Why are the application config values parsed by my custom Spring PropertySourceLoader not being used? - spring

Question

I am attempting to write a TOML PropertySourceLoader implementation. I took a look at some other examples on GitHub and stackoverflow, all of which seem to eventually parse the result out to a map and then return an OriginTrackedMapPropertySource, which is what I tried below:
public final class TomlPropertySourceFactory implements PropertySourceFactory {
#Override
public PropertySource<?> createPropertySource(String name, EncodedResource resource) throws IOException {
if (!ClassUtils.isPresent("com.fasterxml.jackson.dataformat.toml.TomlFactory", null)) {
throw new IllegalStateException(
"Attempted to load " + name + " but jackson-dataformat-toml was not found on the classpath");
}
if (!ClassUtils.isPresent("com.fasterxml.jackson.core.io.ContentReference", null)) {
throw new IllegalStateException(
"Attempted to load " + name + " but jackson-core was either not found on the classpath or below version 2.13.0");
}
final ObjectMapper mapper = new ObjectMapper(new TomlFactory());
final Map<String, Object> resultMap = mapper.convertValue(mapper.readTree(resource.getInputStream()), new TypeReference<Map<String, Object>>(){});
return new OriginTrackedMapPropertySource(Optional.ofNullable(name).orElseGet(resource.getResource()::getFilename), resultMap);
}
}
public final class TomlPropertySourceLoader implements PropertySourceLoader {
#Override
public String[] getFileExtensions() {
return new String[]{"tml", "toml"};
}
#Override
public List<PropertySource<?>> load(final String name, final Resource resource) throws IOException {
final EncodedResource encodedResource = new EncodedResource(resource);
return Collections.singletonList(new TomlPropertySourceFactory().createPropertySource(name, encodedResource));
}
}
This code does seem to more or less do what is expected; it is executed when application.toml is present, it loads and parses the file out to a <String, Object> map, but from there, none of the actual properties seem to be present in the application — be it when using #Value, #ConfigurationProperties or even when attempting to set stuff like the port Tomcat runs on.
There's not a ton of information available on the internet, without digging into the depths of Spring, about what exactly it is expecting. I'm not sure if the problem is due to how my map is structured or perhaps due to something with the name.
Below you can find my application.toml file:
[spring.datasource]
url = "jdbc:hsqldb:file:testdb"
username = "sa"
[spring.thymeleaf]
cache = false
[server]
port = 8085
[myapp]
foo = "Hello"
bar = 42
aUri = "https://example.org/hello"
targetLocale = "en-US"
[myapp.configuration]
endpoints = ["one", "two", "three"]
[myapp.configuration.connectionSettings]
one = "hello"
[myapp.configuration.connectionSettings.two]
two_sub = "world!"
And my configuration classes:
#Data
#NoArgsConstructor
#Component
#ConfigurationProperties("myapp")
public class AppConfig {
private String foo;
private int bar;
private URI aUri;
private Locale targetLocale;
private SubConfiguration configuration;
}
#Data
#NoArgsConstructor
public class SubConfiguration {
private List<String> endpoints;
private Map<String, Object> connectionSettings;
}
As well as my testing controller:
#RestController
#RequiredArgsConstructor
public final class TomlDemoController {
private final AppConfig appConfig;
#GetMapping("/api/config")
AppConfig getConfig() {
return appConfig;
}
}

Answer 1

The issue was the structure of the property map. The keys have to be flattened in order to work. As an example, for a given table:
[server]
port = 8085
Rather than producing a nested map:
Properties = {
"server" = {
"port" = 8085
}
}
Spring is expecting something more like:
Properties = {
"server.port" = 8085
}
A quick solution using the ObjectToMapTransformer found in Spring Integration:
#Override
#SuppressWarnings("unchecked")
public PropertySource<?> createPropertySource(String name, EncodedResource resource) throws IOException {
if (!ClassUtils.isPresent("com.fasterxml.jackson.dataformat.toml.TomlFactory", null)) {
throw new IllegalStateException(
"Attempted to load " + name + " but jackson-dataformat-toml was not found on the classpath");
}
if (!ClassUtils.isPresent("com.fasterxml.jackson.core.io.ContentReference", null)) {
throw new IllegalStateException(
"Attempted to load " + name + " but jackson-core was either not found on the classpath or below version 2.13.0");
}
final ObjectMapper mapper = new ObjectMapper(new TomlFactory());
final Message<JsonNode> message = new GenericMessage<>(mapper.readTree(resource.getInputStream()));
final ObjectToMapTransformer transformer = new ObjectToMapTransformer();
transformer.setShouldFlattenKeys(true);
Map<String,Object> resultMap = (Map<String, Object>) transformer.transform(message).getPayload();
return new OriginTrackedMapPropertySource(Optional.ofNullable(name).orElseGet(resource.getResource()::getFilename), resultMap);
}