sealed: add release-level and Jackson 3.2.3 transcripts

09 shows which language level each sealed feature needs; 10 runs the Payment model through Jackson 3 (jars fetched and sha1-checked, not committed). Co-Authored-By: Claude Sonnet 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01TF9JWFvJSNm6HVzswzZU5a
2026-09-24 12:08:23 +00:00
parent ff6130bede
commit d2c1efc2c4
9 changed files with 193 additions and 0 deletions
@@ -0,0 +1,39 @@
+import com.fasterxml.jackson.annotation.JsonSubTypes;
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import tools.jackson.databind.json.JsonMapper;
+
+public class JsonPayment {
+    // Two annotations tell Jackson which JSON field names the type, and which class each name means.
+    @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property = "type")
+    @JsonSubTypes({
+        @JsonSubTypes.Type(value = Card.class, name = "card"),
+        @JsonSubTypes.Type(value = Upi.class, name = "upi"),
+        @JsonSubTypes.Type(value = NetBanking.class, name = "netbanking")})
+    sealed interface Payment permits Card, Upi, NetBanking {}
+    record Card(String last4, long amount) implements Payment {}
+    record Upi(String vpa, long amount) implements Payment {}
+    record NetBanking(String bank, long amount) implements Payment {}
+
+    static long fee(Payment p) {
+        return switch (p) {
+            case Card(String last4, long amount) -> amount * 2 / 100;
+            case Upi(String vpa, long amount) -> 0;
+            case NetBanking(String bank, long amount) -> 15;
+        };
+    }
+
+    public static void main(String[] args) {
+        JsonMapper mapper = JsonMapper.builder().build();
+        Payment[] all = { new Card("4242", 500), new Upi("ankur@bank", 500), new NetBanking("HDFC", 500) };
+        for (Payment p : all) {
+            String json = mapper.writeValueAsString(p);
+            Payment back = mapper.readValue(json, Payment.class);
+            System.out.println(json + "  ->  " + back + "  equal=" + back.equals(p) + "  fee=" + fee(back));
+        }
+        try {
+            mapper.readValue("{\"type\":\"cheque\",\"amount\":500}", Payment.class);
+        } catch (Exception e) {
+            System.out.println("unknown type: " + e.getClass().getSimpleName() + ": " + e.getMessage().lines().findFirst().orElse(""));
+        }
+    }
+}