HAPI Server在return response前會檢查格式，所以如果想對HAPI Server的response進行修改(如因為資安要求，要進行加密)，使用JAVA的Intercepter或Filter都做不到，會直接跳errror。

既然這樣只好山不轉路轉，路不轉人轉，人不轉頭轉了。使用Spring Cloud Gateway技術，透過URL mapping到HAPI FHIR Server，讓user使用特定的URL取得處理後的Response。

接下來會介紹如何使用Spring Cloud Gateway來對response進行全域加密。

需要先創建一個新的項目，再在POM檔內import dependency。

 <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-gateway</artifactId>
            <version>3.1.5</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-commons</artifactId>
            <version>3.1.5</version>
        </dependency>

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

        <dependency>
            <groupId>io.projectreactor</groupId>
            <artifactId>reactor-core</artifactId>
            <version>3.4.23</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.14.2</version>
        </dependency>

import完dependency後就能進行開發了，主要需要修改兩個檔案，FHIRServerResponseGlobalFilter和application.yml。

FHIRServerResponseGlobalFilter

AESUtils aes = new AESUtils();

    @Override
    public int getOrder() {
        return -1;
    }

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        try {
            //獲取response的數據
            ServerHttpResponse originalResponse = exchange.getResponse();

            DataBufferFactory bufferFactory = originalResponse.bufferFactory();
            HttpStatus statusCode = originalResponse.getStatusCode();


            if (statusCode == HttpStatus.OK) {
                ServerHttpResponseDecorator decoratedResponse = new ServerHttpResponseDecorator(originalResponse) {
                    @Override
                    public Mono<Void> writeWith(Publisher<? extends DataBuffer> body) {
                        Flux<? extends DataBuffer> fluxBody = Flux.from(body);
                        return super.writeWith(fluxBody.buffer().map(dataBuffers -> {
                            DataBufferFactory dataBufferFactory = new DefaultDataBufferFactory();
                            DataBuffer join = dataBufferFactory.join(dataBuffers);
                            byte[] content = new byte[join.readableByteCount()];
                            join.read(content);
                            DataBufferUtils.release(join);
                         
                            String responseData = new String(content, StandardCharsets.UTF_8);


                            String AESKey = "1223334444555556";

                            String encryptedData = aes.encrypt(responseData, AESKey);

                            System.out.println("AES加密內容 : " + encryptedData);
                            byte[] uppedContent = new String(encryptedData.getBytes(), Charset.forName("UTF-8")).getBytes();
                            originalResponse.getHeaders().setContentLength(uppedContent.length);
                            return bufferFactory.wrap(uppedContent);
                        }));
                    }
                };
                return chain.filter(exchange.mutate().response(decoratedResponse).build());
            }
            return chain.filter(exchange);
        } catch (Exception e) {
               e.printStackTrace();
            return chain.filter(exchange);
        }
    }
}

application.yml

spring.application.name: spring-cloud-gateway
server.port: 8081

## gateway配置
spring:
 cloud:
   gateway:
     routes:
       # 註冊的route
       - id: test_route
         uri: http://127.0.0.1:8080
         predicates:
           - Path=/encryption/**
         filters:
           - StripPrefix=1

AES的加密方式非常多，這邊就不貼了，可以依據自己的習慣寫AES加密的方法。

新增完以上程式碼後，記得先執行HAPI Server後再執行Spring Cloud Gateway這個項目。

兩個項目都啟起來後，輸入 http://127.0.0.1:8080/fhir/Observation 後就能取得所有的測量數據。輸入 http://127.0.0.1:8081/encryption/fhir/Observation 後能取得進行AES加密後的所有測量數據。

以上，今天分享一個能對HAPI Server的response進行修改的方法，希望對大家有幫助。