基于Spring boot輕松實(shí)現(xiàn)一個(gè)多數(shù)據(jù)源框架

作者：迷路的架構(gòu)師 2023-10-18 15:25:29

Spring Boot 提供了 Data JPA 的包，允許你使用類似 ORM 的接口連接到 RDMS。它很容易使用和實(shí)現(xiàn)，只需要在 pom.xml 中添加一個(gè)條目（如果使用的是 Maven，Gradle 則是在 build.gradle 文件中）。

<dependencies>
        <!-- Spring boot 依賴 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency> 
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
</dependencies>

在Main Spring Application類中添加 2 個(gè)注釋：

@SpringBootApplication
@EnableJpaRepositories
@EnableAutoConfiguration
public class SpringMainApplication {

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

最后添加一個(gè)數(shù)據(jù)庫(kù)連接包，配置數(shù)據(jù)庫(kù)連接即可實(shí)現(xiàn)與數(shù)據(jù)庫(kù)通信。

接下來(lái)，我們開(kāi)始配置多數(shù)據(jù)源連接。

注意：多個(gè)數(shù)據(jù)庫(kù)應(yīng)該具有相同的驅(qū)動(dòng)程序。無(wú)法連接到不同的數(shù)據(jù)庫(kù)，如 MySql 和 Postgres SQL 數(shù)據(jù)庫(kù)。數(shù)據(jù)庫(kù)必須相同。此外，數(shù)據(jù)庫(kù)模式必須相同，不同模式的 2 個(gè)數(shù)據(jù)庫(kù)無(wú)法進(jìn)行連接。

多數(shù)據(jù)源有哪些應(yīng)用場(chǎng)景？

1.支持具有相同模式的同一應(yīng)用程序內(nèi)的多租戶。

2.動(dòng)態(tài)模擬多個(gè)環(huán)境數(shù)據(jù)庫(kù)上的行為，而不需要重新啟動(dòng)應(yīng)用程序。例如，你可以動(dòng)態(tài)連接到開(kāi)發(fā)數(shù)據(jù)庫(kù)或 QA 數(shù)據(jù)庫(kù)，而無(wú)需重新啟動(dòng)應(yīng)用程序。

3.支持多個(gè)數(shù)據(jù)庫(kù)來(lái)模擬各種自動(dòng)化測(cè)試場(chǎng)景。不同數(shù)據(jù)庫(kù)可能具有不同的配置和靜態(tài)信息，意味著你可以用一個(gè)自動(dòng)化測(cè)試腳本覆蓋多個(gè)測(cè)試用例。

4.在同一個(gè)應(yīng)用程序中支持多個(gè)組織。根據(jù)用戶登錄，可以動(dòng)態(tài)決定他們的數(shù)據(jù)應(yīng)進(jìn)入哪個(gè)組織的數(shù)據(jù)庫(kù)。

5.一次性為多個(gè)數(shù)據(jù)庫(kù)插入數(shù)據(jù)。例如，你有一個(gè)從腳本創(chuàng)建數(shù)據(jù)的批處理作業(yè)，你可以一次性連接到多個(gè)數(shù)據(jù)庫(kù)，并對(duì)所有這些數(shù)據(jù)庫(kù)運(yùn)行腳本，而無(wú)需指向不同的應(yīng)用程序或重新啟動(dòng)服務(wù)器來(lái)執(zhí)行此操作。

多數(shù)據(jù)源示意圖如下：

第一步：添加 pom 依賴

<dependencies>
        <!-- Spring boot dependencies -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
        </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>

        <!-- Swagger dependencies -->
        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger2</artifactId>
            <version>2.9.2</version>
        </dependency>
        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger-ui</artifactId>
            <version>2.9.2</version>
        </dependency>

        <!-- lombok dependency -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.12</version>
            <scope>provided</scope>
        </dependency>

        <!-- Database dependency -->
        <dependency>
            <groupId>org.postgresql</groupId>
            <artifactId>postgresql</artifactId>
        </dependency>


        <!-- test dependencies -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-parent</artifactId>
                <version>${spring-cloud-dependencies.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-gcp-dependencies</artifactId>
                <version>${project.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

