Spring Boot JPA Multiple Datasources

In this article, we will learn how to configure multiple data sources and connect to multiple databases in a typical Spring Boot web application.

We will create a Spring boot project to demonstrate how to configure multiple data sources and connect to multiple databases.

As we know that Spring Boot autoconfiguration works out of the box if you have a single database to work with and provides plenty of customization options through its properties. But if your application demands more control over the application configuration, you can turn off specific auto-configurations and configure the components by yourself.

In this article, we will learn step-by-step how to use multiple databases in the same application. If we need to connect to multiple databases, we need to configure various Spring beans like DataSources, TransactionManagers, EntityManagerFactoryBeans, DataSourceInitializers, etc., explicitly.

What we'll build?

We will build a Spring Boot web application where the security data has been stored in one database and order-related data has been stored in another database.

Let's see how we can work with multiple databases in Spring Boot and use the Spring Data JPA-based application.

Tools and Technologies Used

• Spring Boot - 3+
• JDK - 17 or later
• Spring Framework - 6+
• Hibernate - 6+
• Maven - 3.2+
• JPA
• H2
• Thymeleaf
• IDE - Eclipse or Spring Tool Suite (STS)

Create and Set up a Spring Boot Project

There are many ways to create a Spring Boot application. The simplest way is to use Spring Initializr at http://start.spring.io/, which is an online Spring Boot application generator.

• Generate: Maven Project
• Java Version: 17 (Default)
• Spring Boot: 3.0.4
• Group: net.guides.springboot
• Artifact: springboot-multiple-datasources
• Name: springboot-multiple-datasources
• Description: Rest API for a Simple User Management Application
• Package Name : net.guides.springboot.springbootmultipledatasources
• Packaging: jar (This is the default value)
• Dependencies: Web, JPA, H2, DevTools

Once, all the details are entered, then click on Generate Project button will generate a spring boot project and downloads it. Next, Unzip the downloaded zip file and import it into your favorite IDE.

Maven pom.xml File

<?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>net.guides.springboot</groupId>
	<artifactId>springboot-multiple-datasources</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>springboot-multiple-datasources</name>
	<description>Demo project for Spring Boot</description>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>3.0.4</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>17</java.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-devtools</artifactId>
			<optional>true</optional>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-configuration-processor</artifactId>
			<optional>true</optional>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-data-jpa</artifactId>			
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-thymeleaf</artifactId>			
		</dependency>	
		<dependency>
			<groupId>com.mysql</groupId>
			<artifactId>mysql-connector-j</artifactId>
		</dependency>
		<dependency>
			<groupId>com.h2database</groupId>
			<artifactId>h2</artifactId>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>
</project>

Packaging Structure

Following is the packing structure -

The next step is very important please have a look.

Excluding the AutoConfiguration classes

Let's turn off the DataSource JPA-related autoconfiguration classes. As we are going to configure the database-related beans explicitly, we will turn off the DataSource JPA Autoconfiguration by excluding the AutoConfiguration classes:

package net.guides.springboot.springbootmultipledatasources;

import org.springframework.boot.SpringApplication;

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;
import org.springframework.transaction.annotation.EnableTransactionManagement;

@SpringBootApplication(
  exclude = { DataSourceAutoConfiguration.class, 
     HibernateJpaAutoConfiguration.class,
     DataSourceTransactionManagerAutoConfiguration.class })
@EnableTransactionManagement
public class SpringbootMultipleDatasourcesApplication {

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

Once we have turned off AutoConfigurations, we need to enable TransactionManagement explicitly by using the @EnableTransactionManagement annotation.

