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什么是JTA

JTA，全稱：Java Transaction API。JTA事務比JDBC事務更強大。一個JTA事務可以有多個參與者，而一個JDBC事務則被限定在一個單一的數(shù)據(jù)庫連接。所以，當我們在同時操作多個數(shù)據(jù)庫的時候，使用JTA事務就可以彌補JDBC事務的不足。

在Spring Boot 2.x中，整合了這兩個JTA的實現(xiàn)：

Atomikos：可以通過引入spring-boot-starter-jta-atomikos依賴來使用
Bitronix：可以通過引入spring-boot-starter-jta-bitronix依賴來使用

由于Bitronix自Spring Boot 2.3.0開始不推薦使用，所以在下面的動手環(huán)節(jié)中，我們將使用Atomikos作為例子來介紹JTA的使用。

#動手試試

下面我們就來實操一下，如何在Spring Boot中使用JTA來實現(xiàn)多數(shù)據(jù)源下的事務管理。

準備工作

這里我們將使用最基礎的JdbcTemplate來實現(xiàn)數(shù)據(jù)訪問，所以如果你還不會使用JdbcTemplate配置多數(shù)據(jù)源，建議先看一下JdbcTemplate的多數(shù)據(jù)源配置。
場景設定：

假設我們有兩個庫，分別為：test1和test2
這兩個庫中都有一張User表，我們希望這兩張表中的數(shù)據(jù)是一致的
假設這兩張表中都已經(jīng)有一條數(shù)據(jù)：name=aaa，age=30；因為這兩張表中數(shù)據(jù)是一致的，所以要update的時候，就必須兩個庫中的User表更新時候，要么都成功，要么都失敗。

操作詳細

在pom.xml中加入JTA的實現(xiàn)Atomikos的Starter

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

在application.properties配置文件中配置兩個test1和test2數(shù)據(jù)源

spring.jta.enabled=true

spring.jta.atomikos.datasource.primary.xa-properties.url=jdbc:mysql://localhost:3306/test1
spring.jta.atomikos.datasource.primary.xa-properties.user=root
spring.jta.atomikos.datasource.primary.xa-properties.password=12345678
spring.jta.atomikos.datasource.primary.xa-data-source-class-name=com.mysql.cj.jdbc.MysqlXADataSource
spring.jta.atomikos.datasource.primary.unique-resource-name=test1
spring.jta.atomikos.datasource.primary.max-pool-size=25
spring.jta.atomikos.datasource.primary.min-pool-size=3
spring.jta.atomikos.datasource.primary.max-lifetime=20000
spring.jta.atomikos.datasource.primary.borrow-connection-timeout=10000

spring.jta.atomikos.datasource.secondary.xa-properties.url=jdbc:mysql://localhost:3306/test2
spring.jta.atomikos.datasource.secondary.xa-properties.user=root
spring.jta.atomikos.datasource.secondary.xa-properties.password=12345678
spring.jta.atomikos.datasource.secondary.xa-data-source-class-name=com.mysql.cj.jdbc.MysqlXADataSource
spring.jta.atomikos.datasource.secondary.unique-resource-name=test2
spring.jta.atomikos.datasource.secondary.max-pool-size=25
spring.jta.atomikos.datasource.secondary.min-pool-size=3
spring.jta.atomikos.datasource.secondary.max-lifetime=20000
spring.jta.atomikos.datasource.secondary.borrow-connection-timeout=10000

創(chuàng)建多數(shù)據(jù)源配置類

@Configuration
public class DataSourceConfiguration {

    @Primary
    @Bean
    @ConfigurationProperties(prefix = "spring.jta.atomikos.datasource.primary")
    public DataSource primaryDataSource() {
        return new AtomikosDataSourceBean();
    }

    @Bean
    @ConfigurationProperties(prefix = "spring.jta.atomikos.datasource.secondary")
    public DataSource secondaryDataSource() {
        return new AtomikosDataSourceBean();
    }

    @Bean
    public JdbcTemplate primaryJdbcTemplate(@Qualifier("primaryDataSource") DataSource primaryDataSource) {
        return new JdbcTemplate(primaryDataSource);
    }

    @Bean
    public JdbcTemplate secondaryJdbcTemplate(@Qualifier("secondaryDataSource") DataSource secondaryDataSource) {
        return new JdbcTemplate(secondaryDataSource);
    }

}

注意，這里除了家在的配置不同之外，DataSource也采用了AtomikosDataSourceBean注意與之前配置多數(shù)據(jù)源使用的配置和實現(xiàn)類的區(qū)別。

創(chuàng)建一個Service實現(xiàn)，模擬兩種不同的情況。

@Service
public class TestService {

    private JdbcTemplate primaryJdbcTemplate;
    private JdbcTemplate secondaryJdbcTemplate;

    public TestService(JdbcTemplate primaryJdbcTemplate, JdbcTemplate secondaryJdbcTemplate) {
        this.primaryJdbcTemplate = primaryJdbcTemplate;
        this.secondaryJdbcTemplate = secondaryJdbcTemplate;
    }

