下面這個小項目展示了如何連接2個數(shù)據(jù)庫，一個是Oracle，一個是MySQL。

關(guān)鍵的Maven依賴：

<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-jpa</artifactId> </dependency><!-- https://mvnrepository.com/artifact/oracle/ojdbc6 --> <dependency><groupId>com.oracle</groupId><artifactId>ojdbc6</artifactId><version>11.2.0</version> </dependency><!-- Database and Pooling --> <dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId> </dependency>

這個Oracle的jar包是不再maven倉庫里面的，需要自己手動導(dǎo)入到maven倉庫。

application.properties的代碼如下：

#Oracle DB Config db.dialect=org.hibernate.dialect.Oracle10gDialect db.driver=oracle.jdbc.driver.OracleDriver db.url=jdbc:oracle:thin:@localhost:1521:xe db.user=pavans db.password=******#MySQL DB Config mysql.db.dialect=org.hibernate.dialect.MySQLDialect mysql.db.driver=com.mysql.jdbc.Driver mysql.db.url=jdbc:mysql://localhost:3306/localdb?useSSL=false mysql.db.user=lessroot mysql.db.password=******

所以，要定義2個dataSource的Bean，Spring需要知道那個dataSource是主要的，哪個是次要的。如果不去定義主次，那么Spring程序?qū)邮?。如果不定義主次，那么相同的bean，Spring是不能將其注冊的。

使用@Primary注解定義主要的dataSource的Bean。

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首要的DtaSource配置：

@Configuration @EnableTransactionManagement @EnableJpaRepositories(entityManagerFactoryRef = "entityManagerFactory", transactionManagerRef = "transactionManager", basePackages = "com.opencodez.dao.oracle.repo" ) public class PrimaryDbConfig {public static final String PROPERTY_NAME_HIBERNATE_JDBC_BATCH_SIZE = "hibernate.jdbc.batch_size";public static final String PROPERTY_NAME_HIBERNATE_SHOW_SQL = "hibernate.show_sql";public static final String PROPERTY_NAME_HIBERNATE_FMT_SQL = "hibernate.format_sql";public static final String[] ENTITYMANAGER_PACKAGES_TO_SCAN = { "com.opencodez.dao.oracle.domain" };public static final String DB_URL = "db.url";public static final String DB_USER = "db.user";public static final String DB_PASSWORD = "db.password";public static final String DB_DRIVER = "db.driver";public static final String DB_DIALECT = "db.dialect";@Autowiredprivate Environment env;@Beanpublic AnnotationMBeanExporter annotationMBeanExporter() {AnnotationMBeanExporter annotationMBeanExporter = new AnnotationMBeanExporter();annotationMBeanExporter.addExcludedBean("dataSource");annotationMBeanExporter.setRegistrationPolicy(RegistrationPolicy.IGNORE_EXISTING);return annotationMBeanExporter;}@Bean(destroyMethod = "close")@Primarypublic DataSource dataSource() {ComboPooledDataSource dataSource = new ComboPooledDataSource();try {dataSource.setDriverClass(env.getProperty(DB_DRIVER));} catch (PropertyVetoException e) {e.printStackTrace();}dataSource.setJdbcUrl(env.getProperty(DB_URL));dataSource.setUser(env.getProperty(DB_USER));dataSource.setPassword(env.getProperty(DB_PASSWORD));dataSource.setAcquireIncrement(5);dataSource.setMaxStatementsPerConnection(20);dataSource.setMaxStatements(100);dataSource.setMaxPoolSize(500);dataSource.setMinPoolSize(5);return dataSource;}@Bean(name = "transactionManager")@Primarypublic JpaTransactionManager jpaTransactionManager() {JpaTransactionManager transactionManager = new JpaTransactionManager();transactionManager.setEntityManagerFactory(entityManagerFactoryBean().getObject());return transactionManager;}@Bean(name = "entityManagerFactory")@Primarypublic LocalContainerEntityManagerFactoryBean entityManagerFactoryBean() {LocalContainerEntityManagerFactoryBean entityManagerFactoryBean = new LocalContainerEntityManagerFactoryBean();entityManagerFactoryBean.setJpaVendorAdapter(vendorAdaptor());entityManagerFactoryBean.setDataSource(dataSource());entityManagerFactoryBean.setPersistenceProviderClass(HibernatePersistenceProvider.class);entityManagerFactoryBean.setPersistenceUnitManager(persistenceUnitManager());entityManagerFactoryBean.setPersistenceUnitName("orcl");entityManagerFactoryBean.setPackagesToScan(ENTITYMANAGER_PACKAGES_TO_SCAN);entityManagerFactoryBean.setJpaProperties(jpaHibernateProperties());return entityManagerFactoryBean;}@Bean@Primarypublic DefaultPersistenceUnitManager persistenceUnitManager() {DefaultPersistenceUnitManager persistenceUnitManager = new DefaultPersistenceUnitManager();persistenceUnitManager.setDefaultDataSource(dataSource());return persistenceUnitManager;}private HibernateJpaVendorAdapter vendorAdaptor() {HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();vendorAdapter.setDatabasePlatform(env.getProperty(DB_DIALECT));vendorAdapter.setShowSql(false);return vendorAdapter;}private Properties jpaHibernateProperties() {Properties properties = new Properties();properties.put(PROPERTY_NAME_HIBERNATE_FMT_SQL, env.getProperty(PROPERTY_NAME_HIBERNATE_FMT_SQL));properties.put(PROPERTY_NAME_HIBERNATE_JDBC_BATCH_SIZE, env.getProperty(PROPERTY_NAME_HIBERNATE_JDBC_BATCH_SIZE));properties.put(PROPERTY_NAME_HIBERNATE_SHOW_SQL, env.getProperty(PROPERTY_NAME_HIBERNATE_SHOW_SQL));return properties;} }

