JDBC at first and JPA later.
3.1 Reading and writing data with JDBC
Spring JDBC support is rooted in the JdbcTemplate class. JdbcTemplate provides a means by which developers can perform SQL operations against a relational database without all the ceremony and boilerplate typically required when working with JDBC.
3.2 Persisting data with Spring Data JPA
Summary
- Spring’s JdbcTemplate greatly simplifies working with JDBC.
- PreparedStatementCreator and KeyHolder can be used together when you need to know the value of a database-generated ID.
- For easy execution of data inserts, use SimpleJdbcInsert.
- Spring Data JPA makes JPA persistence as easy as writing a repository interface.
Code
When running the JPA example code: This video may be helpful when you want to use H2 with intellij in spring boot project.
spring.h2.console.enabled=true
# spring.datasource.url=jdbc:h2:file:./src/main/resources/mydb;AUTO_SERVER=true // if you want to use multiple connections
spring.datasource.url=jdbc:h2:mem:default
When connect to database using intellij database tool, use sa as name and you don’t need to input any password.
If there’s an error:
Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]: Invocation of init method failed; nested exception is javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory; nested exception is org.hibernate.MappingException: Could not get constructor for org.hibernate.persister.entity.SingleTableEntityPersister
A quick fix is to add a new dependency.
<dependency>
<groupId>org.javassist</groupId>
<artifactId>javassist</artifactId>
<version>3.27.0-GA</version>
</dependency>
Another error:
"org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]: Initialization of bean failed; nested exception is org.springframework.jdbc.datasource.init.ScriptStatementFailedException: Failed to execute SQL script statement #6 of URL [file:/home/zhu/NetBeansProjects/Jpa-Taco-cloud-chapter3/target/classes/data.sql]: insert into Ingredient (id, name, type) values ('FLTO', 'Flour Tortilla', 'WRAP'); nested exception is org.h2.jdbc.JdbcSQLDataException: Data conversion error converting "'WRAP' (INGREDIENT: ""TYPE"" INTEGER)"; SQL statement:"
After I annotated Type type with @Enumerated(EnumType.STRING) in Ingredient class, it worked.
@Data
@RequiredArgsConstructor
@NoArgsConstructor(access=AccessLevel.PRIVATE, force=true)
@Entity
public class Ingredient {
@Id
private final String id;
private final String name;
@Enumerated(EnumType.STRING)
private final Type type;
public static enum Type {
WRAP, PROTEIN, VEGGIES, CHEESE, SAUCE
}
}