Mybatis使用时通过sqlsessionFactory获取一个sqlsession,而sqlsessionFactory是通过SqlSessionFactoryBuilder来构建一个sqlsessionFactory,通过传入的参数来构建。使用建造者模式,
InputStream configFile = new FileInputStream(
"zjx-mybatis\\src\\main\\java\\com\\zjx\\mybatis\\demo\\mybatis-config.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(configFile);
然后通过SqlSessionFactoryBuilder的build方法解析inputStream获取到mybatis-config.xml的详细配置。把mybatis-config.xml解析XPathParser
public XMLConfigBuilder(InputStream inputStream, String environment, Properties props) {
//解析成为一个XpathParser然后把mybatis设置到configuration中
this(new XPathParser(inputStream, true, props, new XMLMapperEntityResolver()), environment, props);
}
private XMLConfigBuilder(XPathParser parser, String environment, Properties props) {
//创建一个configuration
super(new Configuration());
ErrorContext.instance().resource("SQL Mapper Configuration");
this.configuration.setVariables(props);
this.parsed = false;
this.environment = environment;
this.parser = parser;
}
初始化configuration并且把默认的类型别名注册进去
public Configuration() {
typeAliasRegistry.registerAlias("JDBC", JdbcTransactionFactory.class);
typeAliasRegistry.registerAlias("MANAGED", ManagedTransactionFactory.class);
typeAliasRegistry.registerAlias("JNDI", JndiDataSourceFactory.class);
typeAliasRegistry.registerAlias("POOLED", PooledDataSourceFactory.class);
typeAliasRegistry.registerAlias("UNPOOLED", UnpooledDataSourceFactory.class);
typeAliasRegistry.registerAlias("PERPETUAL", PerpetualCache.class);
typeAliasRegistry.registerAlias("FIFO", FifoCache.class);
typeAliasRegistry.registerAlias("LRU", LruCache.class);
typeAliasRegistry.registerAlias("SOFT", SoftCache.class);
typeAliasRegistry.registerAlias("WEAK", WeakCache.class);
typeAliasRegistry.registerAlias("DB_VENDOR", VendorDatabaseIdProvider.class);
typeAliasRegistry.registerAlias("XML", XMLLanguageDriver.class);
typeAliasRegistry.registerAlias("RAW", RawLanguageDriver.class);
typeAliasRegistry.registerAlias("SLF4J", Slf4jImpl.class);
typeAliasRegistry.registerAlias("COMMONS_LOGGING", JakartaCommonsLoggingImpl.class);
typeAliasRegistry.registerAlias("LOG4J", Log4jImpl.class);
typeAliasRegistry.registerAlias("LOG4J2", Log4j2Impl.class);
typeAliasRegistry.registerAlias("JDK_LOGGING", Jdk14LoggingImpl.class);
typeAliasRegistry.registerAlias("STDOUT_LOGGING", StdOutImpl.class);
typeAliasRegistry.registerAlias("NO_LOGGING", NoLoggingImpl.class);
typeAliasRegistry.registerAlias("CGLIB", CglibProxyFactory.class);
typeAliasRegistry.registerAlias("JAVASSIST", JavassistProxyFactory.class);
languageRegistry.setDefaultDriverClass(XMLLanguageDriver.class);
languageRegistry.register(RawLanguageDriver.class);
}
然后通过XMLConfigBuilder的parse方法解析xmlConfigBuilder,然后调用parseConfiguration方法
public SqlSessionFactory build(Reader reader, String environment, Properties properties) {
try {
XMLConfigBuilder parser = new XMLConfigBuilder(reader, environment, properties);
//解析XMLConfigBuilder 然后构建出一个SqlSessionFactory,XMLConfigBuilder解析调用parse方法解析为Configuration
//SqlSessionFactory 为DefaultSqlSessionFactory
return build(parser.parse());
} catch (Exception e) {
throw ExceptionFactory.wrapException("Error building SqlSession.", e);
} finally {
ErrorContext.instance().reset();
try {
reader.close();
} catch (IOException e) {
// Intentionally ignore. Prefer previous error.