這里有幾個關(guān)鍵地方：

1. dataSource要加上@Primary注解；

2. entityMananger也要加上@Primary注解；

3. persistenceUnitManager同樣也要加上@Primary

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次要DataSource源配置：

@Configuration @EnableTransactionManagement @EnableJpaRepositories(entityManagerFactoryRef = "mysqlEntityManager", transactionManagerRef = "mysqlTransactionManager", basePackages = "com.opencodez.dao.mysql.repo" ) public class SecondaryDbConfig {public static final String PROPERTY_NAME_HIBERNATE_JDBC_BATCH_SIZE = "hibernate.jdbc.batch_size";public static final String PROPERTY_NAME_HIBERNATE_SHOW_SQL = "hibernate.show_sql";public static final String PROPERTY_NAME_HIBERNATE_FMT_SQL = "hibernate.format_sql";public static final String[] ENTITYMANAGER_PACKAGES_TO_SCAN = { "com.opencodez.dao.mysql.domain" };public static final String DB_URL = "mysql.db.url";public static final String DB_USER = "mysql.db.user";public static final String DB_PASSWORD = "mysql.db.password";public static final String DB_DRIVER = "mysql.db.driver";public static final String DB_DIALECT = "mysql.db.dialect";@Autowiredprivate Environment env;@Beanpublic AnnotationMBeanExporter annotationMBeanExporter() {AnnotationMBeanExporter annotationMBeanExporter = new AnnotationMBeanExporter();annotationMBeanExporter.addExcludedBean("dataSource");annotationMBeanExporter.setRegistrationPolicy(RegistrationPolicy.IGNORE_EXISTING);return annotationMBeanExporter;}@Bean(name = "mysqlDataSource", destroyMethod = "close")public DataSource dataSource() {ComboPooledDataSource dataSource = new ComboPooledDataSource();try {dataSource.setDriverClass(env.getProperty(DB_DRIVER));} catch (PropertyVetoException e) {e.printStackTrace();}dataSource.setJdbcUrl(env.getProperty(DB_URL));dataSource.setUser(env.getProperty(DB_USER));dataSource.setPassword(env.getProperty(DB_PASSWORD));dataSource.setAcquireIncrement(5);dataSource.setMaxStatementsPerConnection(20);dataSource.setMaxStatements(100);dataSource.setMaxPoolSize(500);dataSource.setMinPoolSize(5);return dataSource;}@Bean(name = "mysqlTransactionManager")public JpaTransactionManager jpaTransactionManager() {JpaTransactionManager transactionManager = new JpaTransactionManager();transactionManager.setEntityManagerFactory(entityManagerFactoryBean().getObject());return transactionManager;}@Bean(name = "mysqlEntityManager")public LocalContainerEntityManagerFactoryBean entityManagerFactoryBean() {LocalContainerEntityManagerFactoryBean entityManagerFactoryBean = new LocalContainerEntityManagerFactoryBean();entityManagerFactoryBean.setJpaVendorAdapter(vendorAdaptor());entityManagerFactoryBean.setDataSource(dataSource());entityManagerFactoryBean.setPersistenceProviderClass(HibernatePersistenceProvider.class);entityManagerFactoryBean.setPersistenceUnitManager(persistenceUnitManager());entityManagerFactoryBean.setPersistenceUnitName("mysql");entityManagerFactoryBean.setPackagesToScan(ENTITYMANAGER_PACKAGES_TO_SCAN);entityManagerFactoryBean.setJpaProperties(jpaHibernateProperties());return entityManagerFactoryBean;}@Bean(name = "mysqlpersistenceUnitManager")public DefaultPersistenceUnitManager persistenceUnitManager() {DefaultPersistenceUnitManager persistenceUnitManager = new DefaultPersistenceUnitManager();persistenceUnitManager.setDefaultDataSource(dataSource());return persistenceUnitManager;}private HibernateJpaVendorAdapter vendorAdaptor() {HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();vendorAdapter.setDatabasePlatform(env.getProperty(DB_DIALECT));vendorAdapter.setShowSql(false);return vendorAdapter;}private Properties jpaHibernateProperties() {Properties properties = new Properties();properties.put(PROPERTY_NAME_HIBERNATE_FMT_SQL, env.getProperty(PROPERTY_NAME_HIBERNATE_FMT_SQL));properties.put(PROPERTY_NAME_HIBERNATE_JDBC_BATCH_SIZE,env.getProperty(PROPERTY_NAME_HIBERNATE_JDBC_BATCH_SIZE));properties.put(PROPERTY_NAME_HIBERNATE_SHOW_SQL, env.getProperty(PROPERTY_NAME_HIBERNATE_SHOW_SQL));return properties;} }

