本文简单介绍mybatis的SqlSessionFactory和SQLSession初始化与创建，为下面的SQL执行的源码解析打下基础
本章要点
- XML解析
- SqlSessionFactory的创建
- SQLSession的创建
1.XML解析及SqlSessionFactory的创建
- 初始化文件org.apache.ibatis.session.SqlSessionFactoryBuilder.build(Reader)
public SqlSessionFactory build(Reader reader, String environment, Properties properties) {
try {
XMLConfigBuilder parser = new XMLConfigBuilder(reader, environment, properties);
return build(parser.parse());//parser.parse()解析配置文件
} 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.
}
}
}
- 先看怎么初始化配置的org.apache.ibatis.builder.xml.XMLConfigBuilder.parse()
public Configuration parse() {
if (parsed) { //只解析一次
throw new BuilderException("Each XMLConfigBuilder can only be used once.");
}
parsed = true;
parseConfiguration(parser.evalNode("/configuration"));//获取mybatis-config.xml配置文件的configuration节点
return configuration;
}
- 根据configuration节点（根节点来初始化配置信息）org.apache.ibatis.builder.xml.XMLConfigBuilder.parseConfiguration(XNode)
private void parseConfiguration(XNode root) {
try {
Properties settings = settingsAsPropertiess(root.evalNode("settings"));//获取settings节点信息
//issue #117 read properties first
propertiesElement(root.evalNode("properties"));//解析properties放到configuration对象中
loadCustomVfs(settings);
typeAliasesElement(root.evalNode("typeAliases"));//解析typeAliases放到configuration对象中
pluginElement(root.evalNode("plugins"));//解析plugins放到configuration对象中
objectFactoryElement(root.evalNode("objectFactory"));
objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));
reflectorFactoryElement(root.evalNode("reflectorFactory"));
settingsElement(settings);
// read it after objectFactory and objectWrapperFactory issue #631
environmentsElement(root.evalNode("environments"));
databaseIdProviderElement(root.evalNode("databaseIdProvider"));
typeHandlerElement(root.evalNode("typeHandlers"));//解析typeHandlers放到configuration对象中
mapperElement(root.evalNode("mappers"));//这个就十分重要了
} catch (Exception e) {
throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e);
}
}
- 解析mappers：org.apache.ibatis.builder.xml.XMLConfigBuilder.mapperElement(XNode)
private void mapperElement(XNode parent) throws Exception {
if (parent != null) {
for (XNode child : parent.getChildren()) {
if ("package".equals(child.getName())) {
String mapperPackage = child.getStringAttribute("name");
configuration.addMappers(mapperPackage);//配置的package,作用是将下的所有的接口类放到knownMappers（Map）中，key为全类名，value为MapperProxyFactory
} else {
String resource = child.getStringAttribute("resource");
String url = child.getStringAttribute("url");
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.");
}
}
}
}
}
- 获取packageName下的所有的类org.apache.ibatis.binding.MapperRegistry.addMappers(String, Class)
public void addMappers(String packageName, Class superType) {
ResolverUtil> resolverUtil = new ResolverUtil>();
resolverUtil.find(new ResolverUtil.IsA(superType), packageName);//拿到packageName下所有的类，放到org.apache.ibatis.io.ResolverUtil的集合matches中
Set>> mapperSet = resolverUtil.getClasses();//获取matches中的类
for (Class mapperClass : mapperSet) {
addMapper(mapperClass);//遍历循环
}
}
- 将所有的接口放到缓存中：org.apache.ibatis.binding.MapperRegistry.addMapper(Class
)
public void addMapper(Class type) {
if (type.isInterface()) {//是否是接口
if (hasMapper(type)) {
throw new BindingException("Type " + type + " is already known to the MapperRegistry.");
}
boolean loadCompleted = false;
try {
knownMappers.put(type, new MapperProxyFactory(type));
// It's important that the type is added before the parser is run
// otherwise the binding may automatically be attempted by the
// mapper parser. If the type is already known, it won't try.
