简介
上一章我们大概了解了SqlSessionFactoryBuilder和Configuration两个类。这一章我们主要了解XMLConfigBuilder类，它是Mybatis配置文件解析入口。
BaseBuilder 类
在了解XMLConfigBuilder 之前我们先了解一下BaseBuilder
public abstract class BaseBuilder
BaseBuilder是一个抽象类
BaseBuilder 属性
// 上一篇讲过，mybatis所有配置
protected final Configuration configuration;
// 类型别名注册器，里面持有类别名和类的键值对。
protected final TypeAliasRegistry typeAliasRegistry;
// 类型处理注册器。
protected final TypeHandlerRegistry typeHandlerRegistry;
BaseBuilder 构造函数
public BaseBuilder(Configuration configuration) {
this.configuration = configuration;
this.typeAliasRegistry = this.configuration.getTypeAliasRegistry();
this.typeHandlerRegistry = this.configuration.getTypeHandlerRegistry();
}
BaseBuilder 初始化时必须要传configuration对象。通过上一篇我们知道Configuration的typeAliasRegistry类型别名注册器和typeHandlerRegistry类型处理注册器是在Configuration初始化时就被创建。
BaseBuilder 获取配置
public Configuration getConfiguration() {
return configuration;
}
BaseBuilder 字符串转型
protected Pattern parseExpression(String regex, String defaultValue) {
return Pattern.compile(regex == null ? defaultValue : regex);
}
protected Boolean booleanValueOf(String value, Boolean defaultValue) {
return value == null ? defaultValue : Boolean.valueOf(value);
}
protected Integer integerValueOf(String value, Integer defaultValue) {
return value == null ? defaultValue : Integer.valueOf(value);
}
protected Set stringSetValueOf(String value, String defaultValue) {
value = value == null ? defaultValue : value;
return new HashSet<>(Arrays.asList(value.split(",")));
}
BaseBuilder 根据别名获取JDBC类型
protected JdbcType resolveJdbcType(String alias) {
if (alias == null) {
return null;
}
try {
return JdbcType.valueOf(alias);
} catch (IllegalArgumentException e) {
throw new BuilderException("Error resolving JdbcType. Cause: " + e, e);
}
}
BaseBuilder 根据别名获取结果集类型
protected ResultSetType resolveResultSetType(String alias) {
if (alias == null) {
return null;
}
try {
return ResultSetType.valueOf(alias);
} catch (IllegalArgumentException e) {
throw new BuilderException("Error resolving ResultSetType. Cause: " + e, e);
}
}
BaseBuilder 根据类型别名获取对应的类型处理器
protected TypeHandler resolveTypeHandler(Class javaType, String typeHandlerAlias) {
// 判断类型别名是否为空
if (typeHandlerAlias == null) {
return null;
}
// 调用下面resolveClass方法
Class type = resolveClass(typeHandlerAlias);
// 类型不为空并且不是一个TypeHandler时抛异常
if (type != null && !TypeHandler.class.isAssignableFrom(type)) {
throw new BuilderException("Type " + type.getName() +
" is not a valid TypeHandler because it does not implement TypeHandler interface");
}
// 到这一定是TypeHandler
Class> typeHandlerType = (Class>) type;
// 调用resolveTypeHandler
return resolveTypeHandler(javaType, typeHandlerType);
}
protected TypeHandler resolveTypeHandler(Class javaType, Class> typeHandlerType) {
// 判断typeHandlerType 是否为空
if (typeHandlerType == null) {
return null;
}
// 到类型处理注册器中找这个typeHandlerType
TypeHandler handler = typeHandlerRegistry.getMappingTypeHandler(typeHandlerType);
// handler为空就反射出一个
if (handler == null) {
handler = typeHandlerRegistry.getInstance(javaType, typeHandlerType);
}
// 返回handler
return handler;
}
protected Class resolveClass(String alias) {
// 判断别名是否为空
if (alias == null) {
return null;
}
try {
// 调用resolveAlias方法
return resolveAlias(alias);
} catch (Exception e) {
throw new BuilderException("Error resolving class. Cause: " + e, e);
}
}
protected Class resolveAlias(String alias) {
// 到类型别名注册器中找
return typeAliasRegistry.resolveAlias(alias);
}
BaseBuilder 根据别名获取参数类型
protected ParameterMode resolveParameterMode(String alias) {
if (alias == null) {
return null;
}
try {
return ParameterMode.valueOf(alias);
} catch (IllegalArgumentException e) {
throw new BuilderException("Error resolving ParameterMode. Cause: " + e, e);
}
}
BaseBuilder 创建proxyFactory
protected Object createInstance(String alias) {
