venus-cloud-feign

venus-cloud-feign,对Spring Cloud Feign的实战增强

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Release Note

版本	spring boot版本	spring cloud 版本
1.1.0 (开发中)	2.1.x.RELEASE	Greenwich.RELEASE
1.0.0	2.0.x.RELEASE	Finchley.RELEASE

项目开发规范

包名规范

cn.springcloud.feign

使用

目前已经发布到Maven中央仓库：

<dependency>
    <groupId>cn.springcloud.feign</groupId>
    <artifactId>venus-cloud-starter-feign</artifactId>
    <version>1.0.0</version>
</dependency>

应用场景

主要由于使用了API(SDK)为了偷懒，以及Restful API路径中的版本带来的一系列问题。

spring MVC 不支持继承接口中方法参数上的注解（支持继承类、方法上的注解）

API中为了方便，使用feign替代RestTemplate手动调用。带来的问题：springMVC注解想偷懒，只在feign接口写一遍，然后实现类继承此接口即可。 例如： feign接口定义如下

@FeignClient(ProviderApiAutoConfig.PLACE_HOLD_SERVICE_NAME)
public interface ProductService {
    // 为了让spring mvc能够正确绑定变量
    public class Page extends PageRequest<Product> {
    }
    @RequestMapping(value = "/{version}/pt/product", method = RequestMethod.POST)
    Response<Product> insert(@RequestBody Product product);
}

service实现类方法参数必须再写一次@RequestBody注解，方法上的@RequestMapping注解可以省略

@RestController
public class ProductServiceImpl implements ProductService {
    @Override
    public Response<Product> insert(@RequestBody Product product) {
        product.setId(1L);
        return new Response(product);
    }
}

解决办法，@Configuration配置类添加如下代码，扩展spring默认的ArgumentResolvers

public static MethodParameter interfaceMethodParameter(MethodParameter parameter, Class annotationType) {
    if (!parameter.hasParameterAnnotation(annotationType)) {
        for (Class<?> itf : parameter.getDeclaringClass().getInterfaces()) {
            try {
                Method method = itf.getMethod(parameter.getMethod().getName(), parameter.getMethod().getParameterTypes());
                MethodParameter itfParameter = new MethodParameter(method, parameter.getParameterIndex());
                if (itfParameter.hasParameterAnnotation(annotationType)) {
                    return itfParameter;
                }
            } catch (NoSuchMethodException e) {
                continue;
            }
        }
    }
    return parameter;
}
    
@PostConstruct
public void modifyArgumentResolvers() {
    List<HandlerMethodArgumentResolver> list = new ArrayList<>(adapter.getArgumentResolvers());

    list.add(0, new PathVariableMethodArgumentResolver() {  // PathVariable 支持接口注解
        @Override
        public boolean supportsParameter(MethodParameter parameter) {
            return super.supportsParameter(interfaceMethodParameter(parameter, PathVariable.class));
        }

        @Override
        protected NamedValueInfo createNamedValueInfo(MethodParameter parameter) {
            return super.createNamedValueInfo(interfaceMethodParameter(parameter, PathVariable.class));
        }
    });

    list.add(0, new RequestHeaderMethodArgumentResolver(beanFactory) {  // RequestHeader 支持接口注解
        @Override
        public boolean supportsParameter(MethodParameter parameter) {
            return super.supportsParameter(interfaceMethodParameter(parameter, RequestHeader.class));
        }

        @Override
        protected NamedValueInfo createNamedValueInfo(MethodParameter parameter) {
            return super.createNamedValueInfo(interfaceMethodParameter(parameter, RequestHeader.class));
        }
    });

    list.add(0, new ServletCookieValueMethodArgumentResolver(beanFactory) {  // CookieValue 支持接口注解
        @Override
        public boolean supportsParameter(MethodParameter parameter) {
            return super.supportsParameter(interfaceMethodParameter(parameter, CookieValue.class));
        }

        @Override
        protected NamedValueInfo createNamedValueInfo(MethodParameter parameter) {
            return super.createNamedValueInfo(interfaceMethodParameter(parameter, CookieValue.class));
        }
    });

    list.add(0, new RequestResponseBodyMethodProcessor(adapter.getMessageConverters()) {    // RequestBody 支持接口注解
        @Override
        public boolean supportsParameter(MethodParameter parameter) {
            return super.supportsParameter(interfaceMethodParameter(parameter, RequestBody.class));
        }

        @Override
        protected void validateIfApplicable(WebDataBinder binder, MethodParameter methodParam) {    // 支持@Valid验证
            super.validateIfApplicable(binder, interfaceMethodParameter(methodParam, Valid.class));
        }
    });

