版权声明：本文为博主原创文章，转载添加原文链接 https://blog.csdn.net/qq_34190023/article/details/80873736
SqlSessionFactoryBuilder根据传入的数据流生成Configuration对象，然后根据Configuration对象创建默认的SqlSessionFactory实例。
Mybatis初始化要经过简单的以下几步：
1. 调用SqlSessionFactoryBuilder对象的build(inputStream)方法；
2. SqlSessionFactoryBuilder会根据输入流inputStream等信息创建XMLConfigBuilder对象;
3. SqlSessionFactoryBuilder调用XMLConfigBuilder对象的parse()方法；
4. XMLConfigBuilder对象返回Configuration对象；
5. SqlSessionFactoryBuilder根据Configuration对象创建一个DefaultSessionFactory对象；
6. SqlSessionFactoryBuilder返回 DefaultSessionFactory对象给Client，供Client使用。
一、SqlSessionFactory的创建：建造者模式：
SqlSessionFactoryBuilder相关的代码如下所示：
public class SqlSessionFactoryBuilder {
public SqlSessionFactory build(Reader reader) {
return build(reader, null, null);
}
public SqlSessionFactory build(Reader reader, String environment) {
return build(reader, environment, null);
}
public SqlSessionFactory build(Reader reader, Properties properties) {
return build(reader, null, properties);
}
public SqlSessionFactory build(Reader reader, String environment, Properties properties) {
try {
XMLConfigBuilder parser = new XMLConfigBuilder(reader, environment, properties); // Don4j解析器
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 SqlSessionFactory build(InputStream inputStream) {
return build(inputStream, null, null);
}
public SqlSessionFactory build(InputStream inputStream, String environment) {
return build(inputStream, environment, null);
}
public SqlSessionFactory build(InputStream inputStream, Properties properties) {
return build(inputStream, null, properties);
}
public SqlSessionFactory build(InputStream inputStream, String environment, Properties properties) {
try {
//创建XMLConfigBuilder对象用来解析XML配置文件，生成Configuration对象
XMLConfigBuilder parser = new XMLConfigBuilder(inputStream, environment, properties);
//将XML配置文件内的信息解析成Java对象Configuration对象。根据Configuration对象创建出SqlSessionFactory对象
return build(parser.parse());
} catch (Exception e) {
throw ExceptionFactory.wrapException("Error building SqlSession.", e);
} finally {
ErrorContext.instance().reset();
try {
inputStream.close();
} catch (IOException e) {
// Intentionally ignore. Prefer previous error.
}
}
}
//内部通过Configuration对象来创建SqlSessionFactory,也可以自己通过API构造好Configuration对象，调用此方法创建SqlSessionFactory
public SqlSessionFactory build(Configuration config) {
return new DefaultSqlSessionFactory(config);
}
}：SqlSessionFactoryBuilder用于创建SqlSessionFactory。通过传入的xml配置文件，进行解析，保存为内部的Configuration对象，最终调用build方法，new出一个DefaultSqlSessionFactory。
本过程设计的对象：
SqlSessionFactoryBuilder： SqlSessionFactory的构造器，用于创建SqlSessionFactory，采用了Builder设计模式
Configuration ：该对象是mybatis-config.xml文件中所有mybatis配置信息
SqlSessionFactory：SqlSession工厂类，以工厂形式创建SqlSession对象，采用了Factory工厂设计模式
XmlConfigParser ：负责将mybatis-config.xml配置文件解析成Configuration对象，共SqlSessonFactoryBuilder使用，创建SqlSessionFactory
二、解析xml配置为Configuration对象的过程：
这个过程比较复杂，主要是解析配置文件，然后保存到map中。
当SqlSessionFactoryBuilder执行build()方法，调用了XMLConfigBuilder的parse()方法，然后返回了Configuration对象
过程： XMLConfigBuilder会将XML配置文件的信息转换为Document对象，而XML配置定义文件DTD转换成XMLMapperEntityResolver对象，然后将二者封装到XpathParser对象中，XpathParser的作用是提供根据Xpath表达式获取基本的DOM节点Node信息的操作。
