MyBatis源码分析（二续）SqlSource创建流程，SQL如何解析？如何将#{id}变成?的
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文章目录
实例
此处我们分析的sql：
<select id="selectBlog" resultType="com.demo.Blog" useCache="true">
select * from blog where id = #id
</select>
一、SqlSource处理入口
在处理配置文件时，会处理Mapper.xml文件：
// org.apache.ibatis.builder.xml.XMLConfigBuilder#parseConfiguration
private void parseConfiguration(XNode root)
try
// issue #117 read properties first
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 #631
environmentsElement(root.evalNode("environments"));
databaseIdProviderElement(root.evalNode("databaseIdProvider"));
typeHandlerElement(root.evalNode("typeHandlers"));
mapperElement(root.evalNode("mappers")); // 处理mapper标签
catch (Exception e)
throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e);
// org.apache.ibatis.builder.xml.XMLConfigBuilder#mapperElement
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);
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);
try(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);
try(InputStream inputStream = Resources.getUrlAsStream(url))
XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, url, configuration.getSqlFragments());
mapperParser.parse(); // 解析Mapper.xml
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.");
// org.apache.ibatis.builder.xml.XMLMapperBuilder#parse
public void parse()
if (!configuration.isResourceLoaded(resource))
configurationElement(parser.evalNode("/mapper"));
configuration.addLoadedResource(resource);
bindMapperForNamespace();
parsePendingResultMaps();
parsePendingCacheRefs();
// 预处理Statement
parsePendingStatements();
// org.apache.ibatis.builder.xml.XMLMapperBuilder#parsePendingStatements
private void parsePendingStatements()
Collection<XMLStatementBuilder> incompleteStatements = configuration.getIncompleteStatements();
synchronized (incompleteStatements)
Iterator<XMLStatementBuilder> iter = incompleteStatements.iterator();
while (iter.hasNext())
try
iter.next().parseStatementNode(); // 处理node
iter.remove();
catch (IncompleteElementException e)
// Statement is still missing a resource...
// 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;
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());
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;
// 创建SqlSource核心逻辑
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");
builderAssistant.addMappedStatement(id, sqlSource, statementType, sqlCommandType,
fetchSize, timeout, parameterMap, parameterTypeClass, resultMap, resultTypeClass,
resultSetTypeEnum, flushCache, useCache, resultOrdered,
keyGenerator, keyProperty, keyColumn, databaseId, langDriver, resultSets);
我们找到了处理SqlSource的核心入口。
二、SqlSource处理逻辑
创建SqlSource，解析SQL，封装SQL语句（未参数绑定）和入参信息。
// org.apache.ibatis.scripting.xmltags.XMLLanguageDriver#createSqlSource(org.apache.ibatis.session.Configuration, org.apache.ibatis.parsing.XNode, java.lang.Class<?>)
@Override
public SqlSource createSqlSource(Configuration configuration, XNode script, Class<?> parameterType)
// 初始化了动态SQL标签处理器
XMLScriptBuilder builder = new XMLScriptBuilder(configuration, script, parameterType);
// 解析动态SQL
return builder.parseScriptNode();
1、XMLScriptBuilder 构造方法
public XMLScriptBuilder(Configuration configuration, XNode context, Class<?> parameterType)
super(configuration);
this.context = context;
this.parameterType = parameterType;
// 初始化动态SQL中的节点处理器集合
initNodeHandlerMap();
// 动态sql所有的节点
private void initNodeHandlerMap()
nodeHandlerMap.put("trim", new TrimHandler());
nodeHandlerMap.put("where", new WhereHandler());
nodeHandlerMap.put("set", new SetHandler());
nodeHandlerMap.put("foreach", new ForEachHandler());
nodeHandlerMap.put("if", new IfHandler());
nodeHandlerMap.put("choose", new ChooseHandler());
nodeHandlerMap.put("when", new IfHandler());
nodeHandlerMap.put("otherwise", new OtherwiseHandler());
nodeHandlerMap.put("bind", new BindHandler());
2、解析动态sql
XMLScriptBuilder#parseScriptNode用于解析动态sql：
public SqlSource parseScriptNode()
// 解析select\\insert\\ update\\delete标签中的SQL语句，最终将解析到的SqlNode封装到MixedSqlNode中的List集合中
// ****将带有$号的SQL信息封装到TextSqlNode
// ****将带有#号的SQL信息封装到StaticTextSqlNode
// ****将动态SQL标签中的SQL信息分别封装到不同的SqlNode中
MixedSqlNode rootSqlNode = parseDynamicTags(context);
SqlSource sqlSource;
if (isDynamic)
// 如果SQL中包含$和动态SQL语句，则将SqlNode封装到DynamicSqlSource
// 最终结果是：select id from blog where id = $id
sqlSource = new DynamicSqlSource(configuration, rootSqlNode);
else
// 如果SQL中包含#，则将SqlNode封装到RawSqlSource中，并指定parameterType
// 最终的结果是：select id from blog where id = ?
