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Failed to populate Java object from JSON?

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posted 5 years ago

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I'm trying to poulate a list of javaobjects based on a jsonarray that is returned as response.
The objects are being created and the list is populated, but for some reasson all the properties of the object are null.
Anyone an idea why?
This is my pojo:

public class OrderSummary {
    private String order_id;
    private String instrument_code;
    private String time;
    private String side;
    private String price;
    private String amount;
    private String filled_amount;
    private String type;
    private String sequence;
    private String status;
    private String time_last_updated;
    private String average_price;
    private boolean is_post_only;

public OrderSummary() {
    }

public OrderSummary(String order_id, String instrument_code, String time, String side, String price, String amount,
                        String filled_amount, String type, String sequence, String status, String time_last_updated,
                        String average_price, boolean is_post_only) {
        this.order_id = order_id;
        this.instrument_code = instrument_code;
        this.time = time;
        this.side = side;
        this.price = price;
        this.amount = amount;
        this.filled_amount = filled_amount;
        this.type = type;
        this.sequence = sequence;
        this.status = status;
        this.time_last_updated = time_last_updated;
        this.average_price = average_price;
        this.is_post_only = is_post_only;
    }

public String getOrder_id() {
        return order_id;
    }

public String getInstrument_code() {
        return instrument_code;
    }

public String getTime() {
        return time;
    }

public String getSide() {
        return side;
    }

public String getPrice() {
        return price;
    }

public String getAmount() {
        return amount;
    }

public String getFilled_amount() {
        return filled_amount;
    }

public String getType() {
        return type;
    }

public String getSequence() {
        return sequence;
    }

public String getStatus() {
        return status;
    }

public String getTime_last_updated() {
        return time_last_updated;
    }

public String getAverage_price() {
        return average_price;
    }

public boolean isIs_post_only() {
        return is_post_only;
    }

@Override
    public String toString() {
        return "OrderSummary{" +
                "order_id='" + order_id + '\'' +
                ", instrument_code='" + instrument_code + '\'' +
                ", time='" + time + '\'' +
                ", side='" + side + '\'' +
                ", price='" + price + '\'' +
                ", amount='" + amount + '\'' +
                ", filled_amount='" + filled_amount + '\'' +
                ", type='" + type + '\'' +
                ", sequence='" + sequence + '\'' +
                ", status='" + status + '\'' +
                ", time_last_updated='" + time_last_updated + '\'' +
                ", average_price='" + average_price + '\'' +
                ", is_post_only=" + is_post_only +
                '}';
    }
}

The function:

Dave Tolls

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posted 5 years ago

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Have you logged the value of response after your calls to replace?

And then I suggest just trying to get that to work, with no other stuff around it.
A simple test bit of code, with a fixed json String based off that value.

The advantage there is that you can then post it here if it doesn't work and we can see and/or test using the same data and code.

Pieter Vandevelde

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I did all this before creating this post, I use the same way to populate a different object en there it works fine, while the properties of the javaobject dosn't even have the same names as the properties of the jsonobject.
Now the do...
But for the purpose of the example, I'll post the results here:
ResponseString:

example of the toStringmethod of one of the objects:

But you can't test using the same code, it uses other functions I have ommited and it queries a private endpoint, so you would need an apikey

Ron McLeod

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posted 5 years ago

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Here's what your payload looks like:

The data for the order object is wrapped in an unnamed outer object.

This may not be the best solution, but here's an example of something to work with the data that is being returned:

Pieter Vandevelde

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I realized it was wrapped but I account for that don't I? Otherwise it wouldn't even create the object, but throw an exception.
I also don't understand why I would need the wrapperclass, I use the same way before without any issues

Ron McLeod

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Your data is structured as an array of wrapper objects of order object

Your type: List<OrderSummary>> is an array of order objects.
My type: List<WrappedOrder>> is an array of wrapper objects, where the wrapper object contains an order object.

Ron McLeod

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Pieter Vandevelde wrote:I also don't understand why I would need the wrapperclass, I use the same way before without any issues

Compare the structure of the JSON payloads between what you had previously and what you have now to see what the differences might be.

Ron McLeod

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Pieter Vandevelde wrote:I realized it was wrapped but I account for that don't I? Otherwise it wouldn't even create the object, but throw an exception.

I think GSON silently ignores missing fields and leaves them with their default values, which in your case in null.

