Part 3: @JsonInclude and @JsonFormat; ISO-8601 is already the default

src/main/java/com/ankurm/jackson3/part3annotations/D02InclusionAndFormat.java

@@ -0,0 +1,46 @@
+package com.ankurm.jackson3.part3annotations;
+
+import com.fasterxml.jackson.annotation.JsonFormat;
+import com.fasterxml.jackson.annotation.JsonInclude;
+import tools.jackson.databind.json.JsonMapper;
+
+import java.time.LocalDate;
+import java.util.List;
+
+/**
+ * Post: Jackson Annotations Cheat Sheet — https://ankurm.com/jackson-annotations-guide/
+ * Sections: "@JsonInclude" and "@JsonFormat"
+ *
+ * One correction to the post: it says "Without @JsonFormat, Jackson writes LocalDate
+ * as a numeric array by default." That was true in Jackson 2. In Jackson 3, java.time
+ * support is built in and ISO-8601 is the default — the annotation is only needed for
+ * a NON-standard pattern. The `defaultDate` field below proves it.
+ */
+public class D02InclusionAndFormat {
+
+    @JsonInclude(JsonInclude.Include.NON_NULL)
+    public record ProductDetails(String productName, String productDescription, Double discountRate) { }
+
+    @JsonInclude(JsonInclude.Include.NON_EMPTY)
+    public record CompactProduct(String productName, String notes, List<String> tags) { }
+
+    public record InvoiceRecord(
+            Long invoiceId,
+            LocalDate defaultDate,                                        // no annotation
+            @JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "dd/MM/yyyy")
+            LocalDate ukStyleDate,                                        // custom pattern
+            @JsonFormat(shape = JsonFormat.Shape.STRING)
+            double totalAmount) { }                                       // number as string
+
+    public static void main(String[] args) {
+        JsonMapper mapper = JsonMapper.builder().build();
+
+        System.out.println("NON_NULL  : "
+                + mapper.writeValueAsString(new ProductDetails("Keyboard", null, null)));
+        System.out.println("NON_EMPTY : "
+                + mapper.writeValueAsString(new CompactProduct("Keyboard", "", List.of())));
+
+        System.out.println("formats   : " + mapper.writeValueAsString(new InvoiceRecord(
+                500L, LocalDate.of(2026, 4, 9), LocalDate.of(2026, 4, 9), 199.99)));
+    }
+}