sqlSource = new RawSqlSource(configuration, rootSqlNode, parameterType);
return sqlSource;
parseDynamicTags解析sql语句：
解析select\\insert\\ update\\delete标签中的SQL语句，最终将解析到的SqlNode封装到MixedSqlNode中的List集合中。
// org.apache.ibatis.scripting.xmltags.XMLScriptBuilder#parseDynamicTags
protected MixedSqlNode parseDynamicTags(XNode node)
List<SqlNode> contents = new ArrayList<>();
//获取<select>\\<insert>\\<update>\\<delete>4个标签的子节点，子节点包括元素节点和文本节点
NodeList children = node.getNode().getChildNodes();
for (int i = 0; i < children.getLength(); i++)
// 获取标签内的原始自定义sql：select * from blog where id = #id
XNode child = node.newXNode(children.item(i));
// 处理文本节点
if (child.getNode().getNodeType() == Node.CDATA_SECTION_NODE || child.getNode().getNodeType() == Node.TEXT_NODE)
String data = child.getStringBody("");
// 将文本内容封装到SqlNode中，还是原始sql
TextSqlNode textSqlNode = new TextSqlNode(data);
// SQL语句中带有$的话，就表示是dynamic的
if (textSqlNode.isDynamic())
contents.add(textSqlNode);
isDynamic = true;
else
// SQL语句中（除了$和下面的动态SQL标签），就表示是static的
// StaticTextSqlNode的apply只是进行字符串的追加操作
contents.add(new StaticTextSqlNode(data));
//处理元素节点
else if (child.getNode().getNodeType() == Node.ELEMENT_NODE) // issue #628
String nodeName = child.getNode().getNodeName();
// 动态SQL标签处理器
// 策略模式
NodeHandler handler = nodeHandlerMap.get(nodeName);
if (handler == null)
throw new BuilderException("Unknown element <" + nodeName + "> in SQL statement.");
handler.handleNode(child, contents);
// 动态SQL标签是dynamic的
isDynamic = true;
return new MixedSqlNode(contents);
最终返回了携带了原始sql的对象。
3、DynamicSqlSource
如果SQL中包含$和动态SQL语句，则将SqlNode封装到DynamicSqlSource。
咱们此处研究的是简单的、包含#id的sql，暂不研究动态SQL。
select id from blog where id = $id
比如说以上sql，会原封不动的生成SqlSource，并不会进行解析。
4、RawSqlSource解析sql
如果SQL中包含#，则将SqlNode封装到RawSqlSource中，并指定parameterType
我们看一下RawSqlSource的构造方法：
public RawSqlSource以上是关于MyBatis源码分析（二续）SqlSource创建流程，SQL如何解析？如何将#{id}变成?的的主要内容，如果未能解决你的问题，请参考以下文章