Pieter Vandevelde

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Now I see what you ment by it's wrapped, before it was additionally wrapped in an order_History object, but I removed it, for some reasson the same won't work with order.
This is where it did work:

Stephan van Hulst

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This has nothing to do with your problem, I just wanted to tell you that you should stop manipulating the raw JSON and instead use JSON-B or JAX-B. This will prevent a lot of bugs further down the road:

import java.util.*;

import javax.json.bind.annotation.*;
import javax.json.bind.config.*;

import static java.util.Collections.unmodifiableList;

@JsonbPropertyOrder(PropertyOrderStrategy.ANY)
public final class OrderHistoryResponse {
  
  private final List<OrderHistoryItem> orderHistory;
  
  private final int maxPageSize;
  
  @JsonbCreator
  public OrderHistoryResponse(
    @JsonbProperty("order_history") Collection<? extends OrderHistoryItem> orderHistory,
    @JsonbProperty("max_page_size") int maxPageSize
  ) {
    if (orderHistory == null)
      throw new IllegalArgumentException("The order history may not be null.");
    
    if (maxPageSize <= 0)
      throw new IllegalArgumentException("The max page size must be positive.");
    
    this.orderHistory = unmodifiableList(new ArrayList<>(orderHistory));
    this.maxPageSize  = maxPageSize;
    
    if (this.orderHistory.contains(null))
      throw new IllegalArgumentException("The order history may not contain null items.");
  }
  
  public List<OrderHistoryItem> getOrderHistory() {
    return orderHistory;
  }
  
  public int getMaxPageSize() {
    return maxPageSize;
  }
}

import java.math.*;
import java.time.*;

import javax.json.bind.annotation.*;
import javax.json.bind.config.*;

@JsonbPropertyOrder(PropertyOrderStrategy.ANY)
public final class OrderSummary {
  
  private String orderId;
  
  private String accountId;
  
  private String instrumentCode;
  
  private ZonedDateTime time;
  
  private OrderSide side;
  
  private BigDecimal price;
  
  private BigDecimal amount;
  
  private BigDecimal filledAmount;
  
  private OrderType type;
  
  private long sequence;
  
  private OrderStatus status;
  
  private ZonedDateTime timeLastUpdated;
  
  private BigDecimal averagePrice;
  
  private boolean isPostOnly;
  
  public String getOrderId() {
    return orderId;
  }
  
  public void setOrderId(String orderId) {
    this.orderId = orderId;
  }
  
  public String getAccountId() {
    return accountId;
  }
  
  public void setAccountId(String accountId) {
    this.accountId = accountId;
  }
  
  public String getInstrumentCode() {
    return instrumentCode;
  }
  
  public void setInstrumentCode(String instrumentCode) {
    this.instrumentCode = instrumentCode;
  }
  
  public ZonedDateTime getTime() {
    return time;
  }
  
  public void setTime(ZonedDateTime time) {
    this.time = time;
  }
  
  public OrderSide getSide() {
    return side;
  }
  
  public void setSide(OrderSide side) {
    this.side = side;
  }
  
  public BigDecimal getPrice() {
    return price;
  }
  
  public void setPrice(BigDecimal price) {
    this.price = price;
  }
  
  public BigDecimal getAmount() {
    return amount;
  }
  
  public void setAmount(BigDecimal amount) {
    this.amount = amount;
  }
  
  public BigDecimal getFilledAmount() {
    return filledAmount;
  }
  
  public void setFilledAmount(BigDecimal filledAmount) {
    this.filledAmount = filledAmount;
  }
  
  public OrderType getType() {
    return type;
  }
  
  public void setType(OrderType type) {
    this.type = type;
  }
  
  public long getSequence() {
    return sequence;
  }
  
  public void setSequence(long sequence) {
    this.sequence = sequence;
  }
  
  public OrderStatus getStatus() {
    return status;
  }
  
  public void setStatus(OrderStatus status) {
    this.status = status;
  }
  
  public ZonedDateTime getTimeLastUpdated() {
    return timeLastUpdated;
  }
  
  public void setTimeLastUpdated(ZonedDateTime timeLastUpdated) {
    this.timeLastUpdated = timeLastUpdated;
  }
  
  public BigDecimal getAveragePrice() {
    return averagePrice;
  }
  
  public void setAveragePrice(BigDecimal averagePrice) {
    this.averagePrice = averagePrice;
  }
  
  public boolean getIsPostOnly() {
    return isPostOnly;
  }
  
  public void setIsPostOnly(boolean isPostOnly) {
    this.isPostOnly = isPostOnly;
  }
}

