- Step 1 : Object Relational Impedence Mismatch - Understanding the problem that JPA solves
- Step 2 : World before JPA - JDBC, Spring JDBC and myBatis
- Step 3 : Introduction to JPA
- Step 4 : Creating a JPA Project using Spring Initializr
- Step 5 : Defining a JPA Entity - User
- Step 6 : Defining a Service to manage the Entity - UserService and EntityManager
- Step 7 : Using a Command Line Runner to save the User to database.
- Step 8 : Magic of Spring Boot and In Memory Database H2
- Step 9 : Introduction to Spring Data JPA
- Step 10 : More JPA Repository : findById and findAll
- Next Steps
Notes
- http://localhost:8080/h2-console
- Use db url jdbc:h2:mem:testdb
Questions
- Where is the database created?
- What schema is used to create the tables?
- Where are the tables created?
- Can I see the data in the database?
- Where is Hibernate coming in from?
- How is a datasource created?
Magic of Spring Boot and in Memory Database
- Zero project setup or infrastructure
- Zero Configuration
- Zero Maintainance
- Easy to use for Learning and Unit Tests
- Simple Configuration to switch to a real database
# Restrictions of using in-memory database
- Data is not persisted between restarts
Spring Boot chooses a default value for you based on whether it thinks your database is embedded (default create-drop) or not (default none).
HibernateJpaAutoConfiguration matched:
- @ConditionalOnClass found required classes 'org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean', 'javax.persistence.EntityManager'; @ConditionalOnMissingClass did not find unwanted class (OnClassCondition)
- HibernateEntityManager found class 'org.hibernate.ejb.HibernateEntityManager' (HibernateJpaAutoConfiguration.HibernateEntityManagerCondition)
DataSourceAutoConfiguration matched:
- @ConditionalOnClass found required classes 'javax.sql.DataSource', 'org.springframework.jdbc.datasource.embedded.EmbeddedDatabaseType'; @ConditionalOnMissingClass did not find unwanted class (OnClassCondition)
JpaBaseConfiguration#entityManagerFactory matched:
- @ConditionalOnMissingBean (types: org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean,javax.persistence.EntityManagerFactory; SearchStrategy: all) did not find any beans (OnBeanCondition)
JpaBaseConfiguration#transactionManager matched:
- @ConditionalOnMissingBean (types: org.springframework.transaction.PlatformTransactionManager; SearchStrategy: all) did not find any beans (OnBeanCondition)
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.in28minutes.learning.jpa</groupId>
<artifactId>jpa-in-10-steps</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>jpa-in-10-steps</name>
<description>Demo project for Spring Boot</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.0.BUILD-SNAPSHOT</version>
<relativePath /> <!-- lookup parent from repository -->
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
<repositories>
<repository>
<id>spring-snapshots</id>
<name>Spring Snapshots</name>
<url>https://repo.spring.io/snapshot</url>
<snapshots>
<enabled>true</enabled>
</snapshots>
</repository>
<repository>
<id>spring-milestones</id>
<name>Spring Milestones</name>
<url>https://repo.spring.io/milestone</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>
</repositories>
<pluginRepositories>
<pluginRepository>
<id>spring-snapshots</id>
<name>Spring Snapshots</name>
<url>https://repo.spring.io/snapshot</url>
<snapshots>
<enabled>true</enabled>
</snapshots>
</pluginRepository>
<pluginRepository>
<id>spring-milestones</id>
<name>Spring Milestones</name>
<url>https://repo.spring.io/milestone</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
</pluginRepository>
</pluginRepositories>
</project>package com.in28minutes.learning.jpa.jpain10steps.entity;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
//Table - User
@Entity
public class User {
@Id
@GeneratedValue
private long id;
private String name;
private String role;
protected User() {
}
public User(String name, String role) {
super();
this.name = name;
this.role = role;
}
public long getId() {
return id;
}
public String getName() {
return name;
}
public String getRole() {
return role;
}
@Override
public String toString() {
return String.format("User [id=%s, name=%s, role=%s]", id, name, role);
}
}package com.in28minutes.learning.jpa.jpain10steps;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class JpaIn10StepsApplication {
public static void main(String[] args) {
SpringApplication.run(JpaIn10StepsApplication.class, args);
}
}package com.in28minutes.learning.jpa.jpain10steps.service;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.transaction.Transactional;
import org.springframework.stereotype.Repository;
import com.in28minutes.learning.jpa.jpain10steps.entity.User;
@Repository
@Transactional
public class UserDAOService {
@PersistenceContext
private EntityManager entityManager;
public long insert(User user){
entityManager.persist(user);
return user.getId();
}
}
/*
* Spring Data JPA
*
*
*
*/package com.in28minutes.learning.jpa.jpain10steps.service;
import org.springframework.data.jpa.repository.JpaRepository;
import com.in28minutes.learning.jpa.jpain10steps.entity.User;
public interface UserRepository extends JpaRepository<User, Long>{
}package com.in28minutes.learning.jpa.jpain10steps;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.stereotype.Component;
import com.in28minutes.learning.jpa.jpain10steps.entity.User;
import com.in28minutes.learning.jpa.jpain10steps.service.UserDAOService;
@Component
public class UserDaoServiceCommandLineRunner implements CommandLineRunner{
private static final Logger log =
LoggerFactory.getLogger(UserDaoServiceCommandLineRunner.class);
@Autowired
private UserDAOService userDaoService;
@Override
public void run(String... arg0) throws Exception {
User user = new User("Jack", "Admin");
//New User is created : User [id=1, name=Jack, role=Admin]
long insert = userDaoService.insert(user);
log.info("New User is created : " + user);
}
}package com.in28minutes.learning.jpa.jpain10steps;
import java.util.List;
import java.util.Optional;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.stereotype.Component;
import com.in28minutes.learning.jpa.jpain10steps.entity.User;
import com.in28minutes.learning.jpa.jpain10steps.service.UserRepository;
@Component
public class UserRepositoryCommandLineRunner implements CommandLineRunner{
private static final Logger log =
LoggerFactory.getLogger(UserRepositoryCommandLineRunner.class);
@Autowired
private UserRepository userRepository;
@Override
public void run(String... arg0) throws Exception {
User user = new User("Jill", "Admin");
userRepository.save(user);
log.info("New User is created : " + user);
Optional<User> userWithIdOne = userRepository.findById(1L);
log.info("User is retrived : " + userWithIdOne);
List<User> users = userRepository.findAll();
log.info("All Users : " + users);
}
}spring.jpa.show-sql=true
spring.h2.console.enabled=true
logging.level.org.springframework=debugpackage com.in28minutes.learning.jpa.jpain10steps;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
@RunWith(SpringRunner.class)
@SpringBootTest
public class JpaIn10StepsApplicationTests {
@Test
public void contextLoads() {
}
}java -cp /ProgrammingExcellence/Workspaces/Rithus.com/ListDirectoryContentInGitFormat/bin test.ListDirectoryContentInGitFormat $PWD >> $1.md
zip -r $1.zip . -x "target/*" -x ".*/*" -x ".*" -x "*.md" -x "mvn*" -x "*.zip"
git add *; git commit -m "$1"; git push;
java -cp /ProgrammingExcellence/Workspaces/Rithus.com/ListDirectoryContentInGitFormat/bin test.ListDirectoryContentInGitFormat $PWD >> $1.md
zip -r $1.zip . -x "target/*" -x ".*/*" -x ".*" -x "*.md" -x "mvn*" -x "*.zip"