[ADD] Spring Boot Hateoas

Author: heowc

SpringBootHateoas/src/main/java/com/example/Message.java

@@ -42,8 +42,4 @@ public LocalDateTime getCreatedAt() {
     public void setCreatedAt(LocalDateTime createdAt) {
         this.createdAt = createdAt;
     }
-
-    public MessageResource toResource() {
-        return new MessageResource(this);
-    }
 }

SpringBootHateoas/src/main/java/com/example/MessageController.java

@@ -1,40 +1,32 @@
 package com.example;
 
 import org.springframework.hateoas.Link;
-import org.springframework.hateoas.mvc.ControllerLinkBuilder;
 import org.springframework.http.HttpHeaders;
-import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RestController;
 
+import java.net.URI;
+import java.net.URISyntaxException;
 import java.time.Clock;
 import java.time.LocalDateTime;
 
-import static org.springframework.hateoas.mvc.ControllerLinkBuilder.linkTo;
-
 @RestController
 @RequestMapping("/message")
 public class MessageController {
 
     @GetMapping("/{id}")
-    public ResponseEntity<MessageResource> get(@PathVariable Long id) {
+    public ResponseEntity<MessageResource> get(@PathVariable Long id) throws URISyntaxException {
         Message message = new Message(id, "hello", LocalDateTime.now(Clock.systemUTC()));
-        MessageResource messageResource = message.toResource();
-
-//        1)
-//        Link link = new Link("http://localhost:8080/message/" + id);
-//        2)
-        ControllerLinkBuilder linkBuilder = linkTo(MessageController.class).slash(message);
-        Link link = linkBuilder.withSelfRel();
 
-        messageResource.add(link);
+        MessageResourceAssembler assembler = new MessageResourceAssembler();
+        MessageResource resource = assembler.toResource(message);
 
         HttpHeaders headers = new HttpHeaders();
-        headers.setLocation(linkBuilder.toUri());
-        return new ResponseEntity<>(headers, HttpStatus.OK);
+        headers.setLocation(new URI(resource.getLink(Link.REL_SELF).getHref()));
+        return ResponseEntity.ok().headers(headers).body(resource);
     }
 }
 

SpringBootHateoas/src/main/java/com/example/MessageResourceAssembler.java

@@ -0,0 +1,20 @@
+package com.example;
+
+import org.springframework.hateoas.mvc.ResourceAssemblerSupport;
+
+public class MessageResourceAssembler extends ResourceAssemblerSupport<Message, MessageResource> {
+
+    public MessageResourceAssembler() {
+        super(MessageController.class, MessageResource.class);
+    }
+
+    @Override
+    public MessageResource toResource(Message entity) {
+        return createResourceWithId(entity.getId(), entity);
+    }
+
+    @Override
+    protected MessageResource instantiateResource(Message entity) {
+        return new MessageResource(entity);
+    }
+}