Mybatis 原始碼分析初始化
阿新 • • 發佈：2019-01-10
Mybatis使用時通過sqlsessionFactory獲取一個sqlsession，而sqlsessionFactory是通過SqlSessionFactoryBuilder來構建一個sqlsessionFactory,通過傳入的引數來構建。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);
然後通過SqlSessionFactoryBuilder的build方法解析inputStream獲取到mybatis-config.xml的詳細配置。把mybatis-config.xml解析XPathParser
public XMLConfigBuilder(InputStream inputStream, String environment, Properties props) { //解析成為一個XpathParser然後把mybatis設定到configuration中 this(new XPathParser(inputStream, true, props, new XMLMapperEntityResolver()), environment, props); } private XMLConfigBuilder(XPathParser parser, String environment, Properties props) { //建立一個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並且把預設的類型別名註冊進去
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); }
然後通過XMLConfigBuilder的parse方法解析xmlConfigBuilder,然後呼叫parseConfiguration方法
public SqlSessionFactory build(Reader reader, String environment, Properties properties) {
try {
XMLConfigBuilder parser = new XMLConfigBuilder(reader, environment, properties);
//解析XMLConfigBuilder 然後構建出一個SqlSessionFactory，XMLConfigBuilder解析呼叫parse方法解析為Configuration
//SqlSessionFactory 為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標籤解析成一個xnode物件然後解析裡面的所有屬性
parseConfiguration(parser.evalNode("/configuration"));
return configuration;
}
private void parseConfiguration(XNode root) {
try {
//解析properties 然後設定到configuration中
propertiesElement(root.evalNode("properties"));
//解析settings
Properties settings = settingsAsProperties(root.evalNode("settings"));
loadCustomVfs(settings);
//解析typeAliases 然後設定到configuration中
typeAliasesElement(root.evalNode("typeAliases"));
//解析plugins 然後設定到configuration中
pluginElement(root.evalNode("plugins"));
objectFactoryElement(root.evalNode("objectFactory"));
objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));
reflectorFactoryElement(root.evalNode("reflectorFactory"));
//然後設定到configuration中
settingsElement(settings);
// read it after objectFactory and objectWrapperFactory issue #631
//解析environments 然後設定到configuration中
environmentsElement(root.evalNode("environments"));
databaseIdProviderElement(root.evalNode("databaseIdProvider"));
//解析environments 然後設定到configuration中
typeHandlerElement(root.evalNode("typeHandlers"));
//解析mappers 然後設定到configuration中
mapperElement(root.evalNode("mappers"));
} catch (Exception e) {
throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e);
}
}呼叫propertiesElement解析properties 標籤
//解析properties標籤
private void propertiesElement(XNode context) throws Exception {
if (context != null) {
//獲取所有的prop所有子節點然後把資料塞到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不為空那麼把resource的資料放入到Properties中
defaults.putAll(Resources.getResourceAsProperties(resource));
} else if (url != null) {//如果url不為空那麼把resource的資料放入到Properties中
defaults.putAll(Resources.getUrlAsProperties(url));
}
Properties vars = configuration.getVariables();
if (vars != null) {
defaults.putAll(vars);
}
parser.setVariables(defaults);//把Properties的資料設定到XPathParser中
configuration.setVariables(defaults);//把Properties的資料設定到configuration中
}
}呼叫typeAliasesElement解析typeAliases標籤
//解析類型別名
private void typeAliasesElement(XNode parent) {
if (parent != null) {
for (XNode child : parent.getChildren()) {//獲取標籤下的typeAliases 下的所有標籤
if ("package".equals(child.getName())) {//如果是package 類型別名註冊到configuration中
String typeAliasPackage = child.getStringAttribute("name");
configuration.getTypeAliasRegistry().registerAliases(typeAliasPackage);
} else {//如果是typeAlias 類型別名註冊到configuration中，把型別和別名對應起來注入到config總
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);
}
}
}
}
}
電泳pluginElement解析plugin
//解析plugins 然後設定到configuration中，然後新增到攔截器鏈中
private void pluginElement(XNode parent) throws Exception {
if (parent != null) {
for (XNode child : parent.getChildren()) {
String interceptor = child.getStringAttribute("interceptor");
Properties properties = child.getChildrenAsProperties();//獲取攔截器配置的屬性
Interceptor interceptorInstance = (Interceptor) resolveClass(interceptor).newInstance();//建立攔截器例項
interceptorInstance.setProperties(properties);//設定屬性
configuration.addInterceptor(interceptorInstance);//新增到攔截器鏈中對執行操作進行攔截
}
}
}呼叫environmentsElement解析environments
//設定環境
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"));//事物管理庫
DataSourceFactory dsFactory = dataSourceElement(child.evalNode("dataSource"));//資料來源
DataSource dataSource = dsFactory.getDataSource();
Environment.Builder environmentBuilder = new Environment.Builder(id)
.transactionFactory(txFactory)
.dataSource(dataSource);
configuration.setEnvironment(environmentBuilder.build());//設定環境
}
}
}
}呼叫typeHandlerElement解析typeHandler
//把typeHandler註冊到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");//獲取java型別
String jdbcTypeName = child.getStringAttribute("jdbcType");//獲取資料型別