XMLConfigBuilder会将xml以及配置的mapper文件转化成对应的document对象，将配置定义文件dtd加载成EntityResolve对象，组成XPathParser对象，然后根据XPath表达式访问Node节点
XMLConfigBuilder调用parse()方法：从XPathParser中取出<configuration>节点对应的Node对象，然后解析此Node节点的子Node：properties, settings,typeAliases,typeHandlers, objectFactory, objectWrapperFactory, plugins, environments,databaseIdProvider,mappers
源码分析：
public Configuration parse() {
if (parsed) {
throw new BuilderException("Each XMLConfigBuilder can only be used once.");
}
parsed = true;
parseConfiguration(parser.evalNode("/configuration")); //
return configuration;
}
//解析 "/configuration"节点下的子节点信息，然后将解析的结果设置到Configuration对象中
private void parseConfiguration(XNode root) {
try {
propertiesElement(root.evalNode("properties"));//1.首先处理properties 节点
Properties settings = settingsAsProperties(root.evalNode("settings"));
loadCustomVfs(settings);
typeAliasesElement(root.evalNode("typeAliases"));//2.处理typeAliases
pluginElement(root.evalNode("plugins")); //3.处理插件
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")); // 这里解析出SQL。其实也就是mapper文件或mapper注解
} catch (Exception e) {
throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e);
}
}解析mapper的过程：
private void mapperElement(XNode parent) throws Exception {
if (parent != null) {
for (XNode child : parent.getChildren()) { // 遍历
if ("package".equals(child.getName())) { //
String mapperPackage = child.getStringAttribute("name");
configuration.addMappers(mapperPackage); // 这里添加了mappers
} 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.");
}
}
}
}
}这里的Configuration对象在循环中add了mapper
Configuration
public class Configuration {
protected Environment environment;
。。。。
protected final MapperRegistry mapperRegistry = new MapperRegistry(this);
public void addMappers(String packageName, Class<?> superType) {
mapperRegistry.addMappers(packageName, superType);
}
public void addMappers(String packageName) {
mapperRegistry.addMappers(packageName);
}可以看到在Configuration中，使用mapperRegistry进行添加
MapperRegistry：
public void addMappers(String packageName) {
addMappers(packageName, Object.class);
}
public void addMappers(String packageName, Class<?> superType) {
ResolverUtil<Class<?>> resolverUtil = new ResolverUtil<Class<?>>();
resolverUtil.find(new ResolverUtil.IsA(superType), packageName);
Set<Class<? extends Class<?>>> mapperSet = resolverUtil.getClasses();
for (Class<?> mapperClass : mapperSet) {
addMapper(mapperClass);
}
}
public <T> void addMapper(Class<T> type) {
if (type.isInterface()) {
if (hasMapper(type)) {
throw new BindingException("Type " + type + " is already known to the MapperRegistry.");
}
boolean loadCompleted = false;
try {
knownMappers.put(type, new MapperProxyFactory<T>(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();
loadCompleted = true;
} finally {
if (!loadCompleted) {
knownMappers.remove(type);
}
}
}
}MapperRegistry调用用了MapperAnnotationBuilder进行解析
MapperAnnotationBuilder：
MapperAnnotationBuilder：
public class MapperAnnotationBuilder {
private final Set<Class<? extends Annotation>> sqlAnnotationTypes = new HashSet<Class<? extends Annotation>>();
private final Set<Class<? extends Annotation>> sqlProviderAnnotationTypes = new HashSet<Class<? extends Annotation>>();
