[JAVA] Sample web application that handles multiple databases in Spring Boot 1.5

Overview

This is a sample code of a web application that handles multiple databases using Spring Boot.

environment

reference

Database

It is assumed that there are three databases handled by the application, one (test_dev3) is the database common to the application, and the other two (test_dev1, test_dev2) are treated as multi-tenant. The schemas of the test_dev1 and test_dev2 databases are the same, but the data to be stored is different.

In this sample application, the value of the request parameter switches between the test_dev1 and test_dev2 databases. Also, since it is a sample application, the table to be handled has no particular meaning (appropriate). In addition, JpaTransactionManager does not seem to be able to execute transactions that span multiple databases (data sources).

Structural drawing

ds.png

Data source settings

Set the data source in application.yml as follows.

application.yml


spring:
  datasource:
    dev1:
      url: jdbc:postgresql://localhost:5432/test_dev1
      username: user_dev1
      password: pass1
      driverClassName: org.postgresql.Driver
      defaultAutoCommit: false
      defaultReadOnly: false
      validationQuery: SELECT 'dev1'
      timeBetweenEvictionRunsMillis: 3600000
    dev2:
      url: jdbc:postgresql://localhost:5432/test_dev2
      username: user_dev2
      password: pass2
      driverClassName: org.postgresql.Driver
      defaultAutoCommit: false
      defaultReadOnly: false
      validationQuery: SELECT 'dev2'
      timeBetweenEvictionRunsMillis: 3600000
    dev3:
      url: jdbc:postgresql://localhost:5432/test_dev3
      username: user_dev3
      password: pass3
      driverClassName: org.postgresql.Driver
      defaultAutoCommit: false
      defaultReadOnly: false
      validationQuery: SELECT 'dev3'
      timeBetweenEvictionRunsMillis: 3600000
  jpa:
    showSql: true
    formatSql: true

logging:
  level:
    root: INFO
    org.springframework: INFO
#    org.springframework.orm.jpa.JpaTransactionManager: DEBUG
#    org.springframework.transaction: TRACE
    org.hibernate: DEBUG
    org.hibernate.SQL: DEBUG
    org.hibernate.type.descriptor.sql.BasicBinder: TRACE
#    org.hibernate.transaction: DEBUG
#    org.hibernate.jpa.internal: DEBUG
    org.hibernate.event.internal: DEBUG
    org.hibernate.engine.transaction.internal: DEBUG
    org.hibernate.internal.util: DEBUG

Data source configuration code

test_dev1

Data source settings for tenant A. The implementation is just to build the data source from the settings in the property file. Entity manager and transaction manager are implemented in different classes.

Dev1DataSourceConfigure


package com.example.datasource;

import org.springframework.boot.autoconfigure.jdbc.DataSourceBuilder;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import javax.sql.DataSource;

@Configuration
public class Dev1DataSourceConfigure {
    public static final String DEV1_DATASOURCE = "dev1DataSource";

    @ConfigurationProperties(prefix = "spring.datasource.dev1")
    @Bean(DEV1_DATASOURCE)
    public DataSource dataSource() {
        DataSource dev1 = DataSourceBuilder.create().build();
        return dev1;
    }
}

test_dev2

Data source settings for tenant B. It is the same implementation as tenant A.

Dev2DataSourceConfigure


package com.example.datasource;

import org.springframework.boot.autoconfigure.jdbc.DataSourceBuilder;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import javax.sql.DataSource;

@Configuration
public class Dev2DataSourceConfigure {
    public static final String DEV2_DATASOURCE = "dev2DataSource";

    @ConfigurationProperties(prefix = "spring.datasource.dev2")
    @Bean(DEV2_DATASOURCE)
    public DataSource dataSource() {
        DataSource dev2 = DataSourceBuilder.create().build();
        return dev2;
    }
}

Setting the data source that bundles test_dev1 and test_dev2

Implement entity manager and transaction manager that refer to the data source for each tenant implemented above. The point of implementation is

