Jackson 3 series companion code

37 runnable examples covering the eight feature posts on ankurm.com, verified against Jackson 3.2.1 on Temurin 21.0.5. Every output committed under docs/ was produced by run-all.sh. Also documents 11 places where the published snippets do not compile or do not behave as printed against a real Jackson 3 build - most notably that writeValueAsString(List<Base>) silently drops the polymorphic type discriminator, so the post's serialised output cannot be read back.
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+package com.ankurm.jackson3.part1objectmapper;
+
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+import tools.jackson.databind.json.JsonMapper;
+
+/**
+ * BEYOND THE POST — no blog section covers this, but it bites on first run.
+ *
+ * A record serialises in declaration order. A getter-based POJO serialises in
+ * ALPHABETICAL order. If you are diffing Jackson output against a fixture, this
+ * is usually the reason the diff is not empty.
+ */
+public class B04PropertyOrdering {
+
+    /** Getter-based POJO: output is alphabetical, NOT declaration order. */
+    public static class ProductPojo {
+        private Long   productId;
+        private String productName;
+        private double listPrice;
+        public ProductPojo(Long i, String n, double p) { productId = i; productName = n; listPrice = p; }
+        public Long   getProductId()   { return productId; }
+        public String getProductName() { return productName; }
+        public double getListPrice()   { return listPrice; }
+    }
+
+    /** Record: output follows the component declaration order. */
+    public record ProductRecord(Long productId, String productName, double listPrice) { }
+
+    /** Explicit ordering wins over both defaults. */
+    @JsonPropertyOrder({ "productId", "productName", "listPrice" })
+    public static class ProductOrdered {
+        private final Long   productId;
+        private final String productName;
+        private final double listPrice;
+        public ProductOrdered(Long i, String n, double p) { productId = i; productName = n; listPrice = p; }
+        public Long   getProductId()   { return productId; }
+        public String getProductName() { return productName; }
+        public double getListPrice()   { return listPrice; }
+    }
+
+    public static void main(String[] args) {
+        JsonMapper mapper = JsonMapper.builder().build();
+        System.out.println("POJO    : " + mapper.writeValueAsString(
+                new ProductPojo(1L, "Mechanical Keyboard", 79.99)));
+        System.out.println("record  : " + mapper.writeValueAsString(
+                new ProductRecord(1L, "Mechanical Keyboard", 79.99)));
+        System.out.println("ordered : " + mapper.writeValueAsString(
+                new ProductOrdered(1L, "Mechanical Keyboard", 79.99)));
+    }
+}