Use Multiple DataSources with Spring Boot and JPA

Objective of Post
Prepare a Database
Create a Spring Boot project
Configure pom.xml
Configure DataSources
Entities, DAO
Controller
Thymeleaf Template
Appendix: JSP View

1. Objective of Post

No ADS

The post is written based on:

Spring Boot 2.x (or >=1.5.9)
JPA
Thymeleaf (Or JSP)

In this post, I am going to show you how to create a Spring Boot & JPA application using multiple DataSources. To practise with the example, we have 2 databases:

PUBLISHER: This is the first database, which contains one PUBLISHERS table.
ADVERTISER: This is the second database, which contains one ADVERTISERS table.

In this application, the functions (Pages) can use both databases mentioned above at the same time. For example, a page displays a list of publishers and a list of advertisers, therefore, you have to work with the two above databases at the same time.

In another case, if your application needs multiple DataSources, but each function (each page) only works with a specific DataSource, you should use Routing DataSource & DataSource Interceptor.
The Routing DataSource is a special DataSource, which contains a list of DataSources actully to be used in your application.
DataSource Interceptor will decide which DataSource will be used corresponding to each function (each page) in your application.
Use Multiple DataSources with Spring Boot and RoutingDataSource

2. Prepare a Database

No ADS

MySQL, SQL Server, PostGres

-- ===========================================
-- DATABASE FOR PUBLISHER SYSTEM
-- ===========================================
create table PUBLISHERS
(
  ID Bigint,
  NAME VARCHAR(255),
  Primary key (ID)
);

insert into publishers (ID, NAME)
values (1, 'publisher 1');

insert into publishers (ID, NAME)
values (2, 'publisher 2');



-- ===========================================
-- DATABASE FOR ADVERTISER SYSTEM
-- ===========================================
create table ADVERTISERS
(
  ID Bigint,
  NAME VARCHAR(255),
  Primary key (ID)
);

insert into advertisers (ID, NAME)
values (1, 'Advertiser 1');

insert into advertisers (ID, NAME)
values (2, 'Advertiser 2');

Oracle

-- ===========================================
-- DATABASE FOR PUBLISHER SYSTEM
-- ===========================================
create table PUBLISHERS
(
  ID NUMBER(19),
  NAME VARCHAR(255),
  Primary key (ID)
);

insert into publishers (ID, NAME)
values (1, 'publisher 1');

insert into publishers (ID, NAME)
values (2, 'publisher 2');

Commit;

-- ===========================================
-- DATABASE FOR ADVERTISER SYSTEM
-- ===========================================
create table ADVERTISERS
(
  ID NUMBER(19),
  NAME VARCHAR(255),
  Primary key (ID)
);

insert into advertisers (ID, NAME)
values (1, 'Advertiser 1');

insert into advertisers (ID, NAME)
values (2, 'Advertiser 2');

Commit;

3. Create a Spring Boot project

4. Configure pom.xml

No ADS

In the following pom.xml file, I have configured so that the application can work with 4 common database kinds such as MySQL, SQL Server, PostGres, and Oracle.

pom.xml

<?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>org.o7planning</groupId>
    <artifactId>SpringBootJPAMultiDS</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>SpringBootJPAMultiDS</name>
    <description>Spring Boot + JPA + Multiple DataSources</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.0.RELEASE</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>
        
        <!-- Remove Thymeleaf, If you want using JSP View -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>
        
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.postgresql</groupId>
            <artifactId>postgresql</artifactId>
            <scope>runtime</scope>
        </dependency>
        <!-- SQL Server - Mssql-Jdbc driver -->
        <dependency>
            <groupId>com.microsoft.sqlserver</groupId>
            <artifactId>mssql-jdbc</artifactId>
            <scope>runtime</scope>
        </dependency>
        
        <!-- SQL Server - JTDS driver -->
        <dependency>
            <groupId>net.sourceforge.jtds</groupId>
            <artifactId>jtds</artifactId>
            <scope>runtime</scope>
        </dependency>
        