private Configuration configuration;
private MapperBuilderAssistant assistant;
private Class<?> type;
// 这里将注解的情况加入进去，添加注解的，
public MapperAnnotationBuilder(Configuration configuration, Class<?> type) {
String resource = type.getName().replace('.', '/') + ".java (best guess)";
this.assistant = new MapperBuilderAssistant(configuration, resource);
this.configuration = configuration;
this.type = type; // 这个type是接口
sqlAnnotationTypes.add(Select.class);
sqlAnnotationTypes.add(Insert.class);
sqlAnnotationTypes.add(Update.class);
sqlAnnotationTypes.add(Delete.class);
sqlProviderAnnotationTypes.add(SelectProvider.class);
sqlProviderAnnotationTypes.add(InsertProvider.class);
sqlProviderAnnotationTypes.add(UpdateProvider.class);
sqlProviderAnnotationTypes.add(DeleteProvider.class);
}
public void parse() {
String resource = type.toString();
if (!configuration.isResourceLoaded(resource)) {
loadXmlResource(); // 首先这里是先加载xml。如果发现没有xml，不抛出异常，这里是忽略这个异常
configuration.addLoadedResource(resource); // 把加载好的资源放在loadedResources这个set容器中，表示已经加载
assistant.setCurrentNamespace(type.getName()); // 设置当前的namespace为当前类名
parseCache();
parseCacheRef();
Method[] methods = type.getMethods(); // 找到接口的所有方法
for (Method method : methods) {
try {
// issue #237
if (!method.isBridge()) { // 解析方法
parseStatement(method); // 这里对参数进行了解析
}
} catch (IncompleteElementException e) {
configuration.addIncompleteMethod(new MethodResolver(this, method));
}
}
}
parsePendingMethods();
}这个过程先是解析了加载了xml。这里涉及特别精巧，在加载xml的过程中，如果没有xml，那么xml解析器会抛出异常，而mybatis将抛出的异常进行捕获，然后忽略了这个异常，等下一个解析注解。
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"; // 这里就是默认的xml路径了，如果没有配置，那么默认需要同包下的xml
InputStream inputStream = null;
try {
inputStream = Resources.getResourceAsStream(type.getClassLoader(), xmlResource);
} catch (IOException e) { // 如果没有，则忽略这个异常
// ignore, resource is not required
}
if (inputStream != null) {
XMLMapperBuilder xmlParser = new XMLMapperBuilder(inputStream, assistant.getConfiguration(), xmlResource, configuration.getSqlFragments(), type.getName());
xmlParser.parse();
}
}
}
如果有xml，则使用XMLMapperBuilder 进行解析xml。后面讨论
回到解析方法：
public void parse() {
String resource = type.toString();
if (!configuration.isResourceLoaded(resource)) {
loadXmlResource(); // 首先这里是先加载xml。如果发现没有xml，不抛出异常，这里是忽略这个异常
configuration.addLoadedResource(resource); // 把加载好的资源放在loadedResources这个set容器中，表示已经加载
assistant.setCurrentNamespace(type.getName()); // 设置当前的namespace为当前类名
parseCache();
parseCacheRef();
Method[] methods = type.getMethods(); // 找到接口的所有方法
for (Method method : methods) {
try {
// issue #237
if (!method.isBridge()) { // 解析方法
parseStatement(method); // 这里对参数进行了解析
}
} catch (IncompleteElementException e) {
configuration.addIncompleteMethod(new MethodResolver(this, method));
}
}
}
parsePendingMethods();
}
加载xml后，会再次去遍历注解，如果xml和注解同时配置，根据代码先解析xml，后解析注解，可以得知，注解是会覆盖xml的同名方法的。
接下来会对方法参数进行解析。
// 对方法的参数进行解析
void parseStatement(Method method) {
Class<?> parameterTypeClass = getParameterType(method);
LanguageDriver languageDriver = getLanguageDriver(method);
