1.概述
項目中經常會遇到一個應用需要訪問多個數據源的情況，本文介紹在SpringBoot項目中利用SpringDataJpa技術如何支持多個數據庫的數據源。
具體的代碼參照該 示例項目
2.建立實體類（Entity）
首先，我們創建兩個簡單的實體類，分別屬于兩個不同的數據源，用于演示多數據源數據的保存和查詢。
Test實體類：
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package com.example.demo.test.data;import javax.persistence.Entity;import javax.persistence.Id;import javax.persistence.Table;@Entity@Table(name = "test")public class Test { @Id private Integer id; public Test(){ } public Integer getId() { return this.id; } public void setId(Integer id){ this.id = id; }} |
Other實體類：
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package com.example.demo.other.data;import javax.persistence.Entity;import javax.persistence.Id;import javax.persistence.Table;@Entity@Table(name = "other")public class Other { @Id private Integer id; public Integer getId() { return this.id; } public void setId(Integer id){ this.id = id; }} |
需要注意的是，這兩個實體類分屬于不同的package，這一點極為重要，spring會根據實體類所屬的package來決定用那一個數據源進行操作。
3.建立Repository
分別建立兩個實體類對應的Repository，用于進行數據操作。
TestRepository:
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package com.example.demo.test.data;import org.springframework.data.jpa.repository.JpaRepository;public interface TestRepository extends JpaRepository<Test, Integer> {} |
OtherRepository:
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package com.example.demo.other.data;import org.springframework.data.jpa.repository.JpaRepository;public interface OtherRepository extends JpaRepository<Other, Integer> {} |
得益于spring-data-jpa優秀的封裝，我們只需創建一個接口，就擁有了對實體類的操作能力。
3.對多數據源進行配置
分別對Test和Other兩個實體類配置對應的數據源。配置的內容主要包含三個要素：
- dataSource，數據源的連接信息
- entityManagerFactory，數據處理
- transactionManager，事務管理
Test實體類的數據源配置 TestDataConfig：
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package com.example.demo.config;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.autoconfigure.orm.jpa.JpaProperties;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.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 = "entityManagerFactory", basePackages = {"com.example.demo.test.data"})public class TestDataConfig { @Autowired private JpaProperties jpaProperties; @Primary @Bean(name = "dataSource") @ConfigurationProperties(prefix = "spring.datasource") public DataSource dataSource() { return DataSourceBuilder.create().build(); } @Primary @Bean(name = "entityManagerFactory") public LocalContainerEntityManagerFactoryBean entityManagerFactory( EntityManagerFactoryBuilder builder, @Qualifier("dataSource") DataSource dataSource) { return builder .dataSource(dataSource) .packages("com.example.demo.test.data") .properties(jpaProperties.getHibernateProperties(dataSource)) .persistenceUnit("test") .build(); } @Primary @Bean(name = "transactionManager") public PlatformTransactionManager transactionManager( @Qualifier("entityManagerFactory") EntityManagerFactory entityManagerFactory) { return new JpaTransactionManager(entityManagerFactory); }} |
代碼中的Primary注解表示這是默認數據源。
Other實體類的數據源配置 OtherDataConfig：
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package com.example.demo.config;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.autoconfigure.orm.jpa.JpaProperties;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.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 = "otherEntityManagerFactory", transactionManagerRef = "otherTransactionManager", basePackages = {"com.example.demo.other.data"})public class OtherDataConfig { @Autowired private JpaProperties jpaProperties; @Bean(name = "otherDataSource") @ConfigurationProperties(prefix = "other.datasource") public DataSource otherDataSource() { return DataSourceBuilder.create().build(); } @Bean(name = "otherEntityManagerFactory") public LocalContainerEntityManagerFactoryBean otherEntityManagerFactory( EntityManagerFactoryBuilder builder, @Qualifier("otherDataSource") DataSource otherDataSource) { return builder .dataSource(otherDataSource) .packages("com.example.demo.other.data") .properties(jpaProperties.getHibernateProperties(otherDataSource)) .persistenceUnit("other") .build(); } @Bean(name = "otherTransactionManager") public PlatformTransactionManager otherTransactionManager( @Qualifier("otherEntityManagerFactory") EntityManagerFactory otherEntityManagerFactory) { return new JpaTransactionManager(otherEntityManagerFactory); }} |
3.數據操作
我們創建一個Service類TestService來分別對兩個數據源進行數據的操作。
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package com.example.demo.service;import com.example.demo.other.data.Other;import com.example.demo.other.data.OtherRepository;import com.example.demo.test.data.Test;import com.example.demo.test.data.TestRepository;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.beans.factory.annotation.Value;import org.springframework.stereotype.Component;@Componentpublic class TestService { @Autowired private TestRepository testRepository; @Autowired private OtherRepository otherRepository; @Value("${name:World}") private String name; public String getHelloMessage() { Test test = new Test(); test.setId(1); test = testRepository.save(test); Other other = new Other(); other.setId(2); other = otherRepository.save(other); return "Hello " + this.name + " : test's value = " + test.getId() + " , other's value = " + other.getId(); }} |
對Test和Other分別進行數據插入和讀取操作，程序運行后會打印出兩個數據源各自的數據。 數據庫采用的mysql，連接信息在application.yml進行配置。
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spring: datasource: url: jdbc:mysql://localhost:3306/test?characterEncoding=utf-8&useSSL=false testWhileIdle: true validationQuery: SELECT 1 from dual username: test password: 11111111 driverClassName: com.mysql.jdbc.Driver jpa: database: MYSQL show-sql: true hibernate: show-sql: true ddl-auto: create naming-strategy: org.hibernate.cfg.ImprovedNamingStrategy properties: hibernate.dialect: org.hibernate.dialect.MySQL5Dialectother: datasource: url: jdbc:mysql://localhost:3306/other?characterEncoding=utf-8&useSSL=false testWhileIdle: true validationQuery: SELECT 1 username: other password: 11111111 driverClassName: com.mysql.jdbc.Driver jpa: database: MYSQL show-sql: true hibernate: show-sql: true ddl-auto: create naming-strategy: org.hibernate.cfg.ImprovedNamingStrategy properties: hibernate.dialect: org.hibernate.dialect.MySQL5Dialect |
Test實體對應的是主數據源，采用了spring-boot的默認數據源配置項，Other實體單獨配置數據源連接。具體應該讀取哪一段配置內容，是在配置類OtherDataConfig中這行代碼指定的。
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@ConfigurationProperties(prefix = "other.datasource") |
本示例需要建立的數據庫用戶和庫可以通過以下命令處理：
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CREATE USER 'test'@'localhost' IDENTIFIED BY '11111111';GRANT ALL PRIVILEGES ON *.* TO 'test'@'localhost';CREATE USER 'other'@'localhost' IDENTIFIED BY '11111111';GRANT ALL PRIVILEGES ON *.* TO 'other'@'localhost';create database test;create database other; |
4.總結
spring-data-jpa極大的簡化了數據庫操作，對于多數據源的支持，也只是需要增加一下配置文件和配置類而已。其中的關鍵內容有3點：
- 配置文件中數據源的配置
- 配置類的編寫
- 實體類所在的package必須與配置類中指定的package一致，如OtherDataConfig中指定的basePackages = {"com.example.demo.other.data"}
以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持服務器之家。
原文鏈接：https://my.oschina.net/hiease/blog/1553763