        <dependency>
            <groupId>com.oracle</groupId>
            <artifactId>ojdbc6</artifactId>
            <version>11.2.0.3</version>
        </dependency>
        
        
        <!-- For JSP VIEW (Need REMOVE spring-boot-starter-thymeleaf) -->
        <dependency>
            <groupId>org.apache.tomcat.embed</groupId>
            <artifactId>tomcat-embed-jasper</artifactId>
        </dependency>
        
        <!-- For JSP VIEW (Need REMOVE spring-boot-starter-thymeleaf) -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
        </dependency>
        
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <repositories>
    
        <!-- Repository for ORACLE JDBC Driver -->
        <repository>
            <id>codelds</id>
            <url>https://code.lds.org/nexus/content/groups/main-repo</url>
        </repository>
        
    </repositories>
 
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

5. Configure DataSources

No ADS

datasource-cfg.properties (MySQL)

# ===============================
# DATASOURCE
# ===============================

# DataSource (PUBLISHER System).

spring.datasource.driver-class-name.1=com.mysql.jdbc.Driver
spring.datasource.url.1=jdbc:mysql://localhost:3306/publisher
spring.datasource.username.1=root
spring.datasource.password.1=12345



# DataSource (ADVERTISER System).

spring.datasource.driver-class-name.2=com.mysql.jdbc.Driver
spring.datasource.url.2=jdbc:mysql://localhost:3306/advertiser
spring.datasource.username.2=root
spring.datasource.password.2=12345



# ===============================
# JPA / HIBERNATE
# ===============================

spring.jpa.show-sql.1=true
spring.jpa.hibernate.ddl-auto.1=none
spring.jpa.properties.hibernate.dialect.1=org.hibernate.dialect.MySQLDialect
#spring.jpa.properties.hibernate.current_session_context_class.1=org.springframework.orm.hibernate5.SpringSessionContext


spring.jpa.show-sql.2=true
spring.jpa.hibernate.ddl-auto.2=none
spring.jpa.properties.hibernate.dialect.2=org.hibernate.dialect.MySQLDialect
#spring.jpa.properties.hibernate.current_session_context_class.2=org.springframework.orm.hibernate5.SpringSessionContext

datasource-cfg.properties (SQL Server + JTDS Driver)

# ===============================
# DATASOURCE
# ===============================


# DataSource  (PUBLISHER System).

spring.datasource.driver-class-name.1=net.sourceforge.jtds.jdbc.Driver
spring.datasource.url.1=jdbc:jtds:sqlserver://localhost:1433/publisher;instance=SQLEXPRESS
spring.datasource.username.1=sa
spring.datasource.password.1=12345


# DataSource  (ADVERTISER System).

spring.datasource.driver-class-name.2=net.sourceforge.jtds.jdbc.Driver
spring.datasource.url.2=jdbc:jtds:sqlserver://localhost:1433/advertiser;instance=SQLEXPRESS
spring.datasource.username.2=sa
spring.datasource.password.2=12345



# ===============================
# JPA / HIBERNATE
# ===============================

spring.jpa.show-sql.1=true
spring.jpa.hibernate.ddl-auto.1=none
spring.jpa.properties.hibernate.dialect.1=org.hibernate.dialect.SQLServerDialect
#spring.jpa.properties.hibernate.current_session_context_class.1=org.springframework.orm.hibernate5.SpringSessionContext


spring.jpa.show-sql.2=true
spring.jpa.hibernate.ddl-auto.2=none
spring.jpa.properties.hibernate.dialect.2=org.hibernate.dialect.SQLServerDialect
#spring.jpa.properties.hibernate.current_session_context_class.2=org.springframework.orm.hibernate5.SpringSessionContext

datasource-cfg.properties (SQL Server + Mssql-Jdbc Driver)

# ===============================
# DATASOURCE
# ===============================


# DataSource  (PUBLISHER System).

spring.datasource.driver-class-name.1=com.microsoft.sqlserver.jdbc.SQLServerDriver
spring.datasource.url.1=jdbc:sqlserver://tran-vmware-pc\\SQLEXPRESS:1433;databaseName=publisher
spring.datasource.username.1=sa
spring.datasource.password.1=12345


