betacode

Используйте несколько DataSources с Spring Boot и JPA

  1. Цель статьи
  2. Приготовить Database
  3. Создать проект Spring Boot
  4. Конфигурация pom.xml
  5. Конфигурировать DataSource
  6. Entities, DAO
  7. Controller
  8. Thymeleaf Template
  9. Аппендикс: JSP View

1. Цель статьи

Статья основана на:

  • Spring Boot 2.x (or >=1.5.9)

  • JPA

  • Thymeleaf (Or JSP)

В данной статье я покажу вам как создать приложение Spring Boot & JPA используя разные DataSource. Чтобы практиковать с примером у нас есть 2 базы данных:
  • PUBLISHER: Это база данных 1, которая имеет таблицу PUBLISHERS.
  • ADVERTISER: Это база данных 2, которая имеет таблицу ADVERTISERS.
В данном приложении функции (Страницы) могут использовать одновременно оба вышеупомянутых базы данных. Например одна страница отображает список издателей (Publisher), в то же время отображает рекламодателей (Advertiser), таким образом, вам нужно работать одновременно с 2 базами данных упомянутые выше.
В другом случае, если вашему приложению нужно несколько DataSource, но каждая функция (каждая страница) работает только с одним определенным DataSource, вам стоит использовать Routing DataSource & DataSource Interceptor.
  1. Routing DataSource является особым DataSource, он содержит список реальных DataSource, которые будут использоваться в вашем приложении.
  2. DataSource Interceptor решает какой DataSource будет использован соответственно с каждой функцией (каждой страницей) в вашем приложении.

2. Приготовить Database

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. Создать проект Spring Boot

4. Конфигурация pom.xml

В файле pom.xml ниже, я уже конфигурировал чтобы приложение могло работать с 4 видами распространненных баз данных это MySQL, SQL Server, PostGres, 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. Конфигурировать DataSource

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
По умолчанию Spring Boot автоматически конфигурирует DataSource по умолчанию, поэтому вам нужно отключить данную автоматическую конфигурацию у Spring Boot, и конфигурировать ваш отдельный DataSource вручную.
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);
    }
    
}
Далее мы конфигурируем 2 DataSource:
  1. Класс DataSource1Config используется чтобы конфигурировать datasource 1 (PUBLISHER DB).
  2. Класс DataSource2Config используется чтобы конфигурировать datasource 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

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

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

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. Аппендикс: JSP View

No ADS
Смотрите так же:
В случае, если вы используете технологию JSP для уровня View:
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

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