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读取解析配置信息并对其缓存进应用

读取数据源并且设置进环境

private void environmentsElement(XNode context) throws Exception {
//解析mybatis.xml文件
if (context != null) {//如果environment=nullenvironment=myabtis.xml中的default属性的值if (environment == null) {environment = context.getStringAttribute("default");}//遍历mybatis.xml的所有子节点for (XNode child : context.getChildren()) {//获取id的属性值String id = child.getStringAttribute("id");if (isSpecifiedEnvironment(id)) {//解析子节点transactionManager获取事务管理器工厂并转化为TransactionFactoryTransactionFactory txFactory = transactionManagerElement(child.evalNode("transactionManager"));//解析子节点dataSource并转化为DataSourceFactoryDataSourceFactory dsFactory = dataSourceElement(child.evalNode("dataSource"));DataSource dataSource = dsFactory.getDataSource();//把dataSource(数据源)和事务管理器工厂设置进环境Environment.Builder environmentBuilder = new Environment.Builder(id).transactionFactory(txFactory).dataSource(dataSource);configuration.setEnvironment(environmentBuilder.build());}}
}
}

读取mybaits.xml配置信息

private void parseConfiguration(XNode root) {
try {// issue #117 read properties first//解析properties标签propertiesElement(root.evalNode("properties"));Properties settings = settingsAsProperties(root.evalNode("settings"));loadCustomVfs(settings);loadCustomLogImpl(settings);typeAliasesElement(root.evalNode("typeAliases"));pluginElement(root.evalNode("plugins"));objectFactoryElement(root.evalNode("objectFactory"));objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));reflectorFactoryElement(root.evalNode("reflectorFactory"));settingsElement(settings);// read it after objectFactory and objectWrapperFactory issue #631environmentsElement(root.evalNode("environments"));databaseIdProviderElement(root.evalNode("databaseIdProvider"));typeHandlerElement(root.evalNode("typeHandlers"));//解析mapper.xml文件的节点mapperElement(root.evalNode("mappers"));
} catch (Exception e) {throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e);
}
}

mapperElement()源码解析

private void mapperElement(XNode parent) throws Exception {
//如果父节点不等于null
if (parent != null) {//遍历子节点for (XNode child : parent.getChildren()) {//如果child子节点的name=packageif ("package".equals(child.getName())) {//获取子节点的nameString mapperPackage = child.getStringAttribute("name");configuration.addMappers(mapperPackage);} else {//获取子节点的resourceString resource = child.getStringAttribute("resource");//获取子节点的urlString url = child.getStringAttribute("url");//获取子节点的class字符串+String mapperClass = child.getStringAttribute("class");if (resource != null && url == null && mapperClass == null) {ErrorContext.instance().resource(resource);InputStream inputStream = Resources.getResourceAsStream(resource);XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, resource, configuration.getSqlFragments());mapperParser.parse();} else if (resource == null && url != null && mapperClass == null) {ErrorContext.instance().resource(url);InputStream inputStream = Resources.getUrlAsStream(url);XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, url, configuration.getSqlFragments());mapperParser.parse();} else if (resource == null && url == null && mapperClass != null) {Class<?> mapperInterface = Resources.classForName(mapperClass);configuration.addMapper(mapperInterface);} else {throw new BuilderException("A mapper element may only specify a url, resource or class, but not more than one.");}}}
}
}

parse()源码

public void parse() {
if (!configuration.isResourceLoaded(resource)) {//配置mybatis标签configurationElement(parser.evalNode("/mapper"));configuration.addLoadedResource(resource);bindMapperForNamespace();
}parsePendingResultMaps();
parsePendingCacheRefs();
parsePendingStatements();
}

