Vfrdtyky

I need to obtain a currency exchange rate from a rest API into my spring boot application and convert the JSON response to Java class. The API will give me the response as below:-

{

    "USD_INR": {

        "val": 71.884966

    }

}

The code is as shown below:

@RestController

public class MainController {



  @Autowired

  private RestTemplate restTemplate;



  @GetMapping("/hello")

  public float hello(){



     ExchangeRate exchangeRate = restTemplate.getForObject("https://free.currencyconverterapi.com/api/v6/convert?q=Source_Target&compact=y",ExchangeRate.class);

     return exchangeRate.getSource_Target().getVal();

  }

}

-

@JsonIgnoreProperties(ignoreUnknown = true)

public class ExchangeRate {

Source_Target SourceTargetObject;



  public Source_Target getSource_Target() {

      return SourceTargetObject;

  }





  public void setSource_Target(Source_Target SourceTargetObject) {

      this.SourceTargetObject = SourceTargetObject;

  }

}





@JsonIgnoreProperties(ignoreUnknown = true)

public class Source_Target {

private float val;



  public float getVal() {

    return val;

  }



  public void setVal(float val) {

    this.val = val;

  }

}

After executing the REST call, I am getting null exception. Nothing is returned. I am not able to figure out the issue here. Please help

You can use jsonscheme2pojo for generate java beans from json easily.

JSON:

{

"USD_INR": {

    "val": 71.884966

}

}

Corresponding Java bean :

-----------------------------------com.example.Example.java-----------------------------------



package com.example;



import java.io.Serializable;

import java.util.HashMap;

import java.util.Map;

import com.fasterxml.jackson.annotation.JsonAnyGetter;

import com.fasterxml.jackson.annotation.JsonAnySetter;

import com.fasterxml.jackson.annotation.JsonIgnore;

import com.fasterxml.jackson.annotation.JsonInclude;

import com.fasterxml.jackson.annotation.JsonProperty;

import com.fasterxml.jackson.annotation.JsonPropertyOrder;



@JsonInclude(JsonInclude.Include.NON_NULL)

@JsonPropertyOrder({

"USD_INR"

})

public class Example implements Serializable

{



@JsonProperty("USD_INR")

private USDINR uSDINR;

@JsonIgnore

private Map<String, Object> additionalProperties = new HashMap<String, Object>();

private final static long serialVersionUID = -932753391825750904L;



@JsonProperty("USD_INR")

public USDINR getUSDINR() {

return uSDINR;

}



@JsonProperty("USD_INR")

public void setUSDINR(USDINR uSDINR) {

this.uSDINR = uSDINR;

}



public Example withUSDINR(USDINR uSDINR) {

this.uSDINR = uSDINR;

return this;

}



@JsonAnyGetter

public Map<String, Object> getAdditionalProperties() {

return this.additionalProperties;

}



@JsonAnySetter

public void setAdditionalProperty(String name, Object value) {

this.additionalProperties.put(name, value);

}



public Example withAdditionalProperty(String name, Object value) {

this.additionalProperties.put(name, value);

return this;

}



}

-----------------------------------com.example.USDINR.java-----------------------------------



package com.example;



import java.io.Serializable;

import java.util.HashMap;

import java.util.Map;

import com.fasterxml.jackson.annotation.JsonAnyGetter;

import com.fasterxml.jackson.annotation.JsonAnySetter;

import com.fasterxml.jackson.annotation.JsonIgnore;

import com.fasterxml.jackson.annotation.JsonInclude;

import com.fasterxml.jackson.annotation.JsonProperty;

import com.fasterxml.jackson.annotation.JsonPropertyOrder;



@JsonInclude(JsonInclude.Include.NON_NULL)

@JsonPropertyOrder({

"val"

})

public class USDINR implements Serializable

{



@JsonProperty("val")

private Double val;

@JsonIgnore

private Map<String, Object> additionalProperties = new HashMap<String, Object>();

private final static long serialVersionUID = -6384976748235176082L;



@JsonProperty("val")

public Double getVal() {

return val;

}



@JsonProperty("val")

public void setVal(Double val) {

this.val = val;

}



public USDINR withVal(Double val) {

this.val = val;

return this;

}



@JsonAnyGetter

public Map<String, Object> getAdditionalProperties() {

return this.additionalProperties;

}



@JsonAnySetter

public void setAdditionalProperty(String name, Object value) {

this.additionalProperties.put(name, value);

}



public USDINR withAdditionalProperty(String name, Object value) {

this.additionalProperties.put(name, value);

return this;

}



}

Your ExchangeRate class should be:

@JsonInclude(JsonInclude.Include.NON_NULL)

@JsonIgnoreProperties(ignoreUnknown = true)

public class ExchangeRate {

    @JsonProperty("USD_INR")

    Source_Target SourceTargetObject;



    public Source_Target getSource_Target() {

        return SourceTargetObject;

    }



    public void setSource_Target(Source_Target SourceTargetObject) {

        this.SourceTargetObject = SourceTargetObject;

    }

Then your Source_Target class should be:

@JsonInclude(JsonInclude.Include.NON_NULL)

@JsonIgnoreProperties(ignoreUnknown = true)

public class Source_Target {

    @JsonProperty("val")

    private float val;



    public float getVal() {

         return val;

    }



    public void setVal(float val) {

        this.val = val;

    }

}

Please beware of your class naming convention. I would rename Source_Target to SourceTarget to follow Java naming convention

You create a custom map:

public class ExchangeRate extends HashMap<String, ExchangeRateValue> implements Serializable {        

}



public class ExchangeRateValue implements Serializable {



    private float val;



    public float getVal() {

        return val;

    }



    public void setVal(float val) {

        this.val = val;

    }

}

And call it:

 ExchangeRate exchangeRate = restTemplate.getForObject("https://free.currencyconverterapi.com/api/v6/convert?q=Source_Target&compact=y", ExchangeRate.class);

 float data = exchangeRate.get("USD_INR").getVal();