MultiDataSourceConfigure


package com.example.datasource;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.orm.jpa.EntityManagerFactoryBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.annotation.EnableTransactionManagement;

import javax.persistence.EntityManagerFactory;
import javax.sql.DataSource;
import java.util.HashMap;
import java.util.Map;

import static com.example.datasource.Dev1DataSourceConfigure.DEV1_DATASOURCE;
import static com.example.datasource.Dev2DataSourceConfigure.DEV2_DATASOURCE;
import static com.example.datasource.MultiDataSourceConfigure.ENTITY_MANAGER;
import static com.example.datasource.MultiDataSourceConfigure.REPOSITORY_PACKAGE;
import static com.example.datasource.MultiDataSourceConfigure.TRANSACTION_MANAGER;

@Configuration
@EnableTransactionManagement(order = 100)                                                 // (1)
@EnableJpaRepositories(
    basePackages = {REPOSITORY_PACKAGE},
    entityManagerFactoryRef = ENTITY_MANAGER,
    transactionManagerRef = TRANSACTION_MANAGER
)
public class MultiDataSourceConfigure {

    public static final String REPOSITORY_PACKAGE = "com.example.repository.tenantds";
    public static final String ENTITY_PACKAGES = "com.example.entity.tenantds";

    public static final String ENTITY_MANAGER = "multiEntityManagerFactory";
    public static final String TRANSACTION_MANAGER = "multiTransactionManager";

    public static final String MULTI_DATASOURCE_PU = "multiDataSourcePersistenceUnit";
    public static final String MULTI_DATASOURCE = "multiDataSource";

    @Autowired
    @Qualifier(DEV1_DATASOURCE)
    private DataSource dev1;

    @Autowired
    @Qualifier(DEV2_DATASOURCE)
    private DataSource dev2;

    @Bean(MULTI_DATASOURCE)
    public RoutingDataSourceResolver multiDataSource() {                                    // (2)
        RoutingDataSourceResolver resolver = new RoutingDataSourceResolver();

        //Set the data source to switch
        Map<Object, Object> dataSources = new HashMap<Object,Object>();
        dataSources.put(DEV1_DATASOURCE, dev1);
        dataSources.put(DEV2_DATASOURCE, dev2);

        resolver.setTargetDataSources(dataSources);
        resolver.setDefaultTargetDataSource(dev1);
        return resolver;
    }

    @Bean(ENTITY_MANAGER)
    public LocalContainerEntityManagerFactoryBean entityManagerFactory(
            EntityManagerFactoryBuilder builder) {
        LocalContainerEntityManagerFactoryBean emf = builder
                .dataSource(multiDataSource())
                .persistenceUnit(MULTI_DATASOURCE_PU)
                .packages(ENTITY_PACKAGES)
                .build();
        return emf;
    }

    @Bean(TRANSACTION_MANAGER)
    public PlatformTransactionManager transactionManager(
            @Autowired @Qualifier(ENTITY_MANAGER) EntityManagerFactory entityManagerFactory) {
        JpaTransactionManager jtm = new JpaTransactionManager();
        jtm.setEntityManagerFactory(entityManagerFactory);
        //jtm.setDataSource(multiDataSource());
        return jtm;
    }
}

Settings to switch between test_dev1 and test_dev2

Implement the process of inheriting and switching the AbstractRoutingDataSource of Spring Framework.

RoutingDataSourceResolver


package com.example.datasource;

import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;

import static com.example.datasource.Dev1DataSourceConfigure.DEV1_DATASOURCE;
import static com.example.datasource.Dev2DataSourceConfigure.DEV2_DATASOURCE;

public class RoutingDataSourceResolver extends AbstractRoutingDataSource {

    @Override
    protected Object determineCurrentLookupKey() {
        if (MultiDataSourceContextHolder.getTenantType() == null) {
            return DEV1_DATASOURCE;
        }
        //Tenant and data source mapping
        switch (MultiDataSourceContextHolder.getTenantType()) {
            case TENANT_A:
                return DEV1_DATASOURCE;
            case TENANT_B:
                return DEV2_DATASOURCE;
            default:
                throw new RuntimeException("unknown tenant");
        }
    }
}

MultiDataSourceContextHolder


package com.example.datasource;

public class MultiDataSourceContextHolder {
    private static ThreadLocal<TenantType> contextHolder = new ThreadLocal<>();

    public static void setTenantType(TenantType tenantType) {
        if (tenantType == null) {
            throw new NullPointerException();
        }
        contextHolder.set(tenantType);
    }

    public static TenantType getTenantType() {
        return contextHolder.get();
    }

    public static void clearTenantType() {
        contextHolder.remove();
    }
}

Enum that manages the type of tenant.

