Spring Data JPA的多数据源及分布式事务实现

一.Spring data JPA的多数据源实现

将数据源对象作为参数，传递到调用方法内部，这种方式增加额外的编码。
将Repository操作接口分包存放，Spring扫描不同的包，自动注入不同的数据源。这种方式实现简单，也是一种“约定大于配置”思想的典型应用。
使用Spring AOP面向切面编程，然后在持久层接口方法上面加注解，不同的注解使用表示使用不同的数据源。

本文将以第二种方式实现JPA的多数据源支持。

1.1 修改application.yml配置多数据源

配置2个数据源，primary数据源：testdb数据库，secondary数据源：testdb2数据库。

spring:
  datasource:
    primary:
      jdbc-url: jdbc:mysql://localhost:3306/testdb?useUnicode=true&characterEncoding=utf-8&useSSL=false
      username: root
      password: root
      driver-class-name: com.mysql.cj.jdbc.Driver
    secondary:
      jdbc-url: jdbc:mysql://localhost:3306/testdb2?useUnicode=true&characterEncoding=utf-8&useSSL=false
      username: root
      password: root
      driver-class-name: com.mysql.cj.jdbc.Driver
  jpa:
    database-platform: org.hibernate.dialect.MySQL5InnoDBDialect
    hibernate:
      ddl-auto: update
    database: mysql
    show-sql: true

testdb数据库中存在article表，testdb2中存在comment表

1.2 testdb数据库的数据持久层配置

创建cn.lsp.springboot.model.testdb包，将Article实体放入此包中；
创建cn.lsp.springboot.repository.testdb包，将ArticleRepository放入此包中；
testdb数据库的JPA数据持久层配置,需要配置：

DataSource数据源
EntityManager 实体管理器
EntityManagerFactoryBean 实体管理器工厂
PlatformTransactionManager 事务管理器

import org.springframework.boot.autoconfigure.orm.jpa.HibernateProperties;
import org.springframework.boot.autoconfigure.orm.jpa.HibernateSettings;
import org.springframework.boot.autoconfigure.orm.jpa.JpaProperties;
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.annotation.Resource;
import javax.persistence.EntityManager;
import javax.sql.DataSource;
import java.util.Map;

@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(
        entityManagerFactoryRef="entityManagerFactoryPrimary",
        transactionManagerRef="transactionManagerPrimary",
        basePackages= {"cn.lsp.springboot.repository.testdb"})
public class JPAPrimaryConfig2 {

    @Resource
    private JpaProperties jpaProperties;

    @Resource
    private HibernateProperties hibernateProperties;

    @Primary
    @Bean(name = "primaryDataSource")
    @ConfigurationProperties(prefix="spring.datasource.primary")  //使用application.yml的primary数据源配置
    public DataSource primaryDataSource() {
        return DataSourceBuilder.create().build();
    }

    @Primary
    @Bean(name = "entityManagerPrimary")        //primary实体管理器
    public EntityManager entityManager(EntityManagerFactoryBuilder builder) {
         return entityManagerFactoryPrimary(builder).getObject().createEntityManager();
    }

    @Primary
    @Bean(name = "entityManagerFactoryPrimary")    //primary实体工厂
    public LocalContainerEntityManagerFactoryBean entityManagerFactoryPrimary (EntityManagerFactoryBuilder builder) {

        Map<String,Object> properties =
                hibernateProperties.determineHibernateProperties(
                        jpaProperties.getProperties(),
                        new HibernateSettings());
        return builder.dataSource(primaryDataSource())
                .properties(properties)
                .packages("cn.lsp.springboot.model.testdb")
                .persistenceUnit("primaryPersistenceUnit")
                .build();
    }

    @Primary
    @Bean(name = "transactionManagerPrimary")         //primary事务管理器
    public PlatformTransactionManager transactionManagerPrimary(EntityManagerFactoryBuilder builder) {
        return new JpaTransactionManager(entityManagerFactoryPrimary(builder).getObject());
    }
}

1.3 testdb2数据库的数据持久层配置

创建cn.lsp.springboot.model.testdb2包，将Comment实体放入此包中；
创建cn.lsp.springboot.repository.testdb2包，将CommentRepository放入此包中；
testdb2数据库的JPA数据持久层配置，因为这一组配置不是默认配置，该组数据源不是默认数据源，没有@Primary注解。

import org.springframework.boot.autoconfigure.orm.jpa.HibernateProperties;
import org.springframework.boot.autoconfigure.orm.jpa.HibernateSettings;
import org.springframework.boot.autoconfigure.orm.jpa.JpaProperties;
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 java.util.Map;

import javax.annotation.Resource;
import javax.persistence.EntityManager;
import javax.sql.DataSource;

