How do you serialize and deserialize JSON in Apex?

Apex provides the JSON class for converting between Apex objects and JSON strings.

Serialize:

Account a = new Account(Name='Acme', Industry='Tech');
String jsonStr = JSON.serialize(a);
// {"attributes":{"type":"Account"},"Name":"Acme","Industry":"Tech"}

String pretty = JSON.serializePretty(a); // human-readable

Deserialize:

String json = '{"name":"Acme","industry":"Tech"}';

// Type-safe — needs a class with matching fields
public class AccountDto { public String name; public String industry; }
AccountDto dto = (AccountDto) JSON.deserialize(json, AccountDto.class);

// Untyped — returns Object/Map for flexibility
Object parsed = JSON.deserializeUntyped(json);
Map<String,Object> m = (Map<String,Object>) parsed;
String name = (String) m.get('name');

Important nuances:

• Field names are case-sensitive for type-safe deserialization. JSON.deserialize matches the casing exactly. Use @JsonAccess or transform the JSON if external systems use different casing.
• `JSON.deserializeStrict` fails if JSON has fields not in the class (catches typos).
• `JSON.serialize` includes nulls by default. Use JSON.serialize(obj, true) to suppress nulls.
• Lists, Maps, nested objects all serialize naturally.
• DateTime serializes as ISO 8601 string.

Common use cases: REST callouts (request body, response parsing), Platform Event payloads, custom serialization for archival.