfigurationProperties;
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import org.springframework.stereotype.Component;
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@Component
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@ConfigurationProperties("features")
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public class FeatureProperties {
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private boolean featureOne;
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private int featureTwo;
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public FeatureProperties() {
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}
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public boolean getFeatureOne() {
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return featureOne;
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}
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public void setFeatureOne(boolean featureOne) {
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this.featureOne = featureOne;
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}
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public int getFeatureTwo() {
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return featureTwo;
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}
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public void setFeatureTwo(int featureTwo) {
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this.featureTwo = featureTwo;
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}
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}

‎spring-boot/feature-flags/src/main/java/io/reflectoring/featureflags/implementations/properties/PropertiesBackedFeatureFlagService.java‎

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package io.reflectoring.featureflags.implementations.properties;
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import io.reflectoring.featureflags.implementations.FeatureFlagService;
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import org.springframework.stereotype.Component;
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@Component
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public class PropertiesBackedFeatureFlagService implements FeatureFlagService {
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private final FeatureProperties featureProperties;
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public PropertiesBackedFeatureFlagService(FeatureProperties featureProperties) {
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this.featureProperties = featureProperties;
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}
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@Override
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public Boolean featureOne() {
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return featureProperties.getFeatureOne();
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}
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@Override
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public Integer featureTwo() {
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return featureProperties.getFeatureTwo();
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}
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}

‎spring-boot/feature-flags/src/main/resources/application.yml‎

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enabled: true
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secured: false
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path: /togglz
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use-management-port: false
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use-management-port: false
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features:
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featureOne: true
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featureTwo: 42

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