# DataSource  (ADVERTISER System).

spring.datasource.driver-class-name.2=com.microsoft.sqlserver.jdbc.SQLServerDriver
spring.datasource.url.2=jdbc:sqlserver://tran-vmware-pc\\SQLEXPRESS:1433;databaseName=advertiser
spring.datasource.username.2=sa
spring.datasource.password.2=12345


# ===============================
# JPA / HIBERNATE
# ===============================

spring.jpa.show-sql.1=true
spring.jpa.hibernate.ddl-auto.1=none
spring.jpa.properties.hibernate.dialect.1=org.hibernate.dialect.SQLServerDialect
#spring.jpa.properties.hibernate.current_session_context_class.1=org.springframework.orm.hibernate5.SpringSessionContext


spring.jpa.show-sql.2=true
spring.jpa.hibernate.ddl-auto.2=none
spring.jpa.properties.hibernate.dialect.2=org.hibernate.dialect.SQLServerDialect
#spring.jpa.properties.hibernate.current_session_context_class.2=org.springframework.orm.hibernate5.SpringSessionContext

datasource-cfg.properties (Oracle)

# ===============================
# DATASOURCE
# ===============================

# DataSource (PUBLISHER System).

spring.datasource.driver-class-name.1=oracle.jdbc.driver.OracleDriver
spring.datasource.url.1=jdbc:oracle:thin:@localhost:1521:db12c
spring.datasource.username.1=publisher
spring.datasource.password.1=12345


# DataSource (ADVERTISER System).

spring.datasource.driver-class-name.2=oracle.jdbc.driver.OracleDriver
spring.datasource.url.2=jdbc:oracle:thin:@localhost:1521:db12c
spring.datasource.username.2=advertiser
spring.datasource.password.2=12345



# ===============================
# JPA / HIBERNATE
# ===============================

spring.jpa.show-sql.1=true
spring.jpa.hibernate.ddl-auto.1=none
spring.jpa.properties.hibernate.dialect.1=org.hibernate.dialect.Oracle10gDialect
#spring.jpa.properties.hibernate.current_session_context_class.1=org.springframework.orm.hibernate5.SpringSessionContext


spring.jpa.show-sql.2=true
spring.jpa.hibernate.ddl-auto.2=none
spring.jpa.properties.hibernate.dialect.2=org.hibernate.dialect.Oracle10gDialect
#spring.jpa.properties.hibernate.current_session_context_class.2=org.springframework.orm.hibernate5.SpringSessionConte

datasource-cfg.properties (PostGres)

# ===============================
# DATASOURCE
# ===============================

# DataSource (PUBLISHER System).

spring.datasource.driver-class-name.1=org.postgresql.Driver
spring.datasource.url.1=jdbc:postgresql://tran-vmware-pc:5432/publisher
spring.datasource.username.1=postgres
spring.datasource.password.1=12345



# DataSource (ADVERTISER System).

spring.datasource.driver-class-name.2=org.postgresql.Driver
spring.datasource.url.2=jdbc:postgresql://tran-vmware-pc:5432/advertiser
spring.datasource.username.2=postgres
spring.datasource.password.2=12345



# ===============================
# JPA / HIBERNATE
# ===============================

spring.jpa.show-sql.1=true
spring.jpa.hibernate.ddl-auto.1=none
spring.jpa.properties.hibernate.dialect.1=org.hibernate.dialect.PostgreSQL9Dialect
#spring.jpa.properties.hibernate.current_session_context_class.1=org.springframework.orm.hibernate5.SpringSessionContext


spring.jpa.show-sql.2=true
spring.jpa.hibernate.ddl-auto.2=none
spring.jpa.properties.hibernate.dialect.2=org.hibernate.dialect.PostgreSQL9Dialect
#spring.jpa.properties.hibernate.current_session_context_class.2=org.springframework.orm.hibernate5.SpringSessionContext

By default, Spring Boot will automatically configure a default DataSource, therefore, you need to disable this automatical configuration of the Spring Boot, and manually configure your own DataSources.