SqlSource sqlSource = getSqlSourceFromAnnotations(method, parameterTypeClass, languageDriver); //这里会对方法以及参数进行解析，最终封装为一个很重要的类-SqlSource
if (sqlSource != null) {
Options options = method.getAnnotation(Options.class);
final String mappedStatementId = type.getName() + "." + method.getName();
Integer fetchSize = null;
Integer timeout = null;
StatementType statementType = StatementType.PREPARED;
ResultSetType resultSetType = ResultSetType.FORWARD_ONLY;
SqlCommandType sqlCommandType = getSqlCommandType(method);
boolean isSelect = sqlCommandType == SqlCommandType.SELECT;
boolean flushCache = !isSelect;
boolean useCache = isSelect;
KeyGenerator keyGenerator;
String keyProperty = "id";
String keyColumn = null;
if (SqlCommandType.INSERT.equals(sqlCommandType) || SqlCommandType.UPDATE.equals(sqlCommandType)) {
// first check for SelectKey annotation - that overrides everything else
SelectKey selectKey = method.getAnnotation(SelectKey.class);
if (selectKey != null) {
keyGenerator = handleSelectKeyAnnotation(selectKey, mappedStatementId, getParameterType(method), languageDriver);
keyProperty = selectKey.keyProperty();
} else if (options == null) {
keyGenerator = configuration.isUseGeneratedKeys() ? Jdbc3KeyGenerator.INSTANCE : NoKeyGenerator.INSTANCE;
} else {
keyGenerator = options.useGeneratedKeys() ? Jdbc3KeyGenerator.INSTANCE : NoKeyGenerator.INSTANCE;
keyProperty = options.keyProperty();
keyColumn = options.keyColumn();
}
} else {
keyGenerator = NoKeyGenerator.INSTANCE;
}
if (options != null) {
if (FlushCachePolicy.TRUE.equals(options.flushCache())) {
flushCache = true;
} else if (FlushCachePolicy.FALSE.equals(options.flushCache())) {
flushCache = false;
}
useCache = options.useCache();
fetchSize = options.fetchSize() > -1 || options.fetchSize() == Integer.MIN_VALUE ? options.fetchSize() : null; //issue #348
timeout = options.timeout() > -1 ? options.timeout() : null;
statementType = options.statementType();
resultSetType = options.resultSetType();
}
String resultMapId = null;
ResultMap resultMapAnnotation = method.getAnnotation(ResultMap.class);
if (resultMapAnnotation != null) {
String[] resultMaps = resultMapAnnotation.value();
StringBuilder sb = new StringBuilder();
for (String resultMap : resultMaps) {
if (sb.length() > 0) {
sb.append(",");
}
sb.append(resultMap);
}
resultMapId = sb.toString();
} else if (isSelect) {
resultMapId = parseResultMap(method);
}
assistant.addMappedStatement(
mappedStatementId,
sqlSource,
statementType,
sqlCommandType,
fetchSize,
timeout,
// ParameterMapID
null,
parameterTypeClass,
resultMapId,
getReturnType(method),
resultSetType,
flushCache,
useCache,
// TODO gcode issue #577
false,
keyGenerator,
keyProperty,
keyColumn,
// DatabaseID
null,
languageDriver,
// ResultSets
options != null ? nullOrEmpty(options.resultSets()) : null);
}
}
SqlSource的获取：
private SqlSource getSqlSourceFromAnnotations(Method method, Class<?> parameterType, LanguageDriver languageDriver) {
try {
Class<? extends Annotation> sqlAnnotationType = getSqlAnnotationType(method);
Class<? extends Annotation> sqlProviderAnnotationType = getSqlProviderAnnotationType(method);
if (sqlAnnotationType != null) {
if (sqlProviderAnnotationType != null) {