TenantType


package com.example.datasource;

import java.util.Arrays;
import java.util.Optional;

public enum TenantType {
    /* test_dev1 */
    TENANT_A("aaa"),
    /* test_dev2 */
    TENANT_B("bbb")
    ;

    private final String tenantName;

    TenantType(String tenantName) {
        this.tenantName = tenantName;
    }

    public String getTenantName() {
        return this.tenantName;
    }

    public static TenantType byName(final String tenantName) {
        Optional<TenantType> tenantType = Arrays.stream(TenantType.values())
                .filter(t -> t.getTenantName().equals(tenantName))
                .findFirst();
        if (!tenantType.isPresent()) {
            throw new IllegalStateException("unknown tenant name : [" + tenantName + "]");
        }
        return tenantType.get();
    }
}

Switch data sources with AOP

There are several ways to switch data sources, but this sample application uses the Spring AOP feature. Set for the method with the argument "tenant" of the class with the following annotation. The data source is switched by the value of this argument called tenant.

SwitchingDataSource


package com.example.aop;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD, ElementType.TYPE})
public @interface SwitchingDataSource {
}

Adjust the Order annotation so that the data source is switched before the transaction. The point of implementation is

SwitchingDataSourceAop


package com.example.aop;

import com.example.datasource.MultiDataSourceContextHolder;
import com.example.datasource.TenantType;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

@Order(99)                                                                   // (1)
@Aspect
@Component
public class SwitchingDataSourceAop {

    @Around("@annotation(swds) && args(tenant,..)")                          // (2)
    public Object switchingForMethod(ProceedingJoinPoint pjp, SwitchingDataSource swds, String tenant) throws Throwable {
        try {
            switching(tenant);
            Object result = pjp.proceed();
            return result;
        } finally {
            clear();
        }
    }

    @Around("@within(swds) && args(tenant,..)")                              // (3)
    public Object switchingForClass(ProceedingJoinPoint pjp, SwitchingDataSource swds, String tenant) throws Throwable {
        try {
            switching(tenant);
            Object result = pjp.proceed();
            return result;
        } finally {
            clear();
        }
    }

    private void switching(String tenant) {
        TenantType tenantType = TenantType.byName(tenant);
        MultiDataSourceContextHolder.setTenantType(tenantType);
    }
    private void clear() {
        MultiDataSourceContextHolder.clearTenantType();
    }
}

Data source for test_dev3

Since there is no need to switch data sources common to applications, this class even implements entity manager and transaction manager. By the way, the Primary annotation is added so that this setting becomes the default.

SingleDataSourceConfigure


package com.example.datasource;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.autoconfigure.jdbc.DataSourceBuilder;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.orm.jpa.EntityManagerFactoryBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.JpaVendorAdapter;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.annotation.EnableTransactionManagement;

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

import java.util.Properties;

import static com.example.datasource.SingleDataSourceConfigure.ENTITY_MANAGER;
import static com.example.datasource.SingleDataSourceConfigure.REPOSITORY_PACKAGES;
import static com.example.datasource.SingleDataSourceConfigure.TRANSACTION_MANAGER;

@Configuration
@EnableTransactionManagement(order = 101)
@EnableJpaRepositories(
    basePackages = {REPOSITORY_PACKAGES},
    entityManagerFactoryRef = ENTITY_MANAGER,
    transactionManagerRef = TRANSACTION_MANAGER
)
public class SingleDataSourceConfigure {

    public static final String REPOSITORY_PACKAGES = "com.example.repository.appds";
    public static final String ENTITY_PACKAGES = "com.example.entity.appds";

    public static final String ENTITY_MANAGER = "entityManagerFactory";
    public static final String TRANSACTION_MANAGER = "transactionManager";

    public static final String SINGLE_DATASOURCE_PU = "singleDataSourcePersistenceUnit";
    public static final String SINGLE_DATASOURCE = "singleDataSource";

    @Primary
    @ConfigurationProperties(prefix = "spring.datasource.dev3")
    @Bean(SINGLE_DATASOURCE)
    public DataSource singleDataSource() {
        DataSource dataSource = DataSourceBuilder.create().build();
        return dataSource;
    }

