Spring RestTemplate调用时java读取超时

Question

我有一个API，它返回一个json，它的类型是GET-method。因为它是GET，所以当我在浏览器中打开URL时，它可以正常工作并呈现json，但是，在使用RestTemplate检索json时，它失败了

请您提供一种方式来阅读下面的API

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

Spring引导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);

错误：

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]

Answer 1

您可以使用webflux的WebClient：

-添加依赖项

<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打电话

@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());
        };
    }
}

由于请求结果巨大，您必须调整缓冲区大小

也可以考虑使用非阻塞/流解决方案来处理这个问题。

Answer 2

当连续数据包之间达到最大不活动时间时，就会出现这样的读取超时。初始化RestTemplate时，必须为其提供一个读取超时配置的ClientHttpRequestFactoryHere就是这样做的一个例子

您可能还想考虑将REST模板制作成bean，如果您必须多做这些长时间运行的请求。这样，您就不必每次都重新配置

Answer 3

不久前，我在浏览器中测试了API GET请求，结果是高度嵌套的。您试图将结果检索到Map对象中，但没有指定Key或Value的类型，后者可能是Map或List本身

首先，确定是否可以将原始JSON结果检索到String

ResponseEntity<String> response = restTemplate.getForEntity(url, String.class);

如果这样做有效，那么您将知道GET请求通过RestTemplate工作。如果没有，您可以对默认timeout settings进行故障排除，并根据您在浏览器中观察网络响应的时间进行调整

假设您可以将原始JSON结果检索到String，那么下一步将是分析返回的JSON数据的“形状”。如果希望将JSON结果转换为POJO，则必须创建一个与JSON数据的“形状”匹配的类（或一组类）

records:
    
  expiryDates   […]
  data  […]
  timestamp "31-Aug-2020 15:30:00"
  underlyingValue   11387.5
  strikePrices  […]

filtered:   
  data  […]
  CE    
    totOI   367314
    totVol  4988131
  PE    
    totOI   261696
    totVol  5501580