這里配置類，無需@Primary注解，但是@Bean中的name需要唯一。

這樣就完成了數(shù)據(jù)庫的配置，下面定義2個Java類，用于映射數(shù)據(jù)庫表，一個是TblOracle，一個是TblMysql。

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TblOracle

@Entity @Table(name = "TBL_ORCL") public class TblOracle {@Id@GeneratedValue@Column(name = "MESSAGE_ID")private Long id;@Column(name = "MESSAGE")private String message;@Column(name = "CREATED_DATE")private Date created;//Getters and Setters}

TblMysql

@Entity @Table(name = "tbl_mysql") public class TblMysql {@Id@GeneratedValue@Column(name = "MESSAGE_ID")private Long id;@Column(name = "MESSAGE")private String message;@Column(name = "CREATED_DATE")private Date created;//Getters and Setters}

對應(yīng)的persistence.xml如下：

<?xml version="1.0" encoding="UTF-8"?> <persistence xmlns="http://java.sun.com/xml/ns/persistence"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"version="1.0"><persistence-unit name="orcl" transaction-type="RESOURCE_LOCAL"><class>com.opencodez.dao.oracle.domain.TblOracle</class><exclude-unlisted-classes>true</exclude-unlisted-classes></persistence-unit><persistence-unit name="mysql" transaction-type="RESOURCE_LOCAL"><class>com.opencodez.dao.mysql.domain.TblMysql</class><exclude-unlisted-classes>true</exclude-unlisted-classes></persistence-unit></persistence>

在此事例中，定義了相同的controller，這些controller調(diào)用了Spring Data JPA中的Repositories。

倉庫聲明如下：

@Autowired private OracleMessageRepo oracleMessageRepo;@Autowired private MysqlMessageRepo mysqlMessageRepo;

調(diào)用如下：

List<TblOracle> messages = oracleMessageRepo.findAll();List<TblMysql> messages = mysqlMessageRepo.findAll();

上面是使用JPA的方式存儲，如果要使用傳統(tǒng)的實體管理，需要這樣：

@Autowired @Qualifier("entityManagerFactory") private EntityManager oracleEM;@Autowired @Qualifier("mysqlEntityManager") private EntityManager mysqlEM;

這里需要自己提供檢索條件，如下事例：

try {String sql = "select t from TblOracle t";Query query = oracleEM.createQuery(sql);List<TblOracle> list =(List<TblOracle>)query.getResultList( );} catch (Exception e) {e.printStackTrace(); }try {String sql = "select t from TblMysql t";Query query = mysqlEM.createQuery(sql);List<TblMysql> list=(List<TblMysql>)query.getResultList( );} catch (Exception e) {e.printStackTrace(); }

下面是調(diào)用了，運行截圖如下：

總結(jié)：本次實例展示了如何使用Spring Data JPA輕松配置多源數(shù)據(jù)庫。

創(chuàng)庫代碼如下：

https://github.com/pavansolapure/opencodez-samples/tree/master/multi-db

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