Part 3: @JsonCreator, plus @JsonUnwrapped and @JsonAnyGetter/Setter

src/main/java/com/ankurm/jackson3/part3annotations/D04CreatorsAndUnwrapping.java

@@ -0,0 +1,71 @@
+package com.ankurm.jackson3.part3annotations;
+
+import com.fasterxml.jackson.annotation.JsonAnyGetter;
+import com.fasterxml.jackson.annotation.JsonAnySetter;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.annotation.JsonUnwrapped;
+import tools.jackson.databind.json.JsonMapper;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+/**
+ * Post: Jackson Annotations Cheat Sheet — https://ankurm.com/jackson-annotations-guide/
+ * Sections: "@JsonCreator", plus @JsonUnwrapped which the post's table lists but
+ * never demonstrates. @JsonAnyGetter/@JsonAnySetter are beyond the post entirely.
+ */
+public class D04CreatorsAndUnwrapping {
+
+    /** Immutable class with no setters: the creator tells Jackson how to build it. */
+    public static class ImmutablePoint {
+        private final double xCoordinate;
+        private final double yCoordinate;
+
+        @JsonCreator
+        public ImmutablePoint(@JsonProperty("x") double xCoordinate,
+                              @JsonProperty("y") double yCoordinate) {
+            this.xCoordinate = xCoordinate;
+            this.yCoordinate = yCoordinate;
+        }
+        @JsonProperty("x") public double getXCoordinate() { return xCoordinate; }
+        @JsonProperty("y") public double getYCoordinate() { return yCoordinate; }
+        @Override public String toString() {
+            return "ImmutablePoint(x=" + xCoordinate + ", y=" + yCoordinate + ")";
+        }
+    }
+
+    public record Address(String street, String city) { }
+
+    /** @JsonUnwrapped flattens the nested object into the parent's JSON object. */
+    public static class Customer {
+        public String customerName;
+        @JsonUnwrapped public Address address;
+        public Customer() { }
+        public Customer(String n, Address a) { customerName = n; address = a; }
+    }
+
+    /** Any unmapped properties land in a Map instead of being dropped. */
+    public static class FlexiblePayload {
+        public String knownField;
+        private final Map<String, Object> extras = new LinkedHashMap<>();
+        @JsonAnyGetter public Map<String, Object> extras()            { return extras; }
+        @JsonAnySetter public void put(String k, Object v)            { extras.put(k, v); }
+    }
+
+    public static void main(String[] args) {
+        JsonMapper mapper = JsonMapper.builder().build();
+
+        ImmutablePoint point = mapper.readValue("{\"x\":3.5,\"y\":7.2}", ImmutablePoint.class);
+        System.out.println("creator   : " + point);
+        System.out.println("round-trip: " + mapper.writeValueAsString(point));
+
+        System.out.println("unwrapped : " + mapper.writeValueAsString(
+                new Customer("Alice", new Address("123 Main St", "Springfield"))));
+
+        FlexiblePayload flexible = mapper.readValue(
+                "{\"knownField\":\"a\",\"surprise\":1,\"another\":[true,false]}", FlexiblePayload.class);
+        System.out.println("any-setter: " + flexible.extras());
+        System.out.println("any-getter: " + mapper.writeValueAsString(flexible));
+    }
+}