# Spring Boot 建立兩個 postgresql 連線
###### tags: `Spring` `jpa` `java` `postgresql`
## 專案架構
* com.zygroup.ilnd
* config
* CustomerConfig 第一個資料庫Config
* ProductConfig 第二個資料庫Config
* model 第一個資料表
* repository
* 資料表對應repository
* 資料表對應Entity
* modelTo 第二個資料表
* * repository
* 資料表對應repository
* 資料表對應Entity
* rest
* Server
* Controller
* resources
* application.properties
## application.properties 建立兩個連線

#第一個 DB
spring.datasource.jdbc-url=DB_HOST
spring.datasource.username=Username
spring.datasource.password=Password
spring.datasource.driverClassName=org.postgresql.Driver

#第二個 DB
dbto.datasource.jdbc-url=DB_HOST
dbto.datasource.username=Username
dbto.datasource.password=Password
dbto.datasource.driverClassName=org.postgresql.Driver

## 設定第一個資料表config

package com.zygroup.ilnd.config;

import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.jdbc.DataSourceBuilder;
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.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;

@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(
        entityManagerFactoryRef = "customerEntityManagerFactory",//對映(2)
        transactionManagerRef = "customerTransactionManager",//對映(3)
        basePackages = {
                "com.zygroup.ilnd.model.repository" //Repository所在路徑
        }
)
public class CustomerConfig {

    @Primary
    @Bean(name = "customerDataSource") //(1)自訂義定義 DataSource 名稱
    @ConfigurationProperties(prefix = "spring.datasource")//application.properties設定的資料庫連線前綴
    public DataSource customerDataSource() {
        return DataSourceBuilder.create().build();
    }

    @Primary
    @Bean(name = "customerEntityManagerFactory") //(2)自訂義定義EntityManagerFactory名稱
    public LocalContainerEntityManagerFactoryBean
    entityManagerFactory(
            EntityManagerFactoryBuilder builder,
            @Qualifier("customerDataSource") DataSource dataSource
    ) {
        return builder
                .dataSource(dataSource)
                .packages("com.zygroup.ilnd.model")//Model所在路徑
                .persistenceUnit("db1")
                .build();
    }

    @Primary
    @Bean(name = "customerTransactionManager") //(3)自訂義定義 TransactionManager 名稱
    public PlatformTransactionManager customerTransactionManager(
            @Qualifier("customerEntityManagerFactory") EntityManagerFactory customerEntityManagerFactory //對映(2)
    ) {
        return new JpaTransactionManager(customerEntityManagerFactory);//對映(2)
    }
}

## 設定第二個資料表config

package com.zygroup.ilnd.config;

import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.jdbc.DataSourceBuilder;
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;

@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(
        entityManagerFactoryRef = "productEntityManagerFactory",//對映(2)
        transactionManagerRef = "productTransactionManager",//對映(3)
        basePackages = {
                "com.zygroup.ilnd.modelTo.repository"//Repository所在路徑
        }
)
public class ProductConfig {

    @Bean(name = "productDataSource")//(1)自訂義定義 DataSource 名稱
    @ConfigurationProperties(prefix = "dbto.datasource")//application.properties設定的資料庫連線前綴
    public DataSource dataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean(name = "productEntityManagerFactory")//(2)自訂義定義
    public LocalContainerEntityManagerFactoryBean
    barEntityManagerFactory(
            EntityManagerFactoryBuilder builder,
            @Qualifier("productDataSource") DataSource dataSource
    ) {
        return
                builder
                        .dataSource(dataSource)
                        .packages("com.zygroup.ilnd.modelTo")//Model所在路徑
                        .persistenceUnit("db2")
                        .build();
    }

    @Bean(name = "productTransactionManager")//(3)自訂義定義 
    public PlatformTransactionManager productTransactionManager(
            @Qualifier("productEntityManagerFactory") EntityManagerFactory productEntityManagerFactory //對映(2)
    ) {
        return new JpaTransactionManager(productEntityManagerFactory);//對映(2)
    }
}

## 參考網址
>https://www.baeldung.com/spring-data-jpa-multiple-databases
>https://www.javadevjournal.com/spring-boot/multiple-data-sources-with-spring-boot/