    @Transactional
    public void tx() {
        // 修改test1庫中的數(shù)據(jù)
        primaryJdbcTemplate.update("update user set age = ? where name = ?", 30, "aaa");
        // 修改test2庫中的數(shù)據(jù)
        secondaryJdbcTemplate.update("update user set age = ? where name = ?", 30, "aaa");
    }

    @Transactional
    public void tx2() {
        // 修改test1庫中的數(shù)據(jù)
        primaryJdbcTemplate.update("update user set age = ? where name = ?", 40, "aaa");
        // 模擬：修改test2庫之前拋出異常
        throw new RuntimeException();
    }

}

這里tx函數(shù)，是兩句update操作，一般都會成功；而tx2函數(shù)中，我們人為的制造了一個異常，這個異常是在test1庫中的數(shù)據(jù)更新后才產(chǎn)生的，這樣就可以測試一下test1更新成功，之后是否還能在JTA的幫助下實現(xiàn)回滾。

創(chuàng)建測試類，編寫測試用例

@SpringBootTest(classes = Chapter312Application.class)
public class Chapter312ApplicationTests {

    @Autowired
    protected JdbcTemplate primaryJdbcTemplate;
    @Autowired
    protected JdbcTemplate secondaryJdbcTemplate;

    @Autowired
    private TestService testService;

    @Test
    public void test1() throws Exception {
        // 正確更新的情況
        testService.tx();
        Assertions.assertEquals(30, primaryJdbcTemplate.queryForObject("select age from user where name=?", Integer.class, "aaa"));
        Assertions.assertEquals(30, secondaryJdbcTemplate.queryForObject("select age from user where name=?", Integer.class, "aaa"));
    }

    @Test
    public void test2() throws Exception {
        // 更新失敗的情況
        try {
            testService.tx2();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            // 部分更新失敗，test1中的更新應該回滾
            Assertions.assertEquals(30, primaryJdbcTemplate.queryForObject("select age from user where name=?", Integer.class, "aaa"));
            Assertions.assertEquals(30, secondaryJdbcTemplate.queryForObject("select age from user where name=?", Integer.class, "aaa"));
        }
    }

}

這里有兩個測試用例：

test1：因為沒有故意制造的異常，不出意外兩個庫的update都會成功，所以根據(jù)name=aaa去把兩個數(shù)據(jù)查出來，看age是否都被更新到了30。
test2：tx2函數(shù)會把test1中name=aaa的用戶age更新為40，然后拋出異常，JTA事務生效的話，會把age回滾回30，所以這里的檢查也是兩個庫的aaa用戶的age應該都為30，這樣就意味著JTA事務生效，保證了test1和test2兩個庫中的User表數(shù)據(jù)更新一致，沒有制造出臟數(shù)據(jù)。

#測試驗證

將上面編寫的單元測試運行起來:

觀察一下啟動階段的日志，可以看到這些Atomikos初始化日志輸出：

2021-02-02 19:00:36.145  INFO 8868 --- [           main] c.a.icatch.provider.imp.AssemblerImp     : USING: com.atomikos.icatch.default_max_wait_time_on_shutdown = 9223372036854775807
2021-02-02 19:00:36.145  INFO 8868 --- [           main] c.a.icatch.provider.imp.AssemblerImp     : USING: com.atomikos.icatch.allow_subtransactions = true
2021-02-02 19:00:36.145  INFO 8868 --- [           main] c.a.icatch.provider.imp.AssemblerImp     : USING: com.atomikos.icatch.recovery_delay = 10000
2021-02-02 19:00:36.145  INFO 8868 --- [           main] c.a.icatch.provider.imp.AssemblerImp     : USING: com.atomikos.icatch.automatic_resource_registration = true
2021-02-02 19:00:36.145  INFO 8868 --- [           main] c.a.icatch.provider.imp.AssemblerImp     : USING: com.atomikos.icatch.oltp_max_retries = 5
2021-02-02 19:00:36.145  INFO 8868 --- [           main] c.a.icatch.provider.imp.AssemblerImp     : USING: com.atomikos.icatch.client_demarcation = false
2021-02-02 19:00:36.145  INFO 8868 --- [           main] c.a.icatch.provider.imp.AssemblerImp     : USING: com.atomikos.icatch.threaded_2pc = false
2021-02-02 19:00:36.145  INFO 8868 --- [           main] c.a.icatch.provider.imp.AssemblerImp     : USING: com.atomikos.icatch.serial_jta_transactions = true
2021-02-02 19:00:36.145  INFO 8868 --- [           main] c.a.icatch.provider.imp.AssemblerImp     : USING: com.atomikos.icatch.log_base_dir = /Users/didi/Documents/GitHub/SpringBoot-Learning/2.x/chapter3-12/transaction-logs
2021-02-02 19:00:36.145  INFO 8868 --- [           main] c.a.icatch.provider.imp.AssemblerImp     : USING: com.atomikos.icatch.rmi_export_class = none
2021-02-02 19:00:36.145  INFO 8868 --- [           main] c.a.icatch.provider.imp.AssemblerImp     : USING: com.atomikos.icatch.max_actives = 50
2021-02-02 19:00:36.145  INFO 8868 --- [           main] c.a.icatch.provider.imp.AssemblerImp     : USING: com.atomikos.icatch.checkpoint_interval = 500
2021-02-02 19:00:36.145  INFO 8868 --- [           main] c.a.icatch.provider.imp.AssemblerImp     : USING: com.atomikos.icatch.enable_logging = true
2021-02-02 19:00:36.145  INFO 8868 --- [           main] c.a.icatch.provider.imp.AssemblerImp     : USING: com.atomikos.icatch.log_base_name = tmlog
2021-02-02 19:00:36.146  INFO 8868 --- [           main] c.a.icatch.provider.imp.AssemblerImp     : USING: com.atomikos.icatch.max_timeout = 300000
2021-02-02 19:00:36.146  INFO 8868 --- [           main] c.a.icatch.provider.imp.AssemblerImp     : USING: com.atomikos.icatch.trust_client_tm = false
2021-02-02 19:00:36.146  INFO 8868 --- [           main] c.a.icatch.provider.imp.AssemblerImp     : USING: java.naming.factory.initial = com.sun.jndi.rmi.registry.RegistryContextFactory
2021-02-02 19:00:36.146  INFO 8868 --- [           main] c.a.icatch.provider.imp.AssemblerImp     : USING: com.atomikos.icatch.tm_unique_name = 127.0.0.1.tm
2021-02-02 19:00:36.146  INFO 8868 --- [           main] c.a.icatch.provider.imp.AssemblerImp     : USING: com.atomikos.icatch.forget_orphaned_log_entries_delay = 86400000
2021-02-02 19:00:36.146  INFO 8868 --- [           main] c.a.icatch.provider.imp.AssemblerImp     : USING: com.atomikos.icatch.oltp_retry_interval = 10000
2021-02-02 19:00:36.146  INFO 8868 --- [           main] c.a.icatch.provider.imp.AssemblerImp     : USING: java.naming.provider.url = rmi://localhost:1099
2021-02-02 19:00:36.146  INFO 8868 --- [           main] c.a.icatch.provider.imp.AssemblerImp     : USING: com.atomikos.icatch.force_shutdown_on_vm_exit = false
2021-02-02 19:00:36.146  INFO 8868 --- [           main] c.a.icatch.provider.imp.AssemblerImp     : USING: com.atomikos.icatch.default_jta_timeout = 10000
2021-02-02 19:00:36.147  INFO 8868 --- [           main] c.a.icatch.provider.imp.AssemblerImp     : Using default (local) logging and recovery...
2021-02-02 19:00:36.184  INFO 8868 --- [           main] c.a.d.xa.XATransactionalResource         : test1: refreshed XAResource
2021-02-02 19:00:36.203  INFO 8868 --- [           main] c.a.d.xa.XATransactionalResource         : test2: refreshed XAResource

同時，我們在transaction-logs目錄下，還能找到關于事務的日志信息：

{"id":"127.0.0.1.tm161226409083100001","wasCommitted":true,"participants":[{"uri":"127.0.0.1.tm1","state":"COMMITTING","expires":1612264100801,"resourceName":"test1"},{"uri":"127.0.0.1.tm2","state":"COMMITTING","expires":1612264100801,"resourceName":"test2"}]}
{"id":"127.0.0.1.tm161226409083100001","wasCommitted":true,"participants":[{"uri":"127.0.0.1.tm1","state":"TERMINATED","expires":1612264100804,"resourceName":"test1"},{"uri":"127.0.0.1.tm2","state":"TERMINATED","expires":1612264100804,"resourceName":"test2"}]}
{"id":"127.0.0.1.tm161226409092800002","wasCommitted":false,"participants":[{"uri":"127.0.0.1.tm3","state":"TERMINATED","expires":1612264100832,"resourceName":"test1"}]}

本系列教程《Spring Boot 2.x基礎教程》點擊直達！。學習過程中如遇困難，建議加入Spring技術交流群open in new window，參與交流與討論，更好的學習與進步！

#代碼示例

本文的相關例子可以查看下面?zhèn)}庫中的chapter3-12目錄：

Github：https://github.com/dyc87112/SpringBoot-Learning/open in new window
Gitee：https://gitee.com/didispace/SpringBoot-Learning/

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Spring Boot 2.x基礎教程：使用JTA實現(xiàn)多數(shù)據(jù)源的事務管理

什么是JTA

#動手試試

#測試驗證

#代碼示例