/*
* Copyright 2009-2012 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.ibatis.builder.xml;
import java.io.InputStream;
import java.io.Reader;
import java.util.Properties;
import javax.sql.DataSource;
import org.apache.ibatis.builder.BaseBuilder;
import org.apache.ibatis.builder.BuilderException;
import org.apache.ibatis.datasource.DataSourceFactory;
import org.apache.ibatis.executor.ErrorContext;
import org.apache.ibatis.executor.loader.ProxyFactory;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.mapping.DatabaseIdProvider;
import org.apache.ibatis.mapping.Environment;
import org.apache.ibatis.parsing.XNode;
import org.apache.ibatis.parsing.XPathParser;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.reflection.MetaClass;
import org.apache.ibatis.reflection.factory.ObjectFactory;
import org.apache.ibatis.reflection.wrapper.ObjectWrapperFactory;
import org.apache.ibatis.session.AutoMappingBehavior;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.ExecutorType;
import org.apache.ibatis.session.LocalCacheScope;
import org.apache.ibatis.transaction.TransactionFactory;
import org.apache.ibatis.type.JdbcType;
/**
* @author Clinton Begin
*/
/**
* XML配置构建器,建造者模式,继承BaseBuilder
*
*/
public class XMLConfigBuilder extends BaseBuilder {
//是否已解析,XPath解析器,环境
private boolean parsed;
private XPathParser parser;
private String environment;
//以下3个一组
public XMLConfigBuilder(Reader reader) {
this(reader, null, null);
}
public XMLConfigBuilder(Reader reader, String environment) {
this(reader, environment, null);
}
//构造函数,转换成XPathParser再去调用构造函数
public XMLConfigBuilder(Reader reader, String environment, Properties props) {
//构造一个需要验证,XMLMapperEntityResolver的XPathParser
this(new XPathParser(reader, true, props, new XMLMapperEntityResolver()), environment, props);
}
//以下3个一组
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);
}
//上面6个构造函数最后都合流到这个函数,传入XPathParser
private XMLConfigBuilder(XPathParser parser, String environment, Properties props) {
//首先调用父类初始化Configuration
super(new Configuration());
//错误上下文设置成SQL Mapper Configuration(XML文件配置),以便后面出错了报错用吧
ErrorContext.instance().resource("SQL Mapper Configuration");
//将Properties全部设置到Configuration里面去
this.configuration.setVariables(props);
this.parsed = false;
this.environment = environment;
this.parser = parser;
}
//解析配置
public Configuration parse() {
//如果已经解析过了,报错
if (parsed) {
throw new BuilderException("Each XMLConfigBuilder can only be used once.");
}
parsed = true;
// <?xml version="1.0" encoding="UTF-8" ?>
// <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
// "http://mybatis.org/dtd/mybatis-3-config.dtd">
// <configuration>
// <environments default="development">
// <environment id="development">
// <transactionManager type="JDBC"/>
// <dataSource type="POOLED">
// <property name="driver" value="${driver}"/>
// <property name="url" value="${url}"/>
// <property name="username" value="${username}"/>
// <property name="password" value="${password}"/>
// </dataSource>
// </environment>
// </environments>
// <mappers>
// <mapper resource="org/mybatis/example/BlogMapper.xml"/>
// </mappers>
// </configuration>
//根节点是configuration
parseConfiguration(parser.evalNode("/configuration"));
return configuration;
}
//解析配置
private void parseConfiguration(XNode root) {
try {
//分步骤解析
//issue #117 read properties first
//1.properties
propertiesElement(root.evalNode("properties"));
//2.类型别名
typeAliasesElement(root.evalNode("typeAliases"));
//3.插件
pluginElement(root.evalNode("plugins"));
//4.对象工厂
objectFactoryElement(root.evalNode("objectFactory"));
