本文介绍基于spring+mybatis+tkmapper+atomikos+jta实现分布式事务，由程序动态切换数据源，通过atomikos可实现分布式事务一致性。通过继承MapperScannerConfigurer、MapperFactoryBean等类，解决多数据源时，切换到第一个数据源之外的数据源时，找不到tk的Mapper上的方法的问题。
版本：spring-3.2.9.RELEASE、mybatis-3.4.4、atomikos-4.0.5、jdk1.8、tk.mybatis-3.4.3
1，maven配置文件pom.xml如下：
junit junit 4.12 test hamcrest-core org.hamcrest org.hamcrest hamcrest-all 1.3 test org.mockito mockito-core 1.9.5 test hamcrest-core org.hamcrest com.jayway.jsonpath json-path 0.8.1 test org.springframework spring-aop ${spring.version} org.springframework spring-beans ${spring.version} org.springframework spring-context ${spring.version} org.springframework spring-core ${spring.version} org.springframework spring-expression ${spring.version} org.springframework spring-web ${spring.version} org.springframework spring-webmvc ${spring.version} org.springframework spring-webmvc-portlet ${spring.version} org.springframework spring-tx ${spring.version} org.springframework spring-jdbc ${spring.version} org.springframework spring-test 3.2.18.RELEASE org.springframework spring-struts ${spring.version} org.mybatis mybatis 3.4.4 org.mybatis mybatis-spring 1.3.1 tk.mybatis mapper 3.4.3 mysql mysql-connector-java 5.1.27 com.atomikos transactions-jdbc 4.0.5 javax.transaction jta 1.1 org.codehaus.jackson jackson-mapper-asl 1.9.13 org.codehaus.jackson jackson-core-asl 1.9.13 org.aspectj aspectjweaver 1.8.13 log4j log4j 1.2.16 javax.servlet servlet-api 2.5 provided
2，数据库连接配置文件：jdbc.properties
jdbc.xaDataSourceClassName=com.mysql.jdbc.jdbc2.optional.MysqlXADataSourcevalidationQuery=select 1ds1.jdbc.url=jdbc:mysql://xx.xx.xx.xx:3306/test1?characterEncoding=UTF-8ds1.jdbc.username=xxxxds1.jdbc.password=xxxxds2.jdbc.url=jdbc:mysql://xx.xx.xx.xx:3306/test2?characterEncoding=UTF-8ds2.jdbc.username=xxxxds2.jdbc.password=xxxx
3，atomikos配置文件：jta.properties
com.atomikos.icatch.service=com.atomikos.icatch.standalone.UserTransactionServiceFactorycom.atomikos.icatch.console_file_name=tm.release.outcom.atomikos.icatch.log_base_name=tm.releaselogcom.atomikos.icatch.tm_unique_name=com.atomikos.spring.jdbc.tm.releasecom.atomikos.icatch.console_log_level=INFO
4，spring-datasource-jta.xml
classpath*:jdbc.properties
${ds1.jdbc.url} ${ds1.jdbc.username} ${ds1.jdbc.password} ${ds2.jdbc.url} ${ds2.jdbc.username} ${ds2.jdbc.password} true
5，spring-mybatis-tk-dynamic.xml
classpath:mybatis/tk/model/*.xml classpath:mybatis/tk/model/*.xml
6，编写mybatis.tk.model代码，HelloDO.java、HelloMapper.java
package mybatis.tk.model;import javax.persistence.Id;import javax.persistence.Table;@Table(name = "HELLO")public class HelloDO { @Id private Long id; private String name; public Long getId() { return id; } public void setId(Long id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; }}HelloMapper.javapackage mybatis.tk.model;import org.springframework.stereotype.Repository;import tk.mybatis.mapper.common.Mapper;@Repository(value="helloMapper")public interface HelloMapper extends Mapper {} 7，编写service类：HelloWorldService.java
package mybatis.tk.service;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Service;import mybatis.tk.model.HelloDO;import mybatis.tk.model.HelloMapper;@Service("helloWorldService")public class HelloWorldService { @Autowired private HelloMapper helloMapper; public void addHello(HelloDO helloDO) { // TODO Auto-generated method stub helloMapper.insert(helloDO); }} 8，编写controller类：HelloWorldController.java
package mybatis.tk.controller;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Controller;import org.springframework.transaction.annotation.Transactional;import org.springframework.web.bind.annotation.RequestBody;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RequestMethod;import org.springframework.web.bind.annotation.ResponseBody;import mybatis.tk.model.HelloDO;import mybatis.tk.service.HelloWorldService;import spring.jta.util.DataSourceContextHolder;@Controller(value = "helloWorldController")@RequestMapping(value = "/hello")public class HelloWorldControler { @Autowired private HelloWorldService helloWorldService; @Transactional @RequestMapping(value="create",method=RequestMethod.POST) public @ResponseBody long createHelloDynamic(@RequestBody HelloDO helloDO) { DataSourceContextHolder.setDBType("dataSource"); helloWorldService.addHello(helloDO); DataSourceContextHolder.setDBType("dataSource2"); helloWorldService.addHello(helloDO); return helloDO.getId(); }} 9，编写测试类：HelloWorldControlerDynamicTest.java