第二步：添加數(shù)據(jù)庫(kù)連接配置

app.datasource.db1.jdbc-url=jdbc:postgresql://db1.com:5432/dbname1
app.datasource.db1.username=postgres
app.datasource.db1.password=password

app.datasource.db2.jdbc-url=jdbc:postgresql://db2.com:5432/dbname2
app.datasource.db2.username=postgres
app.datasource.db2.password=password

app.datasource.db3.jdbc-url=jdbc:postgresql://db3.com:5432/dbname3
app.datasource.db3.username=postgres
app.datasource.db3.password=password

這是 3 個(gè)獨(dú)立的 PostgresSQL 實(shí)例，具有相同的模式但具有不同的數(shù)據(jù)。

第三步：添加多數(shù)據(jù)庫(kù)配置。

首先，在 Spring 應(yīng)用程序主文件中添加注解：

@SpringBootApplication
@EnableJpaRepositories
@EnableAutoConfiguration
public class MultidatabaseApplication {

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

添加配置類：

@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(
        entityManagerFactoryRef = "multiEntityManager",
        transactionManagerRef = "multiTransactionManager")
@EntityScan("com.sample.client.repositories.dto.entity")
public class DatabaseConfiguration {
    //添加 JPA 實(shí)體路徑
    private final String PACKAGE_SCAN = "com.sample.client.repositories.dto.entity";

    // 將db1設(shè)置為主數(shù)據(jù)庫(kù)
    @Primary
    @Bean(name = "db1DataSource")
    @ConfigurationProperties("app.datasource.db1")
    public DataSource db1DataSource() {
        return DataSourceBuilder.create().type(HikariDataSource.class).build();
    }

    //db2連接數(shù)據(jù)源注入
    @Bean(name = "db2DataSource")
    @ConfigurationProperties("app.datasource.db2")
    public DataSource db2DataSource() {
        return DataSourceBuilder.create().type(HikariDataSource.class).build();
    }
    //db3連接數(shù)據(jù)源注入
    @Bean(name = "db3DataSource")
    @ConfigurationProperties("app.datasource.db3")
    public DataSource db3DataSource() {
        return DataSourceBuilder.create().type(HikariDataSource.class).build();
    }

    //多數(shù)據(jù)源配置
    @Bean(name = "multiRoutingDataSource")
    public DataSource multiRoutingDataSource() {
        Map<Object, Object> targetDataSources = new HashMap<>();
        targetDataSources.put(ClientNames.DB1, db1DataSource());
        targetDataSources.put(ClientNames.DB2, db2DataSource());
        targetDataSources.put(ClientNames.DB3, db3DataSource());
        MultiRoutingDataSource multiRoutingDataSource 
            = new MultiRoutingDataSource();
        multiRoutingDataSource.setDefaultTargetDataSource(db1DataSource());
        multiRoutingDataSource.setTargetDataSources(targetDataSources);
        return multiRoutingDataSource;
    }

    //多實(shí)體配置代碼
    @Bean(name = "multiEntityManager")
    public LocalContainerEntityManagerFactoryBean multiEntityManager() {
        LocalContainerEntityManagerFactoryBean em 
            = new LocalContainerEntityManagerFactoryBean();
        em.setDataSource(multiRoutingDataSource());
        em.setPackagesToScan(PACKAGE_SCAN);
        HibernateJpaVendorAdapter vendorAdapter 
            = new HibernateJpaVendorAdapter();
        em.setJpaVendorAdapter(vendorAdapter);
        em.setJpaProperties(hibernateProperties());
        return em;
    }

    @Bean(name = "multiTransactionManager")
    public PlatformTransactionManager multiTransactionManager() {
        JpaTransactionManager transactionManager
                = new JpaTransactionManager();
        transactionManager.setEntityManagerFactory(
                multiEntityManager().getObject());
        return transactionManager;
    }

    @Primary
    @Bean(name="entityManagerFactory")
    public LocalSessionFactoryBean dbSessionFactory() {
        LocalSessionFactoryBean sessionFactoryBean = new LocalSessionFactoryBean();
        sessionFactoryBean.setDataSource(multiRoutingDataSource());
        sessionFactoryBean.setPackagesToScan(PACKAGE_SCAN);
        sessionFactoryBean.setHibernateProperties(hibernateProperties());
        return sessionFactoryBean;
    }

