Currently, I am developing a configuration system where I aim to load config values from a JSON file and have them automatically converted into the required Java type. My choice for JSON parsing is Jackson, which works well with primitive types like floats and strings. However, I've encountered an issue when it comes to converting enums.
Let's consider the following enum:
public enum SystemMode
{
@JsonProperty("Mode1")
MODE1("Mode1"),
@JsonProperty("Mode2")
MODE2("Mode2"),
@JsonProperty("Mode3")
MODE3("Mode3");
private final String name;
private SystemMode(String name)
{
this.name = name;
}
@Override
@JsonValue
public String toString()
{
return this.name;
}
}
Suppose I want to represent a list of values of this enum in a JSON format as shown below:
{
"Project" : "TEST",
"System" : {
"ValidModes" : ["Mode1", "Mode2"]
}
}
And my desired approach would be something similar to the code snippet below:
ArrayList<SystemMode> validModes = (ArrayList<SystemMode>) configurator.getConfigValue("/System/ValidModes");
In my configurator class, the getConfigValue method simply acts as a thin layer over the Jackson JSON parsing process:
public Object getConfigValue(String JSON_String)
{
JsonNode node = JsonNodeFactory.instance.objectNode().at(JSON_String);
return objectMapper.convertValue(node, Object.class);
}
When I execute the above code, Jackson correctly identifies that an ArrayList is needed but instead of returning an ArrayList of SystemMode enums, it provides an ArrayList of Strings, leading to an exception. Despite trying various data representations, Jackson persists in returning a list of strings rather than enums.
Hence, my query is:
How can I modify Jackson (version 2.9.4) to deserialize a list of enum values accurately in a way that aligns with my single "Object getConfigValue()" method?