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Utiliser plusieurs DataSources avec Spring Boot et JPA

  1. Objectif de cette publication
  2. Préparer Database
  3. Créer un projet Spring Boot
  4. Configurer le fichier pom.xml
  5. Configurer des resources de données
  6. Entities, DAO
  7. Controller
  8. Thymeleaf Template
  9. Annexe : JSP View

1. Objectif de cette publication

Cet article est basé sur :

  • Spring Boot 2.x (or >=1.5.9)

  • JPA

  • Thymeleaf (Or JSP)

Dans cet artcile, je vous donnerai des instructions de comment créer un Spring Boot & JPA utilisant plusieurs DataSource. Afin de pratiquer avec cet exemple, nous avons deux bases de données :
  • PUBLISHER: Celle-ci est la première base de données, elle a untableau PUBLISHERS.
  • ADVERTISER: Celle-ci est la deuxième base de données, elle a un tableau ADVERTISERS.
Dans cette application, les fonctions (les pages) peuvent utiliser simultanément ces deux bases de données mentionnées ci-dessus. Par exemple, une page affiche la liste des éditeurs (Publisher) en montrant ainsi la liste des annonceurs (Advertiser), par conséquent, vous devez travailler avec ces deux bases de données en même temps.
Dans d'autres cas, si votre application a besoin de plusieurs DataSource, mais dans chaque fonction (chaque page) ne travaille qu'avec une DataSource précise, vous devriez utiliser Routing DataSource & DataSource Interceptor.
  1. Routing DataSource est une DataSource particulière, elle contient une liste des DataSource utilisé dans votre application.
  2. DataSource Interceptor va décider quelle DataSource sera utilisée correspondant à chaque fonction (chaque page) dans votre application.

2. Préparer 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. Créer un projet Spring Boot

4. Configurer le fichier pom.xml

Dans le fichier pom.xml ci-dessous, j'ai configuré l'application afin qu'elle puisse travailler avec 4 types de base de données communes, qui sont 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. Configurer des resources de données

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
Par défaut, Spring Boot va automatiquement configurer DataSource, par conséquent, vous devez désactiver cette configuration automatique de Spring Boot, et configurer votre propre DataSource.
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);
    }
    
}
Ensuite, nous allons configurer deux DataSource:
  1. La classe DataSource1Config sert à configurer la ressource de base de donnée 1 (PUBLISHER DB).
  2. La classe DataSource2Config sert à configurer la ressource de base de donnée 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. Annexe : JSP View

Voir plus :
Au cas où vous utilisez la technology JSP pour la couche 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>

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