Class clazz = resolveClass(alias);
if (clazz == null) {
return null;
}
try {
return resolveClass(alias).getDeclaredConstructor().newInstance();
} catch (Exception e) {
throw new BuilderException("Error creating instance. Cause: " + e, e);
}
}
本篇主要讲XMLConfigBuilder，因为XMLConfigBuilder继承BaseBuilder，所以先讲了BaseBuilder
XMLConfigBuilder 类
public class XMLConfigBuilder extends BaseBuilder
XMLConfigBuilder 是BaseBuilder 的其中一个子类，它的作用是把MyBatis的XML及相关配置解析出来，然后保存到Configuration中。
XMLConfigBuilder 属性
// Configuration解析标识
private boolean parsed;
// 解析器模块
private final XPathParser parser;
// 环境变量
private String environment;
// 反射工厂
private final ReflectorFactory localReflectorFactory = new DefaultReflectorFactory();
XMLConfigBuilder 构造函数
public XMLConfigBuilder(Reader reader) {
this(reader, null, null);
}
public XMLConfigBuilder(Reader reader, String environment) {
this(reader, environment, null);
}
public XMLConfigBuilder(Reader reader, String environment, Properties props) {
this(new XPathParser(reader, true, props, new XMLMapperEntityResolver()), environment, props);
}
public XMLConfigBuilder(InputStream inputStream) {
this(inputStream, null, null);
}
public XMLConfigBuilder(InputStream inputStream, String environment) {
this(inputStream, environment, null);
}
public XMLConfigBuilder(InputStream inputStream, String environment, Properties props) {
this(new XPathParser(inputStream, true, props, new XMLMapperEntityResolver()), environment, props);
}
private XMLConfigBuilder(XPathParser parser, String environment, Properties props) {
// 调用父类构造函数
super(new Configuration());
// 初始化ErrorContext
ErrorContext.instance().resource("SQL Mapper Configuration");
// 设置属性
this.configuration.setVariables(props);
// 设置Configuration未解析
this.parsed = false;
// 设置环境变量
this.environment = environment;
// 设置解析器
this.parser = parser;
}
所有的构造函数最终都走到最后一个里面，前其实都是为了拿到parser对象，对于XPathParser解析器模块是怎么构造parser的下一篇我们主要盘它。这里创建了Configuration对象，根据前一篇我们知道系统自带的类别名会在它初始化时注册。初始化了ErrorContext，下下篇将它。初始化时并没有
XMLConfigBuilder 核心方法
// Mybatis配置文件核心解析方法
public Configuration parse() {
// 是否已经解析过，解析过就抛异常
if (parsed) {
throw new BuilderException("Each XMLConfigBuilder can only be used once.");
}
// 设置解析标志
parsed = true;
// 正在的解析方法
parseConfiguration(parser.evalNode("/configuration"));
// 返回解析后的configurtaion对象
return configuration;
}
// Mybatis配置文件解析元素
private void parseConfiguration(XNode root) {
try {
// 解析properties节点
propertiesElement(root.evalNode("properties"));
// 解析settings节点
Properties settings = settingsAsProperties(root.evalNode("settings"));
// 加载settings
loadCustomVfs(settings);
loadCustomLogImpl(settings);
// 解析typeAliases节点
typeAliasesElement(root.evalNode("typeAliases"));
// 解析plugins节点
pluginElement(root.evalNode("plugins"));
// 解析objectFactory节点
objectFactoryElement(root.evalNode("objectFactory"));
// 解析objectWrapperFactory节点
objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));
// 解析reflectorFactory节点
reflectorFactoryElement(root.evalNode("reflectorFactory"));
settingsElement(settings);
// 解析environments节点
environmentsElement(root.evalNode("environments"));
// 解析databaseIdProvider节点
databaseIdProviderElement(root.evalNode("databaseIdProvider"));
// 解析typeHandlers节点
typeHandlerElement(root.evalNode("typeHandlers"));
// 解析mappers节点
mapperElement(root.evalNode("mappers"));
} catch (Exception e) {
throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e);
}
}
后面的会针对每个标签解析单独将。
XMLConfigBuilder 解析settings节点
private Properties settingsAsProperties(XNode context) {
if (context == null) {
return new Properties();
}
Properties props = context.getChildrenAsProperties();
// Check that all settings are known to the configuration class
MetaClass metaConfig = MetaClass.forClass(Configuration.class, localReflectorFactory);
for (Object key : props.keySet()) {
if (!metaConfig.hasSetter(String.valueOf(key))) {
