Can angular take over java controller functionalities?

Below is one of mostly used approach when Angular JS 1 and Spring communication is there.

Like wise people use different approach/ Flavors.

I suggest you try for following way

First of all create new controller with annotation @RestController, then have proper HTTP method for proper operation, look for Rest Maturity model in detail here https://martinfowler.com/articles/richardsonMaturityModel.html;

package com.mycompany.userinfo.controller;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
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.PathVariable;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.util.UriComponentsBuilder;

import com.mycompany.userinfo.model.User;
import com.mycompany.userinfoc.service.UserService;

@RestController
public class UserRestController {

    @Autowired
    UserService userService;  //Service which will do all data retrieval/manipulation work


    //-------------------Retrieve All Users--------------------------------------------------------

    @RequestMapping(value = "/user/", method = RequestMethod.GET)
    public ResponseEntity<List<User>> listAllUsers() {
        List<User> users = userService.findAllUsers();
        if(users.isEmpty()){
            return new ResponseEntity<List<User>>(HttpStatus.NO_CONTENT);//You many decide to return HttpStatus.NOT_FOUND
        }
        return new ResponseEntity<List<User>>(users, HttpStatus.OK);
    }


}

Then client side create Angular Service( It is singleton best for having back end call, sharing data between different component) for calling Back end Spring controller method using angular HTTP service like below

user.service.js
'use strict';

angular.module('myApp').factory('UserService', ['$http', '$q', function($http, $q){

    var REST_SERVICE_URI = 'http://localhost:8080/UserBackend/user/';

    var factory = {
        fetchAllUsers: fetchAllUsers
      };
    return factory;

    function fetchAllUsers() {
        var deferred = $q.defer();
        $http.get(REST_SERVICE_URI)
            .then(
            function (response) {
                deferred.resolve(response.data);
            },
            function(errResponse){
                console.error('Error while fetching Users');
                deferred.reject(errResponse);
            }
        );
        return deferred.promise;
    }

}

Then finally comes your Angular Controller(It get created n destroyed as per view, it is tightly coupled with your html template, So ideally never have any direct back end call from this controller, use angular service)

user.controller.js

'use strict';

angular.module('myApp').controller('UserController', ['$scope', 'UserService', function($scope, UserService) {
    var self = this;
    self.users=[];          

    fetchAllUsers();

    function fetchAllUsers(){
        UserService.fetchAllUsers()
            .then(
            function(d) {
                self.users = d;
            },
            function(errResponse){
                console.error('Error while fetching Users');
            }
        );
    }

}]);

1) Spring Controller and angular JS controller are nothing do with each other.

2) When define something in RequestMapping("/user/"), So then URL to execute that method become like this http://yourdomain.com or localhost:port/applicationname/user/

3) Hit that URL from Angular JS you need to use http service like below

$http.get("http://yourdomain or localhost:port/appname/user/")
            .then(sucessFunction(data){
            //This is callback function, a asynchronous call
            //This will get called on success of http request
        },
        failureFunction(error){
            //This is callback function, a asynchronous call
            //This will get called on failure of http request
        });
Read more about anguls js service , http service and promise.

I strongle recommend you to go through documentation or angular js trainings.

Hope this helps you and clear your doubts.