@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(
        entityManagerFactoryRef="entityManagerFactorySecondary",
        transactionManagerRef="transactionManagerSecondary",
        basePackages= { "cn.lsp.springboot.repository.testdb2" })
public class JPASecondaryConfig {

    @Resource
    private JpaProperties jpaProperties;

    @Resource
    private HibernateProperties hibernateProperties;

    @Bean(name = "secondaryDataSource")
    @ConfigurationProperties(prefix="spring.datasource.secondary")   //使用application.yml的secondary数据源配置
    public DataSource secondaryDataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean(name = "entityManagerSecondary")      //secondary实体管理器
    public EntityManager entityManager(EntityManagerFactoryBuilder builder) {
        return entityManagerFactorySecondary(builder).getObject().createEntityManager();
    }


    @Bean(name = "entityManagerFactorySecondary")
    public LocalContainerEntityManagerFactoryBean entityManagerFactorySecondary (EntityManagerFactoryBuilder builder) {

        Map<String,Object> properties =
                hibernateProperties.determineHibernateProperties(
                        jpaProperties.getProperties(),
                        new HibernateSettings());
        return builder
                .dataSource(secondaryDataSource())
                .properties(properties)
                .packages("cn.lsp.springboot.model.testdb2")
                .persistenceUnit("secondaryPersistenceUnit")
                .build();
    }

    @Bean(name = "transactionManagerSecondary")
    PlatformTransactionManager transactionManagerSecondary(EntityManagerFactoryBuilder builder) {
        return new JpaTransactionManager(entityManagerFactorySecondary(builder).getObject());
    }
}

1.4 多数据源测试

@Slf4j
@SpringBootTest
public class JpaJtaTest {

    @Resource
    private ArticleRepository articleRepository;

    @Resource
    private CommentRepository commentRepository;

    @Test
    public void testJpaJta(){
        Article article = new Article();
        article.setTitle("SpringBoot实战");
        article.setContent("详细介绍SpringBoot的各种姿势");
        article.setAuthor("William");
        article.setCreateTime(new Date());
        Article savedArticle = articleRepository.save(article);

        Comment comment = new Comment();
        comment.setName("Tom");
        comment.setContent("内容详实，偏实战");
        comment.setCreateTime(new Date());
        comment.setArticleId(savedArticle.getId());
        commentRepository.save(comment);
    }
}

二.JPA+atomikos实现分布式事务

2.1整合JTA(atomikos)

通过maven坐标引入JTA atomikos。

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-jta-atomikos</artifactId>
</dependency>

在第一节的配置基础上，把jdbc-url改成url，然后在spring前缀下面加:

spring:
  jta:
    atomikos:
      datasource:
        max-pool-size: 20
        borrow-connection-timeout: 60
      connectionfactory:
        max-pool-size: 20
        borrow-connection-timeout: 60

max-pool-size表示数据连接池最大连接数，请根据自己的应用规模进行调整
borrow-connection-timeout表示连接从连接池“借出”之后的超时时间，超时将抛出异常

2.2分布式事务管理器

删掉第一节的数据源配置及事务配置代码，加入如下代码，AtomikosJtaPlatform为固定代码不需修改；

public class AtomikosJtaPlatform extends AbstractJtaPlatform {

    private static final long serialVersionUID = 1L;

    static TransactionManager transactionManager;
    static UserTransaction transaction;

    @Override
    protected TransactionManager locateTransactionManager() {
        return transactionManager;
    }

    @Override
    protected UserTransaction locateUserTransaction() {
        return transaction;
    }
}

事务管理器的配置JPAAtomikosTransactionConfig ，以下除了设置JPA特性的部分，为固定代码不需修改;

@Configuration
@ComponentScan
@EnableTransactionManagement
public class JPAAtomikosTransactionConfig {

    @Bean
    public PropertySourcesPlaceholderConfigurer propertySourcesPlaceholderConfigurer() {
        return new PropertySourcesPlaceholderConfigurer();
    }

