在現(xiàn)代微服務架構(gòu)中，通常需要與多個數(shù)據(jù)庫交互的服務。這可能是由于各種原因，例如遺留系統(tǒng)集成、不同類型的數(shù)據(jù)存儲需求，或者僅僅是為了優(yōu)化性能。Spring Boot 具有靈活的配置和強大的數(shù)據(jù)訪問庫，可以輕松配置多個數(shù)據(jù)庫。在本綜合指南中，我們將探討如何在 Spring Boot 微服務中設置和管理多個數(shù)據(jù)庫連接。

1. 簡介

微服務通常需要與各種數(shù)據(jù)庫交互。每個微服務可能需要不同類型的數(shù)據(jù)庫，例如用于事務數(shù)據(jù)的 SQL 數(shù)據(jù)庫和用于非結(jié)構(gòu)化數(shù)據(jù)的 NoSQL 數(shù)據(jù)庫。Spring Boot 為配置和管理多個數(shù)據(jù)源提供了出色的支持，使其成為現(xiàn)代微服務架構(gòu)的理想選擇。

2.為什么要使用多個數(shù)據(jù)庫？

您可能需要在微服務中使用多個數(shù)據(jù)庫的原因如下：

• 遺留系統(tǒng)集成：與遺留系統(tǒng)的現(xiàn)有數(shù)據(jù)庫集成。
• 優(yōu)化性能：使用針對特定類型的數(shù)據(jù)（例如關系型與非關系型）優(yōu)化的不同數(shù)據(jù)庫。
• 數(shù)據(jù)隔離：出于安全、合規(guī)或組織原因分離數(shù)據(jù)。
• 可擴展性：在不同的數(shù)據(jù)庫之間分配數(shù)據(jù)負載以提高性能。

3.設置 Spring Boot 項目

首先，創(chuàng)建一個新的 Spring Boot 項目。您可以使用 Spring Initializr 或您喜歡的 IDE 來設置項目。

Maven 依賴項

在您的 中pom.xml包含 Spring Data JPA 和您將使用的數(shù)據(jù)庫的依賴項（例如，內(nèi)存中的 H2、PostgreSQL、MySQL 等）。

<dependencies><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>com.h2database</groupId><artifactId>h2</artifactId><scope>runtime</scope></dependency><dependency><groupId>org.postgresql</groupId><artifactId>postgresql</artifactId><scope>runtime</scope></dependency>
</dependencies>

4.配置多個數(shù)據(jù)源

在application.yml或application.properties文件中，配置每個數(shù)據(jù)庫的連接屬性。

application.yml

spring:datasource:primary:url: jdbc:h2:mem:primarydbdriver-class-name: org.h2.Driverusername: sapassword: passwordsecondary:url: jdbc:postgresql://localhost:5432/secondarydbdriver-class-name: org.postgresql.Driverusername: postgrespassword: password
jpa:primary:database-platform: org.hibernate.dialect.H2Dialecthibernate:ddl-auto: updatesecondary:database-platform: org.hibernate.dialect.PostgreSQLDialecthibernate:ddl-auto: update

5.創(chuàng)建數(shù)據(jù)源配置類

接下來，為每個數(shù)據(jù)源創(chuàng)建單獨的配置類。

主數(shù)據(jù)源配置

package com.example.config;
import org.springframework.beans.factory.annotation.Qualifier;
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.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter;
import org.springframework.transaction.PlatformTransactionManager;
import javax.persistence.EntityManagerFactory;
import javax.sql.DataSource;
@Configuration
@EnableJpaRepositories(basePackages = "com.example.primary.repository",entityManagerFactoryRef = "primaryEntityManagerFactory",transactionManagerRef = "primaryTransactionManager"
)
public class PrimaryDataSourceConfig {@Bean(name = "primaryDataSource")@ConfigurationProperties(prefix = "spring.datasource.primary")public DataSource primaryDataSource() {return DataSourceBuilder.create().build();}@Bean(name = "primaryEntityManagerFactory")public LocalContainerEntityManagerFactoryBean primaryEntityManagerFactory(@Qualifier("primaryDataSource") DataSource dataSource) {LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();em.setDataSource(dataSource);em.setPackagesToScan(new String[] { "com.example.primary.entity" });HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();em.setJpaVendorAdapter(vendorAdapter);return em;}@Bean(name = "primaryTransactionManager")public PlatformTransactionManager primaryTransactionManager(@Qualifier("primaryEntityManagerFactory") EntityManagerFactory entityManagerFactory) {return new JpaTransactionManager(entityManagerFactory);}
}

