快捷实现http客户端神器-feign（私人定制扩展篇）

lyb-geek

发布于 2019-07-22 17:17:45

2.7K0

发布于 2019-07-22 17:17:45

何为feign

直接套用官网的话

Feign is a Java to HTTP client binder inspired by Retrofit, JAXRS-2.0, and WebSocket. Feign's first goal was reducing the complexity of binding Denominator uniformly to HTTP APIs regardless of ReSTfulness.

为什么要使用feign

官网使用文档开篇第一句话

Feign允许我们通过注解的方式实现http客户端的功能，Feign能用最小的性能开销，让我们调用web服务器上基于文本的接口。同时允许我们自定义编码器、解码器和错误处理器等等

feign入门

因为本篇主要是介绍feign的一些功能扩展，具体入门可查看如下文章，本篇就不再论述

https://github.com/OpenFeign/feign

前言

有使用过feign的小伙伴大概都知道，feign post提交的时候可以使用bean传输，不需要每个参数注解@Param,feign会把这个bean的内容写入到http的 body中去，且指定contentType为application/json 。controller接收时，需要在接口对应的bean上注解@RequestBody，从body中读取这个bean的内容。

如下示例

@RequestMapping(value = "/saveOrUpdateUser")
   public Long saveOrUpdateUser(@RequestBody UserDTO userDTO){
        log.info("{}",userDTO);
       return userService.saveOrUpdateUser(userDTO);
   }

@RequestLine("POST /u/saveOrUpdateUser")
    @Headers("Content-Type: application/json")
    Long saveOrUpdateUser(UserDTO userDTO);

但当接收方不是用body接收复杂对象，上面的方案就失效了

出现上面情况，假如我们又不想进行额外扩展，我们可以采用如下方案解决

1、使用@Param注解

@RequestMapping(value = "/saveOrUpdateUser")
   public Long saveOrUpdateUser( UserDTO userDTO){
        log.info("{}",userDTO);
       return userService.saveOrUpdateUser(userDTO);
   }

@RequestLine("POST /u/saveOrUpdateUser?id={id}&name={name}&age={age}")
    @Headers("Content-Type: application/x-www-form-urlencoded")
    Long saveOrUpdateUser(@Param("id")Long id,@Param("name")String name,@Param("age") int age);

2、使用@QueryMap

@RequestLine("POST /u/saveOrUpdateUser")
    @Headers("Content-Type: application/x-www-form-urlencoded")
    Long saveOrUpdateUser(@QueryMap Map<String,Object> param);

虽然使用上面两种方案可以解决，但存在不优雅的地方，比如参数太多，用map语意不直观。那有没有其他方案，答案是有的，feign很贴心的提供了feign-form，这玩儿意可以同时支持json和表单。具体文档可以查看如下链接

https://github.com/OpenFeign/feign-form

不过目前的版本并没提供，比如接口提供方有个字段属性名称叫做order-items，或者bean里面又嵌套bean的解决方案。为了解决这些问题，我就在feign-form的基础进行了再次扩展

正文

1、pom.xml

<properties>
        <java.version>1.8</java.version>
        <feign.version>10.1.0</feign.version>
        <feign.form.version>3.5.0</feign.form.version>
        <findbugs.version>3.0.1</findbugs.version>
    </properties>

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

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-configuration-processor</artifactId>
            <optional>true</optional>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>io.github.openfeign</groupId>
            <artifactId>feign-core</artifactId>
            <version>${feign.version}</version>
        </dependency>

        <dependency>
            <groupId>io.github.openfeign</groupId>
            <artifactId>feign-jackson</artifactId>
            <version>${feign.version}</version>
        </dependency>

        <dependency>
            <groupId>io.github.openfeign</groupId>
            <artifactId>feign-httpclient</artifactId>
            <version>${feign.version}</version>
        </dependency>

        <dependency>
            <groupId>io.github.openfeign.form</groupId>
            <artifactId>feign-form</artifactId>
            <version>${feign.form.version}</version>
        </dependency>

        <dependency>
            <groupId>com.google.code.findbugs</groupId>
            <artifactId>annotations</artifactId>
            <version>${findbugs.version}</version>
        </dependency>

    </dependencies>

注意点：

all feign-form releases before 3.5.0 works with OpenFeign 9.* versions; starting from feign-form's version 3.5.0, the module works with OpenFeign 10.1.0 versions and greater.