Configure Multiple Datasource Properties

H2 Database Configuration

Let's configure the H2 datasource properties. Configure the Security and Orders database connection parameters in the application.properties file.

debug=true

datasource.security.driver-class-name=org.h2.Driver
datasource.security.url=jdbc:h2:mem:securitydb;DB_CLOSE_DELAY=-1
datasource.security.username=sa
datasource.security.password=

datasource.security.initialize=true

datasource.orders.driver-class-name=org.h2.Driver
datasource.orders.url=jdbc:h2:mem:ordersdb;DB_CLOSE_DELAY=-1
datasource.orders.username=sa
datasource.orders.password=

datasource.orders.initialize=true

spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true
            

MySQL Database Configuration

We are using an H2 database to quickly set up the application but you can also use MySQL database for production by replacing the below configuration in an application.properties file.

datasource.security.driver-class-name=com.mysql.jdbc.Driver
datasource.security.url=jdbc:mysql://localhost:3306/securitydb
datasource.security.username=root
datasource.security.password=root

datasource.security.initialize=true

datasource.orders.driver-class-name=com.mysql.jdbc.Driver
datasource.orders.url=jdbc:mysql://localhost:3306/ordersdb
datasource.orders.username=root
datasource.orders.password=root

datasource.orders.initialize=true

spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true

Note that we have used custom property keys to configure the two datasource properties.

In the next step, we will create a security-related JPA entity and a JPA repository.

Create JPA Entites - User and Address

User

package net.guides.springboot.springbootmultipledatasources.security.entities;

import java.util.Set;

import jakarta.persistence.*;

/**
 * @author Ramesh Fadatare
 *
 */
@Entity
@Table(name="USERS")
public class User
{
    @Id @GeneratedValue(strategy=GenerationType.AUTO)
    private Integer id;
    @Column(nullable=false)
    private String name;
    @Column(nullable=false, unique=true)
    private String email;
    private boolean disabled;
    @OneToMany(mappedBy="user")
    private Set<Address> addresses;
 
    public User()
    {
    }

    public User(Integer id, String name, String email)
    {
        this.id = id;
        this.name = name;
        this.email = email;
    }
    public User(Integer id, String name, String email, boolean disabled)
    {
        this.id = id;
        this.name = name;
        this.email = email;
        this.disabled = disabled;
     }
    public Integer getId()
    {
        return id;
    }

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

    public String getName()
    {
        return name;
    }

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

    public String getEmail()
    {
        return email;
    }

    public void setEmail(String email)
    {
        this.email = email;
    }

    public boolean isDisabled()
    {
        return disabled;
    }

    public void setDisabled(boolean disabled)
    {
        this.disabled = disabled;
    }

    public Set<Address> getAddresses()
    {
        return addresses;
    }

    public void setAddresses(Set<Address> addresses)
    {
         this.addresses = addresses;
    } 
}
    

Address

package net.guides.springboot.springbootmultipledatasources.security.entities;

import jakarta.persistence.*;

/**
 * @author Ramesh Fadatare
 *
 */
@Entity
@Table(name="ADDRESSES")
public class Address
{
    @Id @GeneratedValue(strategy=GenerationType.AUTO)
    private Integer id;
    @Column(nullable=false)
    private String city;
    @ManyToOne
    @JoinColumn(name="user_id")
    private User user;
 
    public Integer getId()
    {
        return id;
    }
    public void setId(Integer id)
    {
        this.id = id;
    }
    public String getCity()
    {
        return city;
    }
    public void setCity(String city)
    {
        this.city = city;
    }
    public User getUser()
    {
        return user;
    }
    public void setUser(User user)
    {
        this.user = user;
    } 
}

Spring JPA Repository - UserRepository.java

package net.guides.springboot.springbootmultipledatasources.security.repositories;

import org.springframework.data.jpa.repository.JpaRepository;


import net.guides.springboot.springbootmultipledatasources.security.entities.User;

/**
 * @author Ramesh Fadatare
 *
 */
public interface UserRepository extends JpaRepository
{
 
}

Create JPA Entities - Order and OrderItem

Order

package net.guides.springboot.springbootmultipledatasources.orders.entities;

import java.util.Set;


import jakarta.persistence.*;