//5.对象包装工厂
objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));
//6.设置
settingsElement(root.evalNode("settings"));
// read it after objectFactory and objectWrapperFactory issue #631
//7.环境
environmentsElement(root.evalNode("environments"));
//8.databaseIdProvider
databaseIdProviderElement(root.evalNode("databaseIdProvider"));
//9.类型处理器
typeHandlerElement(root.evalNode("typeHandlers"));
//10.映射器
mapperElement(root.evalNode("mappers"));
} catch (Exception e) {
throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e);
}
}
//2.类型别名
//<typeAliases>
// <typeAlias alias="Author" type="domain.blog.Author"/>
// <typeAlias alias="Blog" type="domain.blog.Blog"/>
// <typeAlias alias="Comment" type="domain.blog.Comment"/>
// <typeAlias alias="Post" type="domain.blog.Post"/>
// <typeAlias alias="Section" type="domain.blog.Section"/>
// <typeAlias alias="Tag" type="domain.blog.Tag"/>
//</typeAliases>
//or
//<typeAliases>
// <package name="domain.blog"/>
//</typeAliases>
private void typeAliasesElement(XNode parent) {
if (parent != null) {
for (XNode child : parent.getChildren()) {
if ("package".equals(child.getName())) {
//如果是package
String typeAliasPackage = child.getStringAttribute("name");
//(一)调用TypeAliasRegistry.registerAliases,去包下找所有类,然后注册别名(有@Alias注解则用,没有则取类的simpleName)
configuration.getTypeAliasRegistry().registerAliases(typeAliasPackage);
} else {
//如果是typeAlias
String alias = child.getStringAttribute("alias");
String type = child.getStringAttribute("type");
try {
Class<?> clazz = Resources.classForName(type);
//根据Class名字来注册类型别名
//(二)调用TypeAliasRegistry.registerAlias
if (alias == null) {
//alias可以省略
typeAliasRegistry.registerAlias(clazz);
} else {
typeAliasRegistry.registerAlias(alias, clazz);
}
} catch (ClassNotFoundException e) {
throw new BuilderException("Error registering typeAlias for '" + alias + "'. Cause: " + e, e);
}
}
}
}
}
//3.插件
//MyBatis 允许你在某一点拦截已映射语句执行的调用。默认情况下,MyBatis 允许使用插件来拦截方法调用
//<plugins>
// <plugin interceptor="org.mybatis.example.ExamplePlugin">
// <property name="someProperty" value="100"/>
// </plugin>
//</plugins>
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).newInstance();
interceptorInstance.setProperties(properties);
//调用InterceptorChain.addInterceptor
configuration.addInterceptor(interceptorInstance);
}
}
}
//4.对象工厂,可以自定义对象创建的方式,比如用对象池?
//<objectFactory type="org.mybatis.example.ExampleObjectFactory">
// <property name="someProperty" value="100"/>
//</objectFactory>
private void objectFactoryElement(XNode context) throws Exception {
if (context != null) {
String type = context.getStringAttribute("type");
Properties properties = context.getChildrenAsProperties();
ObjectFactory factory = (ObjectFactory) resolveClass(type).newInstance();
factory.setProperties(properties);
configuration.setObjectFactory(factory);
}
}
//5.对象包装工厂
private void objectWrapperFactoryElement(XNode context) throws Exception {
if (context != null) {
String type = context.getStringAttribute("type");
ObjectWrapperFactory factory = (ObjectWrapperFactory) resolveClass(type).newInstance();
configuration.setObjectWrapperFactory(factory);
}
}
//1.properties
//<properties resource="org/mybatis/example/config.properties">
// <property name="username" value="dev_user"/>
// <property name="password" value="F2Fa3!33TYyg"/>
//</properties>
private void propertiesElement(XNode context) throws Exception {
if (context != null) {
//如果在这些地方,属性多于一个的话,MyBatis 按照如下的顺序加载它们:
//1.在 properties 元素体内指定的属性首先被读取。
//2.从类路径下资源或 properties 元素的 url 属性中加载的属性第二被读取,它会覆盖已经存在的完全一样的属性。