    @Primary
    @Bean(ENTITY_MANAGER)
    public LocalContainerEntityManagerFactoryBean entityManagerFactory(
            EntityManagerFactoryBuilder builder) {

        LocalContainerEntityManagerFactoryBean emf = new LocalContainerEntityManagerFactoryBean();
        emf.setDataSource(singleDataSource());
        emf.setPersistenceUnitName(SINGLE_DATASOURCE_PU);
        emf.setPackagesToScan(ENTITY_PACKAGES);

        JpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
        emf.setJpaVendorAdapter(vendorAdapter);
        emf.setJpaProperties(additionalProperties());

        return emf;
    }

    @Primary
    @Bean(TRANSACTION_MANAGER)
    public PlatformTransactionManager transactionManager(
            @Autowired @Qualifier(ENTITY_MANAGER) EntityManagerFactory entityManagerFactory) {
        JpaTransactionManager jtm = new JpaTransactionManager();
        jtm.setEntityManagerFactory(entityManagerFactory);
        //jtm.setDataSource(singleDataSource());
        return jtm;
    }

    @Bean
    public PersistenceExceptionTranslationPostProcessor exceptionTranslation(){
        return new PersistenceExceptionTranslationPostProcessor();
    }

    private Properties additionalProperties() {
        Properties properties = new Properties();
        properties.setProperty("hibernate.show_sql", "true");
        properties.setProperty("hibernate.format_sql", "true");
        properties.setProperty("hibernate.use_sql_comments", "true");
        properties.setProperty("hibernate.generate_statistics", "false");
        return properties;
    }

}

Entities and repositories

As shown below, the tenant and application common packages are managed separately. Note that service classes higher than entities and repositories do not need to be separated because it is not necessary to separate packages.

com.example
  |
  +--- entity
  |      |
  |      +--- tenantds            //tenant datasource
  |      |      |
  |      |      +--- Todo
  |      |
  |      +--- appds               //application datasource
  |             |
  |             +--- Memo
  |
  +--- repository
  |      |
  |      +--- tenantds
  |      |      |
  |      |      +--- TodoRepository
  |      |
  |      +--- appds
  |             |
  |             +--- MemoRepository
  |
  +--- service
         |
         +--- impl
         |      |
         |      +--- TodoService
         |      +--- MemoService
         |
         +--- TodoServiceImpl
         +--- MemoServiceImpl

entity

There is nothing special about the implementation, just separate the packages.

Todo


package com.example.entity.tenantds;

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.SequenceGenerator;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import java.util.Date;

@Entity
@Table(name="todo")
@SequenceGenerator(name = "todo_id_gen", sequenceName = "todo_id_seq", allocationSize = 1)
@Data
@AllArgsConstructor
@NoArgsConstructor
@Builder
public class Todo {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @Column(name="title")
    private String title;
    @Column(name="done")
    private Boolean done;
    @Column(name="updated")
    @Temporal(TemporalType.TIMESTAMP)
    private Date updated;
}

Memo


package com.example.entity.appds;

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.SequenceGenerator;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import java.util.Date;

@Entity
@Table(name="memo")
@SequenceGenerator(name = "memo_id_gen", sequenceName = "memo_id_seq", allocationSize = 1)
@Data
@AllArgsConstructor
@NoArgsConstructor
@Builder
public class Memo {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @Column(name="title")
    private String title;
    @Column(name="description")
    private String description;
    @Column(name="done")
    private Boolean done;
    @Column(name="updated")
    @Temporal(TemporalType.TIMESTAMP)
    private Date updated;
}

Repository

TodoRepository


package com.example.repository.tenantds;

import com.example.entity.multids.Todo;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Lock;

import javax.persistence.LockModeType;

public interface TodoRepository extends JpaRepository<Todo, Long> {
    @Lock(LockModeType.PESSIMISTIC_WRITE)
    Todo findById(Long id);
}

MemoRepository


package com.example.repository.appds;

import com.example.entity.singleds.Memo;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Lock;

import javax.persistence.LockModeType;

public interface MemoRepository extends JpaRepository<Memo, Long> {
    @Lock(LockModeType.PESSIMISTIC_WRITE)
    Memo findById(Long id);
}

Controllers and services

controller

Switch the data source with the value of the request parameter "tenant".

