Spring RestTemplate 调用读取超时

我有一个返回 json 的 API，它的类型为 GET 方法。由于它是 GET，当我在浏览器中打开 URL 时，它工作正常并呈现 json，但是，在使用 RestTemplate 检索 json 时，它失败了。

您能否提供一种阅读下面 API 的方法。

API网址：https://www.nseindia.com/api/option-chain-indices?symbol=NIFTY https://www.nseindia.com/api/option-chain-indices?symbol=NIFTY

Spring Boot Rest 模板调用：

final String uri = "https://www.nseindia.com/api/option-chain-indices?symbol=NIFTY";
RestTemplate restTemplate = new RestTemplate();
Map result = restTemplate.getForObject(uri, Map.class);

Error:

java.net.SocketTimeoutException: Read timed out
    at java.base/java.net.SocketInputStream.socketRead0(Native Method) ~[na:na]
    at java.base/java.net.SocketInputStream.socketRead(SocketInputStream.java:115) ~[na:na]
    at java.base/java.net.SocketInputStream.read(SocketInputStream.java:168) ~[na:na]
    at java.base/java.net.SocketInputStream.read(SocketInputStream.java:140) ~[na:na]
    at java.base/sun.security.ssl.SSLSocketInputRecord.read(SSLSocketInputRecord.java:448) ~[na:na]
    at java.base/sun.security.ssl.SSLSocketInputRecord.bytesInCompletePacket(SSLSocketInputRecord.java:68) ~[na:na]
    at java.base/sun.security.ssl.SSLSocketImpl.readApplicationRecord(SSLSocketImpl.java:1104) ~[na:na]
    at java.base/sun.security.ssl.SSLSocketImpl$AppInputStream.read(SSLSocketImpl.java:823) ~[na:na]
    at java.base/java.io.BufferedInputStream.fill(BufferedInputStream.java:252) ~[na:na]
    at java.base/java.io.BufferedInputStream.read1(BufferedInputStream.java:292) ~[na:na]
    at java.base/java.io.BufferedInputStream.read(BufferedInputStream.java:351) ~[na:na]
    at java.base/sun.net.www.http.HttpClient.parseHTTPHeader(HttpClient.java:746) ~[na:na]
    at java.base/sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:689) ~[na:na]

您可以使用 webflux 中的 WebClient 来代替：

- 添加依赖

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

- 创建 POJO

@Data
public class Root {
    private Records records;
    private Filtered filtered;

    @Data
    public static class PE {
        private int strikePrice;
        private String expiryDate;
        private String underlying;
        private String identifier;
        private int openInterest;
        private int changeinOpenInterest;
        private double pchangeinOpenInterest;
        private int totalTradedVolume;
        private double impliedVolatility;
        private double lastPrice;
        private double change;
        private double pChange;
        private int totalBuyQuantity;
        private int totalSellQuantity;
        private int bidQty;
        private double bidprice;
        private int askQty;
        private double askPrice;
        private double underlyingValue;
    }

    @Data
    public static class CE {
        private int strikePrice;
        private String expiryDate;
        private String underlying;
        private String identifier;
        private int openInterest;
        private int changeinOpenInterest;
        private int pchangeinOpenInterest;
        private int totalTradedVolume;
        private int impliedVolatility;
        private int lastPrice;
        private double change;
        private double pChange;
        private int totalBuyQuantity;
        private int totalSellQuantity;
        private int bidQty;
        private double bidprice;
        private int askQty;
        private double askPrice;
        private double underlyingValue;
    }

    @Data
    public static class Datum {
        private int strikePrice;
        private String expiryDate;
        private PE PE;
        private CE CE;
    }

    @Data
    public static class Records {
        private List<String> expiryDates;
        private List<Datum> data;
        private String timestamp;
        private double underlyingValue;
        private List<Integer> strikePrices;
    }

    @Data
    public static class Filtered {
        //TODO
    }
}

- 让 WebClient 进行调用

@SpringBootApplication
public class MultipleConfigurationPropertiesApplication {

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

    @Bean
    CommandLineRunner commandLineRunner() {
        return args -> {
            WebClient client = WebClient.builder()
                    .baseUrl("https://www.nseindia.com")
                    .exchangeStrategies(ExchangeStrategies.builder()
                            .codecs(configurer -> configurer
                                    .defaultCodecs()
                                    .maxInMemorySize(16 * 1024 * 1024))
                            .build())
                    .build();

            Mono<Root> result = client.get()
                    .uri("/api/option-chain-indices?symbol=NIFTY").accept(MediaType.APPLICATION_JSON)
                    .retrieve()
                    .bodyToMono(Root.class);

            System.out.println(result.block());
        };
    }
}

由于请求结果很大，因此必须调整缓冲区大小。

另外，您可能需要考虑使用非阻塞/流解决方案来处理此问题。