SpringBootJPAMultiDsApplication.java

package org.o7planning.sbmultids;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
import org.springframework.boot.autoconfigure.jdbc.DataSourceTransactionManagerAutoConfiguration;
import org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration;

@SpringBootApplication

// Disable some Spring Boot auto config
@EnableAutoConfiguration(exclude = { //
        DataSourceAutoConfiguration.class, //
        DataSourceTransactionManagerAutoConfiguration.class, //
        HibernateJpaAutoConfiguration.class })

public class SpringBootJPAMultiDsApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringBootJPAMultiDsApplication.class, args);
    }
    
}

Next, we will configure 2 DataSources:

The DataSource1Config class is used to configure datasource 1 (PUBLISHER DB).
The DataSource2Config class is used to configure datasource 2 (ADVERTISER DB).

Constants.java

package org.o7planning.sbmultids.config;

public class Constants {
    
    public static final String PACKAGE_ENTITIES_1 = "org.o7planning.sbmultids.entity1";
    
    public static final String PACKAGE_ENTITIES_2 = "org.o7planning.sbmultids.entity2";
    
    public static final String JPA_UNIT_NAME_1 ="PERSITENCE_UNIT_NAME_1";
    public static final String JPA_UNIT_NAME_2 ="PERSITENCE_UNIT_NAME_2";
    
}

DataSource1Config.java

package org.o7planning.sbmultids.config;

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.context.annotation.PropertySources;
import org.springframework.core.env.Environment;
import org.springframework.jdbc.datasource.DriverManagerDataSource;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter;
import org.springframework.transaction.PlatformTransactionManager;

@Configuration
// Load to Environment
// (@see resources/datasource-cfg.properties).
@PropertySources({ @PropertySource("classpath:datasource-cfg.properties") })
public class DataSource1Config {

    @Autowired
    private Environment env; // Contains Properties Load by @PropertySources

    @Bean
    public DataSource ds1Datasource() {

        DriverManagerDataSource dataSource = new DriverManagerDataSource();
        dataSource.setDriverClassName(env.getProperty("spring.datasource.driver-class-name.1"));
        dataSource.setUrl(env.getProperty("spring.datasource.url.1"));
        dataSource.setUsername(env.getProperty("spring.datasource.username.1"));
        dataSource.setPassword(env.getProperty("spring.datasource.password.1"));

        return dataSource;
    }

    @Bean
    public LocalContainerEntityManagerFactoryBean ds1EntityManager() {
        LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
        em.setDataSource(ds1Datasource());

        // Scan Entities in Package:
        em.setPackagesToScan(new String[] { Constants.PACKAGE_ENTITIES_1 });
        em.setPersistenceUnitName(Constants.JPA_UNIT_NAME_1); // Important !!

        //
        HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();

        em.setJpaVendorAdapter(vendorAdapter);

        HashMap<String, Object> properties = new HashMap<>();

        // JPA & Hibernate
        properties.put("hibernate.dialect", env.getProperty("spring.jpa.properties.hibernate.dialect.1"));
        properties.put("hibernate.show-sql", env.getProperty("spring.jpa.show-sql.1"));

        // Solved Error: PostGres createClob() is not yet implemented.
        // PostGres Only:
        // properties.put("hibernate.temp.use_jdbc_metadata_defaults",  false);

        em.setJpaPropertyMap(properties);
        em.afterPropertiesSet();
        return em;
    }

    @Bean
    public PlatformTransactionManager ds1TransactionManager() {

        JpaTransactionManager transactionManager = new JpaTransactionManager();
        transactionManager.setEntityManagerFactory(ds1EntityManager().getObject());
        return transactionManager;
    }

}

DataSource2Config.java

package org.o7planning.sbmultids.config;