Example


/todo/list?tenant=<Tenant code>

TodoController


package com.example.controller;

import com.example.entity.tenantds.Todo;
import com.example.service.TodoService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;

import java.util.Date;
import java.util.List;

@RequestMapping(path = "todo")
@RestController
public class TodoController {

    @Autowired
    private TodoService service;

    @GetMapping(path = "list", produces = MediaType.APPLICATION_JSON_UTF8_VALUE)
    @ResponseBody
    public List<Todo> list(
        @RequestParam(value = "tenant", required = true) String tenant) throws Exception {
        List<Todo> lists = service.list(tenant);
        return lists;
    }

    @GetMapping(path = "update", produces = MediaType.APPLICATION_JSON_UTF8_VALUE)
    @ResponseBody
    public Todo update(
        @RequestParam(value = "tenant", required = true) String tenant,
        @RequestParam(value = "id", required = true) Long id,
        @RequestParam(value = "title") String title,
        @RequestParam(value = "done", defaultValue = "FALSE") Boolean done,
        @RequestParam(value = "wt", defaultValue = "30") Long waittime) throws Exception {
        Todo todo = service.lockAndUpdate(tenant, id, title, done, new Date(), waittime);
        return todo;
    }

    @GetMapping(path = "insert", produces = MediaType.APPLICATION_JSON_UTF8_VALUE)
    @ResponseBody
    public Todo insert(
        @RequestParam(value = "tenant", required = true) String tenant,
        @RequestParam(name = "title", required = true) String title) throws Exception {
        Todo todo = service.insert(tenant, title, Boolean.FALSE, new Date());
        return todo;
    }
}

service

TodoService


package com.example.service;

import com.example.entity.tenantds.Todo;

import java.util.Date;
import java.util.List;

public interface TodoService {
    List<Todo> list(String tenant);
    Todo lockAndUpdate(String tenant, Long id, String title, Boolean done, Date updated, Long waittime) throws Exception;
    Todo insert(String tenant, String title, Boolean done, Date updated) throws Exception;
}

There are some points in the implementation.

(1) and (3) are the implementations required to switch data sources in AOP.

TodoServiceImpl


package com.example.service.impl;

import com.example.aop.SwitchingDataSource;
import com.example.entity.tenantds.Todo;
import com.example.repository.tenantds.TodoRepository;
import com.example.service.TodoService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Sort;
import org.springframework.data.domain.Sort.Order;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.util.Date;
import java.util.List;
import java.util.concurrent.TimeUnit;

import static com.example.datasource.MultiDataSourceConfigure.TRANSACTION_MANAGER;

@Service
@SwitchingDataSource                                                                         // (1)
@Transactional(readOnly = true, timeout = 10, transactionManager = TRANSACTION_MANAGER)      // (2)
public class TodoServiceImpl implements TodoService {

    @Autowired
    private TodoRepository repository;

    @Override
    public List<Todo> list(String tenant) {                                                  // (3)
        Sort sort = new Sort(new Order(Sort.Direction.DESC, "updated"), new Order(Sort.Direction.DESC, "id"));
        List<Todo> lists = repository.findAll(sort);
        return lists;
    }

    @Transactional(readOnly = false, timeout = 120, rollbackFor = Exception.class, transactionManager = TRANSACTION_MANAGER)
    @Override
    public Todo lockAndUpdate(String tenant, Long id, String title, Boolean done, Date updated, Long waittime) throws Exception {

        Todo todo = repository.findById(id);

        todo.setTitle(title);
        todo.setDone(done);
        todo.setUpdated(updated);

        //Time-out test code
        try {
            TimeUnit.SECONDS.sleep(waittime);
        } catch (InterruptedException e) {
            System.out.println("timeout:" + e.getMessage());
            throw new Exception("timeout");
        }

        repository.save(todo);

        return todo;
    }

    @Transactional(readOnly = false, rollbackFor = Exception.class, transactionManager = TRANSACTION_MANAGER)
    @Override
    public Todo insert(String tenant, String title, Boolean done, Date updated) throws Exception {
        Todo todo = Todo.builder().title(title).done(done).updated(updated).build();
        repository.save(todo);
        return todo;
    }
}

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