JPA Repositories with Specification

Source Folder: jpa-specification

Tech Stack:

• spring-boot
• spring-mvc
• spring-data
• hibernate & hibernate metamodel generator
• postgresql
• hibernate-c3p0
• mapstruct (for model transformation)
• log4j2 (slf4j impl)
• project lombok

This is a ready-to-use Maven Java project template with the libraries listed above.

Problems Solved

• ORM with hibernate
• Logging with Slf4j with Log4J2
• Monitoring entities with Spring Data and AuditorAware (@CreatedBy, @CreatedDate, @LastModifiedBy, @LastModifiedDate)
• Connection pooling C3P0
• Model mapping (without reflection) with MapStruct
• Passing LocalDate & LocalDateTime from Client to an endpoint (jackson-datatype-jsr310.jar needed for this)
• Using JPA specification API instead of writing Query

Passing LocalDate & LocalDateTime from Client to Controller

Steps:

1. Add the following dependency:

<dependency>
	<groupId>com.fasterxml.jackson.datatype</groupId>
	<artifactId>jackson-datatype-jsr310</artifactId>
</dependency>

2. Add @JsonFormat to your LocalDate / LocalDateTime field

@JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "dd.MM.yyyy")
private LocalDate birthdate;

You are ready to go.

Using Hibernate Metamodel for Type Safety

Just add the following maven plugin and maven will automatically generate Hibernate Metamodel under "generated-sources"

<plugin>
	<groupId>org.bsc.maven</groupId>
	<artifactId>maven-processor-plugin</artifactId>
	<version>3.2.0</version>
	<executions>
		<execution>
			<id>process</id>
			<goals>
				<goal>process</goal>
			</goals>
			<phase>generate-sources</phase>
			<configuration>
				<processors>
					<processor>org.hibernate.jpamodelgen.JPAMetaModelEntityProcessor</processor>
				</processors>
				<outputDirectory>target/generated-sources/annotations</outputDirectory>
			</configuration>
		</execution>
	</executions>
	<dependencies>
		<dependency>
			<groupId>org.hibernate</groupId>
			<artifactId>hibernate-jpamodelgen</artifactId>
			<version>${hibernate.jpamodelgen-version}</version>
		</dependency>
	</dependencies>
</plugin>