package mybatis.controller;import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;import org.codehaus.jackson.map.ObjectMapper;import org.codehaus.jackson.map.ObjectWriter;import org.junit.Before;import org.junit.Test;import org.junit.runner.RunWith;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.http.MediaType;import org.springframework.test.context.ContextConfiguration;import org.springframework.test.context.junit4.SpringJUnit4Cla***unner;import org.springframework.test.context.web.WebAppConfiguration;import org.springframework.test.web.servlet.MockMvc;import org.springframework.test.web.servlet.setup.MockMvcBuilders;import org.springframework.web.context.WebApplicationContext;import mybatis.model.HelloDO;@RunWith(SpringJUnit4Cla***unner.class)@WebAppConfiguration@ContextConfiguration({ "classpath:spring-datasource-jta.xml", "classpath:spring-mybatis-dynamic.xml" })public class HelloWorldControlerDynamicTest { @Autowired private WebApplicationContext context; private MockMvc mocMvc; @Before public void setUp() throws Exception { mocMvc = MockMvcBuilders.webAppContextSetup(context).build(); } @Test public void test() throws Exception { String data = "{\"id\":1,\"name\":\"abc\"}"; HelloDO hello = new HelloDO(); hello.setId(1L); hello.setName("abc"); ObjectMapper mapper = new ObjectMapper(); ObjectWriter ow = mapper.writer().withDefaultPrettyPrinter(); java.lang.String requestJson = ow.writeValueAsString(hello); mocMvc.perform(post("/hello/create_dynamic").contentType(MediaType.APPLICATION_JSON).content(data)).andExpect(status().isOk()); }} 10，编写数据源切换类 DataSourceContextHolder.java
package spring.jta.util;public class DataSourceContextHolder { private static final ThreadLocal contextHolder = new ThreadLocal (); public static void setDBType(String dbType) { contextHolder.set(dbType); } public static String getDBType() { return ((String) contextHolder.get()); } public static void clearDBType() { contextHolder.remove(); }} 11，编写CustomSqlSessionTemplate.java，该类扩展SqlSessionTemplate，结合DataSourceContextHolder实现sqlSession的切换
package spring.jta.util;import static java.lang.reflect.Proxy.newProxyInstance;import static org.apache.ibatis.reflection.ExceptionUtil.unwrapThrowable;import static org.mybatis.spring.SqlSessionUtils.closeSqlSession;import static org.mybatis.spring.SqlSessionUtils.getSqlSession;import static org.mybatis.spring.SqlSessionUtils.isSqlSessionTransactional;import java.lang.reflect.InvocationHandler;import java.lang.reflect.Method;import java.sql.Connection;import java.util.ArrayList;import java.util.List;import java.util.Map;import org.apache.ibatis.exceptions.PersistenceException;import org.apache.ibatis.executor.BatchResult;import org.apache.ibatis.session.Configuration;import org.apache.ibatis.session.ExecutorType;import org.apache.ibatis.session.ResultHandler;import org.apache.ibatis.session.RowBounds;import org.apache.ibatis.session.SqlSession;import org.apache.ibatis.session.SqlSessionFactory;import org.mybatis.spring.MyBatisExceptionTranslator;import org.mybatis.spring.SqlSessionTemplate;import org.springframework.dao.support.PersistenceExceptionTranslator;import org.springframework.util.Assert;/** * function: 继承SqlSessionTemplate 重写相关方法 * @author hoojo * @createDate 2013-10-18 下午03:07:46 * @file CustomSqlSessionTemplate.java * @package com.hoo.framework.mybatis.support * @project SHMB * @blog http://blog.csdn.net/IBM_hoojo * @email hoojo_@126.com * @version 1.0 */public class CustomSqlSessionTemplate extends SqlSessionTemplate { private final SqlSessionFactory sqlSessionFactory; private final ExecutorType executorType; private final SqlSession sqlSessionProxy; private