[Java][Spring] default value of Arrays and Maps is empty collection #5685
Description
Description
Currently codegen generates empty collections for arrays and maps e.g.
@SerializedName("data")
private List<Account> data = new ArrayList<Account>();
The problem is that by the time the model is deserialised from json, there is no way for the API to distinguish between a missing value and an empty array. This is particularly a problem when building REST PATCH handlers, where we'd like to distinguish between field = null (meaning dont change it - use the current value) and field = [] (meaning, set it to an empty array).
Ideally we'd either just set the empty collection to null e.g.
@SerializedName("data")
private List<Account> data = null;
If this is considered a breaking change, we could introduce an optional switch in codegen to determine which behaviour is required (null vs. empty collection for uninitialised fields).
Swagger-codegen version
latest head
Command line used for generation
generate -i swagger.yaml -l spring
Steps to reproduce
Add an array or map to a model, and look at the source code.
Related issues
Suggest a Fix
Relevant code is in: https://github.com/swagger-api/swagger-codegen/blob/master/modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/AbstractJavaCodegen.java
@Override
public String toDefaultValue(Property p) {
if (p instanceof ArrayProperty) {
final ArrayProperty ap = (ArrayProperty) p;
final String pattern;
if (fullJavaUtil) {
pattern = "new java.util.ArrayList<%s>()";
} else {
pattern = "new ArrayList<%s>()";
}
if (ap.getItems() == null) {
return null;
}
return String.format(pattern, getTypeDeclaration(ap.getItems()));
} else if (p instanceof MapProperty) {
final MapProperty ap = (MapProperty) p;
final String pattern;
if (fullJavaUtil) {
pattern = "new java.util.HashMap<String, %s>()";
} else {
pattern = "new HashMap<String, %s>()";
}
if (ap.getAdditionalProperties() == null) {
return null;
}
return String.format(pattern, getTypeDeclaration(ap.getAdditionalProperties()));
}
change to:
@Override
public String toDefaultValue(Property p) {
if (p instanceof ArrayProperty) {
return "null";
} else if (p instanceof MapProperty) {
return "null";
}