throw new BuilderException("The setting " + key + " is not known. Make sure you spelled it correctly (case sensitive).");
}
}
return props;
}
XMLConfigBuilder 解析settings配置
private void loadCustomVfs(Properties props) throws ClassNotFoundException {
String value = props.getProperty("vfsImpl");
if (value != null) {
String[] clazzes = value.split(",");
for (String clazz : clazzes) {
if (!clazz.isEmpty()) {
@SuppressWarnings("unchecked")
Class vfsImpl = (Class)Resources.classForName(clazz);
configuration.setVfsImpl(vfsImpl);
}
}
}
}
private void loadCustomLogImpl(Properties props) {
Class logImpl = resolveClass(props.getProperty("logImpl"));
configuration.setLogImpl(logImpl);
}
XMLConfigBuilder 解析typeAliases节点
private void typeAliasesElement(XNode parent) {
if (parent != null) {
for (XNode child : parent.getChildren()) {
if ("package".equals(child.getName())) {
String typeAliasPackage = child.getStringAttribute("name");
configuration.getTypeAliasRegistry().registerAliases(typeAliasPackage);
} else {
String alias = child.getStringAttribute("alias");
String type = child.getStringAttribute("type");
try {
Class clazz = Resources.classForName(type);
if (alias == null) {
typeAliasRegistry.registerAlias(clazz);
} else {
typeAliasRegistry.registerAlias(alias, clazz);
}
} catch (ClassNotFoundException e) {
throw new BuilderException("Error registering typeAlias for '" + alias + "'. Cause: " + e, e);
}
}
}
}
}
XMLConfigBuilder 解析plugin节点
private void pluginElement(XNode parent) throws Exception {
if (parent != null) {
for (XNode child : parent.getChildren()) {
String interceptor = child.getStringAttribute("interceptor");
Properties properties = child.getChildrenAsProperties();
Interceptor interceptorInstance = (Interceptor) resolveClass(interceptor).getDeclaredConstructor().newInstance();
interceptorInstance.setProperties(properties);
configuration.addInterceptor(interceptorInstance);
}
}
}
XMLConfigBuilder 解析objectFactory节点
private void objectFactoryElement(XNode context) throws Exception {
if (context != null) {
String type = context.getStringAttribute("type");
Properties properties = context.getChildrenAsProperties();
ObjectFactory factory = (ObjectFactory) resolveClass(type).getDeclaredConstructor().newInstance();
factory.setProperties(properties);
configuration.setObjectFactory(factory);
}
}
XMLConfigBuilder 解析objectWrapperFactory节点
private void objectWrapperFactoryElement(XNode context) throws Exception {
if (context != null) {
String type = context.getStringAttribute("type");
ObjectWrapperFactory factory = (ObjectWrapperFactory) resolveClass(type).getDeclaredConstructor().newInstance();
configuration.setObjectWrapperFactory(factory);
}
}
XMLConfigBuilder 解析reflectorFactory节点
private void reflectorFactoryElement(XNode context) throws Exception {
if (context != null) {
String type = context.getStringAttribute("type");
ReflectorFactory factory = (ReflectorFactory) resolveClass(type).getDeclaredConstructor().newInstance();
configuration.setReflectorFactory(factory);
}
}
XMLConfigBuilder 解析properties节点
private void propertiesElement(XNode context) throws Exception {
if (context != null) {
Properties defaults = context.getChildrenAsProperties();
String resource = context.getStringAttribute("resource");
String url = context.getStringAttribute("url");
if (resource != null && url != null) {
throw new BuilderException("The properties element cannot specify both a URL and a resource based property file reference. Please specify one or the other.");
}
if (resource != null) {
defaults.putAll(Resources.getResourceAsProperties(resource));
} else if (url != null) {
defaults.putAll(Resources.getUrlAsProperties(url));
}
Properties vars = configuration.getVariables();
if (vars != null) {
defaults.putAll(vars);
}
parser.setVariables(defaults);