/**
 * @author Ramesh Fadatare
 *
 */
@Entity
@Table(name="ORDERS")
public class Order
{
    @Id @GeneratedValue(strategy=GenerationType.AUTO)
    private Integer id;
    @Column(nullable=false, name="cust_name")
    private String customerName;
    @Column(nullable=false, name="cust_email")
    private String customerEmail;
 
    @OneToMany(mappedBy="order")
    private Set orderItems;
 
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getCustomerName() {
        return customerName;
    }
    public void setCustomerName(String customerName) {
        this.customerName = customerName;
    }
    public String getCustomerEmail() {
        return customerEmail;
    }
    public void setCustomerEmail(String customerEmail) {
        this.customerEmail = customerEmail;
    }
    public Set<OrderItem> getOrderItems()
    {
        return orderItems;
    }
    public void setOrderItems(Set orderItems)
    {
        this.orderItems = orderItems;
    }
}

OrderItem

package net.guides.springboot.springbootmultipledatasources.orders.entities;

import jakarta.persistence.*;

/**
 * @author Ramesh Fadatare
 *
 */
@Entity
@Table(name="ORDER_ITEMS")
public class OrderItem
{
    @Id @GeneratedValue(strategy=GenerationType.AUTO)
    private Integer id;
    private String productCode;
    private int quantity;
    @ManyToOne
    @JoinColumn(name="order_id")
    private Order order;
 
    public Integer getId()
    {
        return id;
    }
    public void setId(Integer id)
    {
        this.id = id;
    }
    public String getProductCode()
    {
        return productCode;
    }
    public void setProductCode(String productCode)
    {
        this.productCode = productCode;
    }
    public int getQuantity()
    {
        return quantity;
    }
    public void setQuantity(int quantity)
    {
        this.quantity = quantity;
    }
    public Order getOrder()
    {
        return order;
    }
    public void setOrder(Order order)
    {
        this.order = order;
    } 
}

Spring JPA Repository - OrderRepository.java

package net.guides.springboot.springbootmultipledatasources.orders.repositories;

import org.springframework.data.jpa.repository.JpaRepository;

import net.guides.springboot.springbootmultipledatasources.orders.entities.Order;

/**
 * @author Ramesh Fadatare
 *
 */
public interface OrderRepository extends JpaRepository{

}

Initialize Sample Data - security-data.sql script

Create SQL scripts to initialize sample data. Create the security-data.sql script in the src/main/resources folder to initialize the USERS table with sample data.

delete from addresses;
delete from users;

insert into users(id, name, email,disabled) values(1,'John Cena','john@gmail.com', false);
insert into users(id, name, email,disabled) values(2,'Salman Khan','salman@gmail.com', false);
insert into users(id, name, email,disabled) values(3,'Amitr Khan','amir@gmail.com', true);

insert into addresses(id,city,user_id) values(1, 'Pune',1);
insert into addresses(id,city,user_id) values(2, 'Landon',1);
insert into addresses(id,city,user_id) values(3, 'Newyork',2);
insert into addresses(id,city,user_id) values(4, 'Mumbai',3);
insert into addresses(id,city,user_id) values(6, 'Washington',3);

Initialize Sample Data - orders-data.sql script

Create the orders-data.sql script in the src/main/resources folder to initialize the ORDERS table with sample data.

delete from order_items;
delete from orders;

insert into orders(id, cust_name, cust_email) values(1,'John Cena','john@gmail.com');
insert into orders(id, cust_name, cust_email) values(2,'Salman Khan','salman@gmail.com');
insert into orders(id, cust_name, cust_email) values(3,'Amir Khan','amir@gmail.com');

insert into order_items(id, productcode,quantity,order_id) values(1,'order item1', 2, 1);
insert into order_items(id, productcode,quantity,order_id) values(2,'order item2', 1, 1);
insert into order_items(id, productcode,quantity,order_id) values(3,'order item3', 5, 1);
insert into order_items(id, productcode,quantity,order_id) values(4,'order item4', 2, 2);
insert into order_items(id, productcode,quantity,order_id) values(5,'order item5', 1, 2);