    // 修改ArgumentResolvers, 支持接口注解
    adapter.setArgumentResolvers(list);
}

swagger不支持继承接口中方法参数上的注解（支持继承类、方法上的注解）

没有找到swagger自带扩展点能够优雅扩展的方法，只好修改源码了，下载springfox-spring-web 2.8.0 release源码包。 添加pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>io.springfox</groupId>
    <artifactId>springfox-spring-web</artifactId>
    <version>2.8.0-charles</version>
    <packaging>jar</packaging>

    <properties>
        <java.version>1.8</java.version>
        <resource.delimiter>@</resource.delimiter>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <maven.compiler.source>${java.version}</maven.compiler.source>
        <maven.compiler.target>${java.version}</maven.compiler.target>
    </properties>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <!--<version>2.0.0.RELEASE</version>-->
                <version>1.5.10.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.reflections</groupId>
            <artifactId>reflections</artifactId>
            <version>0.9.11</version>
        </dependency>

        <!-- swagger -->
        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger2</artifactId>
            <version>2.8.0</version>
            <exclusions>
                <exclusion>
                    <groupId>io.springfox</groupId>
                    <artifactId>springfox-spring-web</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
    </dependencies>
</project>

添加ResolvedMethodParameterInterface继承ResolvedMethodParameter

public class ResolvedMethodParameterInterface extends ResolvedMethodParameter {
    public ResolvedMethodParameterInterface(String paramName, MethodParameter methodParameter, ResolvedType parameterType) {
        this(methodParameter.getParameterIndex(),
                paramName,
                interfaceAnnotations(methodParameter),
                parameterType);
    }

    public ResolvedMethodParameterInterface(int parameterIndex, String defaultName, List<Annotation> annotations, ResolvedType parameterType) {
        super(parameterIndex, defaultName, annotations, parameterType);
    }

    public static List<Annotation> interfaceAnnotations(MethodParameter methodParameter) {
        List<Annotation> annotationList = new ArrayList<>();
        annotationList.addAll(Arrays.asList(methodParameter.getParameterAnnotations()));

        if (CollectionUtils.isEmpty(annotationList)) {
            for (Class<?> itf : methodParameter.getDeclaringClass().getInterfaces()) {
                try {
                    Method method = itf.getMethod(methodParameter.getMethod().getName(), methodParameter.getMethod().getParameterTypes());
                    MethodParameter itfParameter = new MethodParameter(method, methodParameter.getParameterIndex());
                    annotationList.addAll(Arrays.asList(itfParameter.getParameterAnnotations()));
                } catch (NoSuchMethodException e) {
                    continue;
                }
            }
        }

        return annotationList;
    }
}

修改HandlerMethodResolver类line 181，将ResolvedMethodParameter替换为ResolvedMethodParameterInterface，重新打包deploy，并在swagger相关依赖中强制指定修改后的版本。

<!-- swagger -->
<dependency>
    <groupId>io.springfox</groupId>
    <artifactId>springfox-swagger2</artifactId>
</dependency>
<dependency>
    <groupId>io.springfox</groupId>
    <artifactId>springfox-swagger-ui</artifactId>
</dependency>
<!--扩展swagger支持从接口获得方法参数注解-->
<dependency>
    <groupId>io.springfox</groupId>
    <artifactId>springfox-spring-web</artifactId>
    <version>2.8.0-charles</version>
</dependency>

这样就能够顺利生产swagger文档啦。

feign不支持GET方法传递POJO

由于springMVC是支持GET方法直接绑定POJO的，只是feign实现并未覆盖所有springMVC特效，网上的很多变通方法都不是很好，要么是吧POJO拆散成一个一个单独的属性放在方法参数里，要么是把方法参数变成Map，要么就是要违反Restful规范，GET传递@RequestBody：
https://www.jianshu.com/p/7ce46c0ebe9d
spring-cloud/spring-cloud-netflix#1253
解决办法，使用feign拦截器：

public class CharlesRequestInterceptor implements RequestInterceptor {
    @Autowired
    private ObjectMapper objectMapper;

    @Override
    public void apply(RequestTemplate template) {
        // feign 不支持 GET 方法传 POJO, json body转query
        if (template.method().equals("GET") && template.body() != null) {
            try {
                JsonNode jsonNode = objectMapper.readTree(template.body());
                template.body(null);