throw new BindingException("You cannot supply both a static SQL and SqlProvider to method named " + method.getName());
}
Annotation sqlAnnotation = method.getAnnotation(sqlAnnotationType);
final String[] strings = (String[]) sqlAnnotation.getClass().getMethod("value").invoke(sqlAnnotation);
return buildSqlSourceFromStrings(strings, parameterType, languageDriver);
} else if (sqlProviderAnnotationType != null) {
Annotation sqlProviderAnnotation = method.getAnnotation(sqlProviderAnnotationType);
return new ProviderSqlSource(assistant.getConfiguration(), sqlProviderAnnotation);
}
return null;
} catch (Exception e) {
throw new BuilderException("Could not find value method on SQL annotation. Cause: " + e, e);
}
}
ProviderSqlSource类是SqlSource的子类。存储了封装的SQL信息
public class ProviderSqlSource implements SqlSource {
public ProviderSqlSource(Configuration config, Object provider) {
String providerMethodName;
try {
this.sqlSourceParser = new SqlSourceBuilder(config);
this.providerType = (Class<?>) provider.getClass().getMethod("type").invoke(provider);
providerMethodName = (String) provider.getClass().getMethod("method").invoke(provider);
for (Method m : this.providerType.getMethods()) {
if (providerMethodName.equals(m.getName())) {
if (m.getReturnType() == String.class) {
if (providerMethod != null){
throw new BuilderException("Error creating SqlSource for SqlProvider. Method '"
+ providerMethodName + "' is found multiple in SqlProvider '" + this.providerType.getName()
+ "'. Sql provider method can not overload.");
}
this.providerMethod = m;
this.providerMethodArgumentNames = new ParamNameResolver(config, m).getNames(); // 参数名
}
}
}
} catch (BuilderException e) {
throw e;
} catch (Exception e) {
throw new BuilderException("Error creating SqlSource for SqlProvider. Cause: " + e, e);
}
if (this.providerMethod == null) {
throw new BuilderException("Error creating SqlSource for SqlProvider. Method '"
+ providerMethodName + "' not found in SqlProvider '" + this.providerType.getName() + "'.");
}
}
ParamNameResolver是获取方法参数名称的类：
public class ParamNameResolver {
public ParamNameResolver(Configuration config, Method method) {
final Class<?>[] paramTypes = method.getParameterTypes(); // 这里会先获取方法的参数类型
final Annotation[][] paramAnnotations = method.getParameterAnnotations();
final SortedMap<Integer, String> map = new TreeMap<Integer, String>();
int paramCount = paramAnnotations.length;
// get names from @Param annotations
for (int paramIndex = 0; paramIndex < paramCount; paramIndex++) {
if (isSpecialParameter(paramTypes[paramIndex])) { // 跳过特殊的参数类型，也就是判断参数的类是否是RowBounds或者ResultHandler，如果是，就跳过
// skip special parameters
continue;
}
String name = null;
for (Annotation annotation : paramAnnotations[paramIndex]) {
if (annotation instanceof Param) { // 这里解析了Param
hasParamAnnotation = true;
name = ((Param) annotation).value();
break;
}
}
if (name == null) { // 没有@Param注解
// @Param was not specified.
if (config.isUseActualParamName()) {
name = getActualParamName(method, paramIndex); // 这里会获取到真实的参数名或者是arg+索引值
}
if (name == null) { //如果还是没有取到值
// use the parameter index as the name ("0", "1", ...)
