Question 207858 in Json Question posted in
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Create the instance in Java from a json buffer

I have a JSON (stored in a string, file etc) and I want to read it and create the
java instance.

For example for this class

@Data
public class Rate {

    private String currency;
    private BigDecimal buyRate;
    private BigDecimal midRate;
    private BigDecimal sellRate;
    private String conversionType;

}

I have this buffer in a String

{
  "currency": "BRL",
  "buyRate": 4.18390000,
  "midRate": 4.18390000,
  "sellRate": 4.18390000,
  "conversionType": "D"
}

how can I create the object instance from the string buffer?

Tags:

3

Answers


  1. 0

    If you’re using Spring Boot, you have Jackson lib included by default, so you may read your object like this:

    import com.fasterxml.jackson.databind.ObjectMapper;

// ...

String json = "{ "currency": "BRL", "buyRate": 4.18390000, "midRate": 4.18390000, "sellRate": 4.18390000, "conversionType": "D" }";

ObjectMapper mapper = new ObjectMapper();

Rate rate = null;
try {
    rate = mapper.readValue(json, Rate.class);
} catch (IOException e) {
    e.printStackTrace();
}

// ...
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  2. 0

    Maybe you could try something like that:

    import com.google.gson.Gson;

    Rate rate = new Gson().fromJson(json, Rate.class);

    Where Rate is your class, and json is your json string.

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  3. 0

    As others have suggested, use Jackson:

    import java.io.IOException;
import java.math.BigDecimal;
import com.fasterxml.jackson.databind.ObjectMapper;
import lombok.Data;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class JacksonExample {
    private static final Logger log = LoggerFactory.getLogger(JacksonExample.class);
    private static ObjectMapper mapper = new ObjectMapper();
    private static String jsonData = "{ "currency": "BRL", "buyRate": 4.18390000, "midRate": 4.18390000, "sellRate": 4.18390000, "conversionType": "D" }";

    public static void main(String[] args) {
        Rate rate = parseRateData(jsonData);
        System.out.println(rate); // JacksonExample.Rate(currency=BRL, conversionType=D, buyRate=4.18390000, midRate=4.18390000, sellRate=4.18390000)
    }

    public static Rate parseRateData(String rateData) {
        return parseJsonData(rateData, Rate.class);
    }

    public static <E> E parseJsonData(String jsonData, Class<E> clazz) {
        try {
            return mapper.readValue(jsonData, clazz);
        } catch (IOException e) {
            log.error(String.format("Could not parse: %s", jsonData), e);
        }
        return null;
    }

    @Data
    public static class Rate {
        private String currency, conversionType;
        private BigDecimal buyRate, midRate, sellRate;
    }
}

    <dependencies>
  <!-- DTOs -->
  <dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>${lombok.version}</version>
    <scope>provided</scope>
  </dependency>
  <!-- Deserialization -->
  <dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>${jackson.version}</version>
  </dependency>
  <!-- Logging -->
  <dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-api</artifactId>
    <version>${log4j.version}</version>
  </dependency>
  <dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-core</artifactId>
    <version>${log4j.version}</version>
  </dependency>
  <dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-slf4j-impl</artifactId>
    <version>${log4j.version}</version>
  </dependency>
</dependencies>
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