Relationship between two entities of different schemes - Spring Boot Data JPA

Question

Is it possible to cross join between two different database tables (2 DataSources) in Spring Boot using JPA? If so, how would you configure this configuration? In the application.properties, 4 databases are already being defined and 4 files have been created that represent the configurations of the DataSources. The scenario is that there is a DataSource 1 table that has a FOREIGN KEY with a DataSource 2 table, but when the application is raised an Exception is generated:

@OneToOne or @ManyToOne on com.smart4.bdcentral.domain.files.IndividuoFoto .persons references an unknown entity: com.smart4.bdcentral.domain.main.IndividuoPessoa

DataSource 1

    package com.smart4.configBases;

import java.util.HashMap;

import javax.sql.DataSource;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.core.env.Environment;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.jdbc.datasource.DriverManagerDataSource;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.Database;
import org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter;
import org.springframework.transaction.PlatformTransactionManager;

import com.google.common.base.Preconditions;

@Configuration
@PropertySource({ "classpath:application.properties" })
@EnableJpaRepositories(basePackages             = {"com.smart4.bdcentral.repository.main"}, 
                       entityManagerFactoryRef  = "bdCentralMainEntityManager", 
                       transactionManagerRef    = "bdCentralMainTransactionManager")
public class BdCentralMain {

    @Autowired
    private Environment env;

    public BdCentralMain() {
        super();
    }

    @Bean
    public LocalContainerEntityManagerFactoryBean bdCentralMainEntityManager() {
        final LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
        em.setDataSource(bdCentralMainDataSource());
        em.setPackagesToScan(new String[] { "com.smart4.bdcentral.domain.main" });
        em.setPersistenceUnitName("bdcentralmain");

        final HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
        vendorAdapter.setDatabase(Database.MYSQL);
        vendorAdapter.setShowSql(false);
        vendorAdapter.setGenerateDdl(true);
        vendorAdapter.setDatabasePlatform("org.hibernate.dialect.MySQL5Dialect");

        em.setJpaVendorAdapter(vendorAdapter);
        final HashMap<String, Object> properties = new HashMap<String, Object>();

        properties.put("hibernate.hbm2ddl.auto", env.getProperty("bdcentralmain.hibernate.hbm2ddl.auto"));
        properties.put("hibernate.dialect", env.getProperty("bdcentralmain.hibernate.dialect"));

        em.setJpaPropertyMap(properties);

        return em;
    }

    @Bean
    public DataSource bdCentralMainDataSource() {
        final DriverManagerDataSource dataSource = new DriverManagerDataSource();

        dataSource
                .setDriverClassName(Preconditions.checkNotNull(env.getProperty("bdcentralmain.jdbc.driverClassName")));
        dataSource.setUrl(Preconditions.checkNotNull(env.getProperty("bdcentralmain.jdbc.url")));
        dataSource.setUsername(Preconditions.checkNotNull(env.getProperty("bdcentralmain.jdbc.user")));
        dataSource.setPassword(Preconditions.checkNotNull(env.getProperty("bdcentralmain.jdbc.pass")));

        return dataSource;
    }

    @Bean
    public PlatformTransactionManager bdCentralMainTransactionManager() {
        final JpaTransactionManager transactionManager = new JpaTransactionManager();
        transactionManager.setEntityManagerFactory(bdCentralMainEntityManager().getObject());
        return transactionManager;
    }

}

DataSource 2

package com.smart4.configBases;

import java.util.HashMap;

import javax.sql.DataSource;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.core.env.Environment;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.jdbc.datasource.DriverManagerDataSource;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.Database;
import org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter;
import org.springframework.transaction.PlatformTransactionManager;

import com.google.common.base.Preconditions;

@Configuration
@PropertySource({ "classpath:application.properties" })
@EnableJpaRepositories(basePackages             = {"com.smart4.bdcentral.repository.files"}, 
                       entityManagerFactoryRef  = "bdCentralFilesEntityManager", 
                       transactionManagerRef    = "bdCentralFilesTransactionManager")
public class BdCentralFiles {
    
    @Autowired
    private Environment env;

    public BdCentralFiles() {
        super();
    }

    @Bean
    public LocalContainerEntityManagerFactoryBean bdCentralFilesEntityManager() {
        final LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
        em.setDataSource(bdCentralFilesDataSource());
        em.setPackagesToScan(new String[] { "com.smart4.bdcentral.domain.files" });
        em.setPersistenceUnitName("bdcentralfiles");

        final HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
        vendorAdapter.setDatabase(Database.MYSQL);
        vendorAdapter.setShowSql(false);
        vendorAdapter.setGenerateDdl(true);
        vendorAdapter.setDatabasePlatform("org.hibernate.dialect.MySQL5Dialect");
        em.setJpaVendorAdapter(vendorAdapter);

        final HashMap<String, Object> properties = new HashMap<String, Object>();
        properties.put("hibernate.hbm2ddl.auto", env.getProperty("bdcentralfiles.hibernate.hbm2ddl.auto"));
        properties.put("hibernate.dialect", env.getProperty("bdcentralfiles.hibernate.dialect"));

        em.setJpaPropertyMap(properties);

        return em;
    }

    @Bean
    public DataSource bdCentralFilesDataSource() {
        final DriverManagerDataSource dataSource = new DriverManagerDataSource();

        dataSource
                .setDriverClassName(Preconditions.checkNotNull(env.getProperty("bdcentralfiles.jdbc.driverClassName")));
        dataSource.setUrl(Preconditions.checkNotNull(env.getProperty("bdcentralfiles.jdbc.url")));
        dataSource.setUsername(Preconditions.checkNotNull(env.getProperty("bdcentralfiles.jdbc.user")));
        dataSource.setPassword(Preconditions.checkNotNull(env.getProperty("bdcentralfiles.jdbc.pass")));

        return dataSource;
    }

    @Bean
    public PlatformTransactionManager bdCentralFilesTransactionManager() {
        final JpaTransactionManager transactionManager = new JpaTransactionManager();
        transactionManager.setEntityManagerFactory(bdCentralFilesEntityManager().getObject());
        return transactionManager;
    }

}

Answer 1

not much to say with just the datasources, check the annotation configuration and make sure your objects are @Entity annotated. It doesn't sound like you actually want a "cross join", also you're looking at Hibernate, I kept reading Spring Boot JPA as spring "Data" JPA and was getting confused as to why it wasn't data jpa lol.