Use enum for credentials method

src/main/java/dev/openfga/autoconfigure/ConditionalOnFgaProperties.java

@@ -1,5 +1,7 @@
 package dev.openfga.autoconfigure;
 
+import dev.openfga.sdk.api.client.OpenFgaClient;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 
 import java.lang.annotation.ElementType;
@@ -10,4 +12,5 @@
 @Retention(RetentionPolicy.RUNTIME)
 @Target({ ElementType.TYPE, ElementType.METHOD })
 @ConditionalOnProperty(name = {"openfga.api-url"})
+@ConditionalOnClass(OpenFgaClient.class)
 public @interface ConditionalOnFgaProperties {}

src/main/java/dev/openfga/autoconfigure/OpenFgaAutoConfiguration.java

@@ -9,6 +9,11 @@
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 
+/**
+ * Configures an {@code openFgaClient} bean based on configuration values.
+ * The bean will only be created if the {@link OpenFgaClient} is present on
+ * the classpath, and the {@code openfga.api-url} is specified.
+ */
 @Configuration
 @ConditionalOnFgaProperties
 @EnableConfigurationProperties(OpenFgaProperties.class)
@@ -28,10 +33,10 @@ public ClientConfiguration openFgaConfig() {
         var credentialsProperties = openFgaProperties.getCredentials();
 
         if (credentialsProperties != null) {
-            if ("API_TOKEN".equalsIgnoreCase(credentialsProperties.getMethod())) {
+            if (OpenFgaProperties.CredentialsMethod.API_TOKEN.equals(credentialsProperties.getMethod())) {
                 credentials.setCredentialsMethod(CredentialsMethod.API_TOKEN);
                 credentials.setApiToken(new ApiToken(credentialsProperties.getConfig().getApiToken()));
-            } else if ("CLIENT_CREDENTIALS".equalsIgnoreCase(credentialsProperties.getMethod())) {
+            } else if (OpenFgaProperties.CredentialsMethod.CLIENT_CREDENTIALS.equals(credentialsProperties.getMethod())) {
                 ClientCredentials clientCredentials = new ClientCredentials()
                         .clientId(credentialsProperties.getConfig().getClientId())
                         .clientSecret(credentialsProperties.getConfig().getClientSecret())

src/main/java/dev/openfga/autoconfigure/OpenFgaProperties.java

@@ -5,6 +5,9 @@
 
 import java.util.Set;
 
+/**
+ * Properties used to configure an {@link dev.openfga.sdk.api.client.OpenFgaClient}
+ */
 @ConfigurationProperties(prefix="openfga")
 public class OpenFgaProperties implements InitializingBean {
 
@@ -54,38 +57,41 @@ public void afterPropertiesSet() throws Exception {
     public void validate() {
         Credentials credentialsProperty = getCredentials();
         if (credentialsProperty != null) {
-            String credentialsMethod = getCredentials().getMethod();
+            CredentialsMethod credentialsMethod = getCredentials().getMethod();
             if (credentialsMethod == null) {
                 throw new IllegalStateException("credentials method must not be null");
             }
-            if (!Set.of("NONE", "API_TOKEN", "CLIENT_CREDENTIALS").contains(credentialsMethod.toUpperCase())) {
-                throw new IllegalStateException("credentials method must be either 'NONE', 'API_TOKEN', or 'CLIENT_CREDENTIALS'");
-            }
-
             CredentialsConfiguration credentialsConfig = credentialsProperty.getConfig();
-            if ("API_TOKEN".equalsIgnoreCase(credentialsMethod)) {
-                if (credentialsConfig == null || credentialsConfig.getApiToken() == null) {
-                    throw new IllegalStateException("'API_TOKEN' credentials method specified, but no token specified");
+            switch (credentialsMethod) {
+                case NONE  -> {}
+                case API_TOKEN -> {
+                    if (credentialsConfig == null || credentialsConfig.getApiToken() == null) {
+                        throw new IllegalStateException("'API_TOKEN' credentials method specified, but no token specified");
+                    }
                 }
-            }
-            if ("CLIENT_CREDENTIALS".equalsIgnoreCase(credentialsMethod)) {
-                if (credentialsConfig == null || credentialsConfig.getApiTokenIssuer() == null || credentialsConfig.getClientId() == null || credentialsConfig.getClientSecret() == null) {
-                    throw new IllegalStateException("'CLIENT_CREDENTIALS' configuration must contain 'client-id', 'client-secret', and 'api-token-issuer'");
+                case CLIENT_CREDENTIALS -> {
+                    if (credentialsConfig == null || credentialsConfig.getApiTokenIssuer() == null || credentialsConfig.getClientId() == null || credentialsConfig.getClientSecret() == null) {
+                        throw new IllegalStateException("'CLIENT_CREDENTIALS' configuration must contain 'client-id', 'client-secret', and 'api-token-issuer'");
+                    }
                 }
+                default -> throw new IllegalStateException("credentials method must be either 'NONE', 'API_TOKEN', or 'CLIENT_CREDENTIALS'");
             }
         }
     }
 