configurationElement()源码

//context：mapper.xml中的所有字符
private void configurationElement(XNode context) {
try {String namespace = context.getStringAttribute("namespace");//哦按段根节点namespace属性名是否存在属性值if (namespace == null || namespace.isEmpty()) {throw new BuilderException("Mapper's namespace cannot be empty");}//缓存namespace属性值builderAssistant.setCurrentNamespace(namespace);cacheRefElement(context.evalNode("cache-ref"));cacheElement(context.evalNode("cache"));parameterMapElement(context.evalNodes("/mapper/parameterMap"));resultMapElements(context.evalNodes("/mapper/resultMap"));sqlElement(context.evalNodes("/mapper/sql"));//解析sql语句所在的节点buildStatementFromContext(context.evalNodes("select|insert|update|delete"));
} catch (Exception e) {throw new BuilderException("Error parsing Mapper XML. The XML location is '" + resource + "'. Cause: " + e, e);
}
}

解析sql语句的方法parseStatementNode()

public void parseStatementNode() {
//找出属性名为id的属性值
String id = context.getStringAttribute("id");
//找出属性名为databaseId的属性值
String databaseId = context.getStringAttribute("databaseId");if (!databaseIdMatchesCurrent(id, databaseId, this.requiredDatabaseId)) {return;
}
//解析sql语句的节点类型(判断是select还是insert还是update还是delete)
String nodeName = context.getNode().getNodeName();
//以下为解析xml文件的操作
SqlCommandType sqlCommandType = SqlCommandType.valueOf(nodeName.toUpperCase(Locale.ENGLISH));
boolean isSelect = sqlCommandType == SqlCommandType.SELECT;
boolean flushCache = context.getBooleanAttribute("flushCache", !isSelect);
boolean useCache = context.getBooleanAttribute("useCache", isSelect);
boolean resultOrdered = context.getBooleanAttribute("resultOrdered", false);// Include Fragments before parsing
XMLIncludeTransformer includeParser = new XMLIncludeTransformer(configuration, builderAssistant);
includeParser.applyIncludes(context.getNode());String parameterType = context.getStringAttribute("parameterType");
Class<?> parameterTypeClass = resolveClass(parameterType);String lang = context.getStringAttribute("lang");
LanguageDriver langDriver = getLanguageDriver(lang);// Parse selectKey after includes and remove them.
processSelectKeyNodes(id, parameterTypeClass, langDriver);// Parse the SQL (pre: <selectKey> and <include> were parsed and removed)
KeyGenerator keyGenerator;
String keyStatementId = id + SelectKeyGenerator.SELECT_KEY_SUFFIX;
keyStatementId = builderAssistant.applyCurrentNamespace(keyStatementId, true);
if (configuration.hasKeyGenerator(keyStatementId)) {keyGenerator = configuration.getKeyGenerator(keyStatementId);
} else {keyGenerator = context.getBooleanAttribute("useGeneratedKeys",configuration.isUseGeneratedKeys() && SqlCommandType.INSERT.equals(sqlCommandType))? Jdbc3KeyGenerator.INSTANCE : NoKeyGenerator.INSTANCE;
}SqlSource sqlSource = langDriver.createSqlSource(configuration, context, parameterTypeClass);
StatementType statementType = StatementType.valueOf(context.getStringAttribute("statementType", StatementType.PREPARED.toString()));
Integer fetchSize = context.getIntAttribute("fetchSize");
Integer timeout = context.getIntAttribute("timeout");
String parameterMap = context.getStringAttribute("parameterMap");
String resultType = context.getStringAttribute("resultType");
Class<?> resultTypeClass = resolveClass(resultType);
String resultMap = context.getStringAttribute("resultMap");
String resultSetType = context.getStringAttribute("resultSetType");
ResultSetType resultSetTypeEnum = resolveResultSetType(resultSetType);
if (resultSetTypeEnum == null) {resultSetTypeEnum = configuration.getDefaultResultSetType();
}
String keyProperty = context.getStringAttribute("keyProperty");
String keyColumn = context.getStringAttribute("keyColumn");
String resultSets = context.getStringAttribute("resultSets");//解析完成,处理mapper.处理xml->把mapper的子节点(sql元素)加入全局配置
builderAssistant.addMappedStatement(id, sqlSource, statementType, sqlCommandType,fetchSize, timeout, parameterMap, parameterTypeClass, resultMap, resultTypeClass,resultSetTypeEnum, flushCache, useCache, resultOrdered,keyGenerator, keyProperty, keyColumn, databaseId, langDriver, resultSets);
}