2、核心代码类

public class CustomFormEncoder implements Encoder {

    private static final String CONTENT_TYPE_HEADER = "Content-Type";
    private static final Pattern CHARSET_PATTERN = Pattern.compile("(?<=charset=)([\\w\\-]+)");
    private final Encoder delegate;
    private final Map<ContentType, ContentProcessor> processors;

    public CustomFormEncoder() {
        this(new Default());
    }

    public CustomFormEncoder(Encoder delegate) {
        this.delegate = delegate;
        List<ContentProcessor> list = Arrays.asList(new MultipartFormContentProcessor(delegate), new UrlencodedFormContentProcessor());
        this.processors = new HashMap(list.size(), 1.0F);
        Iterator iterator = list.iterator();

        while(iterator.hasNext()) {
            ContentProcessor processor = (ContentProcessor)iterator.next();
            this.processors.put(processor.getSupportedContentType(), processor);
        }

    }

    public void encode(Object object, Type bodyType, RequestTemplate template) throws EncodeException {
        String contentTypeValue = this.getContentTypeValue(template.headers());
        ContentType contentType = ContentType.of(contentTypeValue);
        if (!this.processors.containsKey(contentType)) {
            this.delegate.encode(object, bodyType, template);
        } else {
            Map data;
            if (MAP_STRING_WILDCARD.equals(bodyType)) {
                data = (Map)object;
            } else {
                if (!PojoUtils.isUserPojo(object)) {
                    this.delegate.encode(object, bodyType, template);
                    return;
                }

                data = PojoUtils.toMap(object);
            }

            Charset charset = this.getCharset(contentTypeValue);
            ((ContentProcessor)this.processors.get(contentType)).process(template, charset, data);
        }
    }

    public final ContentProcessor getContentProcessor(ContentType type) {
        return (ContentProcessor)this.processors.get(type);
    }

    private String getContentTypeValue(Map<String, Collection<String>> headers) {
        Iterator iterator = headers.entrySet().iterator();

        while(true) {
            Map.Entry entry;
            do {
                if (!iterator.hasNext()) {
                    return null;
                }

                entry = (Map.Entry)iterator.next();
            } while(!((String)entry.getKey()).equalsIgnoreCase(CONTENT_TYPE_HEADER));

            Iterator var = ((Collection)entry.getValue()).iterator();

            while(var.hasNext()) {
                String contentTypeValue = (String)var.next();
                if (contentTypeValue != null) {
                    return contentTypeValue;
                }
            }
        }
    }

    private Charset getCharset(String contentTypeValue) {
        Matcher matcher = CHARSET_PATTERN.matcher(contentTypeValue);
        return matcher.find() ? Charset.forName(matcher.group(1)) : CharsetUtil.UTF_8;
    }


}

1、使用入门

1、创建示例bean

@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder
public class UserPageDTO {

    @FieldAlias(isPojo = true)
    private UserDTO userDTO;

    private int pageSize;

    @FieldAlias("pageIndex")
    private int pageNo;
}

@FieldAlias 为自定义注解，用来标注接口提供方的特殊字段属性名，其中还有一个属性isPojo来指定字段是不是复杂对象，当使用isPojo对象里面又包含特殊字段属性名，则该特殊字段属性名上方要加上@JsonProperty注解，比如@JsonProperty("user.name")

private String userName

2、示例接口提供方

@RequestMapping(value = "/listPage")   public List<User> listPage( UserDTO userDTO, int pageIndex, int pageSize){
        log.info("userDTO:{},pageIndex:{},pageSize:{}",userDTO,pageIndex,pageSize);
       return userService.listPage(userDTO,pageIndex,pageSize);
   }

3、示例客户端调用

@CustomFeignClient(url="http://localhost:8080")
public interface UserHttpClient {



    @RequestLine("POST /u/listPage")
    @Headers("Content-Type: application/x-www-form-urlencoded")
    List<User> listPage(UserPageDTO userPageDTO);





}

当客户端接口上有CustomFeignClient注解，且springboot启动类上面有配置EnableCustomFeignClients注解时，程序会自动把接口注册到spring容器中，如果不在springboot启动类上加EnableCustomFeignClients，则可以额外编写一个配置类。配置类上加入EnableCustomFeignClients注解并指定扫描的类包，比如@EnableCustomFeignClients(basePackages = "abc.com")

如果不和spring集成，也可以单独使用，如下

UseUserHttpClient userHttpClient = FeignClientUtils.getInstance().getClient(UserHttpClient.class, Constant.REMOTE_URL);

4、测试

@SpringBootTest
@RunWith(SpringRunner.class)
public class UserHttpClientSpringTest {

    @Autowired
    private UserHttpClient userHttpClient;


    @Test
    public void testListPage(){
        UserDTO userDTO = new UserDTO();
//        userDTO.setAge(25);
//        userDTO.setId(2L);
//        userDTO.setName("李四");
        userDTO.setSex("男");

        UserPageDTO userPageDTO = UserPageDTO.builder().userDTO(userDTO).pageNo(1).pageSize(5).build();

        List<User> users = userHttpClient.listPage(userPageDTO);

        users.forEach(user-> System.out.println(user));
    }
}

User(id=1, name=张三, age=20, sex=男, password=zhangsan)
User(id=2, name=李四, age=25, sex=男, password=lisi)
User(id=4, name=王五, age=30, sex=男, password=wangwu)

demo链接

https://github.com/lyb-geek/feign-complex-demo

总结

feign是一个挺好用的http客户端类库，其通过注解加接口的实现方式确实比传统用apache的HttpComponents方便很多，且性能也比较优越。之前接单，为了简化http的客户端代码的编写，我也造了一个类似的接口+注解http客户端，在maven的中央仓库就可以搜到，感兴趣的小伙伴可以蛮看一下，后面有机会会介绍一下