ps) {
// 1.生成Cache对象
Cache cache = new CacheBuilder(currentNamespace)
//这里如果我们定义了<cache/>中的type，就使用自定义的Cache,否则使用和一级缓存相同的PerpetualCache
.implementation(valueOrDefault(typeClass, PerpetualCache.class))
.addDecorator(valueOrDefault(evictionClass, LruCache.class))
.clearInterval(flushInterval)
.size(size)
.readWrite(readWrite)
.blocking(blocking)
.properties(props)
.build();
// 2.添加到Configuration中
configuration.addCache(cache);
// 3.并将cache赋值给MapperBuilderAssistant.currentCache
currentCache = cache;
return cache;
}
我们看到一个Mapper.xml只会解析一次
标签，也就是只创建一次Cache对象，放进configuration中，并将cache赋值给MapperBuilderAssistant.currentCache
buildStatementFromContext(context.eva lNodes("select|insert|update|delete"));将Cache包装到MappedStatement
// buildStatementFromContext()
private void buildStatementFromContext(List<XNode> list) {
if (configuration.getDatabaseId() != null) {
buildStatementFromContext(list, configuration.getDatabaseId());
}
buildStatementFromContext(list, null);
}
//buildStatementFromContext()
private void buildStatementFromContext(List<XNode> list, String requiredDatabaseId) {
for (XNode context : list) {
final XMLStatementBuilder statementParser = new XMLStatementBuilder(configuration, builderAssistant, context, requiredDatabaseId);
try {
// 每一条执行语句转换成一个MappedStatement
statementParser.parseStatementNode();
} catch (IncompleteElementException e) {
configuration.addIncompleteStatement(statementParser);
}
}
}
// XMLStatementBuilder.parseStatementNode();
public void parseStatementNode() {
String id = context.getStringAttribute("id");
String databaseId = context.getStringAttribute("databaseId");
...
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);
...
// 创建MappedStatement对象
builderAssistant.addMappedStatement(id, sqlSource, statementType, sqlCommandType,
fetchSize, timeout, parameterMap, parameterTypeClass, resultMap, resultTypeClass,
resultSetTypeEnum, flushCache, useCache, resultOrdered,
keyGenerator, keyProperty, keyColumn, databaseId, langDriver, resultSets);
}
// builderAssistant.addMappedStatement()
public MappedStatement addMappedStatement(
String id,
...) {
if (unresolvedCacheRef) {
throw new IncompleteElementException("Cache-ref not yet resolved");
}
id = applyCurrentNamespace(id, false);
boolean isSelect = sqlCommandType == SqlCommandType.SELECT;
//创建MappedStatement对象
MappedStatement.Builder statementBuilder = new MappedStatement.Builder(configuration, id, sqlSource, sqlCommandType)
...
.flushCacheRequired(valueOrDefault(flushCache, !isSelect))
.useCache(valueOrDefaul