    //添加 hibernate 屬性
    private Properties hibernateProperties() {
        Properties properties = new Properties();
        properties.put("hibernate.show_sql", true);
        properties.put("hibernate.format_sql", true);
        properties.put("hibernate.dialect", "org.hibernate.dialect.PostgreSQLDialect");
        properties.put("hibernate.id.new_generator_mappings", false);
        properties.put("hibernate.jdbc.lob.non_contextual_creation", true);
        return properties;
    }
}

這樣就完成了我們的多數(shù)據(jù)庫(kù)配置。

com.sample.client.repositories.dto.entity — 此目錄包含 3 個(gè)數(shù)據(jù)庫(kù)通用的 JPA 實(shí)體。

MultiRoutingDataSource類是我們的實(shí)際實(shí)現(xiàn)，允許我們連接到多個(gè)數(shù)據(jù)庫(kù)

接下來(lái)，我們還需要一個(gè)DBContextHolder類來(lái)保存數(shù)據(jù)庫(kù)引用并在運(yùn)行時(shí)動(dòng)態(tài)更改數(shù)據(jù)庫(kù)。

public class DBContextHolder {
    private static final ThreadLocal<ClientNames> contextHolder = new ThreadLocal<>();
    public static void setCurrentDb(ClientNames dbType) {
        contextHolder.set(dbType);
    }
    public static ClientNames getCurrentDb() {
        return contextHolder.get();
    }
    public static void clear() {
        contextHolder.remove();
    }
}

ClientNames枚舉類如下：

public enum ClientNames {
    DB1, DB2, DB3
}

接下來(lái)我們需要對(duì)MultiRoutingDataSource進(jìn)行重寫(xiě)：

public class MultiRoutingDataSource extends AbstractRoutingDataSource {
    @Override
    protected Object determineCurrentLookupKey() {
        return DBContextHolder.getCurrentDb();
    }
}

determineCurrentLookupKey 方法用于決定應(yīng)用程序應(yīng)該動(dòng)態(tài)連接到哪個(gè)數(shù)據(jù)庫(kù)。

好了，我們的配置就完成了。接下來(lái)，我們測(cè)試下多數(shù)據(jù)源是否生效：

@RestController
@RequestMapping("/client")
public class ClientDataController {

    @Autowired
    private ClientMasterService clientMasterService;

    @GetMapping("/{clientdb}")
    public String findFromDatabase(@PathVariable String clientdbName) {
        return clientMasterService.getClientNames(clientdbName);
    }
}

ClientMasterService實(shí)現(xiàn)如下：

@Service
public class ClientMasterService {

    @Autowired
    private ClientMasterRepository clientMasterRepository;

    public String getClientNames(String client) {
        switch (client) {
            case "db1":
                DBContextHolder.setCurrentDb(ClientNames.DB1);
                break;
            case "db2":
                DBContextHolder.setCurrentDb(ClientNames.DB2);
                break;
            case "db3":
                DBContextHolder.setCurrentDb(ClientNames.DB3);
                break;
        }
        Entity1 e1 = clientMasterRepository.findByEntity1Name("John Doe");
        if(e1 != null) {
            return "found in database: " + client + " with id " + e1.getId();
        }
        return "found in " + client + " nada!";
    }
}

ClientMasterService使用DBContextHolder類根據(jù)從 Rest 端點(diǎn)傳入的數(shù)據(jù)庫(kù)名稱（db1、db2 或 db3）設(shè)置要指向的數(shù)據(jù)庫(kù)。

最后，編寫(xiě) JPA Repository 基礎(chǔ)代碼：

@Repository
public interface ClientMasterRepository extends JpaRepository<Entity1, String> {
    Entity1 findByEntity1Name(String name);
}

Entity1 類如下：

@Entity
@Table(name = "entity1")
@Getter
@Setter
public class Entity1 implements Serializable {
  @Id
  @Column(name = "id", nullable = false)
  private Integer id;
    
  @Column(name = "entity1Name")
  private String entity1Name; 
}

這樣就完成了整個(gè)多數(shù)據(jù)源的配置！！！