[JAVA] DB access using repository with SpringData.

Convenient interface to automatically create access to DB

JPA repository is a convenient interface that automatically implements CRUD to DB. Once the environment is set, the DB access function can be implemented with a considerably small amount of code, but it is quite difficult to set the environment, so I summarized it.

Introduce SpringData library

Refer to the article below until the JDBC template works for the time being.

SpringDataJPA Access 1 SpringDataJPA Access 2

Create a repository interface

Create the repository body.

MyPesononalDataDaoRepository.java

package com.tsugaruinfo.repository;

@Repository
public interface MyPesononalDataDaoRepository
	extends JpaRepository<Mypersonaldata, Integer> {

}

It's just an interface. There is no need to implement the contents.

Register repository in DI

Register the repository in the bean configuration file.

appllicatio-config.xml

<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns:context="http://www.springframework.org/schema/context"
	xmlns:jdbc="http://www.springframework.org/schema/jdbc"
	xmlns:tx="http://www.springframework.org/schema/tx"
	xmlns:jpa="http://www.springframework.org/schema/data/jpa"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
		http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc.xsd
		http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.0.xsd
		http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa.xsd">



		<!--JPA Repository settings-->
	<jpa:repositories base-package="com.tsugaruinfo.repository" />
	
     <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
        <property name="entityManagerFactory" ref="entityManagerFactory" />
        <property name="dataSource" ref="dataSource" />
    </bean>

Two points

1. Add namespace

Added tx and jpa to namespace

application-config.xml

	xmlns:tx="http://www.springframework.org/schema/tx"
	xmlns:jpa="http://www.springframework.org/schema/data/jpa"

In the schema

application-config.xml

		http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.0.xsd
		http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa.xsd"

To make JPA and Transaction beans available. This is because Transaction is used by JPA without permission when creating a repository.

2. Add repository package and TransactionManager

This is the main DI registration Register the jpa repository package and a bean called transactionManager.

appliction-config.xml

		<!--JPA Repository settings-->
	<jpa:repositories base-package="com.tsugaruinfo.repository" />
	
     <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
        <property name="entityManagerFactory" ref="entityManagerFactory" />
        <property name="dataSource" ref="dataSource" />
    </bean>

Please change "com.tsugaruinfo.repository" to your own package when you actually use it. The repository is now registered in the DI container.

Inject with @Autowired

This time it is an implementation in Servlet. (Well, as in the textbook ...)

BeanAutowiredFilterServlet.java

public class BeanAutowiringFilterServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	
	@Override
	public void init() throws ServletException {
		super.init();
		SpringBeanAutowiringSupport
			.processInjectionBasedOnCurrentContext(this);
	}

This ** SpringBeanAutowiringSupport.processInjectionBasedOnCurrentContext (this); ** command is the key to using the @Autowired annotation. The moment this command is executed, the Bean registered in DI is injected into the annotated variable.

I think that the variable to be injected is a field of the class, so it may be good to execute it in the constructor. This time, set up a parent class and execute it with the initialization method of the Servlet.

With Spring Boot It seems to run automatically with the annotation @SpringBootApplication

Inject and materialize

MyPersonalDataServlet.java

@WebServlet("/person")
public class MyPersonalDataServlet extends BeanAutowiringFilterServlet {
	private static final long serialVersionUID = 1L;
       

	@Autowired
	MyPesononalDataDaoRepository repository;

Injected into a Servlet field. JPA and DI container will materialize without new.

Run immediately

Let's run it in a Servlet. Get all the contents of DB

MyPersonalDataServlet.java

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		List<Mypersonaldata> list = repository.findAll();

		request.setAttribute("entities", list);

		response.getWriter().append("Served at: ").append(request.getContextPath());

		request.getRequestDispatcher("/WEB-INF/index.jsp").forward(request, response);
	}

index.jsp

<!DOCTYPE html>

<%@ page import="java.util.List" %>
<%@ page import="com.tsugaruinfo.model.Mypersonaldata" %>

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
    
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ taglib prefix="spring" uri="http://www.springframework.org/tags"%>

<html>
	<head>
		<meta charset="utf-8">
		<title>JPA Sample1</title>
	</head> 
	<body>
		<h1>Welcome to JPA Sample!</h1>
		
		<form method="post" action="person">
		<table>
			<tr><td>Name:Input<input type ="text" name="name"></td></tr>
			<tr><td>Mail:Input<input type ="text" name="mail"></td></tr>
			<tr><td>Age:Input<input type ="text" name="age"></td></tr>
			<tr><td><input type ="submit" value="add to"></td></tr>
		</table>
		</form>
		<c:url value="/showMessage.html" var="messageUrl" />
		<a href="${messageUrl}">Click to enter</a>
		<ol>
		 
			<% for(Object entity : (List)request.getAttribute("entities")){ %>
				<li><%=entity %></li>
			<% } %>
		</ol>
	</body>
</html>

result

I was able to confirm that the repository is working properly.