<br /> I tested it like this: <br />

import java.io.*;
import java.math.*;
import java.nio.charset.*;

import javax.json.bind.*;
import javax.json.bind.config.*;

import org.junit.jupiter.api.Test;

import static java.util.stream.Collectors.toList;

import static javax.json.bind.config.PropertyNamingStrategy.LOWER_CASE_WITH_UNDERSCORES;

final class OrderHistoryResponseTest {
  
  private static final JsonbConfig JSON_CONFIG = new JsonbConfig()
    .withPropertyNamingStrategy(LOWER_CASE_WITH_UNDERSCORES)
    .withFormatting(true)
    .withPropertyOrderStrategy(PropertyOrderStrategy.ANY);
  
  private static final MathContext MATH_CONTEXT = new MathContext(2, RoundingMode.HALF_EVEN);
  
  @Test
  void testParseOrderHistoryResponse() throws Exception {
    var jsonB = JsonbBuilder.create(JSON_CONFIG);
    
    OrderHistoryResponse response;
    try (
      var reader = new InputStreamReader(
        OrderHistoryResponseTest.class.getResourceAsStream("order-history.json"),
        StandardCharsets.UTF_8
      );
    ) {
      response = jsonB.fromJson(reader, OrderHistoryResponse.class);
    }
      
    var orders = response.getOrderHistory().stream()
      .map(OrderHistoryItem::getOrder)
      .collect(toList());
      
    var sum = orders.stream()
      .filter(order -> order.getSide() == OrderSide.BUY)
      .map(OrderSummary::getAveragePrice)
      .reduce(BigDecimal.ZERO, BigDecimal::add);
      
    var average = sum.divide(BigDecimal.valueOf(orders.size()), MATH_CONTEXT);
    
    orders.forEach(order -> jsonB.toJson(order, System.out));
    System.out.printf("%n%n%s%n", average);
  }
}

Pieter Vandevelde

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I tried to make an implementation based on your tip, but getting following error:

Exception in thread "pool-2-thread-1" javax.json.bind.JsonbException: JSON Binding provider org.eclipse.yasson.JsonBindingProvider not found
	at javax.json.bind.spi.JsonbProvider.provider(JsonbProvider.java:120)
	at javax.json.bind.JsonbBuilder.create(JsonbBuilder.java:123)
	at net.goanation.services.BitPandaService.getAveragePrice(BitPandaService.java:182)
	at net.goanation.services.BitPandaService.getMarketTicker(BitPandaService.java:67)
	at net.goanation.MainApp.lambda$start$0(MainApp.java:46)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at java.base/java.lang.Thread.run(Unknown Source)
Caused by: java.lang.ClassNotFoundException: org.eclipse.yasson.JsonBindingProvider
	at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(Unknown Source)
	at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(Unknown Source)
	at java.base/java.lang.ClassLoader.loadClass(Unknown Source)
	at java.base/java.lang.Class.forName0(Native Method)
	at java.base/java.lang.Class.forName(Unknown Source)
	at javax.json.bind.spi.JsonbProvider.provider(JsonbProvider.java:117)
	... 7 more

Although I added both dependencies needed:

When googling the error online I saw that they used:

While I was using

but changing that resulted in:

Exception in thread "pool-2-thread-1" javax.json.bind.JsonbException: JSON Binding provider org.eclipse.yasson.JsonBindingProvider could not be instantiated: java.lang.ClassCastException: class org.eclipse.yasson.JsonBindingProvider cannot be cast to class javax.json.bind.spi.JsonbProvider (org.eclipse.yasson.JsonBindingProvider and javax.json.bind.spi.JsonbProvider are in unnamed module of loader 'app')
	at javax.json.bind.spi.JsonbProvider.provider(JsonbProvider.java:122)
	at javax.json.bind.JsonbBuilder.create(JsonbBuilder.java:123)
	at net.goanation.services.BitPandaService.getAveragePrice(BitPandaService.java:182)
	at net.goanation.services.BitPandaService.getMarketTicker(BitPandaService.java:67)
	at net.goanation.MainApp.lambda$start$0(MainApp.java:46)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at java.base/java.lang.Thread.run(Unknown Source)
Caused by: java.lang.ClassCastException: class org.eclipse.yasson.JsonBindingProvider cannot be cast to class javax.json.bind.spi.JsonbProvider (org.eclipse.yasson.JsonBindingProvider and javax.json.bind.spi.JsonbProvider are in unnamed module of loader 'app')
	at javax.json.bind.spi.JsonbProvider.provider(JsonbProvider.java:118)
	... 7 more

Any idea how come?

Stephan van Hulst

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posted 5 years ago

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Continued here: https://coderanch.com/t/733426/java/Error-binding-json-java-object

Consider Paul's rocket mass heater.