    //设置JPA特性
    @Bean
    public JpaVendorAdapter jpaVendorAdapter() {
        HibernateJpaVendorAdapter hibernateJpaVendorAdapter = new HibernateJpaVendorAdapter();
        //显示sql
        hibernateJpaVendorAdapter.setShowSql(true);
        //自动生成/更新表
        hibernateJpaVendorAdapter.setGenerateDdl(true);
        //设置数据库类型
        hibernateJpaVendorAdapter.setDatabase(Database.MYSQL);
        return hibernateJpaVendorAdapter;
    }

    @Bean(name = "userTransaction")
    public UserTransaction userTransaction() throws Throwable {
        UserTransactionImp userTransactionImp = new UserTransactionImp();
        userTransactionImp.setTransactionTimeout(10000);
        return userTransactionImp;
    }

    @Bean(name = "atomikosTransactionManager", initMethod = "init", destroyMethod = "close")
    public TransactionManager atomikosTransactionManager() throws Throwable {
        UserTransactionManager userTransactionManager = new UserTransactionManager();
        userTransactionManager.setForceShutdown(false);
        AtomikosJtaPlatform.transactionManager = userTransactionManager;
        return userTransactionManager;
    }

    @Bean(name = "transactionManager")
    @DependsOn({"userTransaction", "atomikosTransactionManager"})
    public PlatformTransactionManager transactionManager() throws Throwable {
        UserTransaction userTransaction = userTransaction();
        AtomikosJtaPlatform.transaction = userTransaction;
        TransactionManager atomikosTransactionManager = atomikosTransactionManager();
        return new JtaTransactionManager(userTransaction, atomikosTransactionManager);
    }

}

2.3数据源及实体管理配置(多数据源多份)

设置第一个数据库的primary数据源及实体扫描管理(扫描testdb目录)，实体管理器、数据源都要加上primary，以示区分:

@Configuration
@DependsOn("transactionManager")
@EnableJpaRepositories(basePackages = "cn.lsp.springboot.repository.testdb",  //注意这里
        entityManagerFactoryRef = "primaryEntityManager",
        transactionManagerRef = "transactionManager")
public class JPAPrimaryConfig {
    @Autowired
    private JpaVendorAdapter jpaVendorAdapter;

    //primary
    @Primary
    @Bean(name = "primaryDataSourceProperties")
    @ConfigurationProperties(prefix = "spring.datasource.primary")     //注意这里
    public DataSourceProperties primaryDataSourceProperties() {
        return new DataSourceProperties();
    }

    @Primary
    @Bean(name = "primaryDataSource", initMethod = "init", destroyMethod = "close")
    @ConfigurationProperties(prefix = "spring.datasource.primary")
    public DataSource primaryDataSource() throws SQLException {
        MysqlXADataSource mysqlXaDataSource = new MysqlXADataSource();
        mysqlXaDataSource.setUrl(primaryDataSourceProperties().getUrl());
        mysqlXaDataSource.setPinGlobalTxToPhysicalConnection(true);
        mysqlXaDataSource.setPassword(primaryDataSourceProperties().getPassword());
        mysqlXaDataSource.setUser(primaryDataSourceProperties().getUsername());
        AtomikosDataSourceBean xaDataSource = new AtomikosDataSourceBean();
        xaDataSource.setXaDataSource(mysqlXaDataSource);
        xaDataSource.setUniqueResourceName("primary");
        xaDataSource.setBorrowConnectionTimeout(60);
        xaDataSource.setMaxPoolSize(20);
        return xaDataSource;
    }

    @Primary
    @Bean(name = "primaryEntityManager")
    @DependsOn("transactionManager")
    public LocalContainerEntityManagerFactoryBean primaryEntityManager() throws Throwable {

        Map<String, Object> properties = new HashMap<>();
        properties.put("hibernate.transaction.jta.platform", AtomikosJtaPlatform.class.getName());
        properties.put("javax.persistence.transactionType", "JTA");
        LocalContainerEntityManagerFactoryBean entityManager = new LocalContainerEntityManagerFactoryBean();
        entityManager.setJtaDataSource(primaryDataSource());
        entityManager.setJpaVendorAdapter(jpaVendorAdapter);
        //这里要修改成主数据源的扫描包
        entityManager.setPackagesToScan("cn.lsp.springboot.model.testdb");
        entityManager.setPersistenceUnitName("primaryPersistenceUnit");
        entityManager.setJpaPropertyMap(properties);
        return entityManager;
    }
}