}
}
}
public Configuration parse() {
if (parsed) {
throw new BuilderException("Each XMLConfigBuilder can only be used once.");
}
parsed = true;
//先把configuration标签解析成一个xnode对象然后解析里面的所有属性
parseConfiguration(parser.evalNode("/configuration"));
return configuration;
}
private void parseConfiguration(XNode root) {
try {
//解析properties 然后设置到configuration中
propertiesElement(root.evalNode("properties"));
//解析settings
Properties settings = settingsAsProperties(root.evalNode("settings"));
loadCustomVfs(settings);
//解析typeAliases 然后设置到configuration中
typeAliasesElement(root.evalNode("typeAliases"));
//解析plugins 然后设置到configuration中
pluginElement(root.evalNode("plugins"));
objectFactoryElement(root.evalNode("objectFactory"));
objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));
reflectorFactoryElement(root.evalNode("reflectorFactory"));
//然后设置到configuration中
settingsElement(settings);
// read it after objectFactory and objectWrapperFactory issue #631
//解析environments 然后设置到configuration中
environmentsElement(root.evalNode("environments"));
databaseIdProviderElement(root.evalNode("databaseIdProvider"));
//解析environments 然后设置到configuration中
typeHandlerElement(root.evalNode("typeHandlers"));
//解析mappers 然后设置到configuration中
mapperElement(root.evalNode("mappers"));
} catch (Exception e) {
throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e);
}
}
调用propertiesElement解析properties 标签
//解析properties标签
private void propertiesElement(XNode context) throws Exception {
if (context != null) {
//获取所有的prop所有子节点然后把数据塞到Properties中
Properties defaults = context.getChildrenAsProperties();
String resource = context.getStringAttribute("resource");
String url = context.getStringAttribute("url");
if (resource != null && url != null) {
throw new BuilderException("The properties element cannot specify both a URL and a resource based property file reference. Please specify one or the other.");
}
if (resource != null) {//如果resource不为空那么把resource的数据放入到Properties中
defaults.putAll(Resources.getResourceAsProperties(resource));
} else if (url != null) {//如果url不为空那么把resource的数据放入到Properties中
defaults.putAll(Resources.getUrlAsProperties(url));
}
Properties vars = configuration.getVariables();
if (vars != null) {
defaults.putAll(vars);
}
parser.setVariables(defaults);//把Properties的数据设置到XPathParser中
configuration.setVariables(defaults);//把Properties的数据设置到configuration中
}
}
调用typeAliasesElement解析typeAliases标签
//解析类型别名
private void typeAliasesElement(XNode parent) {
if (parent != null) {
for (XNode child : parent.getChildren()) {//获取标签下的typeAliases 下的所有标签
if ("package".equals(child.getName())) {//如果是package 类型别名注册到configuration中
String typeAliasPackage = child.getStringAttribute("name");
configuration.getTypeAliasRegistry().registerAliases(typeAliasPackage);
} else {//如果是typeAlias 类型别名注册到configuration中,把类型和别名对应起来注入到config总
String alias = child.getStringAttribute("alias");
String type = child.getStringAttribute("type");
try {
Class<?> clazz = Resources.classForName(type);
if (alias == null) {
typeAliasRegistry.registerAlias(clazz);
} else {
typeAliasRegistry.registerAlias(alias, clazz);
}
} catch (ClassNotFoundException e) {
throw new BuilderException("Error registering typeAlias for '" + alias + "'. Cause: " + e, e);
}
}
}
}
}
电泳pluginElement解析plugin
//解析plugins 然后设置到configuration中,然后添加到拦截器链中
private void pluginElement(XNode parent) throws Exception {
if (parent != null) {
for (XNode child : parent.getChildren()) {
