feat: Add method argument resolver for tenant identifier

Signed-off-by: Thomas Vitale <[email protected]>

arconia-spring-boot-autoconfigure/build.gradle

@@ -23,7 +23,7 @@ dependencies {
     optional 'jakarta.servlet:jakarta.servlet-api'
 
     optional 'org.springframework:spring-context'
-    optional 'org.springframework:spring-web'
+    optional 'org.springframework:spring-webmvc'
 
     testImplementation 'org.springframework.boot:spring-boot-starter-test'
 }

arconia-spring-boot-autoconfigure/src/main/java/io/arconia/autoconfigure/multitenancy/web/MultitenancyWebAutoConfiguration.java

@@ -11,7 +11,7 @@
  */
 @AutoConfiguration(after = MultitenancyCoreAutoConfiguration.class)
 @ConditionalOnWebApplication(type = ConditionalOnWebApplication.Type.SERVLET)
-@Import(HttpTenantResolutionConfiguration.class)
+@Import({ HttpTenantResolutionConfiguration.class, WebMvcConfiguration.class })
 public class MultitenancyWebAutoConfiguration {
 
 }

arconia-spring-boot-autoconfigure/src/main/java/io/arconia/autoconfigure/multitenancy/web/WebMvcConfiguration.java

@@ -0,0 +1,22 @@
+package io.arconia.autoconfigure.multitenancy.web;
+
+import java.util.List;
+
+import org.springframework.context.annotation.Configuration;
+import org.springframework.web.method.support.HandlerMethodArgumentResolver;
+import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
+
+import io.arconia.web.multitenancy.context.annotations.TenantIdentifierArgumentResolver;
+
+/**
+ * Register Arconia-specific Spring Web MVC configuration.
+ */
+@Configuration(proxyBeanMethods = false)
+public class WebMvcConfiguration implements WebMvcConfigurer {
+
+    @Override
+    public void addArgumentResolvers(List<HandlerMethodArgumentResolver> resolvers) {
+        resolvers.add(new TenantIdentifierArgumentResolver());
+    }
+
+}

arconia-web/src/main/java/io/arconia/web/multitenancy/context/annotations/TenantIdentifier.java

@@ -0,0 +1,17 @@
+package io.arconia.web.multitenancy.context.annotations;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Annotation that is used to resolve the current tenant identifier as a method argument.
+ */
+@Target(ElementType.PARAMETER)
+@Retention(RetentionPolicy.RUNTIME)
+@Documented
+public @interface TenantIdentifier {
+
+}

arconia-web/src/main/java/io/arconia/web/multitenancy/context/annotations/TenantIdentifierArgumentResolver.java

@@ -0,0 +1,43 @@
+package io.arconia.web.multitenancy.context.annotations;
+
+import org.springframework.core.MethodParameter;
+import org.springframework.lang.Nullable;
+import org.springframework.web.bind.support.WebDataBinderFactory;
+import org.springframework.web.context.request.NativeWebRequest;
+import org.springframework.web.method.support.HandlerMethodArgumentResolver;
+import org.springframework.web.method.support.ModelAndViewContainer;
+
+import io.arconia.core.multitenancy.context.TenantContextHolder;
+
+/**
+ * Allows resolving the current tenant identifier using the {@link TenantIdentifier}
+ * annotation.
+ * <p>
+ * Example:
+ *
+ * <pre>
+ * &#64;RestController
+ * class MyRestController {
+ *     &#64;GetMapping("/tenant")
+ *     String getCurrentTenant(@CurrentTenantIdentifier String tenantIdentifier) {
+ *         return tenantIdentifier;
+ *     }
+ * }
+ * </pre>
+ */
+public final class TenantIdentifierArgumentResolver implements HandlerMethodArgumentResolver {
+
+    @Override
+    public boolean supportsParameter(MethodParameter parameter) {
+        return parameter.getParameterAnnotation(TenantIdentifier.class) != null
+                && parameter.getParameterType().getTypeName().equals(String.class.getTypeName());
+    }
+
+    @Nullable
+    @Override
+    public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
+            NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) {
+        return TenantContextHolder.getTenantIdentifier();
+    }
+
+}

arconia-web/src/main/java/io/arconia/web/multitenancy/context/annotations/package-info.java

@@ -0,0 +1,6 @@
+@NonNullApi
+@NonNullFields
+package io.arconia.web.multitenancy.context.annotations;
+
+import org.springframework.lang.NonNullApi;
+import org.springframework.lang.NonNullFields;

arconia-web/src/test/java/io/arconia/web/multitenancy/context/annotations/TenantIdentifierArgumentResolverTests.java

@@ -0,0 +1,80 @@
+package io.arconia.web.multitenancy.context.annotations;
+
+import java.lang.reflect.Method;
+
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.Test;
+import org.springframework.core.MethodParameter;
+import org.springframework.util.ReflectionUtils;
+
+import io.arconia.core.multitenancy.context.TenantContextHolder;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Unit tests for {@link TenantIdentifierArgumentResolver}.
+ */
+class TenantIdentifierArgumentResolverTests {
+
+    private final TenantIdentifierArgumentResolver argumentResolver = new TenantIdentifierArgumentResolver();
+
+    @AfterEach
+    void cleanup() {
+        TenantContextHolder.clear();
+    }
+
+    @Test
+    void doesNotSupportParameterWithoutAnnotation() {
+        assertThat(argumentResolver.supportsParameter(showTenantIdentifierNoAnnotation())).isFalse();
+    }
+
+    @Test
+    void supportsParameterWithAnnotation() {
+        assertThat(argumentResolver.supportsParameter(showTenantIdentifierAnnotation())).isTrue();
+    }
+
+    @Test
+    void doesNotSupportParameterWithWrongType() {
+        assertThat(argumentResolver.supportsParameter(showTenantIdentifierErrorOnInvalidType())).isFalse();
+    }
+
+    @Test
+    void resolveTenantIdentifierArgument() {
+        String expectedTenantIdentifier = "acme";
+        TenantContextHolder.setTenantIdentifier(expectedTenantIdentifier);
+        String actualTenantIdentifier = (String) argumentResolver.resolveArgument(showTenantIdentifierAnnotation(),
+                null, null, null);
+        assertThat(actualTenantIdentifier).isEqualTo(expectedTenantIdentifier);
+    }
+
+    private MethodParameter showTenantIdentifierNoAnnotation() {
+        return getMethodParameter("showTenantIdentifierNoAnnotation", String.class);
+    }
+
+    private MethodParameter showTenantIdentifierAnnotation() {
+        return getMethodParameter("showTenantIdentifierAnnotation", String.class);
+    }
+
+    private MethodParameter showTenantIdentifierErrorOnInvalidType() {
+        return getMethodParameter("showTenantIdentifierErrorOnInvalidType", Long.class);
+    }
+
+    private MethodParameter getMethodParameter(String methodName, Class<?>... paramTypes) {
+        Method method = ReflectionUtils.findMethod(TestController.class, methodName, paramTypes);
+        return new MethodParameter(method, 0);
+    }
+
+    static class TestController {
+
+        public void showTenantIdentifierNoAnnotation(String tenantIdentifier) {
+        }
+
+        public void showTenantIdentifierAnnotation(@TenantIdentifier String tenantIdentifier) {
+        }
+
+        public void showTenantIdentifierErrorOnInvalidType(@TenantIdentifier Long tenantIdentifier) {
+        }
+
+    }
+
+}