graphql.schema.FieldDataFetcher Maven / Gradle / Ivy
package graphql.schema;
import java.lang.reflect.Field;
import java.util.Map;
/**
* Fetches data directly from a field.
*/
public class FieldDataFetcher implements DataFetcher {
/**
* The name of the field.
*/
private final String fieldName;
/**
* Ctor.
*
* @param fieldName The name of the field.
*/
public FieldDataFetcher(String fieldName) {
this.fieldName = fieldName;
}
@SuppressWarnings("unchecked")
@Override
public T get(DataFetchingEnvironment environment) {
Object source = environment.getSource();
if (source == null) return null;
if (source instanceof Map) {
return (T) ((Map) source).get(fieldName);
}
return (T) getFieldValue(source, environment.getFieldType());
}
/**
* Uses introspection to get the field value.
*
* @param object The object being acted on.
* @param outputType The output type; ignored in this case.
* @return An object, or null.
*/
private Object getFieldValue(Object object, GraphQLOutputType outputType) {
try {
Field field = object.getClass().getField(fieldName);
return field.get(object);
} catch (NoSuchFieldException e) {
return null;
} catch (IllegalAccessException e) {
throw new RuntimeException(e);
}
}
}