Create Security Datasource Configuration - SecurityDataSourceConfig.java

Create the SecurityDataSourceConfig.java configuration class. we will configure the Spring beans such as DataSource, TransactionManager, EntityManagerFactoryBean, and DataSourceInitializer by connecting to the Security database in SecurityDataSourceConfig.java

package net.guides.springboot.springbootmultipledatasources.config;

import java.util.Properties;

import jakarta.persistence.EntityManagerFactory;
import javax.sql.DataSource;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.jdbc.DataSourceProperties;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.jdbc.DataSourceBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.env.Environment;
import org.springframework.core.io.ClassPathResource;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.jdbc.datasource.init.DataSourceInitializer;
import org.springframework.jdbc.datasource.init.ResourceDatabasePopulator;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter;
import org.springframework.transaction.PlatformTransactionManager;

/**
 * @author Ramesh Fadatare
 * 
 */
@Configuration
@EnableJpaRepositories(
  basePackages = "net.guides.springboot.springbootmultipledatasources.security.repositories",
        entityManagerFactoryRef = "securityEntityManagerFactory",
        transactionManagerRef = "securityTransactionManager"
)
public class SecurityDataSourceConfig
{
       @Autowired
       private Environment env;
  
       @Bean
       @ConfigurationProperties(prefix="datasource.security")
       public DataSourceProperties securityDataSourceProperties() {
           return new DataSourceProperties();
       }
    
       @Bean
       public DataSource securityDataSource() {
            DataSourceProperties securityDataSourceProperties = securityDataSourceProperties();
            return DataSourceBuilder.create()
           .driverClassName(securityDataSourceProperties.getDriverClassName())
           .url(securityDataSourceProperties.getUrl())
           .username(securityDataSourceProperties.getUsername())
           .password(securityDataSourceProperties.getPassword())
           .build();
       }
    
       @Bean
       public PlatformTransactionManager securityTransactionManager()
       {
           EntityManagerFactory factory = securityEntityManagerFactory().getObject();
           return new JpaTransactionManager(factory);
       }

       @Bean
       public LocalContainerEntityManagerFactoryBean securityEntityManagerFactory()
       {
           LocalContainerEntityManagerFactoryBean factory = new LocalContainerEntityManagerFactoryBean();
           factory.setDataSource(securityDataSource());
           factory.setPackagesToScan(new String[]{"net.guides.springboot.springbootmultipledatasources.security.entities"});
           factory.setJpaVendorAdapter(new HibernateJpaVendorAdapter());
        
           Properties jpaProperties = new Properties();
           jpaProperties.put("hibernate.hbm2ddl.auto", env.getProperty("spring.jpa.hibernate.ddl-auto"));
           jpaProperties.put("hibernate.show-sql", env.getProperty("spring.jpa.show-sql"));
           factory.setJpaProperties(jpaProperties);
        
           return factory;
       }
    
       @Bean
       public DataSourceInitializer securityDataSourceInitializer() 
       {
           DataSourceInitializer dataSourceInitializer = new DataSourceInitializer();
           dataSourceInitializer.setDataSource(securityDataSource());
           ResourceDatabasePopulator databasePopulator = new ResourceDatabasePopulator();
           databasePopulator.addScript(new ClassPathResource("security-data.sql"));
           dataSourceInitializer.setDatabasePopulator(databasePopulator);
           dataSourceInitializer.setEnabled(env.getProperty("datasource.security.initialize", Boolean.class, false));
           return dataSourceInitializer;
       }   
}

Note that you have populated the datasource.security.* properties into DataSourceProperties by using @ConfigurationProperties(prefix="datasource.security") and DataSourceBuilder fluent API to create the DataSource bean.

While creating the LocalContainerEntityManagerFactoryBean bean, you have configured the package called net.guides.springboot.springbootmultipledatasources.security.entities to scan for JPA entities. You have configured the DataSourceInitializer bean to initialize the sample data from security-data.sql.