//3.作为方法参数传递的属性最后被读取, 它也会覆盖任一已经存在的完全一样的属性,这些属性可能是从 properties 元素体内和资源/url 属性中加载的。
//传入方式是调用构造函数时传入,public XMLConfigBuilder(Reader reader, String environment, Properties props)
//1.XNode.getChildrenAsProperties函数方便得到孩子所有Properties
Properties defaults = context.getChildrenAsProperties();
//2.然后查找resource或者url,加入前面的Properties
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));
}
//3.Variables也全部加入Properties
Properties vars = configuration.getVariables();
if (vars != null) {
defaults.putAll(vars);
}
parser.setVariables(defaults);
configuration.setVariables(defaults);
}
}
//6.设置
//这些是极其重要的调整, 它们会修改 MyBatis 在运行时的行为方式
//<settings>
// <setting name="cacheEnabled" value="true"/>
// <setting name="lazyLoadingEnabled" value="true"/>
// <setting name="multipleResultSetsEnabled" value="true"/>
// <setting name="useColumnLabel" value="true"/>
// <setting name="useGeneratedKeys" value="false"/>
// <setting name="enhancementEnabled" value="false"/>
// <setting name="defaultExecutorType" value="SIMPLE"/>
// <setting name="defaultStatementTimeout" value="25000"/>
// <setting name="safeRowBoundsEnabled" value="false"/>
// <setting name="mapUnderscoreToCamelCase" value="false"/>
// <setting name="localCacheScope" value="SESSION"/>
// <setting name="jdbcTypeForNull" value="OTHER"/>
// <setting name="lazyLoadTriggerMethods" value="equals,clone,hashCode,toString"/>
//</settings>
private void settingsElement(XNode context) throws Exception {
if (context != null) {
Properties props = context.getChildrenAsProperties();
// Check that all settings are known to the configuration class
//检查下是否在Configuration类里都有相应的setter方法(没有拼写错误)
MetaClass metaConfig = MetaClass.forClass(Configuration.class);
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).");
}
}
//下面非常简单,一个个设置属性
//如何自动映射列到字段/ 属性
configuration.setAutoMappingBehavior(AutoMappingBehavior.valueOf(props.getProperty("autoMappingBehavior", "PARTIAL")));
//缓存
configuration.setCacheEnabled(booleanValueOf(props.getProperty("cacheEnabled"), true));
//proxyFactory (CGLIB | JAVASSIST)
//延迟加载的核心技术就是用代理模式,CGLIB/JAVASSIST两者选一
configuration.setProxyFactory((ProxyFactory) createInstance(props.getProperty("proxyFactory")));
//延迟加载
configuration.setLazyLoadingEnabled(booleanValueOf(props.getProperty("lazyLoadingEnabled"), false));
//延迟加载时,每种属性是否还要按需加载
configuration.setAggressiveLazyLoading(booleanValueOf(props.getProperty("aggressiveLazyLoading"), true));
//允不允许多种结果集从一个单独 的语句中返回
configuration.setMultipleResultSetsEnabled(booleanValueOf(props.getProperty("multipleResultSetsEnabled"), true));
//使用列标签代替列名
configuration.setUseColumnLabel(booleanValueOf(props.getProperty("useColumnLabel"), true));
//允许 JDBC 支持生成的键
configuration.setUseGeneratedKeys(booleanValueOf(props.getProperty("useGeneratedKeys"), false));
//配置默认的执行器
configuration.setDefaultExecutorType(ExecutorType.valueOf(props.getProperty("defaultExecutorType", "SIMPLE")));
//超时时间
configuration.setDefaultStatementTimeout(integerValueOf(props.getProperty("defaultStatementTimeout"), null));
//是否将DB字段自动映射到驼峰式Java属性(A_COLUMN-->aColumn)
configuration.setMapUnderscoreToCamelCase(booleanValueOf(props.getProperty("mapUnderscoreToCamelCase"), false));
//嵌套语句上使用RowBounds
configuration.setSafeRowBoundsEnabled(booleanValueOf(props.getProperty("safeRowBoundsEnabled"), false));
//默认用session级别的缓存
configuration.setLocalCacheScope(LocalCacheScope.valueOf(props.getProperty("localCacheScope", "SESSION")));
//为null值设置jdbctype
configuration.setJdbcTypeForNull(JdbcType.valueOf(props.getProperty("jdbcTypeForNull", "OTHER")));
//Object的哪些方法将触发延迟加载
