Accessing Java’s closable response body values
When working with Binance API WebSocket endpoints, you may receive a list of data as part of the response. However, not all responses are easily accessible from Java code. In this article, we will look at how to extract values from a closable response body.
Binance API WebSocket Overview
Before we dive into the solution, let’s quickly review the basics of Binance API WebSocket. The BinanceApiWebSocketClient
class provides an interface for sending and receiving messages over the WebSocket protocol. When a message arrives, it contains various fields that can be accessed using the methods provided.
Problem: List of data as response body
In your case, you will likely receive a list of data from Binance in response to a candlestick request. However, if no such field exists in the API’s response structure, you will encounter an org.binance.client.exceptions.BinanceApiException'.
To solve this problem, we can use the following techniques:
- Check for the existence of certain fields: Check whether certain keys exist in the data list before attempting to access them.
- Use a try-catch block: Wrap the code in a try-catch block to catch exceptions that occur when accessing non-existent fields.
Solution: Extract values from the closable response body
Here is an example implementation:
import java.util.ArrayList;
import java.util.List;
public class CandleStickRequest {
private List dataList;
public List getDataList() {
if (dataList == null || dataList.isEmpty()) {
// Handle the case where no data is received or there is no list
return new ArrayList<>();
}
return dataList;
}
public static class CandlestickData {
private String symbol;
private List values;
public CandlestickData(String symbol, List values) {
this.symbol = symbol;
this.values = values;
}
}
public Closeable candleStick() throws BinanceApiException {
// Create a new instance of the API client
BinanceApiWebSocketClient client = ...;
try (Closeable response = client.getNewestCandlestick()) {
List dataList = response.getDataList();
for (CandlestickData data : dataList) {
if (data.getValues() != null && !data.getValues().isEmpty()) {
// Extract values from candlestick data
String symbol = data.symbol;
List values = data.values;
// Handle the given fields as needed (e.g. use a separate method for "Open")
handlestickFields(symbol, values);
}
}
return response; // Return the original response object
} catch (BinanceApiException e) {
// Log and rethrow the exception for robustness
System.err.println("Error receiving candlestick data: " + e.getMessage());
throw e;
}
}
}
private static void handleCandlestickFields(String symbol, List values) {
// Handle the given fields as needed (e.g. use a separate method for "Open")
// ...
}
}
In this solution:
- First, we check if the data list is null or empty to avoid possible null pointer exceptions.
- If the data list contains non-null data, we extract the values from each field using a try-catch block to catch exceptions that occur when accessing fields that do not exist in the response object.
- We use a separate method (handleCandlestickFields
) to handle certain fields of the
CandlestickData` class.