final PersistenceExceptionTranslator exceptionTranslator; private Map targetSqlSessionFactorys; private SqlSessionFactory defaultTargetSqlSessionFactory; public void setTargetSqlSessionFactorys(Map targetSqlSessionFactorys) { this.targetSqlSessionFactorys = targetSqlSessionFactorys; } public void setDefaultTargetSqlSessionFactory(SqlSessionFactory defaultTargetSqlSessionFactory) { this.defaultTargetSqlSessionFactory = defaultTargetSqlSessionFactory; } public CustomSqlSessionTemplate(SqlSessionFactory sqlSessionFactory) { this(sqlSessionFactory, sqlSessionFactory.getConfiguration().getDefaultExecutorType()); } public CustomSqlSessionTemplate(SqlSessionFactory sqlSessionFactory, ExecutorType executorType) { this(sqlSessionFactory, executorType, new MyBatisExceptionTranslator(sqlSessionFactory.getConfiguration() .getEnvironment().getDataSource(), true)); } public CustomSqlSessionTemplate(SqlSessionFactory sqlSessionFactory, ExecutorType executorType, PersistenceExceptionTranslator exceptionTranslator) { super(sqlSessionFactory, executorType, exceptionTranslator); this.sqlSessionFactory = sqlSessionFactory; this.executorType = executorType; this.exceptionTranslator = exceptionTranslator; this.sqlSessionProxy = (SqlSession) newProxyInstance( SqlSessionFactory.class.getClassLoader(), new Class[] { SqlSession.class }, new SqlSessionInterceptor()); this.defaultTargetSqlSessionFactory = sqlSessionFactory; } @Override public SqlSessionFactory getSqlSessionFactory() { SqlSessionFactory targetSqlSessionFactory = targetSqlSessionFactorys.get(DataSourceContextHolder.getDBType()); if (targetSqlSessionFactory != null) { return targetSqlSessionFactory; } else if (defaultTargetSqlSessionFactory != null) { return defaultTargetSqlSessionFactory; } else { Assert.notNull(targetSqlSessionFactorys, "Property 'targetSqlSessionFactorys' or 'defaultTargetSqlSessionFactory' are required"); Assert.notNull(defaultTargetSqlSessionFactory, "Property 'defaultTargetSqlSessionFactory' or 'targetSqlSessionFactorys' are required"); } return this.sqlSessionFactory; } public List getAllConfigurations() { List list = new ArrayList (); for(Map.Entry entry : targetSqlSessionFactorys.entrySet()) { SqlSessionFactory sqlSessionFactory = entry.getValue(); list.add(sqlSessionFactory.getConfiguration()); } return list; } @Override public Configuration getConfiguration() { return this.getSqlSessionFactory().getConfiguration(); } public ExecutorType getExecutorType() { return this.executorType; } public PersistenceExceptionTranslator getPersistenceExceptionTranslator() { return this.exceptionTranslator; } /** * {@inheritDoc} */ public T selectOne(String statement) { return this.sqlSessionProxy. selectOne(statement); } /** * {@inheritDoc} */ public T selectOne(String statement, Object parameter) { return this.sqlSessionProxy. selectOne(statement, parameter); } /** * {@inheritDoc} */ public Map selectMap(String statement, String mapKey) { return this.sqlSessionProxy. selectMap(statement, mapKey); } /** * {@inheritDoc} */ public Map selectMap(String statement, Object parameter, String mapKey) { return this.sqlSessionProxy. selectMap(statement, parameter, mapKey); } /** * {@inheritDoc} */ public Map selectMap(String statement, Object parameter, String mapKey, RowBounds rowBounds) { return this.sqlSessionProxy. selectMap(statement, parameter, mapKey, rowBounds); } /** * {@inheritDoc} */ public List selectList(String statement) { return this.sqlSessionProxy. selectList(statement); } /** * {@inheritDoc} */ public List selectList(String statement, Object parameter) { return this.sqlSessionProxy. selectList(statement, parameter); } /** * {@inheritDoc} */ public List selectList(String statement, Object parameter, RowBounds rowBounds) { return this.sqlSessionProxy. selectList(statement, parameter, rowBounds); } /** * {@inheritDoc} */ public void select(String statement, ResultHandler handler) { this.sqlSessionProxy.select(statement, handler); } /** * {@inheritDoc} */ public void select(String statement, Object parameter, ResultHandler