configuration.setLazyLoadTriggerMethods(stringSetValueOf(props.getProperty("lazyLoadTriggerMethods"), "equals,clone,hashCode,toString"));
//使用安全的ResultHandler
configuration.setSafeResultHandlerEnabled(booleanValueOf(props.getProperty("safeResultHandlerEnabled"), true));
//动态SQL生成语言所使用的脚本语言
configuration.setDefaultScriptingLanguage(resolveClass(props.getProperty("defaultScriptingLanguage")));
//当结果集中含有Null值时是否执行映射对象的setter或者Map对象的put方法。此设置对于原始类型如int,boolean等无效。
configuration.setCallSettersOnNulls(booleanValueOf(props.getProperty("callSettersOnNulls"), false));
//logger名字的前缀
configuration.setLogPrefix(props.getProperty("logPrefix"));
//显式定义用什么log框架,不定义则用默认的自动发现jar包机制
configuration.setLogImpl(resolveClass(props.getProperty("logImpl")));
//配置工厂
configuration.setConfigurationFactory(resolveClass(props.getProperty("configurationFactory")));
}
}
//7.环境
// <environments default="development">
// <environment id="development">
// <transactionManager type="JDBC">
// <property name="..." value="..."/>
// </transactionManager>
// <dataSource type="POOLED">
// <property name="driver" value="${driver}"/>
// <property name="url" value="${url}"/>
// <property name="username" value="${username}"/>
// <property name="password" value="${password}"/>
// </dataSource>
// </environment>
// </environments>
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");
//循环比较id是否就是指定的environment
if (isSpecifiedEnvironment(id)) {
//7.1事务管理器
TransactionFactory txFactory = transactionManagerElement(child.evalNode("transactionManager"));
//7.2数据源
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());
}
}
}
}
//8.databaseIdProvider
//可以根据不同数据库执行不同的SQL,sql要加databaseId属性
//这个功能感觉不是很实用,真要多数据库支持,那SQL工作量将会成倍增长,用mybatis以后一般就绑死在一个数据库上了。但也是一个不得已的方法吧
//可以参考org.apache.ibatis.submitted.multidb包里的测试用例
// <databaseIdProvider type="VENDOR">
// <property name="SQL Server" value="sqlserver"/>
// <property name="DB2" value="db2"/>
// <property name="Oracle" value="oracle" />
// </databaseIdProvider>
private void databaseIdProviderElement(XNode context) throws Exception {
DatabaseIdProvider databaseIdProvider = null;
if (context != null) {
String type = context.getStringAttribute("type");
// awful patch to keep backward compatibility
//与老版本兼容
if ("VENDOR".equals(type)) {
type = "DB_VENDOR";
}
Properties properties = context.getChildrenAsProperties();
//"DB_VENDOR"-->VendorDatabaseIdProvider
databaseIdProvider = (DatabaseIdProvider) resolveClass(type).newInstance();
databaseIdProvider.setProperties(properties);
}
Environment environment = configuration.getEnvironment();
if (environment != null && databaseIdProvider != null) {
//得到当前的databaseId,可以调用DatabaseMetaData.getDatabaseProductName()得到诸如"Oracle (DataDirect)"的字符串,
//然后和预定义的property比较,得出目前究竟用的是什么数据库
String databaseId = databaseIdProvider.getDatabaseId(environment.getDataSource());
configuration.setDatabaseId(databaseId);
}
}
//7.1事务管理器
//<transactionManager type="JDBC">
// <property name="..." value="..."/>
//</transactionManager>
private TransactionFactory transactionManagerElement(XNode context) throws Exception {
if (context != null) {
String type = context.getStringAttribute("type");
Properties props = context.getChildrenAsProperties();
//根据type="JDBC"解析返回适当的TransactionFactory
TransactionFactory factory = (TransactionFactory) resolveClass(type).newInstance();
factory.setProperties(props);
return factory;
}
throw new BuilderException("Environment declaration requires a TransactionFactory.");
}
//7.2数据源
//<dataSource type="POOLED">
// <property name="driver" value="${driver}"/>
// <property name="url" value="${url}"/>
