Linkchecker Persistence API

Introduction

The linkchecker persistence API (LPA) is a project, based on Spring data JPA 2.7.10, which serves as a common persistence layer for the following projects:

• Clarin Curation Dashboard
• Link Checker
• Link Checker Web
• Virtual Language Observatory

Set up

When you load LPA as a dependency into your Spring boot parent project, you have to specify a database connection there.
A typical entry in the application.yml of your project would look like this:

spring:
   datasource:
      url: jdbc:mariadb://<databse server address>:3306/<your database>
      username: <your database user>
      password: <your database user's password>
      driver-class-name: <your database driver class>
   jpa:
      hibernate:
         ddl-auto: none

Spring data JPA uses the Hikari connection pool by default. Hikari specific properties can be set by:

spring:
   datasource:
      hikari:
         <hikari-property>: <value>

For details on Hikari properties, have a look on the Hikari Readme page, please.

Important notes

• linkchecker-persistence is using a schema.sql file to set up database structure with tables and views. The SQL script works for H2 and MariaDB and we strongly discourage an automatic setup via hibernate.ddl-auto=create.

• version 0.0.6+ uses the hibernate-enhance-maven-plugin to allow lazy fetching for toOne associations. This is basically important when you lookup a significant number of Url instances since otherwise for each instance a query is send to the database to look up the associated Status instance. If you use another persistence API than hibernate, which is currently the default in Spring data JPA, you should make sure lazy loading for toOne associations.