在上一章中我們講述在Mapper資源文件解析過(guò)程中的ResultMap的解析過(guò)程，本章我們來(lái)收個(gè)尾，把剩下的解析全部講完。
還記得：
// XMLMapperBuilder
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. The XML location is '" + resource + "'. Cause: " + e, e);
}
}
代碼么，我們?cè)谥耙呀?jīng)分析到了resultMapElements過(guò)程，接下來(lái)我們繼續(xù)分析。
1. XMLMapperBuilder的sqlElement方法解析
private void sqlElement(List<XNode> list) {
if (configuration.getDatabaseId() != null) {
sqlElement(list, configuration.getDatabaseId());
}
sqlElement(list, null);
}
private void sqlElement(List<XNode> list, String requiredDatabaseId) {
for (XNode context : list) {
String databaseId = context.getStringAttribute("databaseId");
String id = context.getStringAttribute("id");
id = builderAssistant.applyCurrentNamespace(id, false);
if (databaseIdMatchesCurrent(id, databaseId, requiredDatabaseId)) {
sqlFragments.put(id, context);
}
}
}
這里我們分析下：
- 在邏輯上還是比較簡(jiǎn)單的，這里主要會(huì)有一個(gè)databaseId會(huì)干擾我們更好的理解閱讀，其實(shí)你可以把這個(gè)相關(guān)的代碼去掉，那么到最后其實(shí)就剩下了 sqlFragments.put(id, context)這個(gè)代碼
- 重點(diǎn)邏輯也就是在xml使用sql標(biāo)簽里的內(nèi)容，放入到sqlFragments變量中。
就這么簡(jiǎn)單的把今天二分之一的工作量分析完了，開(kāi)心~~~我們繼續(xù)往下分析buildStatementFromContext方法。
2. XMLMapperBuilder的buildStatementFromContext方法解析
private void buildStatementFromContext(List<XNode> list) {
if (configuration.getDatabaseId() != null) {
buildStatementFromContext(list, configuration.getDatabaseId());
}
buildStatementFromContext(list, null);
}
private void buildStatementFromContext(List<XNode> list, String requiredDatabaseId) {
for (XNode context : list) {
final XMLStatementBuilder statementParser = new XMLStatementBuilder(configuration, builderAssistant, context, requiredDatabaseId);
try {
statementParser.parseStatementNode();
} catch (IncompleteElementException e) {
configuration.addIncompleteStatement(statementParser);
}
}
}
跟上面的sqlElement源碼類似，當(dāng)我們?nèi)サ鬱atabaseId這個(gè)平常來(lái)講對(duì)我們無(wú)關(guān)緊要的代碼后，邏輯其實(shí)就剩下了XMLStatementBuilder類了。
2.1 XMLStatementBuilder源碼分析
我們先來(lái)看屬性和構(gòu)造方法：
private final MapperBuilderAssistant builderAssistant;
private final XNode context;
private final String requiredDatabaseId;
public XMLStatementBuilder(Configuration configuration, MapperBuilderAssistant builderAssistant, XNode context, String databaseId) {
super(configuration);
this.builderAssistant = builderAssistant;
this.context = context;
this.requiredDatabaseId = databaseId;
}
在來(lái)看上面調(diào)用的方法parseStatementNode：
public void parseStatementNode() {
String id = context.getStringAttribute("id");
String databaseId = context.getStringAttribute("databaseId");
if (!databaseIdMatchesCurrent(id, databaseId, this.requiredDatabaseId)) {
return;
}
//獲取node的DML標(biāo)簽并解析
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
//<1>解析<include>標(biāo)簽
XMLIncludeTransformer includeParser = new XMLIncludeTransformer(configuration, builderAssistant);
includeParser.applyIncludes(context.getNode());
String parameterType = context.getStringAttribute("parameterType");
Class<?> parameterTypeClass = resolveClass(parameterType);
//LanguageDriver我沒(méi)用到過(guò)，所以不做解析
String lang = context.getStringAttribute("lang");
LanguageDriver langDriver = getLanguageDriver(lang);
// Parse selectKey after includes and remove them.