Finally, we enabled Spring Data JPA support by using the @EnableJpaRepositories annotation. As we are going to have multiple EntityManagerFactory and TransactionManager beans, we configured the bean IDs for entityManagerFactoryRef and transactionManagerRef by pointing to the respective bean names. we also configured the basePackages property to indicate where to look for the Spring Data JPA repositories (the packages).

Create Security Datasource Configuration - OrdersDataSourceConfig.java

Create the OrdersDataSourceConfig.java configuration class. Similar to SecurityDataSourceConfig.java, you will create OrdersDataSourceConfig.java but point it to the Orders database.

package net.guides.springboot.springbootmultipledatasources.config;

import java.util.Properties;

import jakarta.persistence.EntityManagerFactory;
import javax.sql.DataSource;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.jdbc.DataSourceProperties;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.jdbc.DataSourceBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.env.Environment;
import org.springframework.core.io.ClassPathResource;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.jdbc.datasource.init.DataSourceInitializer;
import org.springframework.jdbc.datasource.init.ResourceDatabasePopulator;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter;
import org.springframework.transaction.PlatformTransactionManager;

/**
 * @author Ramesh Fadatare
 * 
 */
@Configuration
@EnableJpaRepositories(
    basePackages = "net.guides.springboot.springbootmultipledatasources.orders.repositories",
    entityManagerFactoryRef = "ordersEntityManagerFactory",
    transactionManagerRef = "ordersTransactionManager"
)
public class OrdersDataSourceConfig {

    @Autowired
    private Environment env;

    @Bean
    @ConfigurationProperties(prefix = "datasource.orders")
    public DataSourceProperties ordersDataSourceProperties() {
        return new DataSourceProperties();
    }

    @Bean
    public DataSource ordersDataSource() {
        DataSourceProperties primaryDataSourceProperties = ordersDataSourceProperties();
        return DataSourceBuilder.create()
            .driverClassName(primaryDataSourceProperties.getDriverClassName())
            .url(primaryDataSourceProperties.getUrl())
            .username(primaryDataSourceProperties.getUsername())
            .password(primaryDataSourceProperties.getPassword())
            .build();
    }

    @Bean
    public PlatformTransactionManager ordersTransactionManager() {
        EntityManagerFactory factory = ordersEntityManagerFactory().getObject();
        return new JpaTransactionManager(factory);
    }

    @Bean
    public LocalContainerEntityManagerFactoryBean ordersEntityManagerFactory() {
        LocalContainerEntityManagerFactoryBean factory = new LocalContainerEntityManagerFactoryBean();
        factory.setDataSource(ordersDataSource());
        factory.setPackagesToScan(new String[] {
            "net.guides.springboot.springbootmultipledatasources.orders.entities"
        });
        factory.setJpaVendorAdapter(new HibernateJpaVendorAdapter());

        Properties jpaProperties = new Properties();
        jpaProperties.put("hibernate.hbm2ddl.auto", env.getProperty("spring.jpa.hibernate.ddl-auto"));
        jpaProperties.put("hibernate.show-sql", env.getProperty("spring.jpa.show-sql"));
        factory.setJpaProperties(jpaProperties);

        return factory;

    }

    @Bean
    public DataSourceInitializer ordersDataSourceInitializer() {
        DataSourceInitializer dataSourceInitializer = new DataSourceInitializer();
        dataSourceInitializer.setDataSource(ordersDataSource());
        ResourceDatabasePopulator databasePopulator = new ResourceDatabasePopulator();
        databasePopulator.addScript(new ClassPathResource("orders-data.sql"));
        dataSourceInitializer.setDatabasePopulator(databasePopulator);
        dataSourceInitializer.setEnabled(env.getProperty("datasource.orders.initialize", Boolean.class, false));
        return dataSourceInitializer;
    }
}

Create UserOrdersService.java

package net.guides.springboot.springbootmultipledatasources.services;

import java.util.List;


import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import net.guides.springboot.springbootmultipledatasources.orders.entities.Order;
import net.guides.springboot.springbootmultipledatasources.orders.repositories.OrderRepository;
import net.guides.springboot.springbootmultipledatasources.security.entities.User;
import net.guides.springboot.springbootmultipledatasources.security.repositories.UserRepository;