handler) { this.sqlSessionProxy.select(statement, parameter, handler); } /** * {@inheritDoc} */ public void select(String statement, Object parameter, RowBounds rowBounds, ResultHandler handler) { this.sqlSessionProxy.select(statement, parameter, rowBounds, handler); } /** * {@inheritDoc} */ public int insert(String statement) { return this.sqlSessionProxy.insert(statement); } /** * {@inheritDoc} */ public int insert(String statement, Object parameter) { return this.sqlSessionProxy.insert(statement, parameter); } /** * {@inheritDoc} */ public int update(String statement) { return this.sqlSessionProxy.update(statement); } /** * {@inheritDoc} */ public int update(String statement, Object parameter) { return this.sqlSessionProxy.update(statement, parameter); } /** * {@inheritDoc} */ public int delete(String statement) { return this.sqlSessionProxy.delete(statement); } /** * {@inheritDoc} */ public int delete(String statement, Object parameter) { return this.sqlSessionProxy.delete(statement, parameter); } /** * {@inheritDoc} */ public T getMapper(Class type) { return getConfiguration().getMapper(type, this); } /** * {@inheritDoc} */ public void commit() { throw new UnsupportedOperationException("Manual commit is not allowed over a Spring managed SqlSession"); } /** * {@inheritDoc} */ public void commit(boolean force) { throw new UnsupportedOperationException("Manual commit is not allowed over a Spring managed SqlSession"); } /** * {@inheritDoc} */ public void rollback() { throw new UnsupportedOperationException("Manual rollback is not allowed over a Spring managed SqlSession"); } /** * {@inheritDoc} */ public void rollback(boolean force) { throw new UnsupportedOperationException("Manual rollback is not allowed over a Spring managed SqlSession"); } /** * {@inheritDoc} */ public void close() { throw new UnsupportedOperationException("Manual close is not allowed over a Spring managed SqlSession"); } /** * {@inheritDoc} */ public void clearCache() { this.sqlSessionProxy.clearCache(); } /** * {@inheritDoc} */ public Connection getConnection() { return this.sqlSessionProxy.getConnection(); } /** * {@inheritDoc} * @since 1.0.2 */ public List flushStatements() { return this.sqlSessionProxy.flushStatements(); } /** * Proxy needed to route MyBatis method calls to the proper SqlSession got from Spring's Transaction Manager It also * unwraps exceptions thrown by {@code Method#invoke(Object, Object...)} to pass a {@code PersistenceException} to * the {@code PersistenceExceptionTranslator}. */ private class SqlSessionInterceptor implements InvocationHandler { public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { final SqlSession sqlSession = getSqlSession( CustomSqlSessionTemplate.this.getSqlSessionFactory(), CustomSqlSessionTemplate.this.executorType, CustomSqlSessionTemplate.this.exceptionTranslator); try { Object result = method.invoke(sqlSession, args); if (!isSqlSessionTransactional(sqlSession, CustomSqlSessionTemplate.this.getSqlSessionFactory())) { // force commit even on non-dirty sessions because some databases require // a commit/rollback before calling close() sqlSession.commit(true); } return result; } catch (Throwable t) { Throwable unwrapped = unwrapThrowable(t); if (CustomSqlSessionTemplate.this.exceptionTranslator != null && unwrapped instanceof PersistenceException) { Throwable translated = CustomSqlSessionTemplate.this.exceptionTranslator .translateExceptionIfPossible((PersistenceException) unwrapped); if (translated != null) { unwrapped = translated; } } throw unwrapped; } finally { closeSqlSession(sqlSession, CustomSqlSessionTemplate.this.getSqlSessionFactory()); } } }} 12，编写MapperFactoryBean.java，该类继承org.mybatis.spring.mapper.MapperFactoryBean，通过重写checkDaoConfig()，把tk的Mapper接口的所有方法配置到org.apache.ibatis.session.Configuration上，解决多个数据源时找不到方法的问题。