輔助數(shù)據(jù)源配置

package com.example.config;
import org.springframework.beans.factory.annotation.Qualifier;
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.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter;
import org.springframework.transaction.PlatformTransactionManager;
import javax.persistence.EntityManagerFactory;
import javax.sql.DataSource;
@Configuration
@EnableJpaRepositories(basePackages = "com.example.secondary.repository",entityManagerFactoryRef = "secondaryEntityManagerFactory",transactionManagerRef = "secondaryTransactionManager"
)
public class SecondaryDataSourceConfig {@Bean(name = "secondaryDataSource")@ConfigurationProperties(prefix = "spring.datasource.secondary")public DataSource secondaryDataSource() {return DataSourceBuilder.create().build();}@Bean(name = "secondaryEntityManagerFactory")public LocalContainerEntityManagerFactoryBean secondaryEntityManagerFactory(@Qualifier("secondaryDataSource") DataSource dataSource) {LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();em.setDataSource(dataSource);em.setPackagesToScan(new String[] { "com.example.secondary.entity" });HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();em.setJpaVendorAdapter(vendorAdapter);return em;}@Bean(name = "secondaryTransactionManager")public PlatformTransactionManager secondaryTransactionManager(@Qualifier("secondaryEntityManagerFactory") EntityManagerFactory entityManagerFactory) {return new JpaTransactionManager(entityManagerFactory);}
}

6. 定義實體管理器

為每個數(shù)據(jù)庫定義實體類。確保將它們放在配置類中指定的相應包中。

主數(shù)據(jù)庫實體

package com.example.primary.entity;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
@Entity
public class PrimaryEntity {@Id@GeneratedValue(strategy = GenerationType.IDENTITY)private Long id;private String name;// getters and setters
}

輔助數(shù)據(jù)庫實體

package com.example.secondary.entity;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
@Entity
public class SecondaryEntity {@Id@GeneratedValue(strategy = GenerationType.IDENTITY)private Long id;private String description;// getters and setters
}

7. 創(chuàng)建存儲庫

為每個數(shù)據(jù)庫創(chuàng)建存儲庫接口，確保它們按照配置放置在正確的包中。

主存儲庫

package com.example.primary.repository;
import com.example.secondary.entity.SecondaryEntity;
import org.springframework.data.jpa.repository.JpaRepository;
public interface SecondaryRepository extends JpaRepository<SecondaryEntity, Long> {
}

二級存儲庫

package com.example.secondary.repository;
import com.example.secondary.entity.SecondaryEntity;
import org.springframework.data.jpa.repository.JpaRepository;
public interface SecondaryRepository extends JpaRepository<SecondaryEntity, Long> {
}

8.測試配置

最后，創(chuàng)建一個簡單的 REST 控制器來測試設置。此控制器將使用兩個存儲庫來執(zhí)行 CRUD 操作。

package com.example.controller;
import com.example.primary.entity.PrimaryEntity;
import com.example.primary.repository.PrimaryRepository;
import com.example.secondary.entity.SecondaryEntity;
import com.example.secondary.repository.SecondaryRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class TestController {@Autowiredprivate PrimaryRepository primaryRepository;@Autowiredprivate SecondaryRepository secondaryRepository;@GetMapping("/test")public String test() {PrimaryEntity primaryEntity = new PrimaryEntity();primaryEntity.setName("Primary Entity");primaryRepository.save(primaryEntity);SecondaryEntity secondaryEntity = new SecondaryEntity();secondaryEntity.setDescription("Secondary Entity");secondaryRepository.save(secondaryEntity);return "Entities saved!";}
}