//解析<selectKey>標(biāo)簽在<include>之后，問(wèn)題：如果先解析<selectKey>標(biāo)簽，在解析<include>標(biāo)簽，可行否？
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;
}
//解析動(dòng)態(tài)Sql
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);
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);
}
我們先來(lái)看<1>處邏輯：
這里是在解析<include>標(biāo)簽，我們深入來(lái)看XMLIncludeTransformer類：
繼續(xù)來(lái)看屬性和構(gòu)造方法：
// XMLIncludeTransformer
private final Configuration configuration;
private final MapperBuilderAssistant builderAssistant;
public XMLIncludeTransformer(Configuration configuration, MapperBuilderAssistant builderAssistant) {
this.configuration = configuration;
this.builderAssistant = builderAssistant;
}
繼續(xù)來(lái)看它的調(diào)用方法：
public void applyIncludes(Node source) {
Properties variablesContext = new Properties();
Properties configurationVariables = configuration.getVariables();
Optional.ofNullable(configurationVariables).ifPresent(variablesContext::putAll);
applyIncludes(source, variablesContext, false);
}
/**
* Recursively apply includes through all SQL fragments.
* @param source Include node in DOM tree
* @param variablesContext Current context for static variables with values
*/
private void applyIncludes(Node source, final Properties variablesContext, boolean included) {
if (source.getNodeName().equals("include")) {
//<1>查詢對(duì)應(yīng)的sqlfragment
Node toInclude = findSqlFragment(getStringAttribute(source, "refid"), variablesContext);
Properties toIncludeContext = getVariablesContext(source, variablesContext);
//<2>
applyIncludes(toInclude, toIncludeContext, true);
if (toInclude.getOwnerDocument() != source.getOwnerDocument()) {
toInclude = source.getOwnerDocument().importNode(toInclude, true);
}
source.getParentNode().replaceChild(toInclude, source);
while (toInclude.hasChildNodes()) {
toInclude.getParentNode().insertBefore(toInclude.getFirstChild(), toInclude);
}
toInclude.getParentNode().removeChild(toInclude);
} else if (source.getNodeType() == Node.ELEMENT_NODE) {
if (included && !variablesContext.isEmpty()) {
// replace variables in attribute values
NamedNodeMap attributes = source.getAttributes();
for (int i = 0; i < attributes.getLength(); i++) {
Node attr = attributes.item(i);
attr.setNodeValue(PropertyParser.parse(attr.getNodeValue(), variablesContext));
}
}
NodeList children = source.getChildNodes();
for (int i = 0; i < children.getLength(); i++) {
applyIncludes(children.item(i), variablesContext, included);
}
} else if (included && source.getNodeType() == Node.TEXT_NODE
&& !variablesContext.isEmpty()) {
// replace variables in text node
source.setNodeValue(PropertyParser.parse(source.getNodeValue(), variablesContext));
}
}
- 第<1>處：
private Node findSqlFragment(String refid, Properties variables) {
refid = PropertyParser.parse(refid, variables);
refid = builderAssistant.applyCurrentNamespace(refid, true);
try {
XNode nodeToInclude = configuration.getSqlFragments().get(refid);
return nodeToInclude.getNode().cloneNode(true);
} catch (IllegalArgumentException e) {
throw new IncompleteElementException("Could not find SQL statement to include with refid '" + refid + "'", e);
}
}
不知還記得否在本章開(kāi)篇分析的sqlFragment解析，這里就是通過(guò)refid直接獲取。
- 第<2>處代碼的源碼我就不貼了，看了會(huì)影響你閱讀的興趣，功能是解析${}的變量替換對(duì)應(yīng)的內(nèi)容。
之后的內(nèi)容就比較無(wú)關(guān)了。
講完了關(guān)于XMLIncludeTransformer類的解釋，我們可以看到下面是分別解析了KeyGenerator和SqlSource，最后組裝成了MappedStatement。后面會(huì)詳細(xì)講解，這里就不做展示了。
3. 今日總結(jié)
我們把剩下的mapper解析方法都已經(jīng)講完了，雖然很多重要解析我們都沒(méi)有深入分析，可能會(huì)讓你覺(jué)得很不爽，但是我們得一步步來(lái)，一口吃成胖子做不到。好啦，那你今天會(huì)有收貨么？