// <property name="username" value="${username}"/>
// <property name="password" value="${password}"/>
//</dataSource>
private DataSourceFactory dataSourceElement(XNode context) throws Exception {
if (context != null) {
String type = context.getStringAttribute("type");
Properties props = context.getChildrenAsProperties();
//根据type="POOLED"解析返回适当的DataSourceFactory
DataSourceFactory factory = (DataSourceFactory) resolveClass(type).newInstance();
factory.setProperties(props);
return factory;
}
throw new BuilderException("Environment declaration requires a DataSourceFactory.");
}
//9.类型处理器
// <typeHandlers>
// <typeHandler handler="org.mybatis.example.ExampleTypeHandler"/>
// </typeHandlers>
//or
// <typeHandlers>
// <package name="org.mybatis.example"/>
// </typeHandlers>
private void typeHandlerElement(XNode parent) throws Exception {
if (parent != null) {
for (XNode child : parent.getChildren()) {
//如果是package
if ("package".equals(child.getName())) {
String typeHandlerPackage = child.getStringAttribute("name");
//(一)调用TypeHandlerRegistry.register,去包下找所有类
typeHandlerRegistry.register(typeHandlerPackage);
} else {
//如果是typeHandler
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);
//(二)调用TypeHandlerRegistry.register(以下是3种不同的参数形式)
if (javaTypeClass != null) {
if (jdbcType == null) {
typeHandlerRegistry.register(javaTypeClass, typeHandlerClass);
} else {
typeHandlerRegistry.register(javaTypeClass, jdbcType, typeHandlerClass);
}
} else {
typeHandlerRegistry.register(typeHandlerClass);
}
}
}
}
}
//10.映射器
// 10.1使用类路径
// <mappers>
// <mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
// <mapper resource="org/mybatis/builder/BlogMapper.xml"/>
// <mapper resource="org/mybatis/builder/PostMapper.xml"/>
// </mappers>
//
// 10.2使用绝对url路径
// <mappers>
// <mapper url="file:///var/mappers/AuthorMapper.xml"/>
// <mapper url="file:///var/mappers/BlogMapper.xml"/>
// <mapper url="file:///var/mappers/PostMapper.xml"/>
// </mappers>
//
// 10.3使用java类名
// <mappers>
// <mapper class="org.mybatis.builder.AuthorMapper"/>
// <mapper class="org.mybatis.builder.BlogMapper"/>
// <mapper class="org.mybatis.builder.PostMapper"/>
// </mappers>
//
// 10.4自动扫描包下所有映射器
// <mappers>
// <package name="org.mybatis.builder"/>
// </mappers>
private void mapperElement(XNode parent) throws Exception {
if (parent != null) {
for (XNode child : parent.getChildren()) {
if ("package".equals(child.getName())) {
//10.4自动扫描包下所有映射器
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) {
//10.1使用类路径
ErrorContext.instance().resource(resource);
InputStream inputStream = Resources.getResourceAsStream(resource);
//映射器比较复杂,调用XMLMapperBuilder
//注意在for循环里每个mapper都重新new一个XMLMapperBuilder,来解析
XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, resource, configuration.getSqlFragments());
mapperParser.parse();
} else if (resource == null && url != null && mapperClass == null) {
//10.2使用绝对url路径
ErrorContext.instance().resource(url);
InputStream inputStream = Resources.getUrlAsStream(url);
//映射器比较复杂,调用XMLMapperBuilder
XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, url, configuration.getSqlFragments());
mapperParser.parse();
} else if (resource == null && url == null && mapperClass != null) {
//10.3使用java类名
Class<?> mapperInterface = Resources.classForName(mapperClass);
//直接把这个映射加入配置
configuration.addMapper(mapperInterface);
} else {
throw new BuilderException("A mapper element may only specify a url, resource or class, but not more than one.");
}
}
}
}
}
//比较id和environment是否相等
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;
}
}