String handlerTypeName = child.getStringAttribute("handler");//獲取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);
}
}
}
}
}呼叫mapperElement解析mappers，把mapper解析成XMLMapperBuilder 然後解析資料，設定到configuration中
//解析mapper標籤然後把mapper註冊到configuration中
private void mapperElement(XNode parent) throws Exception {
if (parent != null) {
for (XNode child : parent.getChildren()) {
if ("package".equals(child.getName())) {//通過註解方式來讀取資訊
String mapperPackage = child.getStringAttribute("name");
configuration.addMappers(mapperPackage);//把mapperpackage新增到configuration中然後在新增以後解析mapper
} else {
String resource = child.getStringAttribute("resource");
String url = child.getStringAttribute("url");
String mapperClass = child.getStringAttribute("class");
if (resource != null && url == null && mapperClass == null) {//獲取resource然後解析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) {//獲取url然後解析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) {//獲取mapperClass然後解析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.");
}
}
}
}
}呼叫configurationElement解析mapper檔案
//解析mapper檔案
public void parse() {
if (!configuration.isResourceLoaded(resource)) {
//解析mapper標籤然後返回xnode物件，然後進行處理
configurationElement(parser.evalNode("/mapper"));
//把解析的resource新增到configuration中然後避免重複載入
configuration.addLoadedResource(resource);
//繫結mapper和namespace
bindMapperForNamespace();
}
//沒有解析的東西在這裡解析？？？
parsePendingResultMaps();
parsePendingCacheRefs();
parsePendingStatements();
}
//解析mapper檔案
private void configurationElement(XNode context) {
try {
//獲取namespace如果空丟擲異常
String namespace = context.getStringAttribute("namespace");
if (namespace == null || namespace.equals("")) {
throw new BuilderException("Mapper's namespace cannot be empty");
}
//把mapper包裝成一個MapperBuilderAssistant 然後用來解析
builderAssistant.setCurrentNamespace(namespace);
//解析cache-ref 並且把兩個namespace繫結起來 二級快取
cacheRefElement(context.evalNode("cache-ref"));
//解析cache 二級快取
cacheElement(context.evalNode("cache"));
//解析parameterMap，解析出所有的parameterMap 然後儲存到MapperBuilderAssistant中
//然後新增到configuration中的parameterMaps，<namespace+parameterMap.id,parameterMap>
parameterMapElement(context.evalNodes("/mapper/parameterMap"));
//解析resultMap ,儲存到MapperBuilderAssistant中
//resultMap新增到configuration中的resultMaps中儲存型別為<namespace+resultMap.id,resultMap>
resultMapElements(context.evalNodes("/mapper/resultMap"));
//解析sql語句然後把sql語句儲存到本地sqlFragments中<namespace+sql.id,sql>
sqlElement(context.evalNodes("/mapper/sql"));
//解析sql語句，吧sql語句解析成MappedStatement，然後把資料新增到configuration中
//configuration儲存資料為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);
}
}呼叫bindMapperForNamespace用於繫結型別和namespace
//繫結mapper和namespace
private void bindMapperForNamespace() {
//獲取namespace
String namespace = builderAssistant.getCurrentNamespace();
if (namespace != null) {
Class<?> boundType = null;
try {
//獲取namespace對應的介面
boundType = Resources.classForName(namespace);
} catch (ClassNotFoundException e) {
//ignore, bound type is not required
}
//如果是個類或者是個介面
if (boundType != null) {
//如果型別不為空且沒有解析過該mapper
if (!configuration.hasMapper(boundType)) {
//把namespace新增到已解析namespace中
configuration.addLoadedResource("namespace:" + namespace);
//把namespace對應的型別新增到configuration中
configuration.addMapper(boundType);
}
}
}
}全部解析完成以後，呼叫SqlSessionFactoryBuilder的build的方法，把所有解析的配置資訊存放到configuration中然後賦值給預設的DefaultSqlSessionFactory中，在整個mybatis中configuration使用頻率相當之高
public SqlSessionFactory build(Configuration config) {
return new DefaultSqlSessionFactory(config);
}通過程式碼獲取一個SqlSession 呼叫sqlSessionFactory.openSession()方法，獲取預設的sqlsession
private SqlSession openSessionFromDataSource(ExecutorType execType, TransactionIsolationLevel level, boolean autoCommit) {
Transaction tx = null;
try {
//獲取環境資訊
final Environment environment = configuration.getEnvironment();
//獲取事務管理器從環境資訊
final TransactionFactory transactionFactory = getTransactionFactoryFromEnvironment(environment);
//建立一個事務管理器，，預設自動提交為false
tx = transactionFactory.newTransaction(environment.getDataSource(), level, autoCommit);
//通過事務管理器和執行器獲取一個執行器
final Executor executor = configuration.newExecutor(tx, execType);
//然後設定給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();
}
}獲取mapper檔案，通過sqlSession呼叫getMapper方法獲取mapper物件的動態代理物件，從configuration中獲取物件
//獲取mapper物件
public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
return mapperRegistry.getMapper(type, sqlSession);
}
public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
//從knownMappers獲取MapperProxyFactory的mapper資料
final MapperProxyFactory<T> mapperProxyFactory = (MapperProxyFactory<T>) knownMappers.get(type);
if (mapperProxyFactory == null) {
throw new BindingException("Type " + type + " is not known to the MapperRegistry.");
}
try {
//然後sqlsqssion放到mapper物件中然後獲取
return mapperProxyFactory.newInstance(sqlSession);
} catch (Exception e) {
throw new BindingException("Error getting mapper instance. Cause: " + e, e);
}
}