configuration.setVariables(defaults);
}
}
XMLConfigBuilder 解析setting中子节点
private void settingsElement(Properties props) {
configuration.setAutoMappingBehavior(AutoMappingBehavior.valueOf(props.getProperty("autoMappingBehavior", "PARTIAL")));
configuration.setAutoMappingUnknownColumnBehavior(AutoMappingUnknownColumnBehavior.valueOf(props.getProperty("autoMappingUnknownColumnBehavior", "NONE")));
configuration.setCacheEnabled(booleanValueOf(props.getProperty("cacheEnabled"), true));
configuration.setProxyFactory((ProxyFactory) createInstance(props.getProperty("proxyFactory")));
configuration.setLazyLoadingEnabled(booleanValueOf(props.getProperty("lazyLoadingEnabled"), false));
configuration.setAggressiveLazyLoading(booleanValueOf(props.getProperty("aggressiveLazyLoading"), false));
configuration.setMultipleResultSetsEnabled(booleanValueOf(props.getProperty("multipleResultSetsEnabled"), true));
configuration.setUseColumnLabel(booleanValueOf(props.getProperty("useColumnLabel"), true));
configuration.setUseGeneratedKeys(booleanValueOf(props.getProperty("useGeneratedKeys"), false));
configuration.setDefaultExecutorType(ExecutorType.valueOf(props.getProperty("defaultExecutorType", "SIMPLE")));
configuration.setDefaultStatementTimeout(integerValueOf(props.getProperty("defaultStatementTimeout"), null));
configuration.setDefaultFetchSize(integerValueOf(props.getProperty("defaultFetchSize"), null));
configuration.setDefaultResultSetType(resolveResultSetType(props.getProperty("defaultResultSetType")));
configuration.setMapUnderscoreToCamelCase(booleanValueOf(props.getProperty("mapUnderscoreToCamelCase"), false));
configuration.setSafeRowBoundsEnabled(booleanValueOf(props.getProperty("safeRowBoundsEnabled"), false));
configuration.setLocalCacheScope(LocalCacheScope.valueOf(props.getProperty("localCacheScope", "SESSION")));
configuration.setJdbcTypeForNull(JdbcType.valueOf(props.getProperty("jdbcTypeForNull", "OTHER")));
configuration.setLazyLoadTriggerMethods(stringSetValueOf(props.getProperty("lazyLoadTriggerMethods"), "equals,clone,hashCode,toString"));
configuration.setSafeResultHandlerEnabled(booleanValueOf(props.getProperty("safeResultHandlerEnabled"), true));
configuration.setDefaultScriptingLanguage(resolveClass(props.getProperty("defaultScriptingLanguage")));
configuration.setDefaultEnumTypeHandler(resolveClass(props.getProperty("defaultEnumTypeHandler")));
configuration.setCallSettersOnNulls(booleanValueOf(props.getProperty("callSettersOnNulls"), false));
configuration.setUseActualParamName(booleanValueOf(props.getProperty("useActualParamName"), true));
configuration.setReturnInstanceForEmptyRow(booleanValueOf(props.getProperty("returnInstanceForEmptyRow"), false));
configuration.setLogPrefix(props.getProperty("logPrefix"));
configuration.setConfigurationFactory(resolveClass(props.getProperty("configurationFactory")));
}
XMLConfigBuilder 解析环境节点
private void environmentsElement(XNode context) throws Exception {
if (context != null) {
if (environment == null) {
environment = context.getStringAttribute("default");
}
for (XNode child : context.getChildren()) {
String id = child.getStringAttribute("id");
if (isSpecifiedEnvironment(id)) {
TransactionFactory txFactory = transactionManagerElement(child.evalNode("transactionManager"));
DataSourceFactory dsFactory = dataSourceElement(child.evalNode("dataSource"));
DataSource dataSource = dsFactory.getDataSource();
Environment.Builder environmentBuilder = new Environment.Builder(id)
.transactionFactory(txFactory)
.dataSource(dataSource);
configuration.setEnvironment(environmentBuilder.build());
}
}
}
}
XMLConfigBuilder 解析databaseIdProvider节点
private void databaseIdProviderElement(XNode context) throws Exception {
DatabaseIdProvider databaseIdProvider = null;
if (context != null) {
