Spring Cloud Feign Clients 无需 Controller自动暴露Restful接口

前言

在开发SpringCloud应用中，Feign作为声明式调用的事实标准极大的简化了Rest远程调用，提供了类本地化的调用方式。服务提供方的接口暴露方式是通过Controller暴露Restful，而在这个Controller的代码现实中大部分都是处理请求然后再调用Service中的方法，是一个比较模板化的功能，但是工作量确不少。本文介绍一种通过动态代理的方式无需Controller直接暴露Restful接口。
本文中使用笔者在Github开源的框架来实现，本文的讲解也在这个框架基础之上来说明
Git路径：https://github.com/leecho/spr...

依赖

<dependency>
        <groupId>com.github.leecho</groupId>
        <artifactId>spring-cloud-starter-feign-proxy</artifactId>
        <version>{last-version}</version>
    </dependency>

实现

定义Service Interface

首先定义服务接口，使用@FeignClient标示是一个Feign接口，在这个示例Sevice中定义了CURD和文件上传方法，并使用了一些常用参数注解

@Api(tags = "DemoService", description = "Demo Feign Client")
@FeignClient("demo-service")
public interface DemoService {

    /**
     * create demo
     *
     * @param demo
     * @return
     */
    @ApiOperation(value = "Create demo")
    @PostMapping(value = "/demo")
    Demo create(@RequestBody @Valid @ApiParam Demo demo);

    /**
     * update demo
     *
     * @param demo
     * @return
     */
    @PutMapping(value = "/demo")
    Demo update(@RequestBody @Valid Demo demo);

    /**
     * delete demo
     *
     * @param id
     * @return
     */
    @DeleteMapping(value = "/demo/{id}")
    Demo delete(@PathVariable(name = "id") String id);

    /**
     * list demo
     *
     * @param id
     * @param headerValue test header value
     * @return
     */
    @GetMapping(value = "/demo/{id}")
    Demo get(@PathVariable(name = "id") String id, @RequestHeader(name = "header") String headerValue);

    /**
     * list demos
     *
     * @return
     */
    @GetMapping(value = "/demos")
    List<Demo> list();

    /**
     * upload file
     *
     * @param file
     * @return
     */
    @PostMapping(value = "/demo/upload")
    String upload(@RequestPart(name = "file") MultipartFile file);
}

实现Service

在实现类中简单的实现了CURD和上传文件的方法

@Slf4j
@Primary
@Service
public class DemoServiceImpl implements DemoService {

    @Override
    public Demo create(Demo demo) {
        log.info("Create executed : " + demo);
        return demo;
    }

    @Override
    public Demo update(Demo demo) {
        log.info("Update execute :" + demo);
        return demo;
    }

    @Override
    public Demo delete(String id) {
        log.info("Delete execute : " + id);
        return Demo.builder().name("demo-" + id).data("data-" + id).build();
    }

    @Override
    public Demo get(String id, String header) {
        Demo demo = Demo.builder()
                .name(header)
                .data(header).build();
        System.out.println("Get execute : " + id + "," + header);
        return demo;
    }

    @Override
    public List<Demo> list() {
        System.out.println("List execute");
        List<Demo> demos = new ArrayList<>();
        for (int i = 0; i < 5; i++) {
            Demo demo = Demo.builder()
                    .name("demo-" + i)
                    .data("data" + i).build();
            demos.add(demo);
        }
        return demos;
    }

    @Override
    public String upload(MultipartFile file) {
        return file.getOriginalFilename();
    }
}

动态生成Restful接口的原理是动态生成Controller类实现ServiceInterface，如果真正的实现类会被其他BEAN依赖，需要通过注解@Primary来方式来防止依赖冲突

配置应用

在应用中通过@EnableFeignProxies来标示应用在启动的过程中会扫描所有的FeignClients并暴露Restful接口

@EnableFeignProxies(basePackages = "com.github.leecho")
@ComponentScan("com.github.leecho")
@SpringBootApplication
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

}

测试用例

在测试用例中对Service的接口进行测试

@SpringBootTest
@RunWith(SpringJUnit4ClassRunner.class)
@WebAppConfiguration
public class DemoApplicationTest {
    @Autowired
    private WebApplicationContext context;

    private MockMvc mvc;

    @Before
    public void setUp() {
        mvc = MockMvcBuilders.webAppContextSetup(context).build();
    }

    @Test
    public void create() throws Exception {
        mvc.perform(MockMvcRequestBuilders.post("/demo")
                .contentType(MediaType.APPLICATION_JSON_UTF8)
                .content(new ObjectMapper().writeValueAsString(Demo.builder().name("create").data("data").build()))
                .accept(MediaType.APPLICATION_JSON))
                .andExpect(MockMvcResultMatchers.status().isOk())
                .andDo(MockMvcResultHandlers.print());

    }

    @Test
    public void update() throws Exception {
        mvc.perform(MockMvcRequestBuilders.put("/demo")
                .contentType(MediaType.APPLICATION_JSON_UTF8)
                .content(new ObjectMapper().writeValueAsString(Demo.builder().name("update").data("data").build()))
                .accept(MediaType.APPLICATION_JSON))
                .andExpect(MockMvcResultMatchers.status().isOk())
                .andDo(MockMvcResultHandlers.print());

    }

    @Test
    public void delete() throws Exception {
        mvc.perform(MockMvcRequestBuilders.delete("/demo/{id}", "1")
                .contentType(MediaType.APPLICATION_JSON_UTF8)
                .accept(MediaType.APPLICATION_JSON))
                .andExpect(MockMvcResultMatchers.status().isOk())
                .andDo(MockMvcResultHandlers.print());

    }

    @Test
    public void get() throws Exception {
        mvc.perform(MockMvcRequestBuilders.get("/demo/{id}", "1")
                .contentType(MediaType.APPLICATION_JSON_UTF8)
                .header("header", "header-value")
                .accept(MediaType.APPLICATION_JSON))
                .andExpect(MockMvcResultMatchers.status().isOk())
                .andDo(MockMvcResultHandlers.print());

    }

    @Test
    public void list() throws Exception {
        mvc.perform(MockMvcRequestBuilders.get("/demos")
                .contentType(MediaType.APPLICATION_JSON_UTF8)
                .accept(MediaType.APPLICATION_JSON))
                .andExpect(MockMvcResultMatchers.status().isOk())
                .andDo(MockMvcResultHandlers.print());

    }

    @Test
    public void upload() throws Exception {
        mvc.perform(MockMvcRequestBuilders.multipart("/demo/upload").file(new MockMultipartFile("file", "test.txt", ",multipart/form-data", "upload test".getBytes()))
                .accept(MediaType.APPLICATION_JSON))
                .andExpect(MockMvcResultMatchers.status().isOk())
                .andDo(MockMvcResultHandlers.print());

    }
}

在启动日志中也可以看到Restful接口已经暴露成功。

后语

关于这个框架的介绍，后续详细的给大家进行介绍。文中所涉及到的代码也在Git中：spring-cloud-feign-proxy-sample