Spring Boot ログイン機能

前提・実現したいこと

作成した予定管理表にログイン機能を持たせたいです。
現在の構成を、皆様はどのように変更するのでしょうか？
恥ずかしながら、私には想像がつかないので参考にさせてください。

UserController.java

package com.example.springsample.controller;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;

import com.example.springsample.dto.UserPRequest;
import com.example.springsample.dto.UserRequest;
import com.example.springsample.entity.User;
import com.example.springsample.entity.UserPlan;
import com.example.springsample.service.UserService;


@Controller
public class UserController {

	@Autowired
	UserService userService;

	@RequestMapping(value = "/user/list", method = RequestMethod.GET)
	public String displayList(Model model) {
		List<User> userlist = userService.searchAll();
		model.addAttribute("userlist", userlist);//modelにSELECTしたデータを追加
		return "user/list";
	}

	@RequestMapping(value = "/user/add", method = RequestMethod.GET)
	public String displayAdd(Model model) {
		model.addAttribute("userRequest", new UserRequest());
		return "user/add";
	}

	@RequestMapping(value="/user/create", method = RequestMethod.POST)
    public String create(@ModelAttribute UserRequest userRequest, Model model) {
		// ユーザー情報の登録
		userService.create(userRequest);
		return "redirect:/user/list";
	}

	@RequestMapping(value = "/user/tes", method = RequestMethod.POST)
	public String detailModel(Model model, @RequestParam((String) "id") Long id) {
		//選択ユーザーの抽出
		List<UserPlan> userPlan = userService.findUser(id);
		model.addAttribute("id", id);
		model.addAttribute("userdata", userPlan);
		return "user/tes";
	}

	@RequestMapping(value = "/user/planadd", method = RequestMethod.POST)
	public String planAdd(Model model, @RequestParam((String) "id") Long id) {
		UserPRequest userPRequest = new UserPRequest();
		userPRequest.setId(id);
		model.addAttribute("userPRequest", userPRequest);
		return "user/planadd";
	}

	@RequestMapping(value = "/user/edit", method = RequestMethod.POST)
	public String planEdit(Model model, @RequestParam((String) "id") Long id) {
		//UserPlanのUserにidをセットするためにリクエストしたidでSELECTする
		UserPlan userPlan = new UserPlan();
		userPlan = userService.findId(id);
		model.addAttribute("userplan", userPlan);//UserPlanのUser.idにSELECTされたデータが入っているのでモデルに追加する
		return "user/edit";
	}

	@RequestMapping(value="/user/plancreate", method = RequestMethod.POST)
    public String planCreate(@ModelAttribute UserPRequest userPRequest) {
		// 予定情報の登録
		userService.planCreate(userPRequest);
		return "redirect:/user/list";
	}

	@RequestMapping(value = "/user/delete", method = RequestMethod.POST)
	public String delete(@RequestParam((String) "id") Long id) {
		//選択ユーザーの抽出
		userService.delete(id);
		return "redirect:/user/list";
	}

	@RequestMapping(value="/user/editcheck", method = RequestMethod.POST)
    public String planEdit(@ModelAttribute UserPRequest userPRequest,@RequestParam((String) "plan_id") Long id) {
		// userPRequestのIDに編集したい予定のplan_idをセット
		userPRequest.setId(id);
		userService.planEdit(userPRequest);
		return "redirect:/user/list";
	}
}

UserPRequest.java

package com.example.springsample.dto;

import java.io.Serializable;
import java.util.Date;

import lombok.Data;

@Data
public class UserPRequest implements Serializable {
	private String plan;

	private Date date;

	private Long id;
}

UserRequest.java

package com.example.springsample.dto;

import java.io.Serializable;

import lombok.Data;

@Data
public class UserRequest implements Serializable {

	private String name;

	private String address;

	private String phone;
}

User.java

package com.example.springsample.entity;

import java.io.Serializable;
import java.util.Date;
import java.util.List;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;

import lombok.Data;

@Entity
@Data
@Table(name="user")
public class User implements Serializable {
	//ユーザー情報のエンティティ
	@Id
	@Column(name="id")
    @GeneratedValue(strategy=GenerationType.IDENTITY)
	private Long id;

	@Column(name="name")
	private String name;

	@Column(name="address")
	private String address;

	@Column(name="phone")
	private String phone;

	@Column(name="update_date")
	private Date updateDate;

	@Column(name="create_date")
	private Date createDate;

	@Column(name="delete_date")
	private Date deleteDate;

	@OneToMany(mappedBy = "user", cascade = CascadeType.ALL)
	private List<UserPlan> userPList;
}

UserPlan.java

package com.example.springsample.entity;

import java.io.Serializable;
import java.util.Date;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

import lombok.Data;

@Entity
@Data
@Table(name="user_plan")
public class UserPlan implements Serializable {
	//ユーザー予定情報のエンティティ
	@Id
	@Column(name="plan_id")
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	private Long plan_id;

	@Column(name="plan")
	private String plan;

	@Column(name="date")
	private Date date;

	@ManyToOne
	@JoinColumn(name="id")
	private User user;
}

UserPlanRepository.java

package com.example.springsample.repository;

import java.util.List;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;
import org.springframework.stereotype.Repository;

import com.example.springsample.entity.UserPlan;

@Repository
public interface UserPlanRepository extends JpaRepository<UserPlan, Long> {

	@Query("SELECT up FROM UserPlan up INNER JOIN up.user WHERE up.user.id = :id")
	List<UserPlan> find(@Param("id") Long id);

	@Query("SELECT up FROM UserPlan up INNER JOIN up.user WHERE up.user.id = :id")
	UserPlan findOne(@Param("id") Long id);

}

UserRepository.java

package com.example.springsample.repository;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

import com.example.springsample.entity.User;

@Repository
public interface UserRepository extends JpaRepository<User, Long> {

}