MapperAnnotationBuilder parser = new MapperAnnotationBuilder(config, type);
parser.parse();//解析相应的mapper的xml文件
loadCompleted = true;
} finally {
if (!loadCompleted) {
knownMappers.remove(type);
}
}
}
}
- 解析对应的每个mapper.xml文件 org.apache.ibatis.builder.annotation.MapperAnnotationBuilder.parse()
public void parse() {
String resource = type.toString();
if (!configuration.isResourceLoaded(resource)) {//判断是都加载过文件
loadXmlResource();//加载xml文件，并解析mapper节点，并将接口全类名注册到mapperRegistry中
configuration.addLoadedResource(resource);//加载过的文件放到loadedResources
assistant.setCurrentNamespace(type.getName());
parseCache();
parseCacheRef();
Method[] methods = type.getMethods();
for (Method method : methods) {
try {
// issue #237
if (!method.isBridge()) {
parseStatement(method);//解析接口中的每个方法中的参数，对应MappedStatement放入到mappedStatements,
}
} catch (IncompleteElementException e) {
configuration.addIncompleteMethod(new MethodResolver(this, method));
}
}
}
parsePendingMethods();
}
org.apache.ibatis.builder.annotation.MapperAnnotationBuilder.loadXmlResource()
private void loadXmlResource() {
// Spring may not know the real resource name so we check a flag
// to prevent loading again a resource twice
// this flag is set at XMLMapperBuilder#bindMapperForNamespace
if (!configuration.isResourceLoaded("namespace:" + type.getName())) {
String xmlResource = type.getName().replace('.', '/') + ".xml";//接口名对应的xml文件
InputStream inputStream = null;
try {
inputStream = Resources.getResourceAsStream(type.getClassLoader(), xmlResource);
} catch (IOException e) {
// ignore, resource is not required
}
if (inputStream != null) {
XMLMapperBuilder xmlParser = new XMLMapperBuilder(inputStream, assistant.getConfiguration(), xmlResource, configuration.getSqlFragments(), type.getName());
xmlParser.parse();
}
}
}
- 解析每个mapper接口中的方法：org.apache.ibatis.builder.xml.XMLMapperBuilder.parse()
public void parse() {
if (!configuration.isResourceLoaded(resource)) {
configurationElement(parser.evalNode("/mapper"));//解析mapper下的子节点
configuration.addLoadedResource(resource);
bindMapperForNamespace();
}
parsePendingResultMaps();
parsePendingChacheRefs();
parsePendingStatements();
}
- 解析mapper
private void configurationElement(XNode context) {
try {
String namespace = context.getStringAttribute("namespace");
if (namespace == null || namespace.equals("")) {
throw new BuilderException("Mapper's namespace cannot be empty");
}
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"));
buildStatementFromContext(context.evalNodes("select|insert|update|delete"));
} catch (Exception e) {
throw new BuilderException("Error parsing Mapper XML. Cause: " + e, e);
}
}
- 解析SQL语句
org.apache.ibatis.builder.xml.XMLMapperBuilder.buildStatementFromContext(List, String)
private void buildStatementFromContext(List list, String requiredDatabaseId) {//requiredDatabaseId多数据源，数据库id
for (XNode context : list) {
final XMLStatementBuilder statementParser = new XMLStatementBuilder(configuration, builderAssistant, context, requiredDatabaseId);
try {
statementParser.parseStatementNode();//解析sql片段成MappedStatement放到mappedStatements中
} catch (IncompleteElementException e) {
configuration.addIncompleteStatement(statementParser);//解析sql片段成XMLStatementBuilder放到incompleteStatements中
}
}
}
-解析xml中的sql片段org.apache.ibatis.builder.xml.XMLStatementBuilder.parseStatementNode()
public void parseStatementNode() {
String id = context.getStringAttribute("id");
String databaseId = context.getStringAttribute("databaseId");
if (!databaseIdMatchesCurrent(id, databaseId, this.requiredDatabaseId)) {
return;
}
Integer fetchSize = context.getIntAttribute("fetchSize");
Integer timeout = context.getIntAttribute("timeout");
String parameterMap = context.getStringAttribute("parameterMap");
String parameterType = context.getStringAttribute("parameterType");
Class parameterTypeClass = resolveClass(parameterType);
String resultMap = context.getStringAttribute("resultMap");
String resultType = context.getStringAttribute("resultType");
String lang = context.getStringAttribute("lang");
LanguageDriver langDriver = getLanguageDriver(lang);
Class resultTypeClass = resolveClass(resultType);
String resultSetType = context.getStringAttribute("resultSetType");
StatementType statementType = StatementType.valueOf(context.getStringAttribute("statementType", StatementType.PREPARED.toString()));
ResultSetType resultSetTypeEnum = resolveResultSetType(resultSetType);
String nodeName = context.getNode().getNodeName();
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());
// Parse selectKey after includes and remove them.
