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可能有这么一个场景，项目需要接入某个平台，需要使用http调平台的各API，假设API需要通用基本参数，比如时间戳，Token，AppKey…参数，我们就可以把这些参数封装成一个类(通用参数基本类)，然后在把各个接口具体的参数同样的封装成一个类，去继承这个通用基本参数类。
如果因为业务的不同，某接口请求封装的类可能存在不需要拼接的字段，这时候就可以自定义注解，反射的时候判断字段是否注解，做出不同的判断

@Slf4j
public class ShpFactory {
    public static final String GET_ITEM_BASE_INFO = "/api/v2/product/get_item_base_info";
    public static final String GET_ITEM_LIST = "/api/v2/product/get_item_list";
    public static final String GET_MODEL_LIST = "/api/v2/product/get_model_list";
    public static final String AMPERSAND = "&";
    public static final String POST = "POST";
    public static final String GET = "GET";
    public static ShpBasePlatformRqDTO getRequestClient(String url, ShpBaseConfig config) {
        ShpBasePlatformRqDTO request = null;
        try {
            switch (url) {
                case GET_ITEM_BASE_INFO:
                    request = ShpPlatformGetItemInfoListRqDTO.create(config);
                    break;
                case GET_ITEM_LIST:
                    request = ShpPlatformGetItemListRqDTO.create(config);
                    break;
                case GET_MODEL_LIST:
                    request = ShpPlatformGetModelListRqDTO.create(config);
                default:
                    new IllegalArgumentException("参数错误,没有对应的实现类");
            }
        } catch (Exception e) {
            log.info("创建请求对象失败了,失败原因是：{},堆栈信息是：{}", JSON.toJSONString(e.getMessage()),JSON.toJSONString(e.getStackTrace()));
        }
        return request;
    }
    public static long getTimestamp() {
        return System.currentTimeMillis() / 1000;
    }
    /**
     * 拼接真实的url,get请求的对象需要
     *
     * @param request
     * @return
     * @throws NoSuchMethodException
     * @throws InvocationTargetException
     * @throws IllegalAccessException
     */
    public static String getUrl(String uri, ShpBasePlatformRqDTO request, ShpBaseConfig config) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {
        String url = String.format(config.getHost() + uri + "?partner_id=%s&shop_id=%s&timestamp=%s&access_token=%s&sign=%s",
                config.getAppKey(), config.getShopId(),request.getTimestamp(), request.getAccessToken(), request.getSign());
        if (request.getMethod().equals(GET)) {
            StringBuilder stringBuilder = new StringBuilder();
            //遍历request属性,对url进行追加参数
            List<Field> fields = new ArrayList<Field>(Arrays.asList(request.getClass().getDeclaredFields()));
            //获取父类属性
            Class<?> clazz = request.getClass();
            if (clazz != Object.class) {
                Class<?> superClazz = clazz.getSuperclass();
                List<Field> superFields = Arrays.asList(superClazz.getDeclaredFields());
                List<Field> superFieldList = new ArrayList<Field>(superFields);
                fields.addAll(superFieldList);
            }
            for (Field field : fields) {
                ShpParam fieldAnnotation = field.getAnnotation(ShpParam.class);
                if (Objects.nonNull(fieldAnnotation)) {
                    String propertyName = fieldAnnotation.propertyName();
                    Method m = (Method) request.getClass().getMethod(
                            "get" + getMethodName(field.getName()));
                    // 调用getter方法获取属性值
                    Object val = m.invoke(request);
                    if (Objects.nonNull(val)) {
                        stringBuilder.append(propertyName);
                        stringBuilder.append("=");
                        if (val instanceof List) {
                            String str4 = StringUtils.join((List) val, ",");
                            stringBuilder.append(str4);
                        } else {
                            stringBuilder.append(val);
                        }
                        stringBuilder.append(AMPERSAND);
                    }
                }
            }
            if (StringUtils.isNotBlank(stringBuilder.toString())) {
                return url + "&" + urlSplit(stringBuilder.toString());
            }
        }
        return url;
    }
    /**
     * 把一个字符串的第一个字母大写、效率是最高的、
     *
     * @param fieldName
     * @return
     */
    protected static String getMethodName(String fieldName) {
        byte[] items = fieldName.getBytes();
        items[0] = (byte) ((char) items[0] - 'a' + 'A');
        return new String(items);
    }
    /**
     * 字符串中如果最后一位是"&",则截取掉最后一位
     *
     * @param wholeUrl
     * @return
     */
    protected static String urlSplit(String wholeUrl) {
        if (AMPERSAND.equals(wholeUrl.substring(wholeUrl.length() - 1))) {
            return wholeUrl.substring(0, wholeUrl.length() - 1);
        }
        return wholeUrl;
    }
    public static String buildSign(String url, ShpBaseConfig config) {
        String  baseSign= String.format("%s%s%s%s%s", config.getAppKey(), url, getTimestamp(), config.getAccessToken(), config.getShopId());
        return HashingUtils.hmacSHA256Digest(baseSign, config.getAppSecret());
    }
}