String interceptor = child.getStringAttribute("interceptor");
Properties properties = child.getChildrenAsProperties();//获取拦截器配置的属性
Interceptor interceptorInstance = (Interceptor) resolveClass(interceptor).newInstance();//创建拦截器实例
interceptorInstance.setProperties(properties);//设置属性
configuration.addInterceptor(interceptorInstance);//添加到拦截器链中对执行操作进行拦截
}
}
}
调用environmentsElement解析environments
//设置环境
private void environmentsElement(XNode context) throws Exception {
if (context != null) {
if (environment == null) {
environment = context.getStringAttribute("default");
}
for (XNode child : context.getChildren()) {
String id = child.getStringAttribute("id");
if (isSpecifiedEnvironment(id)) {
TransactionFactory txFactory = transactionManagerElement(child.evalNode("transactionManager"));//事物管理库
DataSourceFactory dsFactory = dataSourceElement(child.evalNode("dataSource"));//数据源
DataSource dataSource = dsFactory.getDataSource();
Environment.Builder environmentBuilder = new Environment.Builder(id)
.transactionFactory(txFactory)
.dataSource(dataSource);
configuration.setEnvironment(environmentBuilder.build());//设置环境
}
}
}
}
调用typeHandlerElement解析typeHandler
//把typeHandler注册到configuration
private void typeHandlerElement(XNode parent) throws Exception {
if (parent != null) {
for (XNode child : parent.getChildren()) {
if ("package".equals(child.getName())) {//把typehandler注入configuration
String typeHandlerPackage = child.getStringAttribute("name");
typeHandlerRegistry.register(typeHandlerPackage);
} else {
String javaTypeName = child.getStringAttribute("javaType");//获取java类型
String jdbcTypeName = child.getStringAttribute("jdbcType");//获取数据类型
String handlerTypeName = child.getStringAttribute("handler");//获取handler
Class<?> javaTypeClass = resolveClass(javaTypeName);
JdbcType jdbcType = resolveJdbcType(jdbcTypeName);
Class<?> typeHandlerClass = resolveClass(handlerTypeName);
if (javaTypeClass != null) {//把typehandler注入configuration
if (jdbcType == null) {
typeHandlerRegistry.register(javaTypeClass, typeHandlerClass);
} else {
typeHandlerRegistry.register(javaTypeClass, jdbcType, typeHandlerClass);
}
} else {
typeHandlerRegistry.register(typeHandlerClass);
}
}
}
}
}
调用mapperElement解析mappers,把mapper解析成XMLMapperBuilder 然后解析数据,设置到configuration中
//解析mapper标签然后把mapper注册到configuration中
private void mapperElement(XNode parent) throws Exception {
if (parent != null) {
for (XNode child : parent.getChildren()) {
if ("package".equals(child.getName())) {//通过注解方式来读取信息
String mapperPackage = child.getStringAttribute("name");
configuration.addMappers(mapperPackage);//把mapperpackage添加到configuration中然后在添加以后解析mapper
} else {
String resource = child.getStringAttribute("resource");
String url = child.getStringAttribute("url");
String mapperClass = child.getStringAttribute("class");
if (resource != null && url == null && mapperClass == null) {//获取resource然后解析mapper
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) {//获取url然后解析mapper
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) {//获取mapperClass然后解析mapper
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.");
}
}
}
}
}
调用configurationElement解析mapper文件
//解析mapper文件
public void parse() {
if (!configuration.isResourceLoaded(resource)) {
//解析mapper标签然后返回xnode对象,然后进行处理
configurationElement(parser.evalNode("/mapper"));
//把解析的resource添加到configuration中然后避免重复加载
configuration.addLoadedResource(resource);
//绑定mapper和namespace
bindMapperForNamespace();
}
//没有解析的东西在这里解析???