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.context.annotation.PropertySources;
import org.springframework.core.env.Environment;
import org.springframework.jdbc.datasource.DriverManagerDataSource;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter;
import org.springframework.transaction.PlatformTransactionManager;

@Configuration
// Load to Environment
// (@see resources/datasource-cfg.properties).
@PropertySources({ @PropertySource("classpath:datasource-cfg.properties") })
public class DataSource2Config {

    @Autowired
    private Environment env; // Contains Properties Load by @PropertySources

    @Bean
    public DataSource ds2Datasource() {
        DriverManagerDataSource dataSource = new DriverManagerDataSource();

        dataSource.setDriverClassName(env.getProperty("spring.datasource.driver-class-name.2"));
        dataSource.setUrl(env.getProperty("spring.datasource.url.2"));
        dataSource.setUsername(env.getProperty("spring.datasource.username.2"));
        dataSource.setPassword(env.getProperty("spring.datasource.password.2"));

        return dataSource;
    }

    @Bean
    public LocalContainerEntityManagerFactoryBean ds2EntityManager() {
        LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
        em.setDataSource(ds2Datasource());

        // Scan Entities in Package:
        em.setPackagesToScan(new String[] { Constants.PACKAGE_ENTITIES_2 });

        em.setPersistenceUnitName(Constants.JPA_UNIT_NAME_2);
        HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
        em.setJpaVendorAdapter(vendorAdapter);

        HashMap<String, Object> properties = new HashMap<>();
        // JPA & Hibernate
        properties.put("hibernate.dialect", env.getProperty("spring.jpa.properties.hibernate.dialect.2"));
        properties.put("hibernate.show-sql", env.getProperty("spring.jpa.show-sql.2"));

        // Solved Error: PostGres createClob() is not yet implemented.
        // PostGres Only.
        // properties.put("hibernate.temp.use_jdbc_metadata_defaults",  false);

        em.setJpaPropertyMap(properties);
        em.afterPropertiesSet();
        return em;
    }

    @Bean
    public PlatformTransactionManager ds2TransactionManager() {

        JpaTransactionManager transactionManager = new JpaTransactionManager();
        transactionManager.setEntityManagerFactory(ds2EntityManager().getObject());
        return transactionManager;
    }

}

6. Entities, DAO

No ADS

Publisher.java

package org.o7planning.sbmultids.entity1;

import java.io.Serializable;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name = "Publishers")
public class Publisher implements Serializable {

    private static final long serialVersionUID = 746237126088051312L;

    @Id
    @GeneratedValue
    @Column(name = "Id")
    private Long id;

    @Column(name = "Name", length = 255, nullable = false)
    private String name;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

}

Advertiser.java

package org.o7planning.sbmultids.entity2;

import java.io.Serializable;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name = "Advertisers")
public class Advertiser implements Serializable {

    private static final long serialVersionUID = 746237126088051312L;

    @Id
    @GeneratedValue
    @Column(name = "Id")
    private Long id;

    @Column(name = "Name", length = 255, nullable = false)
    private String name;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

}

PublisherDAO.java

package org.o7planning.sbmultids.dao;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.Query;

import org.o7planning.sbmultids.config.Constants;
import org.o7planning.sbmultids.entity1.Publisher;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;

@Repository
public class PublisherDAO {

    @Autowired
    @PersistenceContext( unitName= Constants.JPA_UNIT_NAME_1)
    private EntityManager entityManager;

    public List<Publisher> listPublishers() {
        String sql = "Select e from " + Publisher.class.getName() + " e ";
        Query query = entityManager.createQuery(sql, Publisher.class);
        return query.getResultList();
    }

    public Publisher findById(Long id) {
        return this.entityManager.find(Publisher.class, id);
    }
    
}

AdvertiserDAO.java

package org.o7planning.sbmultids.dao;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.Query;

import org.o7planning.sbmultids.config.Constants;
import org.o7planning.sbmultids.entity2.Advertiser;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;