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@Component
public class ApplicationContextHelper implements ApplicationContextAware {
    private static ApplicationContext applicationContext;
    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        ApplicationContextHelper.applicationContext = applicationContext;
    }
    public static ApplicationContext getApplicationContext(){
        return  ApplicationContextHelper.applicationContext;
    }
    public static<T> T getBean(Class<T> targetClz){
        T beanInstance = null;
        //优先按type查
        try {
            beanInstance = (T) applicationContext.getBean(targetClz);
        }catch (Exception e){
        }
        //按name查
        if(beanInstance == null){
            String simpleName = targetClz.getSimpleName();
            //首字母小写
            simpleName = Character.toLowerCase(simpleName.charAt(0)) + simpleName.substring(1);
            beanInstance = (T) applicationContext.getBean(simpleName);
        }
        return beanInstance;
    }
    public static Object getBean(String claz){
        return ApplicationContextHelper.applicationContext.getBean(claz);
    }
}

调用API的url，appkey.. 单独写一个配置类

@Component
@Data
public class AliBaseConfog {
    @Value("${ali.category.appKey}")
    private String appKey;
    @Value("${ali.category.accessToken}")
    private String accessToken;
    @Value("${ali.category.url}")
    private String url;
}

声明配置DTO类

@Data
@Component
@Scope(value = "prototype")
public class AliBaseConfigDTO<T> {
    public String host;
    public Integer appKey;
    private String accessToken;
    private T data;
}

自定义，用反射来判断类属性是否拼Get请求

/**
 * Ali url后面是否追加属性参数
 *
 * @author liuhuan
 */
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface AliParam {
    /**
     * 属性名 所有Ali get请求需要拼接参数都要打上这个注解
     *
     * @return
     */
    String propertyName() default "";
}

接入某平台API，可能需要一些通用参数，但是具体的接口又需要不同的参数，所有分别把参数封装

@Data
public class AliPlatformRqDTO implements Serializable {
    @AliParam(propertyName="_aop_timestamp")
    private String aopTimestamp;
    @AliParam(propertyName="_aop_signature")
    private String aopSignature;
    @AliParam(propertyName="access_token")
    private String accessToken;
    private String url;
    private String method;
}

具体接口需要的参数也封装,继承平台通用参数类

@EqualsAndHashCode(callSuper = true)
@Data
public class AliCategoryRqDTO extends AliBaseCategoryRqDTO {
    @AliParam(propertyName = "categoryID")
    private Long categoryID;
    public static AliBaseCategoryRqDTO create(AliBaseConfigDTO config) {
        return null;
    }
}

平台通用返回值也封装

@Data
@AllArgsConstructor
@NoArgsConstructor
public class AliPlatformRpDTO {
    private Boolean succes;
    private String errorMsg;
    private String errorCode;
}

具体接口返回对象封装

@Data
@AllArgsConstructor
@NoArgsConstructor
public class AliCategoryGetRpDTO extends AliPlatformRpDTO {
    private List<CategoryInfo> categoryInfo;
}

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