                Map<String, Collection<String>> queries = new HashMap<>();
                buildQuery(jsonNode, "", queries);
                template.queries(queries);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    private void buildQuery(JsonNode jsonNode, String path, Map<String, Collection<String>> queries) {
        if (!jsonNode.isContainerNode()) {   // 叶子节点
            if (jsonNode.isNull()) {
                return;
            }
            Collection<String> values = queries.get(path);
            if (null == values) {
                values = new ArrayList<>();
                queries.put(path, values);
            }
            values.add(jsonNode.asText());
            return;
        }
        if (jsonNode.isArray()) {   // 数组节点
            Iterator<JsonNode> it = jsonNode.elements();
            while (it.hasNext()) {
                buildQuery(it.next(), path, queries);
            }
        } else {
            Iterator<Map.Entry<String, JsonNode>> it = jsonNode.fields();
            while (it.hasNext()) {
                Map.Entry<String, JsonNode> entry = it.next();
                if (StringUtils.hasText(path)) {
                    buildQuery(entry.getValue(), path + "." + entry.getKey(), queries);
                } else {  // 根节点
                    buildQuery(entry.getValue(), entry.getKey(), queries);
                }
            }
        }
    }
}

feign不支持路径中的{version}

对于一个典型的Restful API定义如下：

@ApiOperation("带过滤条件和排序的分页查询")
@RequestMapping(value = "/{version}/pb/product", method = RequestMethod.GET)
// 当前版本新开发api 随微服务整体升级 pt=protected 受保护的网关token验证合法可调用
@ApiImplicitParam(name = "version", paramType = "path", allowableValues = ProviderApiAutoConfig.CURRENT_VERSION, required = true)
Response<PageData<Product, Product>> selectAllGet(Page page);

我们并不关心路径中的{version}，因此方法参数中也没有@PathVariable("version")，这个时候feign就傻了，不知道路径中的{version}应该被替换成什么值。 解决办法 使用自己的Contract替换SpringMvcContract，先将SpringMvcContract代码复制过来，修改其中processAnnotationOnMethod方法的代码，从swagger注解中获得{version}的值：

public class CharlesSpringMvcContract extends Contract.BaseContract
        implements ResourceLoaderAware {
    @Override
    protected void processAnnotationOnMethod(MethodMetadata data,
                                             Annotation methodAnnotation, Method method) {
        if (!RequestMapping.class.isInstance(methodAnnotation) && !methodAnnotation
                .annotationType().isAnnotationPresent(RequestMapping.class)) {
            return;
        }

        RequestMapping methodMapping = AnnotatedElementUtils.findMergedAnnotation(method, RequestMapping.class);
        // HTTP Method
        RequestMethod[] methods = methodMapping.method();
        if (methods.length == 0) {
            methods = new RequestMethod[]{RequestMethod.GET};
        }
        checkOne(method, methods, "method");
        data.template().method(methods[0].name());

        // path
        checkAtMostOne(method, methodMapping.value(), "value");
        if (methodMapping.value().length > 0) {
            String pathValue = Util.emptyToNull(methodMapping.value()[0]);
            if (pathValue != null) {
                pathValue = resolve(pathValue);
                // Append path from @RequestMapping if value is present on method
                if (!pathValue.startsWith("/")
                        && !data.template().toString().endsWith("/")) {
                    pathValue = "/" + pathValue;
                }
                // 处理version
                if (pathValue.contains("/{version}/")) {
                    Set<ApiImplicitParam> apiImplicitParams = AnnotatedElementUtils.findAllMergedAnnotations(method, ApiImplicitParam.class);
                    for (ApiImplicitParam apiImplicitParam : apiImplicitParams) {
                        if ("version".equals(apiImplicitParam.name())) {
                            String version = apiImplicitParam.allowableValues().split(",")[0].trim();
                            pathValue = pathValue.replaceFirst("\\{version\\}", version);
                        }
                    }
                }
                data.template().append(pathValue);
            }
        }

        // produces
        parseProduces(data, method, methodMapping);

        // consumes
        parseConsumes(data, method, methodMapping);

        // headers
        parseHeaders(data, method, methodMapping);

        data.indexToExpander(new LinkedHashMap<Integer, Param.Expander>());
    }
}

然后在自己的AutoConfig中声明成spring的bean

@Configuration
@ConditionalOnClass(Feign.class)
public class FeignAutoConfig {
    @Bean
    public Contract charlesSpringMvcContract(ConversionService conversionService) {
        return new CharlesSpringMvcContract(Collections.emptyList(), conversionService);
    }

    @Bean
    public CharlesRequestInterceptor charlesRequestInterceptor(){
        return new CharlesRequestInterceptor();
    }
}