Let's make the service return some students.

1. Start H2 if you haven't already.

2. Add a StudentDAO field named dao to the Server class. Initialise the field with an instance of StudentJdbiDAO (use the factory).

3. Change the Hello World code in the constructor to:

     get("/api/students", ctx -> dao.getStudents());

4. Stop and run the server again.

5. Reload the page in the browser. Append api/products to the URI.

   You should see some students. Jooby is using the toString method to display the students.

   REST APIs were covered in lecture 8. Recall from that lecture that an operation is made up of:

   • A path that represents a unique resource, or a collection of resources. In this case /api/students refers to a collection of students.

   • An HTTP method that defines what the operation will do to the resource. In this case GET.

   So this route (that is what Jooby calls these things) will return the collection of students.

6. Add the following to the constructor (below what is already here).

   get("/api/students/{id}", ctx -> {
   
       Integer id = ctx.path("id").intValue();
   
       Student student = dao.getByID(id);
   
       if(student == null) {
           // no product with that ID found, so return a 404/Not Found error
           return ctx.send(StatusCode.NOT_FOUND);
       } else {
           return product;
       }
   });

   The variable ctx holds the HTTP context which includes the request details. In this case we are extracting a path parameter named id out of the context.

   If a non-existent ID is provided then the service should return a 404/Not Found response rather than a null.

7. Stop and run. Append a student ID for a student that exists in your database to the end of the URI in the browser. You should see the details for a that student appear in the browser.

   The ID that you added to the end of the URI becomes the id path parameter.