parsePendingResultMaps();
parsePendingCacheRefs();
parsePendingStatements();
}
//解析mapper文件
private void configurationElement(XNode context) {
try {
//获取namespace如果空抛出异常
String namespace = context.getStringAttribute("namespace");
if (namespace == null || namespace.equals("")) {
throw new BuilderException("Mapper's namespace cannot be empty");
}
//把mapper包装成一个MapperBuilderAssistant 然后用来解析
builderAssistant.setCurrentNamespace(namespace);
//解析cache-ref 并且把两个namespace绑定起来 二级缓存
cacheRefElement(context.evalNode("cache-ref"));
//解析cache 二级缓存
cacheElement(context.evalNode("cache"));
//解析parameterMap,解析出所有的parameterMap 然后保存到MapperBuilderAssistant中
//然后添加到configuration中的parameterMaps,<namespace+parameterMap.id,parameterMap>
parameterMapElement(context.evalNodes("/mapper/parameterMap"));
//解析resultMap ,保存到MapperBuilderAssistant中
//resultMap添加到configuration中的resultMaps中保存类型为<namespace+resultMap.id,resultMap>
resultMapElements(context.evalNodes("/mapper/resultMap"));
//解析sql语句然后把sql语句保存到本地sqlFragments中<namespace+sql.id,sql>
sqlElement(context.evalNodes("/mapper/sql"));
//解析sql语句,吧sql语句解析成MappedStatement,然后把数据添加到configuration中
//configuration存储数据为map<namespace+id,MappedStatement>
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);
}
}
调用bindMapperForNamespace用于绑定类型和namespace
//绑定mapper和namespace
private void bindMapperForNamespace() {
//获取namespace
String namespace = builderAssistant.getCurrentNamespace();
if (namespace != null) {
Class<?> boundType = null;
try {
//获取namespace对应的接口
boundType = Resources.classForName(namespace);
} catch (ClassNotFoundException e) {
//ignore, bound type is not required
}
//如果是个类或者是个接口
if (boundType != null) {
//如果类型不为空且没有解析过该mapper
if (!configuration.hasMapper(boundType)) {
//把namespace添加到已解析namespace中
configuration.addLoadedResource("namespace:" + namespace);
//把namespace对应的类型添加到configuration中
configuration.addMapper(boundType);
}
}
}
}
全部解析完成以后,调用SqlSessionFactoryBuilder的build的方法,把所有解析的配置信息存放到configuration中然后赋值给默认的DefaultSqlSessionFactory中,在整个mybatis中configuration使用频率相当之高
public SqlSessionFactory build(Configuration config) {
return new DefaultSqlSessionFactory(config);
}
通过代码获取一个SqlSession 调用sqlSessionFactory.openSession()方法,获取默认的sqlsession
private SqlSession openSessionFromDataSource(ExecutorType execType, TransactionIsolationLevel level, boolean autoCommit) {
Transaction tx = null;
try {
//获取环境信息
final Environment environment = configuration.getEnvironment();
//获取事务管理器从环境信息
final TransactionFactory transactionFactory = getTransactionFactoryFromEnvironment(environment);
//创建一个事务管理器,,默认自动提交为false
tx = transactionFactory.newTransaction(environment.getDataSource(), level, autoCommit);
//通过事务管理器和执行器获取一个执行器
final Executor executor = configuration.newExecutor(tx, execType);
//然后设置给sqlsession中
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();
}
}
获取mapper文件,通过sqlSession调用getMapper方法获取mapper对象的动态代理对象,从configuration中获取对象
//获取mapper对象
public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
return mapperRegistry.getMapper(type, sqlSession);
}
public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
//从knownMappers获取MapperProxyFactory的mapper数据
final MapperProxyFactory<T> mapperProxyFactory = (MapperProxyFactory<T>) knownMappers.get(type);
if (mapperProxyFactory == null) {
throw new BindingException("Type " + type + " is not known to the MapperRegistry.");
}
try {
//然后sqlsqssion放到mapper对象中然后获取
return mapperProxyFactory.newInstance(sqlSession);
} catch (Exception e) {
throw new BindingException("Error getting mapper instance. Cause: " + e, e);
}
}