《Spring技术内幕》学习笔记13——SqlMapClientTemplate对Ibatis的封装

1. SqlMapClientFactoryBean：

Spring中通过SqlMapClientTemplate提供对Ibatis的支持，与Spring对Hibernate的支持类似，Spring中SqlMapClientFactoryBean就是管理Ibatis的IoC容器，我们首先分析SqlMapClientFactoryBean的源码：

//Spring管理Ibatis的IoC容器public class SqlMapClientFactoryBean implements FactoryBean<SqlMapClient>, InitializingBean {//当前线程绑定Ibatis blob/clob等大字段数据处理器资源private static final ThreadLocal<LobHandler> configTimeLobHandlerHolder = new ThreadLocal<LobHandler>();public static LobHandler getConfigTimeLobHandler() {return configTimeLobHandlerHolder.get();}//Ibatis配置文件路径private Resource[] configLocations;//Ibatis映射文件路径private Resource[] mappingLocations;//Ibatis sqlMapClient属性private Properties sqlMapClientProperties;//数据源private DataSource dataSource;//使用Spring事务包装数据源private boolean useTransactionAwareDataSource = true;//事务配置类private Class transactionConfigClass = ExternalTransactionConfig.class;//事务配置属性private Properties transactionConfigProperties;//blob/clob等lob类型处理器private LobHandler lobHandler;//Ibatis sqlMapClientprivate SqlMapClient sqlMapClient;public SqlMapClientFactoryBean() {this.transactionConfigProperties = new Properties();//不允许事务自动提交this.transactionConfigProperties.setProperty("SetAutoCommitAllowed", "false");}//指定Ibatis sqlMapClient配置文件路径public void setConfigLocation(Resource configLocation) {this.configLocations = (configLocation != null ? new Resource[] {configLocation} : null);}//指定多个sqlMapClient配置文件路径，这些配置文件在运行时合并public void setConfigLocations(Resource[] configLocations) {this.configLocations = configLocations;}//指定Ibatis映射文件路径，这些映射文件在运行时被合并到SqlMapClient的配置中public void setMappingLocations(Resource[] mappingLocations) {this.mappingLocations = mappingLocations;}//指定Ibatis SqlMapClient可选的属性，即在SqlMapClient配置文件中通过属性//文件设置的属性public void setSqlMapClientProperties(Properties sqlMapClientProperties) {this.sqlMapClientProperties = sqlMapClientProperties;}//设置Ibatis使用的数据源public void setDataSource(DataSource dataSource) {this.dataSource = dataSource;}//设置数据源是否使用事务包装public void setUseTransactionAwareDataSource(boolean useTransactionAwareDataSource) {this.useTransactionAwareDataSource = useTransactionAwareDataSource;}//设置Ibatis使用的事务配置类，默认是//com.ibatis.sqlmap.engine.transaction.external.ExternalTransactionConfigpublic void setTransactionConfigClass(Class transactionConfigClass) {if (transactionConfigClass == null || !TransactionConfig.class.isAssignableFrom(transactionConfigClass)) {throw new IllegalArgumentException("Invalid transactionConfigClass: does not implement " +"com.ibatis.sqlmap.engine.transaction.TransactionConfig");}this.transactionConfigClass = transactionConfigClass;}//设置Ibatis事务配置类属性public void setTransactionConfigProperties(Properties transactionConfigProperties) {this.transactionConfigProperties = transactionConfigProperties;}//设置Ibatis使用的处理clob/blob等大字段的处理器public void setLobHandler(LobHandler lobHandler) {this.lobHandler = lobHandler;}//IoC容器初始化完成之后的回调方法，是InitializingBean接口的实现方法public void afterPropertiesSet() throws Exception {//配置lob处理器if (this.lobHandler != null) {configTimeLobHandlerHolder.set(this.lobHandler);}//创建Ibatis的SqlMapClienttry {this.sqlMapClient = buildSqlMapClient(this.configLocations, this.mappingLocations, this.sqlMapClientProperties);//为创建的SqlMapClient设置数据源if (this.dataSource != null) {//创建事务配置实例TransactionConfig transactionConfig = (TransactionConfig) this.transactionConfigClass.newInstance();//获取数据源DataSource dataSourceToUse = this.dataSource;//如果Ibatis配置指定使用事务包装的数据源，并且当前获取到的数据源//不是事务包装数据源代理类型if (this.useTransactionAwareDataSource && !