/**
 * @author Ramesh Fadatare
 *
 */
@Service
public class UserOrdersService
{
    @Autowired
    private OrderRepository orderRepository;
 
    @Autowired
    private UserRepository userRepository;
 
    @Transactional(transactionManager="securityTransactionManager")
    public List<User> getUsers()
    {
        return userRepository.findAll();
    }
 
    @Transactional(transactionManager="ordersTransactionManager")
    public List<Order> getOrders()
    {
        return orderRepository.findAll();
    }
}

Create HomeController.java

package net.guides.springboot.springbootmultipledatasources.controllers;

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;

import net.guides.springboot.springbootmultipledatasources.services.UserOrdersService;

/**
 * @author Ramesh Fadatare
 *
 */
@Controller
public class HomeController
{
    @Autowired
    private UserOrdersService userOrdersService;
 
    @RequestMapping(value = {"/", "/app/users"}, method = RequestMethod.GET)
    public String getUsers(Model model)
    {
        model.addAttribute("users", userOrdersService.getUsers());
        model.addAttribute("orders", userOrdersService.getOrders());
  
        return "users";
    }
}

Use OpenEntityManagerInViewFilter for Multiple Data Sources

Let's see how to use OpenEntityManagerInViewFilter to enable lazy loading of JPA entity LAZY associated collections while rendering the view, you need to register the OpenEntityManagerInViewFilter beans.

 /**
 * 
 */
package net.guides.springboot.springbootmultipledatasources.config;

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.Configuration;
import org.springframework.orm.jpa.support.OpenEntityManagerInViewFilter;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

/**
 * @author Ramesh Fadatare
 * 
 */
@Configuration
public class WebMvcConfig extends WebMvcConfigurerAdapter
{
 
    @Bean
    public OpenEntityManagerInViewFilter securityOpenEntityManagerInViewFilter()
    {
        OpenEntityManagerInViewFilter osivFilter = new OpenEntityManagerInViewFilter();
        osivFilter.setEntityManagerFactoryBeanName("securityEntityManagerFactory");
        return osivFilter;
    }
 
    @Bean
    public OpenEntityManagerInViewFilter ordersOpenEntityManagerInViewFilter()
    {
        OpenEntityManagerInViewFilter osivFilter = new OpenEntityManagerInViewFilter();
        osivFilter.setEntityManagerFactoryBeanName("ordersEntityManagerFactory");
        return osivFilter;
    }
}

As we are building a web application so the method returns the users.html view.

Create Thymeleaf page - users.html

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" 
	  xmlns:th="http://www.thymeleaf.org">
      
      <head>
        <title>SpringBoot</title>
    </head>
    <body>
    <div style="width: 20%; float:left">
    	<h1>Users</h1>
    	<hr/>
    	<div th:each="user : ${users}">
    		<h2>Name: <span th:text="${user.name}">Name</span></h2>
    		<h4>Addresses</h4>
    		<div th:each="addr : ${user.addresses}">
    			<p th:text="${addr.city}">City</p>
    		</div>	
    	</div>
    	</div>
    	<div style="width: 80%; float:right">
    	<h1>Orders</h1>
    	<hr/>
    	<div th:each="order : ${orders}">
    		<h2>Customer Name: <span th:text="${order.customerName}">customerName</span></h2>
    		<h4>Order Items</h4>
    		<div th:each="item : ${order.orderItems}">
    			<p th:text="${item.productCode}">productCode</p>
    		</div>	
    	</div>
    	</div>
    </body>
</html>

Running an Application

The SpringbootMultipleDatasourcesApplication.java is an entry point so right-click and choose run as in your IDE will start the embedded tomcat server on port 8080.

Hit http://localhost:8080/ link in a browser will display below web page on a browser.

Output

That's all, I am done with developing a Spring Boot web application with multiple datasources.