Deserializing JSON with Reserved Words as Properties in Apex

Question

How to Deserialize JSON with Reserved Words as Property Names in Apex?

Is there a way to deserialize JSON into an Apex object using JSON.deserialize, even if some of the property names in the JSON correspond to reserved keywords in Apex? For example, when deserializing JSON with reserved words, I want to deserialize a JSON string like this:

string jsonString = '{"currency" : "ABC"}';
public class JSONResult {
    public string currency;
}
JSONResult res = (JSONResult) JSON.deserialize(jsonString, JSONResult.class);
system.debug(res);

However, when I try to do this, I encounter an error because the identifier name is a reserved word in Apex. How can I handle this scenario?

Answer

When deserializing JSON into Apex objects using JSON.deserialize, you may encounter issues if the property names in the JSON are reserved words in Apex. For example, property names like class, new, object, etc., are reserved keywords in Apex and cannot be directly used as field names in a class. This will result in errors when you try to deserialize the JSON data.

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To handle this, you can use a technique to programmatically suffix the reserved words in the JSON before deserializing it. One way to do this is by writing a custom class that traverses the JSON data and appends a suffix (like _x) to the reserved words, making them safe to use in Apex. Here’s an example of how this can be done:

Example Code:

public class DTO {
    String toString_x;
    String object_x;
    String class_x;
    String new_x;
}

String jsonString = '{"class": "ABC"}';  // This is the bad word (reserved word)
Object input = Json.deserializeUntyped(jsonString);

String suffixed = new ReservedWordSerializer(input).getAsString();
DTO dto = (DTO)Json.deserialize(suffixed, DTO.class);

System.debug(dto.class_x);  // This will now work as 'class_x' is safe

In this solution, we use a custom ReservedWordSerializer class that takes the JSON object, traverses it, and appends a suffix (_x) to any key that is a reserved word. This makes the field names safe for deserialization into Apex classes.

See also: How to generate JSON for a APEX REST Post callout in Salesforce

ReservedWordSerializer Class:

public class ReservedWordSerializer {
    JsonGenerator g = Json.createGenerator(true); // true for pretty printing
    
    public ReservedWordSerializer(Object obj) {
        if (obj == null) {
            g.writeNull();
        } else if (obj instanceof Map<String,Object>) {
            traverseMap((Map<String,Object>)obj);
        } else if (obj instanceof List<Object>) {
            traverseList((List<Object>)obj);
        } else {
            g.writeObject(obj);
        }
    }

    public String getAsString() {
        return g.getAsString();
    }

    void traverseMap(Map<String,Object> obj) {
        List<String> keys = new List<String>(obj.keySet());
        keys.sort();
        
        g.writeStartObject();
        for (String key : keys) {
            Object value = obj.get(key);
            g.writeFieldName(key + '_x'); // Appending '_x' to avoid reserved words

            if (value == null) {
                g.writeNull();
            } else if (value instanceof Map<String,Object>) {
                traverseMap((Map<String,Object>)value);
            } else if (value instanceof List<Object>) {
                traverseList((List<Object>)value);
            } else {
                g.writeObject(value);
            }
        }
        g.writeEndObject();
    }

    void traverseList(List<Object> objs) {
        g.writeStartArray();
        for (Object obj : objs) {
            if (obj == null) {
                g.writeNull();
            } else if (obj instanceof Map<String,Object>) {
                traverseMap((Map<String,Object>)obj);
            } else if (obj instanceof List<Object>) {
                traverseList((List<Object>)obj);
            } else {
                g.writeObject(obj);
            }
        }
        g.writeEndArray();
    }
}

In this code, the ReservedWordSerializer class uses a JsonGenerator to serialize the data. It checks each field name and appends _x to the field name if it is a reserved word. This approach ensures that the JSON can be deserialized into an Apex object, even if it contains reserved words.

By using this method, you can safely deserialize JSON data with reserved words and access those fields in your Apex class without encountering errors.

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