(this.dataSource instanceof TransactionAwareDataSourceProxy)) {//为指定数据源创建事务包装代理dataSourceToUse = new TransactionAwareDataSourceProxy(this.dataSource);}//事务配置对象设置数据源transactionConfig.setDataSource(dataSourceToUse);//初始化事务配置对象transactionConfig.initialize(this.transactionConfigProperties);applyTransactionConfig(this.sqlMapClient, transactionConfig);}}//创建SqlMapClient成功后，清除当前线程绑定的Lob处理器资源finally {if (this.lobHandler != null) {configTimeLobHandlerHolder.remove();}}}//具体创建SqlMapClient的方法，根据给定的Ibatis配置文件、Ibatis映射文件//和Ibatis配置中的属性文件创建SqlMapClientprotected SqlMapClient buildSqlMapClient(Resource[] configLocations, Resource[] mappingLocations, Properties properties)throws IOException {//如果给定Ibatis配置文件路径为空if (ObjectUtils.isEmpty(configLocations)) {throw new IllegalArgumentException("At least 1 'configLocation' entry is required");}SqlMapClient client = null;//创建Ibatis配置文件解析器SqlMapConfigParser configParser = new SqlMapConfigParser();//遍历所有的Ibatis配置文件for (Resource configLocation : configLocations) {//获取Ibatis配置文件输入流InputStream is = configLocation.getInputStream();try {//创建Ibatis SqlMapClientclient = configParser.parse(is, properties);}catch (RuntimeException ex) {throw new NestedIOException("Failed to parse config resource: " + configLocation, ex.getCause());}}//如果Ibatis映射文件不为nullif (mappingLocations != null) {//根据Ibatis配置文件解析器创建Ibatis映射文件解析器SqlMapParser mapParser = SqlMapParserFactory.createSqlMapParser(configParser);//遍历所给定的Ibatis映射文件for (Resource mappingLocation : mappingLocations) {try {//解析Ibatis映射文件mapParser.parse(mappingLocation.getInputStream());}catch (NodeletException ex) {throw new NestedIOException("Failed to parse mapping resource: " + mappingLocation, ex);}}}//返回创建的SqlMapClient对象return client;}//将Ibatis配置中指定的事务配置应用到SqlMapClient上protected void applyTransactionConfig(SqlMapClient sqlMapClient, TransactionConfig transactionConfig) {//如果SqlMapClient不是ExtendedSqlMapClient类型，则无法将Ibatis配置//中指定的事务配置应用到SqlMapClient对象if (!(sqlMapClient instanceof ExtendedSqlMapClient)) {throw new IllegalArgumentException("Cannot set TransactionConfig with DataSource for SqlMapClient if not of type " +"ExtendedSqlMapClient: " + sqlMapClient);}ExtendedSqlMapClient extendedClient = (ExtendedSqlMapClient) sqlMapClient;//设置最大并发Ibatis事务数量transactionConfig.setMaximumConcurrentTransactions(extendedClient.getDelegate().getMaxTransactions());//为SqlMapClient设置事务处理器extendedClient.getDelegate().setTxManager(new TransactionManager(transactionConfig));}//Spring IoC容器中对应用提供的一个获取被管理对象的方法，应该通过此方法获//取被Spring IoC容器管理的Ibatis SqlMapClient对象public SqlMapClient getObject() {return this.sqlMapClient;}//获取SqlMapClient的类型public Class<? extends SqlMapClient> getObjectType() {return (this.sqlMapClient != null ? this.sqlMapClient.getClass() : SqlMapClient.class);}//默认Spring IoC容器中管理的对象是单态模式的public boolean isSingleton() {return true;}//Ibatis映射解析器工厂，内部类private static class SqlMapParserFactory {//创建Ibatis映射解析器public static SqlMapParser createSqlMapParser(SqlMapConfigParser configParser) {XmlParserState state = null;try {//使用JDK反射机制获取SqlMapConfigParser类中的state字段Field stateField = SqlMapConfigParser.class.getDeclaredField("state");//使用JDK反射机制使state字段可以被访问，主要解决private、//protect和默认访问权限没有提供get方法的情况stateField.setAccessible(true);//使用Ibatis配置解析器获取指定字段的值state = (XmlParserState) stateField.get(configParser);}catch (Exception ex) {throw new IllegalStateException("iBATIS 2.3.2 'state' field not found in SqlMapConfigParser class - " +"please upgrade to IBATIS 2.3.2 or higher in order to use the new 'mappingLocations' feature. " + ex);}//为指定字段值创建Ibatis映射解析器return new SqlMapParser(state);}}}

