Expensive Construction¶

Rule details


Rule ID	`expensive-construction`
Severity	INFO — worth knowing, may not matter at your scale
Confidence	LOW — heuristic-heavy, may produce false positives
Category	Construction cost
Complexity	O(init) per call → O(1) amortized

Description¶

Detects creation of heavyweight objects (like ObjectMapper, Gson, DocumentBuilderFactory) inside method bodies. These objects are expensive to construct and should typically be reused as static fields or injected dependencies.

Typical¶

public String generateJson(Invoice invoice) {
    ObjectMapper mapper = new ObjectMapper(); // Created on every call
    return mapper.writeValueAsString(invoice);
}

After¶

Reuse the ObjectMapper as a static field:

private static final ObjectMapper MAPPER = new ObjectMapper();

public String generateJson(Invoice invoice) {
    return MAPPER.writeValueAsString(invoice);
}

Default Heavyweight Types¶

ObjectMapper
Gson
XmlMapper
DocumentBuilderFactory
TransformerFactory

Additional types can be configured in .algorilla.yml:

heavyweight-types:
  - ObjectMapper
  - Gson
  - JAXBContext
  - MyCustomExpensiveFactory

Suggestion¶

Reuse as a static final field or inject via dependency injection