processSelectKeyNodes(id, parameterTypeClass, langDriver);
// Parse the SQL (pre: and were parsed and removed)
SqlSource sqlSource = langDriver.createSqlSource(configuration, context, parameterTypeClass);//非常重要，解析xml并组装sql
String resultSets = context.getStringAttribute("resultSets");
String keyProperty = context.getStringAttribute("keyProperty");
String keyColumn = context.getStringAttribute("keyColumn");
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))
? new Jdbc3KeyGenerator() : new NoKeyGenerator();
}
builderAssistant.addMappedStatement(id, sqlSource, statementType, sqlCommandType,
fetchSize, timeout, parameterMap, parameterTypeClass, resultMap, resultTypeClass,
resultSetTypeEnum, flushCache, useCache, resultOrdered,
keyGenerator, keyProperty, keyColumn, databaseId, langDriver, resultSets);
}
- 解析xml并组装sql
public SqlSource createSqlSource(Configuration configuration, XNode script, Class parameterType) {
XMLScriptBuilder builder = new XMLScriptBuilder(configuration, script, parameterType);
return builder.parseScriptNode();
}
- org.apache.ibatis.scripting.xmltags.XMLScriptBuilder.parseScriptNode()
public SqlSource parseScriptNode() {
List contents = parseDynamicTags(context);
MixedSqlNode rootSqlNode = new MixedSqlNode(contents);
SqlSource sqlSource = null;
if (isDynamic) {
sqlSource = new DynamicSqlSource(configuration, rootSqlNode);
} else {
sqlSource = new RawSqlSource(configuration, rootSqlNode, parameterType);
}
return sqlSource;
}
- RawSqlSource构造函数org.apache.ibatis.scripting.defaults.RawSqlSource.RawSqlSource(Configuration, SqlNode, Class)
public RawSqlSource(Configuration configuration, SqlNode rootSqlNode, Class parameterType) {
this(configuration, getSql(configuration, rootSqlNode), parameterType);
}
- 获取xml中的原始sql
org.apache.ibatis.scripting.defaults.RawSqlSource.getSql(Configuration, SqlNode)
private static String getSql(Configuration configuration, SqlNode rootSqlNode) {
DynamicContext context = new DynamicContext(configuration, null);
rootSqlNode.apply(context);
return context.getSql();
}
-org.apache.ibatis.scripting.defaults.RawSqlSource.RawSqlSource(Configuration, String, Class)
public RawSqlSource(Configuration configuration, String sql, Class parameterType) {
SqlSourceBuilder sqlSourceParser = new SqlSourceBuilder(configuration);
Class clazz = parameterType == null ? Object.class : parameterType;
sqlSource = sqlSourceParser.parse(sql, clazz, new HashMap());
}
-将#占位符替换成？占位符
public SqlSource parse(String originalSql, Class parameterType, Map additionalParameters) {
ParameterMappingTokenHandler handler = new ParameterMappingTokenHandler(configuration, parameterType, additionalParameters);
GenericTokenParser parser = new GenericTokenParser("#{", "}", handler);
String sql = parser.parse(originalSql);
return new StaticSqlSource(configuration, sql, handler.getParameterMappings());//参数list
}
2.SQLSession创建
public SqlSession openSession() {
return openSessionFromDataSource(configuration.getDefaultExecutorType(), null, false);
}
private SqlSession openSessionFromDataSource(ExecutorType execType, TransactionIsolationLevel level, boolean autoCommit) {
Transaction tx = null;
try {
final Environment environment = configuration.getEnvironment();
final TransactionFactory transactionFactory = getTransactionFactoryFromEnvironment(environment);
tx = transactionFactory.newTransaction(environment.getDataSource(), level, autoCommit);
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();
}
}
3.大致流程图
sqlSession.jpg