// gcode issue #71
name = String.valueOf(map.size());
}
}
map.put(paramIndex, name); // 参数索引 + 参数名
}
names = Collections.unmodifiableSortedMap(map);
}
可以看到，这里会先判断方法参数是否有@Param注解，如果有，则获取值，然后保存到map中，如果没有，判断isUseActualParamName。如果判断成功，会获取真实参数名或者是arg+索引值。如果不是，则命名默认为索引值。
参数的解析就到这里一段落。接下来是之前没有解决的xml解析的问题。
动态SQL是如何解析出来的？
XMLMapperBuilder的parse方法：
public void parse() {
if (!configuration.isResourceLoaded(resource)) {
configurationElement(parser.evalNode("/mapper"));
configuration.addLoadedResource(resource);
bindMapperForNamespace();
}
parsePendingResultMaps();
parsePendingCacheRefs();
parsePendingStatements();
}
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);
}
}
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);
}
}
}最终是使用 XMLStatementBuilder进行解析元素
XMLStatementBuilder
public class XMLStatementBuilder extends BaseBuilder {
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); // 对传入的参数进行类型解析[其实就是看是否有别名]
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())); // 默认是使用PreparedStatement，如果配置了，就使用配置的
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: <selectKey> and <include> were parsed and removed) 这里解析了SQL
SqlSource sqlSource = langDriver.createSqlSource(configuration, context, parameterTypeClass); // 这里创建了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)) ? Jdbc3KeyGenerator.INSTANCE : NoKeyGenerator.INSTANCE;
}
builderAssistant.addMappedStatement(id, sqlSource, statementType, sqlCommandType,
fetchSize, timeout, parameterMap, parameterTypeClass, resultMap, resultTypeClass,
resultSetTypeEnum, flushCache, useCache, resultOrdered,
keyGenerator, keyProperty, keyColumn, databaseId, langDriver, resultSets);
}首先，可以看到它从上下文中获取了配置文件配置的信息。根据这些信息决定创建sql的策略。
如StatementType如果没有配置的话，默认就是PreparedStatement。
关键点在于langDriver的createSqlSource方法。这里创建了SqlSource
LanguageDriver是一个就接口，xmlLanguageDriver是其实现类
public interface LanguageDriver {
ParameterHandler createParameterHandler(MappedStatement mappedStatement, Object parameterObject, BoundSql boundSql);
SqlSource createSqlSource(Configuration configuration, XNode script, Class<?> parameterType);
SqlSource createSqlSource(Configuration configuration, String script, Class<?> parameterType);
}
public class XMLLanguageDriver implements LanguageDriver {
@Override
public ParameterHandler createParameterHandler(MappedStatement mappedStatement, Object parameterObject, BoundSql boundSql) {
return new DefaultParameterHandler(mappedStatement, parameterObject, boundSql);
}
@Override
public SqlSource createSqlSource(Configuration configuration, XNode script, Class<?> parameterType) {
XMLScriptBuilder builder = new XMLScriptBuilder(configuration, script, parameterType);
return builder.parseScriptNode();
}
@Override
public SqlSource createSqlSource(Configuration configuration, String script, Class<?> parameterType) {
// issue #3
if (script.startsWith("<script>")) {
XPathParser parser = new XPathParser(script, false, configuration.getVariables(), new XMLMapperEntityResolver());
return createSqlSource(configuration, parser.evalNode("/script"), parameterType);
} else {
// issue #127
script = PropertyParser.parse(script, configuration.getVariables());
TextSqlNode textSqlNode = new TextSqlNode(script);
if (textSqlNode.isDynamic()) {
return new DynamicSqlSource(configuration, textSqlNode);
} else {
return new RawSqlSource(configuration, script, parameterType);
}
}
}
}
XMLScriptBuilder是SqlSource创建的关键类。
// 将xml中的sql封装为动态的SqlSource，最后会解析成静态的
public SqlSource parseScriptNode() {
List<SqlNode> contents = parseDynamicTags(context);
MixedSqlNode rootSqlNode = new MixedSqlNode(contents);
SqlSource sqlSource = null;
if (isDynamic) {
sqlSource = new DynamicSqlSource(configuration, rootSqlNode); // 创建动态的sql
} else {
sqlSource = new RawSqlSource(configuration, rootSqlNode, parameterType); // 创建原始的sql
}
return sqlSource;
}
List<SqlNode> parseDynamicTags(XNode node) {
List<SqlNode> contents = new ArrayList<SqlNode>();
