[JAVA] Until the use of Spring Data and JPA Part 2

The difficulty of setting is quite high.

Continued from last time

For the time being, I used Spring to connect to the DB. From here, we will use a full-fledged DB operation framework called JPA.

Divide goals

    1. What you need just to connect with SQL -Hibernate EntityManager library ・ Spring JDBC library ・ Database driver PostgreSQL or H2 ·Property file -Bean configuration file (xml) JavaConfig is not used this time. Maybe it's going to get confusing ** ← So far **
  1. In addition, what is required for JPA ** ← From here ** ・ Spring Data JPA library ・ Entity class -Persistence.xml file (Java EJB function) -Bean configuration file (xml) -Execution class with main method

Add library

Add library as usual. When you use new features in Spring, you usually edit the library.


		<!-- Spring Data JPA -->
		<!-- Spring ORM -->

After saving ** Maven → update Project **

Entity class

Click here for how to create an entity class from a table. wrap up Right click and convert from configuration to JPA project. When it becomes a JPA project, an entity will be automatically generated from the table.


It's really hard to see,


When the Entity is created, add an annotation such as @Id and pick up the error. You may want to use ** lombok ** and omit the getter setter in @Data

Auto-implemented entity class


Creating persistence.xml

Create a META-INF folder in src / main / resources and a persistance.xml file in it. It seems to be a Java-EE function called ** persistence file ** (If you created it with JPA, it is created in src / main / java, so move it)

Sketch src/main/resources/   |   |---META-INF   |    |   |    |--persistance.xml   |---bean.xml   |---database.properties


<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1"
	<persistence-unit name="persistance-unit">
		<!--HibernatePersistance definition-->
			<property name="hibernate.dialect" value="org.hibernate.dialect.PostgreSQLDialect"/>
			<property name="hibernate.hbm2ddl.auto" value="create" />
				<!--Driver properties-->
				<property name="javax.persistance.jdbc.driver"
					value="${jdbc.driverClassname}" />
				<property name="javax.persistance.jdbc.url"
					value="${jdbc.url}" />
				<property name="javax.persistance.jdbc.user"
					value="${jdbc.username}" />
				<property name="javax.persistance.jdbc.password"
					value="${jdbc.password}" />	


Creating a bean configuration file

Finally, create a bean configuration file. Namespace xmlns = http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/spring-jpa.xsd Add Register the entity manager with the DI container.


<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"

	<!--Settings for embedded database>
	<jdbc:embedded-database id="dataSource" type="H2">
		<jdbc:script location="classpath:script.sql"/>

	<!--Setting database properties-->
	<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
	  	<property name="location" value="database.properties" />

	<!--EntityManager settings-->
	<bean id="entityManagerFactory"
		<property name="dataSource" ref="dataSource" />
		<property name="jpaVendorAdapter">
			<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
				<property name="generateDdl" value="true" />

	<!--Settings for DB connection-->
	<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource" >
		<property name="driverClassName" value="${jdbc.driverClassName}" />
		<property name="url" value="${jdbc.url}" />
		<property name="username" value="${jdbc.username}" />
		<property name="password" value="${jdbc.password}" />

	<!--Creating a JDBC template bean-->
	<bean class="org.springframework.jdbc.core.JdbcTemplate">
		<constructor-arg ref="dataSource" />

		<!--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" />

Let's run

Let's put the entity manager in the main class and perform JPA functions!


public class App{
	public static void main(String args[]) {
		//Creating a template using annotations
		//context = new AnnotationConfigApplicationContext(DataSourceConfig.class);
		//JdbcTemplate jdbcTemplate = (JdbcTemplate)context.getBean(JdbcTemplate.class);
		//Get context
//		context = new ClassPathXmlApplicationContext("bean.xml");
//		jdbcTemplate = context.getBean(JdbcTemplate.class);
		context = new ClassPathXmlApplicationContext("bean.xml");
		LocalContainerEntityManagerFactoryBean factory =
		manager = factory.getNativeEntityManagerFactory().createEntityManager();
		Mypersonaldata data = manager.find(Mypersonaldata.class, 1);

Run this from Java Application


At the bottom, you can see the data read from postgresql.


Well, with Spring-Boot, this procedure is all done automatically, I couldn't keep the basics down and it stopped working, so for reference.

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