MethodArgumentResolver example

spring-boot/argumentresolver/src/main/java/io/reflectoring/argumentresolver/ArgumentresolverApplication.java

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+package io.reflectoring.argumentresolver;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class ArgumentresolverApplication {
+
+	public static void main(String[] args) {
+		SpringApplication.run(ArgumentresolverApplication.class, args);
+	}
+
+}

spring-boot/argumentresolver/src/main/java/io/reflectoring/argumentresolver/ErrorHandler.java

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+package io.reflectoring.argumentresolver;
+
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.ControllerAdvice;
+import org.springframework.web.bind.annotation.ExceptionHandler;
+import org.springframework.web.client.HttpStatusCodeException;
+
+@ControllerAdvice
+class ErrorHandler {
+
+  @ExceptionHandler(HttpStatusCodeException.class)
+  ResponseEntity<?> handleHttpStatusCodeException(HttpStatusCodeException e) {
+    return ResponseEntity.status(e.getStatusCode()).build();
+  }
+
+}

spring-boot/argumentresolver/src/main/java/io/reflectoring/argumentresolver/NotFoundException.java

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+package io.reflectoring.argumentresolver;
+
+import org.springframework.http.HttpStatus;
+import org.springframework.web.client.HttpStatusCodeException;
+
+public class NotFoundException extends HttpStatusCodeException {
+
+  protected NotFoundException() {
+    super(HttpStatus.NOT_FOUND);
+  }
+}

spring-boot/argumentresolver/src/main/java/io/reflectoring/argumentresolver/Repository.java

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+package io.reflectoring.argumentresolver;
+
+
+import lombok.Value;
+
+@Value
+public class Repository {
+
+  private final Long id;
+  private final String slug;
+
+}

spring-boot/argumentresolver/src/main/java/io/reflectoring/argumentresolver/RepositoryArgumentResolver.java

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+package io.reflectoring.argumentresolver;
+
+import java.util.Optional;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+import lombok.RequiredArgsConstructor;
+import org.springframework.core.MethodParameter;
+import org.springframework.web.bind.support.WebDataBinderFactory;
+import org.springframework.web.context.request.NativeWebRequest;
+import org.springframework.web.context.request.ServletWebRequest;
+import org.springframework.web.method.support.HandlerMethodArgumentResolver;
+import org.springframework.web.method.support.ModelAndViewContainer;
+
+@RequiredArgsConstructor
+class RepositoryArgumentResolver implements HandlerMethodArgumentResolver {
+
+  private static final Pattern SLUG_PATTERN = Pattern.compile("^/([^/]*).*$");
+
+  private final RepositoryFinder repositoryFinder;
+
+  @Override
+  public boolean supportsParameter(MethodParameter parameter) {
+    return parameter.getParameter().getType() == Repository.class;
+  }
+
+  @Override
+  public Object resolveArgument(
+      MethodParameter parameter,
+      ModelAndViewContainer mavContainer,
+      NativeWebRequest webRequest,
+      WebDataBinderFactory binderFactory) {
+
+    String requestPath = ((ServletWebRequest) webRequest).getRequest().getPathInfo();
+
+    Matcher matcher = SLUG_PATTERN.matcher(requestPath);
+
+    if (!matcher.matches()) {
+      throw new IllegalArgumentException(String.format(
+          "Cannot resolve argument of type Site. Expecting the slug to be the first part of the request path (%s).",
+          requestPath));
+    }
+
+    String slug = matcher.group(1);
+    if (slug == null || slug.isBlank()) {
+      throw new IllegalArgumentException(String.format(
+          "Cannot resolve argument of type Site. Slug is empty (request path: %s).",
+          requestPath));
+    }
+
+    Optional<Repository> repository = repositoryFinder.findBySlug(slug);
+
+    if (repository.isEmpty()) {
+      throw new NotFoundException();
+    }
+
+    return repository.get();
+  }
+}

spring-boot/argumentresolver/src/main/java/io/reflectoring/argumentresolver/RepositoryArgumentResolverConfiguration.java

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+package io.reflectoring.argumentresolver;
+
+import java.util.List;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Component;
+import org.springframework.web.method.support.HandlerMethodArgumentResolver;
+import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
+
+@Component
+@RequiredArgsConstructor
+class RepositoryArgumentResolverConfiguration implements WebMvcConfigurer {
+
+  private final RepositoryFinder repositoryFinder;
+
+  @Override
+  public void addArgumentResolvers(List<HandlerMethodArgumentResolver> resolvers) {
+    resolvers.add(new RepositoryArgumentResolver(repositoryFinder));
+  }
+
+}

spring-boot/argumentresolver/src/main/java/io/reflectoring/argumentresolver/RepositoryFinder.java

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+package io.reflectoring.argumentresolver;
+
+import java.util.Optional;
+
+public interface RepositoryFinder {
+
+  Optional<Repository> findBySlug(String slug);
+
+}

spring-boot/argumentresolver/src/test/java/io/reflectoring/argumentresolver/RepositoryArgumentResolverTest.java

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+package io.reflectoring.argumentresolver;
+
+import static org.mockito.BDDMockito.given;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+import java.util.Optional;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
+import org.springframework.boot.test.mock.mockito.MockBean;
+import org.springframework.test.web.servlet.MockMvc;
+
+@WebMvcTest(controllers = TestController.class)
+class RepositoryArgumentResolverTest {
+
+  @Autowired
+  private MockMvc mockMvc;
+
+  @MockBean
+  private RepositoryFinder repositoryFinder;
+
+  @Test
+  void resolvesSiteSuccessfully() throws Exception {
+
+    given(repositoryFinder.findBySlug("my-repo"))
+        .willReturn(Optional.of(new Repository(1L, "my-repo")));
+
+    mockMvc.perform(get("/my-repo/foo"))
+        .andExpect(status().isOk());
+  }
+
+  @Test
+  void notFoundOnUnknownSlug() throws Exception {
+
+    given(repositoryFinder.findBySlug("unknownSlug"))
+        .willReturn(Optional.empty());
+
+    mockMvc.perform(get("/unknownSlug/foo"))
+        .andExpect(status().isNotFound());
+  }
+
+}

spring-boot/argumentresolver/src/test/java/io/reflectoring/argumentresolver/TestController.java

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+package io.reflectoring.argumentresolver;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+class TestController {
+
+  @GetMapping("/{slug}/foo")
+  String getSomething(Repository repository) {
+    assertThat(repository.getId()).isEqualTo(1L);
+    return "test";
+  }
+
+}