NodeList children = node.getNode().getChildNodes();
for (int i = 0; i < children.getLength(); i++) {
XNode child = node.newXNode(children.item(i));
if (child.getNode().getNodeType() == Node.CDATA_SECTION_NODE || child.getNode().getNodeType() == Node.TEXT_NODE) {
String data = child.getStringBody("");
TextSqlNode textSqlNode = new TextSqlNode(data);
if (textSqlNode.isDynamic()) {
contents.add(textSqlNode);
isDynamic = true;
} else {
contents.add(new StaticTextSqlNode(data));
}
} else if (child.getNode().getNodeType() == Node.ELEMENT_NODE) { // issue #628
String nodeName = child.getNode().getNodeName();
NodeHandler handler = nodeHandlers(nodeName);
if (handler == null) {
throw new BuilderException("Unknown element <" + nodeName + "> in SQL statement.");
}
handler.handleNode(child, contents);
isDynamic = true;
}
}
return contents;
}
NodeHandler nodeHandlers(String nodeName) {
Map<String, NodeHandler> map = new HashMap<String, NodeHandler>();
map.put("trim", new TrimHandler());
map.put("where", new WhereHandler());
map.put("set", new SetHandler());
map.put("foreach", new ForEachHandler());
map.put("if", new IfHandler());
map.put("choose", new ChooseHandler());
map.put("when", new IfHandler());
map.put("otherwise", new OtherwiseHandler());
map.put("bind", new BindHandler());
return map.get(nodeName);
}
这里进行了动态SQL的解析，可以看到nodeHandlers方法，对不同的元素，进行不同的Handler进行解析。
最终根据判断isDynamic判断是否创建动态的SQL或静态的。最后返回这个SqlSource。
对于SqlSource的解析：
SqlSource是获取了，但是还需要经过解析，
以动态的SqlSource为例子
public class DynamicSqlSource implements SqlSource {
private Configuration configuration;
private SqlNode rootSqlNode;
public DynamicSqlSource(Configuration configuration, SqlNode rootSqlNode) {
this.configuration = configuration;
this.rootSqlNode = rootSqlNode;
}
// 在会话创建时，会被调用，然后会生成一个静态的sql，带？参数的【也就是去掉参数】
@Override
public BoundSql getBoundSql(Object parameterObject) {
DynamicContext context = new DynamicContext(configuration, parameterObject);
rootSqlNode.apply(context);
SqlSourceBuilder sqlSourceParser = new SqlSourceBuilder(configuration);
Class<?> parameterType = parameterObject == null ? Object.class : parameterObject.getClass();
SqlSource sqlSource = sqlSourceParser.parse(context.getSql(), parameterType, context.getBindings());
BoundSql boundSql = sqlSource.getBoundSql(parameterObject);
for (Map.Entry<String, Object> entry : context.getBindings().entrySet()) {
boundSql.setAdditionalParameter(entry.getKey(), entry.getValue());
}
return boundSql;
}
}sqlSourceBuilder
public class SqlSourceBuilder extends BaseBuilder {
private static final String parameterProperties = "javaType,jdbcType,mode,numericScale,resultMap,typeHandler,jdbcTypeName";
public SqlSourceBuilder(Configuration configuration) {
super(configuration);
}
public SqlSource parse(String originalSql,Class<?> parameterType,Map<String,Object> 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());
}
public class GenericTokenParser {
public String parse(String text) {
if (text == null || text.isEmpty()) { return ""; }
char[] src = text.toCharArray();
int offset = 0;
// search open token
int start = text.indexOf(openToken, offset);
if (start == -1) { return text; }
final StringBuilder builder = new StringBuilder();
StringBuilder expression = null;
while (start > -1) {
if (start > 0 && src[start - 1] == '\\') {
// this open token is escaped. remove the backslash and continue.
builder.append(src, offset, start - offset - 1).append(openToken);
offset = start + openToken.length();
} else {
// found open token. let's search close token.
if (expression == null) { expression = new StringBuilder(); }
else { expression.setLength(0); }
builder.append(src, offset, start - offset);
offset = start + openToken.length();
int end = text.indexOf(closeToken, offset);
while (end > -1) {
if (end > offset && src[end - 1] == '\\') {
// this close token is escaped. remove the backslash and continue.