String type = context.getStringAttribute("type");
// awful patch to keep backward compatibility
if ("VENDOR".equals(type)) {
type = "DB_VENDOR";
}
Properties properties = context.getChildrenAsProperties();
databaseIdProvider = (DatabaseIdProvider) resolveClass(type).getDeclaredConstructor().newInstance();
databaseIdProvider.setProperties(properties);
}
Environment environment = configuration.getEnvironment();
if (environment != null && databaseIdProvider != null) {
String databaseId = databaseIdProvider.getDatabaseId(environment.getDataSource());
configuration.setDatabaseId(databaseId);
}
}
XMLConfigBuilder 解析环境中transactionManager节点
private TransactionFactory transactionManagerElement(XNode context) throws Exception {
if (context != null) {
String type = context.getStringAttribute("type");
Properties props = context.getChildrenAsProperties();
TransactionFactory factory = (TransactionFactory) resolveClass(type).getDeclaredConstructor().newInstance();
factory.setProperties(props);
return factory;
}
throw new BuilderException("Environment declaration requires a TransactionFactory.");
}
XMLConfigBuilder 解析环境中dataSource节点
private DataSourceFactory dataSourceElement(XNode context) throws Exception {
if (context != null) {
String type = context.getStringAttribute("type");
Properties props = context.getChildrenAsProperties();
DataSourceFactory factory = (DataSourceFactory) resolveClass(type).getDeclaredConstructor().newInstance();
factory.setProperties(props);
return factory;
}
throw new BuilderException("Environment declaration requires a DataSourceFactory.");
}
XMLConfigBuilder 解析typeHandlers节点
private void typeHandlerElement(XNode parent) {
if (parent != null) {
for (XNode child : parent.getChildren()) {
if ("package".equals(child.getName())) {
String typeHandlerPackage = child.getStringAttribute("name");
typeHandlerRegistry.register(typeHandlerPackage);
} else {
String javaTypeName = child.getStringAttribute("javaType");
String jdbcTypeName = child.getStringAttribute("jdbcType");
String handlerTypeName = child.getStringAttribute("handler");
Class javaTypeClass = resolveClass(javaTypeName);
JdbcType jdbcType = resolveJdbcType(jdbcTypeName);
Class typeHandlerClass = resolveClass(handlerTypeName);
if (javaTypeClass != null) {
if (jdbcType == null) {
typeHandlerRegistry.register(javaTypeClass, typeHandlerClass);
} else {
typeHandlerRegistry.register(javaTypeClass, jdbcType, typeHandlerClass);
}
} else {
typeHandlerRegistry.register(typeHandlerClass);
}
}
}
}
}
XMLConfigBuilder 解析mappers节点
private void mapperElement(XNode parent) throws Exception {
// 头节点不能为空
if (parent != null) {
// 遍历子节点
for (XNode child : parent.getChildren()) {
// 子节点是否是package
if ("package".equals(child.getName())) {
String mapperPackage = child.getStringAttribute("name");
configuration.addMappers(mapperPackage);
}
// 子节点是mapper
else {
// 获取属性
String resource = child.getStringAttribute("resource");
String url = child.getStringAttribute("url");
String mapperClass = child.getStringAttribute("class");
// 配置resource
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();
}
// 配置url
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();
}
// 配置mapperClass
else if (resource == null && url == null && mapperClass != null) {
Class mapperInterface = Resources.classForName(mapperClass);
configuration.addMapper(mapperInterface);
}
// 否则抛异常
else {
throw new BuilderException("A mapper element may only specify a url, resource or class, but not more than one.");
}
}
}
}
}
XMLConfigBuilder 判断环境
private boolean isSpecifiedEnvironment(String id) {
if (environment == null) {
throw new BuilderException("No environment specified.");
} else if (id == null) {
throw new BuilderException("Environment requires an id attribute.");
} else if (environment.equals(id)) {
return true;
}
return false;
}