如何使用java（spring boot）以json格式检索完整值（带小数的大整数值）？

Question

I am created a rest API in spring boot which consumes third party API response and return the response.

Challenges : Third party API response {"price":123456789123456789123456789.05}

I want to get the "price" from the single object ,So it will return 123456789123456789123456789.05 as expected

Expected Output : 123456789123456789123456789.05

Actual Output : 1.2345678912345679e+26

Note:

The actual output will given as exponential format but i want actual data without exponential.

Code: pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.3.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>sample</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>sample</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!-- tag::actuator[] -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <!-- end::actuator[] -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <!-- https://mvnrepository.com/artifact/com.googlecode.json-simple/json-simple -->
        <dependency>
            <groupId>com.googlecode.json-simple</groupId>
            <artifactId>json-simple</artifactId>
            <version>1.1</version>
        </dependency>


    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

SampleApplication.java

package com.example.sample;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;


@SpringBootApplication
public class SampleApplication {

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

    @Bean
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

HelloController.java

package com.example.sample;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.bind.annotation.RequestMapping;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpMethod;
import org.springframework.http.ResponseEntity;
import org.springframework.web.client.RestTemplate;

@RestController
public class HelloController {
 @Autowired
 RestTemplate restTemplate;

 @RequestMapping("/")
 public double index() throws Exception {
  HttpHeaders headers = new HttpHeaders();
  headers.set("token", "rtp");
  HttpEntity entity = new HttpEntity < String > ("parameters", headers);
  String END_Point_Test_API = "http://localhost:8080/api/test";
  ResponseEntity < String > responseData = restTemplate.exchange(END_Point_Test_API, HttpMethod.GET, entity, String.class);
  //Third party response {"price":123456789123456789123456789.05}
  System.out.println(responseData.getBody());
  String data = responseData.getBody();

  JSONParser parser = new JSONParser();
  JSONObject jsobj = (JSONObject) parser.parse(data);
  //double price =(double)jsobj.get("price");
  double price = Double.parseDouble(String.valueOf(jsobj.get("price")));
  return price;

 }

}

Answer 1

The correct way to convert BigDecimal to double is:

((BigDecimal) jsobj.get("price")).doubleValue()

However, you are converting BigDecimal to double. Double has a vast range, but even this range has limits. When you exceed it you will run into conversion problems.

My suggested answer is, do not convert it to double use BigDecimal for your price.

Answer 2

To make it clear: as soon as double is used, you have an approximation of the actual value, without defined precision and everything will just be some imperfect repair.

BigDecimal price = (BigDecimal) jsobj.get("price");
System.out.println(price.toPlainString());

This is probably also mentioned in the provided links. toPlainString will avoid using the scientific E-notation.