SqlMapClientFactoryBean实现了Spring的FactoryBean接口，是Spring中管理Ibatis的IoC容器，在IoC容器初始化过程中主要完成定位Ibatis配置文件和Ibatis映射文件等工作。同时SqlMapClientFactoryBean实现了InitializingBean接口，实现了afterPropertiesSet方法，该方法是在IoC容器初始化完成之后由IoC容器进行回调的，在该方法中主要是根据定义的Ibatis配置和映射文件创建Ibatis的SqlMapClient对象的过程。

2.SqlMapClientTemplate：

Spring通过SqlMapClientTemplate对Ibatis一些通用操作做统一的封装处理，同时也对Ibatis的API做了一些封装，方便开发者使用，下面我们继续分析SqlMapClientTemplate对Ibatis封装的实现。

(1).execute方法的实现：

同JdbcTemplate和HibernateTemplate一样，Spring在SqlMapClientTemplate中也是通过execute方法封装Ibatis增删改查前的通用操作，同时在execute方法中调用相应的回调对象的回调方法来真正完成Ibatis的处理操作，execute方法源码如下：

public <T> T execute(SqlMapClientCallback<T> action) throws DataAccessException {Assert.notNull(action, "Callback object must not be null");Assert.notNull(this.sqlMapClient, "No SqlMapClient specified");//通过SqlMapClient对象打开一个Ibatis SqlMapSessionSqlMapSession session = this.sqlMapClient.openSession();if (logger.isDebugEnabled()) {logger.debug("Opened SqlMapSession [" + session + "] for iBATIS operation");}Connection ibatisCon = null;try {Connection springCon = null;//获取数据源DataSource dataSource = getDataSource();//根据数据源是否是事务包装数据源代理类型，判断数据源是否需要事务包装boolean transactionAware = (dataSource instanceof TransactionAwareDataSourceProxy);try {//获取连接ibatisCon = session.getCurrentConnection();//如果当前Ibatis SqlMapSession还没有创建过连接if (ibatisCon == null) {//如果Ibatis数据源已经在Spring事务管理之下，则直接使用数据源//创建连接，否则，使用DataSourceUtils创建连接，并且创建的连//接置于Spring事务管理之中springCon = (transactionAware ?dataSource.getConnection() : DataSourceUtils.doGetConnection(dataSource));session.setUserConnection(springCon);if (logger.isDebugEnabled()) {logger.debug("Obtained JDBC Connection [" + springCon + "] for iBATIS operation");}}//如果当前Ibatis SqlMapSession已经创建过连接，则直接使用else {if (logger.isDebugEnabled()) {logger.debug("Reusing JDBC Connection [" + ibatisCon + "] for iBATIS operation");}}}catch (SQLException ex) {throw new CannotGetJdbcConnectionException("Could not get JDBC Connection", ex);}//调用具体增删改查操作回调对象的方法try {return action.doInSqlMapClient(session);}catch (SQLException ex) {throw getExceptionTranslator().translate("SqlMapClient operation", null, ex);}finally {try {//释放连接if (springCon != null) {if (transactionAware) {springCon.close();}else {DataSourceUtils.doReleaseConnection(springCon, dataSource);}}}catch (Throwable ex) {logger.debug("Could not close JDBC Connection", ex);}}}//关闭Ibatis的SqlMapSessionfinally {if (ibatisCon == null) {session.close();}}}

(2).Spring封装Ibatis API的方法：

我们以Spring的queryForObject方法为例，分析Spring封装Ibatis API的实现，源码如下：

//查询对象public Object queryForObject(final String statementName, final Object parameterObject)throws DataAccessException {//调用execute方法，参数是实现了SqlMapClientCallback接口的匿名内部类，//execute方法中回调该对象的doInSqlMapClient方法return execute(new SqlMapClientCallback<Object>() {//真正调用Ibatis API做具体操作处理的方法public Object doInSqlMapClient(SqlMapExecutor executor) throws SQLException {//调用Ibatis SqlMapSession对象的queryForObejct方法return executor.queryForObject(statementName, parameterObject);}});}