执行sql

mybatis的三种执行器

SIMPLE

每一句sql都编译执行

[2019-06-13 11:30:38:812][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==>  Preparing: insert into t_student values (null , ?, ?, ?, ?) 
[2019-06-13 11:30:38:819][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==> Parameters: zhangsan_0(String), 20(Integer), M(String), 2019-06-13(Date)
[2019-06-13 11:30:38:824][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- <==    Updates: 1[2019-06-13 11:30:38:827][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==>  Preparing: insert into t_student values (null , ?, ?, ?, ?) 
[2019-06-13 11:30:38:828][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==> Parameters: zhangsan_1(String), 21(Integer), M(String), 2019-06-13(Date)
[2019-06-13 11:30:38:832][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- <==    Updates: 1[2019-06-13 11:30:38:833][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==>  Preparing: insert into t_student values (null , ?, ?, ?, ?) 
[2019-06-13 11:30:38:839][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==> Parameters: zhangsan_2(String), 22(Integer), M(String), 2019-06-13(Date)
[2019-06-13 11:30:38:841][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- <==    Updates: 1
...
耗时:21575 ms!

REUSE

只有第一次的insert操作才对sql编译,后面的只设置参数,执行每一条sql

[2019-06-13 11:31:11:752][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==>  Preparing: insert into t_student values (null , ?, ?, ?, ?) [2019-06-13 11:31:11:757][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==> Parameters: zhangsan_0(String), 20(Integer), M(String), 2019-06-13(Date)
[2019-06-13 11:31:11:759][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- <==    Updates: 1[2019-06-13 11:31:11:761][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==> Parameters: zhangsan_1(String), 21(Integer), M(String), 2019-06-13(Date)
[2019-06-13 11:31:11:764][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- <==    Updates: 1[2019-06-13 11:31:11:776][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==> Parameters: zhangsan_2(String), 22(Integer), M(String), 2019-06-13(Date)
[2019-06-13 11:31:11:778][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- <==    Updates: 1
...
耗时:19322 ms!

BATCH

只有第一次的insert操作才对sql编译,后面的只设置参数,到最后统一执行sql

[2019-06-13 11:31:29:270][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==>  Preparing: insert into t_student values (null , ?, ?, ?, ?) 
[2019-06-13 11:31:29:276][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==> Parameters: zhangsan_0(String), 20(Integer), M(String), 2019-06-13(Date)
[2019-06-13 11:31:29:277][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==> Parameters: zhangsan_1(String), 21(Integer), M(String), 2019-06-13(Date)
[2019-06-13 11:31:29:277][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==> Parameters: zhangsan_2(String), 22(Integer), M(String), 2019-06-13(Date)
...
耗时:835 ms!

首先打开session,调用方法DefaultSqlSessionFactory.openSessionFromDataSource()

private SqlSession openSessionFromDataSource(ExecutorType execType, TransactionIsolationLevel level, boolean autoCommit) {
Transaction tx = null;
try {//读取环境信息final Environment environment = configuration.getEnvironment();//从环境信息中读取事务处理器工厂final TransactionFactory transactionFactory = getTransactionFactoryFromEnvironment(environment);tx = transactionFactory.newTransaction(environment.getDataSource(), level, autoCommit);//获取sqlSession执行器final Executor executor = configuration.newExecutor(tx, execType);return new DefaultSqlSession(configuration, executor, autoCommit);
} catch (Exception e) {closeTransaction(tx); // may have fetched a connection so lets call close()throw ExceptionFactory.wrapException("Error opening session.  Cause: " + e, e);
} finally {ErrorContext.instance().reset();
}
}