@Repository
public class AdvertiserDAO {
 

    @Autowired
    @PersistenceContext(unitName = Constants.JPA_UNIT_NAME_2)
    private EntityManager entityManager;

    public List<Advertiser> listAdvertisers() {
        String sql = "Select e from " + Advertiser.class.getName() + " e ";
        Query query = entityManager.createQuery(sql, Advertiser.class);
        return query.getResultList();
    }

    public Advertiser findById(Long id) {
        return this.entityManager.find(Advertiser.class, id);
    }
    
}

7. Controller

No ADS

MainController.java

package org.o7planning.sbmultids.controller;

import java.util.List;

import org.o7planning.sbmultids.dao.AdvertiserDAO;
import org.o7planning.sbmultids.dao.PublisherDAO;
import org.o7planning.sbmultids.entity1.Publisher;
import org.o7planning.sbmultids.entity2.Advertiser;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

@Controller
public class MainController {

    @Autowired
    private PublisherDAO publisherDAO;

    @Autowired
    private AdvertiserDAO advertiserDAO;

    @RequestMapping(value = "/", method = RequestMethod.GET)
    public String homePage(Model model) {

        List<Advertiser> advertisers = advertiserDAO.listAdvertisers();
        List<Publisher> publishers = publisherDAO.listPublishers();

        model.addAttribute("advertisers", advertisers);
        model.addAttribute("publishers", publishers);

        return "home";
    }

}

8. Thymeleaf Template

No ADS

home.html

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
   <head>
      <meta charset="UTF-8"/>
      <title>Home</title>
      <style>
        th, td {
          padding: 5px;
        }
        table  {
           border-collapse: collapse;
        }
      
      </style>
   </head>
   
   <body>
      
      <h3>Using Publisher-DB</h3>
      
      <table border="1">
        <tr>
           <th>ID</th>
           <th>Name</th>
        </tr>
        <tr th:each="publisher : ${publishers}">
           <td th:utext="${publisher.id}"></td>
           <td th:utext="${publisher.name}"></td>
        </tr>
      </table>
      
      <h3>Using Advertiser-DB</h3>
      
      <table border="1">
        <tr>
           <th>ID</th>
           <th>Name</th>
        </tr>
        <tr th:each="advertiser : ${advertisers}">
           <td th:utext="${advertiser.id}"></td>
           <td th:utext="${advertiser.name}"></td>
        </tr>
      </table>
     
      
   </body>
   
</html>

9. Appendix: JSP View

No ADS

See more:
Spring Boot and JSP

In case, you use the JSP technology for the View layer:

home.jsp

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%@ page contentType="text/html; charset=UTF-8" %>

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
   <head>
      <meta charset="UTF-8"/>
      <title>Home</title>
      <style>
        th, td {
          padding: 5px;
        }
        table  {
           border-collapse: collapse;
        }
      
      </style>
   </head>
   
   <body>
      
      <h3>Using Publisher-DB</h3>
      
      <table border="1">
        <tr>
           <th>ID</th>
           <th>Name</th>
        </tr>
        <c:forEach items="${publishers}" var="publisher">
            <tr>
               <td th:utext="${publisher.id}"></td>
               <td th:utext="${publisher.name}"></td>
            </tr>
        </c:forEach>
      </table>
      
      <h3>Using Advertiser-DB</h3>
      
      <table border="1">
        <tr>
           <th>ID</th>
           <th>Name</th>
        </tr>
        <c:forEach items="${advertisers}" var="advertiser">
            <tr>
               <td th:utext="${advertiser.id}"></td>
               <td th:utext="${advertiser.name}"></td>
            </tr>
        </c:forEach>
      </table>
     
      
   </body>
   
</html>

No ADS

Use Multiple DataSources with Spring Boot and JPA

1. Objective of Post

Spring Boot 2.x (or >=1.5.9)

JPA

Thymeleaf (Or JSP)

2. Prepare a Database

3. Create a Spring Boot project

4. Configure pom.xml

5. Configure DataSources

6. Entities, DAO

7. Controller

8. Thymeleaf Template

9. Appendix: JSP View

Spring Boot Tutorials

Spring Boot Tutorials

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