设置第二个数据库的数据源及实体扫描管理(扫描testdb2目录):

@Configuration
@DependsOn("transactionManager")
@EnableJpaRepositories(basePackages = "cn.lsp.springboot.repository.testdb2",   //注意这里
        entityManagerFactoryRef = "secondaryEntityManager",
        transactionManagerRef = "transactionManager")
public class JPASecondaryConfig2 {
    @Autowired
    private JpaVendorAdapter jpaVendorAdapter;


    @Bean(name = "secondaryDataSourceProperties")
    @ConfigurationProperties(prefix = "spring.datasource.secondary")    //注意这里
    public DataSourceProperties masterDataSourceProperties() {
        return new DataSourceProperties();
    }


    @Bean(name = "secondaryDataSource", initMethod = "init", destroyMethod = "close")
    @ConfigurationProperties(prefix = "spring.datasource.secondary")
    public DataSource masterDataSource() throws SQLException {
        MysqlXADataSource mysqlXaDataSource = new MysqlXADataSource();
        mysqlXaDataSource.setUrl(masterDataSourceProperties().getUrl());
        mysqlXaDataSource.setPinGlobalTxToPhysicalConnection(true);
        mysqlXaDataSource.setPassword(masterDataSourceProperties().getPassword());
        mysqlXaDataSource.setUser(masterDataSourceProperties().getUsername());
        AtomikosDataSourceBean xaDataSource = new AtomikosDataSourceBean();
        xaDataSource.setXaDataSource(mysqlXaDataSource);
        xaDataSource.setUniqueResourceName("secondary");
        xaDataSource.setBorrowConnectionTimeout(60);
        xaDataSource.setMaxPoolSize(20);
        return xaDataSource;
    }

    @Bean(name = "secondaryEntityManager")
    @DependsOn("transactionManager")
    public LocalContainerEntityManagerFactoryBean masterEntityManager() throws Throwable {

        Map<String, Object> properties = new HashMap<>();
        properties.put("hibernate.transaction.jta.platform", AtomikosJtaPlatform.class.getName());
        properties.put("javax.persistence.transactionType", "JTA");
        LocalContainerEntityManagerFactoryBean entityManager = new LocalContainerEntityManagerFactoryBean();
        entityManager.setJtaDataSource(masterDataSource());
        entityManager.setJpaVendorAdapter(jpaVendorAdapter);
        //这里要修改成主数据源的扫描包
        entityManager.setPackagesToScan("cn.lsp.springboot.model.testdb2");
        entityManager.setPersistenceUnitName("secondaryPersistenceUnit");
        entityManager.setJpaPropertyMap(properties);
        return entityManager;
    }
}

DataSourceProperties数据源配置、Datasource数据源、EntityManager实体管理器都是2套。分别是primary和secondary
实体和Repository的扫描目录也是2组，分别是testdb和testdb2
但是事务管理器只有一个，那就是transactionManager，是基于atomikos实现的。事务管理器只有一个，决定了不同的数据源使用同一个事务管理器，从而实现分布式事务。

2.4 JPA分布式事务测试

service代码：

@Slf4j
@Service
public class ArticleServiceImpl implements ArticleService {

    @Resource
    private ArticleRepository articleRepository;

    @Resource
    private CommentRepository commentRepository;

    @Override
    @Transactional
    public Article saveArticleAndComment(Article article, Comment comment) {
        Article savedArticle = articleRepository.save(article);
        comment.setArticleId(savedArticle.getId());
        commentRepository.save(comment);
//        int a= 2/0;
        return  article;
    }
}

test代码：

@Slf4j
@SpringBootTest
public class JpaJtaTest {

    @Resource
    private ArticleService articleService;

    @Test
    public void saveArticle() {
        Article article = new Article();
        article.setTitle("SpringBoot实战");
        article.setContent("详细介绍SpringBoot的各种姿势");
        article.setAuthor("William");
        article.setCreateTime(new Date());

        Comment comment = new Comment();
        comment.setName("Tom");
        comment.setContent("内容详实，偏实战");
        comment.setCreateTime(new Date());

        articleService.saveArticleAndComment(article, comment);
    }
}

service里面分别向testdb插入article，testdb2插入comment，数据插入都成功。人为制造一个被除数为0的异常，数据插入都失败。

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