+    /**
+     * {@link dev.openfga.sdk.api.client.OpenFgaClient} credentials properties
+     */
     public static class Credentials {
 
-        private String method;
+        private CredentialsMethod method;
         private CredentialsConfiguration config;
 
-        public String getMethod() {
+        public CredentialsMethod getMethod() {
             return method;
         }
 
-        public void setMethod(String method) {
+        public void setMethod(CredentialsMethod method) {
             this.method = method;
         }
 
@@ -98,6 +104,33 @@ public void setConfig(CredentialsConfiguration config) {
         }
     }
 
+    /**
+     * OpenFgaClient credentials methods
+     */
+    public enum CredentialsMethod {
+
+        /**
+         * No authentication
+         */
+        NONE,
+
+        /**
+         * A static API token. In OAuth2 terms, this indicates an "access token"
+         * that will be used to make a request. When used, an {@code api-token} must
+         * also be configured.
+         */
+        API_TOKEN,
+
+        /**
+         * OAuth2 client credentials that can be used to acquire an OAuth2 access
+         * token. When used, you must also configure {@link CredentialsConfiguration}.
+         */
+        CLIENT_CREDENTIALS
+    }
+
+    /**
+     * {@link dev.openfga.sdk.api.client.OpenFgaClient} credentials configuration properties
+     */
     public static class CredentialsConfiguration {
         private String apiToken;
         private String apiTokenIssuer;

src/test/java/dev/openfga/autoconfigure/FgaAutoConfigurationTests.java

@@ -78,7 +78,7 @@ public void beanConfiguredForApiToken() {
                         "openfga.authorization-model-id=authorization model ID",
                         "openfga.store-id=store ID",
                         "openfga.credentials.method=API_TOKEN",
-                        "openfga.credentials.config.api-token=XYZ"//,
+                        "openfga.credentials.config.api-token=XYZ"
                 )
                 .withConfiguration(AutoConfigurations.of(OpenFgaAutoConfiguration.class))
                 .run((context) -> {
@@ -168,4 +168,19 @@ public void failsIfCredentialsWithNoMethod() {
 
         assertThat(exception.getCause().getMessage(), containsString("credentials method must not be null"));
     }
+
+    @Test
+    public void failsIfCredentialsWithInvalidMethod() {
+        assertThrows(IllegalStateException.class, () -> {
+            this.contextRunner
+                    .withPropertyValues("openfga.api-url=https://api.fga.example",
+                            "openfga.authorization-model-id=authorization model ID",
+                            "openfga.store-id=store ID",
+                            "openfga.credentials.method=INVALID",
+                            "openfga.credentials.config.api-token=API_TOKEN"
+                    )
+                    .withConfiguration(AutoConfigurations.of(OpenFgaAutoConfiguration.class))
+                    .run((context) -> context.getBean("openFgaConfig"));
+        });
+    }
 }