ResponseEntity builder examples

spring-mvc-java/src/main/java/com/baeldung/annotations/CustomResponseWithBuilderController.java

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+package com.baeldung.annotations;
+
+import java.time.Year;
+
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.stereotype.Controller;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+
+@Controller
+@RequestMapping("/customResponseWithBuilder")
+public class CustomResponseWithBuilderController {
+
+    @GetMapping("/hello")
+    public ResponseEntity<String> hello() {
+        return ResponseEntity.ok("Hello World!");
+    }
+
+    @GetMapping("/age")
+    public ResponseEntity<String> age(@RequestParam("yearOfBirth") int yearOfBirth) {
+        if (isInFuture(yearOfBirth)) {
+            return ResponseEntity.badRequest()
+                .body("Year of birth cannot be in the future");
+        }
+
+        return ResponseEntity.status(HttpStatus.OK)
+            .body("Your age is " + calculateAge(yearOfBirth));
+    }
+
+    private int calculateAge(int yearOfBirth) {
+        return currentYear() - yearOfBirth;
+    }
+
+    private boolean isInFuture(int year) {
+        return currentYear() < year;
+    }
+
+    private int currentYear() {
+        return Year.now()
+            .getValue();
+    }
+
+    @GetMapping("/customHeader")
+    public ResponseEntity<String> customHeader() {
+        return ResponseEntity.ok()
+            .header("Custom-Header", "foo")
+            .body("Custom header set");
+    }
+
+}