[SpringBoot2.4.3] エンティティの連携

複数のテーブルが関連して動かしたい場合は、「アソシエーション」という機能によりエンティティ同士を連携して処理する

＠OneToOne,@OneToMany, @ManyToOne, @ManyToMany

package com.example.demo;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
import javax.validation.constraints.NotNull;

import org.hibernate.validator.constraints.NotEmpty;

@Entity
@Table(name = "msgdata")
public class MsgData {
	
	@Id
	@GeneratedValue(strategy = GenerationType.AUTO)
	@Column
	@NotNull
	private long id;
	
	@Column
	private String title;
	
	@Column(nullable = false)
	@NotEmpty
	private String message;
	
	@ManyToOne
	private MyData mydata;
	
	public MsgData() {
		super();
		mydata = new MyData();
	}
	
	public long getId() {
		return id;
	}
	
	public void setId(long id) {
		this.id = id;
	}
	
	public String getTitle() {
		return title;
	}
	
	public void setTitle(String title) {
		this.title = title;
	}
	
	public String getMessage() {
		return message;
	}
	
	public void setMessage(String message) {
		this.message = message;
	}
	
	public MyData getMyData() {
		return mydata;
	}
	
	public void setMydata(MyData mydata) {
		this.mydata = mydata;
	}
}

MsgDataRepository.java

package com.example.demo.repositories;

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

import com.example.demo.MsgData;

@Repository
public interface MsgDataRepository extends JpaRepository<MsgData, Long>{

}

MsgDataDao.java

package com.example.demo;

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

public interface MsgDataDao<T> {
	
	public List<MsgData> getAll();
	public MsgData findById(long id);
}

MsgDataDaoImpl.java

package com.example.demo;

import java.util.List;
import javax.persistence.EntityManager;

import org.springframework.stereotype.Repository;

@SuppressWarnings("rawtypes")
@Repository
public class MsgDataDaoImpl implements MsgDataDao<MsgDataDao>{
	
	private EntityManager entityManager;
	
	public MsgDataDaoImpl() {
		super();
	}
	public MsgDataDaoImpl(EntityManager manager) {
		entityManager = manager;
	}
	
	@SuppressWarnings("unchecked")
	@Override
	public List<MsgData> getAll(){
		return entityManager
				.createQuery("from MsgData")
				.getResultList();
	}
	
	@Override
	public MsgData findById(long id) {
		return (MsgData)entityManager
				.createQuery("from MsgData where id = "
						+ id).getSingleResult();
	}

}

showMsgData.html

	<h1 th:text="${title}">MyMsg page</h1>
	<p th:text="${msg}"></p>
	<table>
		<form method="post" action="/msg" th:object="${formModel}">
		<input type="hidden" name="id" th:value="*{id}">
		<tr>
			<td><label for="title">タイトル</label></td>
			<td><input type="text" name="title" th:value="*{title}"></td>
		</tr>
		<tr>
			<td><label for="message">メッセージ</label></td>
			<td><textarea name="message" th:text="*{message}"></textarea></td>
		</tr>
		<tr>
			<td><label for="mydata">MYDATA_ID</label></td>
			<td><input type="text" name="mydata"></td>
		</tr>
		<tr>
			<td></td>
			<td><input type="submit"></td>
		</tr>
		</form>
	</table>
	<hr>
	<table>
		<tr><th>ID</th><th>名前</th><th>タイトル</th></tr>
		<tr th:each="obj : ${datalist}">
			<td th:text="${obj.id}"></td>
			<td th:text="${obj.mydata.name}"></td>
			<td th:text="${obj.title}"></td>
		</tr>
	</table>

MsgDataController.java

package com.example.demo;

import java.util.List;

import javax.annotation.PostConstruct;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.validation.Valid;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.validation.Errors;
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.servlet.ModelAndView;

import com.example.demo.repositories.MsgDataRepository;

@Controller
public class MsgDataController {

		@Autowired
		MsgDataRepository repository;
		
		@PersistenceContext
		EntityManager entityManager;
		
		MsgDataDaoImpl dao;
		
		@RequestMapping(value = "/msg", method=RequestMethod.GET)
		public ModelAndView msg(ModelAndView mav) {
			mav.setViewName("showMsgData");
			mav.addObject("title", "Sample");
			mav.addObject("msg","MsgDataのsampleです");
			MsgData msgdata = new MsgData();
			mav.addObject("formModel", msgdata);
			List<MsgData> list = (List<MsgData>)dao.getAll();
			mav.addObject("datalist", list);
			return mav;
		}
		
		@RequestMapping(value="/msg", method=RequestMethod.POST)
		public ModelAndView msgform(
				@Valid @ModelAttribute MsgData msgdata,
				Errors result,
				ModelAndView mav) {
			if(result.hasErrors()) {
				mav.setViewName("showMsgData");
				mav.addObject("title", "Sample [Error]");
				mav.addObject("msg", "値を再チェックして下さい");
				return mav;
			} else {
				repository.saveAndFlush(msgdata);
				return new ModelAndView("redirect:/msg");
			}
		}
		
		@PostConstruct
		public void init() {
			System.out.println("ok");
			dao = new MsgDataDaoImpl(entityManager);
		}
		
}

んん？あれ？