Implementing a UserDetailsService

Our next order of business is to integrate spring security with our user and 0:00 role entities. 0:04 In general what we'll need to do is to implement the user details service 0:05 interface. 0:08 If we open this interface in the spring docs when we go there now, 0:09 we open this interface we'll see by scrolling down, 0:15 that there is exactly one method to implement and it's this load ByUsername. 0:18 Method. It locates the user based on 0:24 the user name. 0:27 So when we implement this method we'll call upon our user DAO which we 0:29 haven't written yet to grab the user entity from the database via hibernate and 0:33 use it as the methods return value. 0:38 Let's start coding our service in dao now. 0:40 I'll switch back to IntelliJ and first I'll create the user service interface. 0:42 So in my service package I will create a new, I'll choose Java class, 0:48 user service and all select interface. 0:54 There we go, and I'll make this service, 0:57 extend user, details, service. 1:00 So that my implementation class will need to include that load by user name method. 1:06 And the one additional method that all include here is a find by user name 1:12 method, which is a method that's completely for our application purposes 1:15 and that doesn't have anything To do with spring security so let me add that now. 1:20 I'll say, findByUsername(String username). 1:24 And let's make sure to import the right user here. 1:30 Now, this is our users so if you choose one of the ones up top, 1:34 you're gonna be importing the wrong user. 1:38 It's the user that comes from com.teamtree house. 1:41 Right there, cool. 1:44 And that's it for our interface. 1:47 Let's now create the implementation. 1:48 So again in the service package I'll right-click New Java Class and 1:50 I'll call it UserServiceImpl. 1:54 And let me include that service annotation here. 1:59 As well as indicate that it should be implementing the user service. 2:03 And in doing so, we'll need to add all unimplemented methods. 2:11 There should be two, one that comes from that user detail service that 2:19 the user service extends, and one that comes from user service that 2:24 we explicitly coded in the user service interface. 2:28 Now before we dive into this class we'll first need a way to grab 2:33 user data from the database. 2:36 Of course this will require a da o. 2:38 for the user entity. 2:40 Let's go ahead and create that interface in the dao package right click. 2:41 New job a class I'll call it user dao and 2:47 I want this to be an interface there it is right there. 2:50 The cool thing here is how little work we have to do. 2:54 If you recall, we are using spring data JPA. 2:57 So all we have to do here is extend CrudRepository. 3:00 And when you extend CrudRepository, 3:06 you tell it the kind of entity that you're after in the database. 3:09 As well as the class used for the identifier again. 3:12 Make sure you are importing the correct 3:17 User com.teamtreehouse.todotoday.model.User. 3:19 And after this we intelligently code our query methods. 3:23 In our case it will suffice to include a findByUsername method. 3:29 So let's do that now here's how that looks. 3:35 I want it to return a single user and 3:38 will say findByUsername(String username). 3:40 And finally let's apply the repository annotation to this interface. 3:47 And this is to make sure spring picks this up as a DAO and 3:55 now when we boot the app spring data will generate the implementation of the DAO so 3:59 we don't have to code it that is. 4:03 It will see a method name FindByUsername. 4:05 And it includes a string parameter so 4:09 it will generate a method that will find a user in the database 4:11 that has a user name column that uses the method name right here. 4:16 It has a user name column equal to whatever value was passed in so 4:21 cool okay back to the user service amperes class. 4:27 We can now auto wire a user dao into our service which will 4:33 need to start combining our user database data that is users and rows So 4:37 that we can integrate it with spring security. 4:41 So lets auto wire that up top. 4:44 Auto wired, private, user DAO, user DAO. 4:47 Cool. 4:52 Let me make sure to import that class. 4:54 There we go. 4:58 User DAO is imported. 4:58 The find my username method will be fairly quick here since it only 5:01 involves calling upon the DAOs method of the same name. 5:04 So let's return whatever value. 5:08 The DAO returns. 5:10 By calling its method of. 5:11 The same name. 5:13 As for the load by user name method this one will involve barely more work 5:17 Here's what will need to do. 5:22 I'm gonna add some comments in here. 5:24 First we'll need to load the user from the database. 5:28 And we'll throw an exception if not found. 5:31 And then we'll return the user object. 5:39 So really, we're just doing one extra thing here. 5:45 And that is that we are throwing an exception if that specific username 5:49 is not found. 5:53 And that is expected by the load by user name method which, again, comes from that 5:54 user details service interface, which our user interface extended. 5:59 Let me go back and remind you of that. 6:05 So the load by user name method comes from the user details service interface. 6:07 Okay, so back to these comments. 6:15 For loading the user from the database we use the same approach we did 6:18 in the findByUsername method. 6:22 That is will use that userDao so let's create a user object. 6:23 And call upon the DAO to find the user by the username and 6:27 we'll pass in the username that we received here in this method. 6:32 Now, because this method should throw the username not found exception, 6:37 which will be detected by Spring Security, 6:43 if upon authenticating, a user is not found with the provided username. 6:46 Then we should do that now if the value that stored in user at this point 6:51 happens to be no. 6:56 So will say if the user is null then we'll throw that exception. 6:57 UsernameNotFoundException. 7:06 And will throw a message in there too. 7:09 User not found. 7:11 Cool, and let's not forget to return that user object instead of returning null. 7:15 All finished. 7:22 So we finished our service and DAO layers. 7:24 Next we'll add some application level configuration to our Spring app 7:27 that switches on all of our Spring security functionality. 7:31