expression.append(src, offset, end - offset - 1).append(closeToken);
offset = end + closeToken.length();
end = text.indexOf(closeToken, offset);
} else {
expression.append(src, offset, end - offset);
offset = end + closeToken.length();
break;
}
}
if (end == -1) {
// close token was not found.
builder.append(src, start, src.length - start);
offset = src.length;
} else {
builder.append(handler.handleToken(expression.toString())); // 添加？
offset = end + closeToken.length();
}
}
start = text.indexOf(openToken, offset);
}
if (offset < src.length) {
builder.append(src, offset, src.length - offset);
}
return builder.toString();
}
这里做了很多很复杂的事情，但是handler的handlerToken就是将用户在SQL里面写的#{}替换成?，最终由PreparedStatement编织最终传给数据库的SQL。
SqlSourceBuilder
public class SqlSourceBuilder extends BaseBuilder {
private static class ParameterMappingTokenHandler extends BaseBuilder implements TokenHandler {
@Override
public String handleToken(String content) {
parameterMappings.add(buildParameterMapping(content));
return "?";
}
private ParameterMapping buildParameterMapping(String content) {
Map<String, String> propertiesMap = parseParameterMapping(content);
String property = propertiesMap.get("property");
Class<?> propertyType;
if (metaParameters.hasGetter(property)) { // issue #448 get type from additional params
propertyType = metaParameters.getGetterType(property);
} else if (typeHandlerRegistry.hasTypeHandler(parameterType)) {
propertyType = parameterType;
} else if (JdbcType.CURSOR.name().equals(propertiesMap.get("jdbcType"))) {
propertyType = java.sql.ResultSet.class;
} else if (property != null) {
MetaClass metaClass = MetaClass.forClass(parameterType, configuration.getReflectorFactory());
if (metaClass.hasGetter(property)) {
propertyType = metaClass.getGetterType(property);
} else {
propertyType = Object.class;
}
} else {
propertyType = Object.class;
}
ParameterMapping.Builder builder = new ParameterMapping.Builder(configuration, property, propertyType);
Class<?> javaType = propertyType;
String typeHandlerAlias = null;
for (Map.Entry<String, String> entry : propertiesMap.entrySet()) {
String name = entry.getKey();
String value = entry.getValue();
if ("javaType".equals(name)) {
javaType = resolveClass(value);
builder.javaType(javaType);
} else if ("jdbcType".equals(name)) {
builder.jdbcType(resolveJdbcType(value));
} else if ("mode".equals(name)) {
builder.mode(resolveParameterMode(value));
} else if ("numericScale".equals(name)) {
builder.numericScale(Integer.valueOf(value));
} else if ("resultMap".equals(name)) {
builder.resultMapId(value);
} else if ("typeHandler".equals(name)) {
typeHandlerAlias = value;
} else if ("jdbcTypeName".equals(name)) {
builder.jdbcTypeName(value);
} else if ("property".equals(name)) {
// Do Nothing
} else if ("expression".equals(name)) {
throw new BuilderException("Expression based parameters are not supported yet");
} else {
throw new BuilderException("An invalid property '" + name + "' was found in mapping #{" + content + "}. Valid properties are " + parameterProperties);
}
}
if (typeHandlerAlias != null) {
builder.typeHandler(resolveTypeHandler(javaType, typeHandlerAlias));
}
return builder.build();
}
private Map<String, String> parseParameterMapping(String content) {
try {
return new ParameterExpression(content);
} catch (BuilderException ex) {
throw ex;
} catch (Exception ex) {
throw new BuilderException("Parsing error was found in mapping #{" + content + "}. Check syntax #{property|(expression), var1=value1, var2=value2, ...} ", ex);
}
}
}
}
在整个过程比较复杂，其实也就是不断解析xml或注解的过程
流程图