jonikarppinen · November 17, 2021 11:49 · Oct 28, 2015 · Oct 28, 2015 · Oct 28, 2015 · Oct 28, 2015
diff --git a/PdfOrErrorController.java b/PdfOrErrorController.java
@@ -44,7 +44,6 @@ public ResponseEntity<byte[]> test() {
      */
     @ExceptionHandler(OriginalExceptionFromAnotherApi.class)
     @ResponseStatus(HttpStatus.SERVICE_UNAVAILABLE)
-    @ResponseBody
     public ErrorResponse handle(OriginalExceptionFromAnotherApi e) {
         return new ErrorResponse(e.getMessage()); // use message from the original exception
     }

diff --git a/PdfOrErrorController.java b/PdfOrErrorController.java
@@ -12,6 +12,8 @@
  * Example of a Spring Boot controller method that can return either:
  *  - 200 OK with binary data (application/pdf)
  *  - 503 Service Unavailable with JSON error message
+ * 
+ * (Everything defined as static nested classes just for readability of this example.) 
  *
  * @author Joni Karppinen
  * @since 2015-10-28

diff --git a/PdfOrErrorController.java b/PdfOrErrorController.java
@@ -20,14 +20,14 @@
 public class PdfOrErrorController {
 
     /**
-     * Successful case, return type is byte[] (fake PDF data)
+     * Successful case, returns byte[] (fake PDF data)
      * Content type will be application/pdf
      */
     @RequestMapping(value = "/test", method = RequestMethod.GET)
     public ResponseEntity<byte[]> test() {
         // Set Content-Type header (+ content disposition, etc, if you want)
-        // (Not using "produces", because that depends on request's Accept header including "application/pdf"
-        // and otherwise returns 406 Not Acceptable.)
+        // (Not using "produces", because that depends on request's Accept header including 
+        // "application/pdf" and otherwise returns 406 Not Acceptable.)
         HttpHeaders headers = new HttpHeaders();
         headers.setContentType(MediaType.parseMediaType("application/pdf"));
         String filename = "output.pdf";
@@ -37,7 +37,7 @@ public ResponseEntity<byte[]> test() {
     }
 
     /**
-     * Error case, return type is ErrorResponse which Spring automatically converts to JSON (using Jackson)
+     * Error case, returns ErrorResponse which Spring automatically converts to JSON (using Jackson)
      * Content type will be application/json
      */
     @ExceptionHandler(OriginalExceptionFromAnotherApi.class)
@@ -58,7 +58,7 @@ private byte[] getDataOrThrowException() {
             return getBinaryData();
         }
         else {
-            throw new OriginalExceptionFromAnotherApi("Failed because the other API is unavailable!");
+            throw new OriginalExceptionFromAnotherApi("Failed because the other API is down!");
         }
     }
 

diff --git a/PdfOrErrorController.java b/PdfOrErrorController.java
@@ -0,0 +1,88 @@
+package com.company.project.controllers;
+
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.MediaType;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.*;
+
+import java.util.Random;
+
+/**
+ * Example of a Spring Boot controller method that can return either:
+ *  - 200 OK with binary data (application/pdf)
+ *  - 503 Service Unavailable with JSON error message
+ *
+ * @author Joni Karppinen
+ * @since 2015-10-28
+ */
+@RestController
+public class PdfOrErrorController {
+
+    /**
+     * Successful case, return type is byte[] (fake PDF data)
+     * Content type will be application/pdf
+     */
+    @RequestMapping(value = "/test", method = RequestMethod.GET)
+    public ResponseEntity<byte[]> test() {
+        // Set Content-Type header (+ content disposition, etc, if you want)
+        // (Not using "produces", because that depends on request's Accept header including "application/pdf"
+        // and otherwise returns 406 Not Acceptable.)
+        HttpHeaders headers = new HttpHeaders();
+        headers.setContentType(MediaType.parseMediaType("application/pdf"));
+        String filename = "output.pdf";
+        headers.setContentDispositionFormData(filename, filename);
+
+        return new ResponseEntity<>(getDataOrThrowException(), headers, HttpStatus.OK);
+    }
+
+    /**
+     * Error case, return type is ErrorResponse which Spring automatically converts to JSON (using Jackson)
+     * Content type will be application/json
+     */
+    @ExceptionHandler(OriginalExceptionFromAnotherApi.class)
+    @ResponseStatus(HttpStatus.SERVICE_UNAVAILABLE)
+    @ResponseBody
+    public ErrorResponse handle(OriginalExceptionFromAnotherApi e) {
+        return new ErrorResponse(e.getMessage()); // use message from the original exception
+    }
+
+
+    private Random random = new Random();
+
+    /**
+     * Fake "service layer"
+     */
+    private byte[] getDataOrThrowException() {
+        if (random.nextBoolean()) {
+            return getBinaryData();
+        }
+        else {
+            throw new OriginalExceptionFromAnotherApi("Failed because the other API is unavailable!");
+        }
+    }
+
+    private byte[] getBinaryData() {
+        byte[] b = new byte[20];
+        random.nextBytes(b);
+        return b;
+    }
+
+    /**
+     * Defines the JSON output format of error responses
+     */
+    private static class ErrorResponse {
+        public String message;
+
+        public ErrorResponse(String message) {
+            this.message = message;
+        }
+    }
+
+    private static class OriginalExceptionFromAnotherApi extends RuntimeException {
+        public OriginalExceptionFromAnotherApi(String message) {
+            super(message);
+        }
+    }
+
+}
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