package spring.jta.util;import java.util.List;import org.apache.ibatis.executor.ErrorContext;import org.apache.ibatis.session.Configuration;import org.springframework.beans.BeansException;import org.springframework.context.ApplicationContext;import org.springframework.context.ApplicationContextAware;import tk.mybatis.mapper.mapperhelper.MapperHelper;public class MapperFactoryBean extends org.mybatis.spring.mapper.MapperFactoryBean implements ApplicationContextAware{ private MapperHelper mapperHelper; private String sqlSessionTemplateBeanName; private ApplicationContext applicationContext; public MapperFactoryBean() { super(); } public MapperFactoryBean(Class mapperInterface) { super(mapperInterface); } public void setSqlSessionTemplateBeanName(String sqlSessionTemplateBeanName) { this.sqlSessionTemplateBeanName = sqlSessionTemplateBeanName; } public void setMapperHelper(MapperHelper mapperHelper) { this.mapperHelper = mapperHelper; } @Override protected void checkDaoConfig() { CustomSqlSessionTemplate customSqlSessionTemplate = (CustomSqlSessionTemplate)this.applicationContext.getBean(this.sqlSessionTemplateBeanName); List configurations = customSqlSessionTemplate.getAllConfigurations(); for (Configuration configuration : configurations) { if (isAddToConfig() && !configuration.hasMapper(getMapperInterface())) { try { configuration.addMapper(getMapperInterface()); } catch (Exception e) { logger.error("Error while adding the mapper '" + getMapperInterface() + "' to configuration.", e); throw new IllegalArgumentException(e); } finally { ErrorContext.instance().reset(); } } // 通用Mapper if (mapperHelper.isExtendCommonMapper(getObjectType())) { mapperHelper.processConfiguration(configuration, getObjectType()); } } } @Override public void setApplicationContext(ApplicationContext applicationContext) throws BeansException { // TODO Auto-generated method stub this.applicationContext = applicationContext; }}
13，编写MyMapperScannerConfigurer.java，该类继承org.mybatis.spring.mapper.MapperScannerConfigurer
package spring.jta.util;import java.util.Properties;import org.springframework.beans.factory.config.BeanDefinition;import org.springframework.beans.factory.support.BeanDefinitionRegistry;import org.springframework.beans.factory.support.GenericBeanDefinition;import tk.mybatis.mapper.common.Marker;import tk.mybatis.mapper.mapperhelper.MapperHelper;import tk.mybatis.mapper.util.StringUtil;import org.mybatis.spring.mapper.MapperScannerConfigurer;public class MyMapperScannerConfigurer extends MapperScannerConfigurer { private MapperHelper mapperHelper = new MapperHelper(); private String sqlSessionTemplateBeanName; public void setMarkerInterface(Class superClass) { super.setMarkerInterface(superClass); if (Marker.class.isAssignableFrom(superClass)) { mapperHelper.registerMapper(superClass); } } public MapperHelper getMapperHelper() { return mapperHelper; } public void setMapperHelper(MapperHelper mapperHelper) { this.mapperHelper = mapperHelper; } public void setSqlSessionTemplateBeanName(String sqlSessionTemplateBeanName) { super.setSqlSessionTemplateBeanName(sqlSessionTemplateBeanName); this.sqlSessionTemplateBeanName = sqlSessionTemplateBeanName; } /** * 属性注入 * * @param properties */ public void setProperties(Properties properties) { mapperHelper.setProperties(properties); } @Override public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) { super.postProcessBeanDefinitionRegistry(registry); // 如果没有注册过接口，就注册默认的Mapper接口 this.mapperHelper.ifEmptyRegisterDefaultInterface(); String[] names = registry.getBeanDefinitionNames(); GenericBeanDefinition definition; for (String name : names) { BeanDefinition beanDefinition = registry.getBeanDefinition(name); if (beanDefinition instanceof GenericBeanDefinition) { definition = (GenericBeanDefinition) beanDefinition; if (StringUtil.isNotEmpty(definition.getBeanClassName()) && definition.getBeanClassName().equals("org.mybatis.spring.mapper.MapperFactoryBean")) { definition.setBeanClass(MapperFactoryBean.class); definition.getPropertyValues().add("mapperHelper", this.mapperHelper); definition.getPropertyValues().add("sqlSessionTemplateBeanName", this.sqlSessionTemplateBeanName); } } } }} 14，至此，基于tkmapper的可由程序动态切换数据源，并实现分布式事务一致性已经实现，对于单表的CRUD操作，可以省略xml映射文件的编写。