Spring集成MyBaties中sqlSessionFactory的创建[通俗易懂]

大家好，又见面了，我是你们的朋友全栈君。

Spring 的核心思想就是IOC（Inversion Of Control）,中文意思就是控制反转，将创建对象的任务交由工厂来处理，同时还可以管理类与类之间的关系，从而提出了依赖注入的概念。

先来了解对象的分类：

 1.简单对象：可以通过new的方式创建的对象，例如UserServiceImle 、User类等

 2.复杂对象：不能通过new的方式创建的对象，例如sqlSessionFactory等

对于简单对象来讲，我们只需要配置相关的spring配置文件即可：

	//配置UserServiceImpl
    <bean id="userService" class="com.baizhi.staticproxy.UserServiceImpl"></bean>
    //依赖注入
    <bean id="userServiceStaticProxy" class="com.baizhi.staticproxy.UserServiceStaticProxy">
        <property name="userService" ref="userService"></property>
    </bean>

那么问题来了，我们如何来创建复杂对象的，这也就是MyBaties解决和spring集成的一个问题：

	如何创建复杂对象sqlSessionFactory？？？？？

spring官方是没有给MyBaties提供相关的服务的，因为spring有自己的数据化持久的工具jdbcTemplate，为了推广自己的工具，所以就造成了今天问题的来源。但是spring的用户量还是很大的，MyBaties必须自己想办法解决问题，于是就自己开发相关jar包，共大家做spring和MyBaties的集成：

其中问题的核心就是	如何创建复杂对象sqlSessionFactory？？？？？

Spring为我们提供了一个解决创建复杂对象的接口，叫做FactoryBean:

package org.springframework.beans.factory;

public interface FactoryBean<T> {
//创建sqlSessionFactory
    T getObject() throws Exception;
//获取返回值类型
    Class<?> getObjectType();
//单例还是多例
    boolean isSingleton();
}

我们只需要实现这个接口，并覆盖这三个方法即可，当然你，这个类不需要我们自己写，mybaties已经帮我们写了：

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//
package org.mybatis.spring;
import java.io.IOException;
import java.sql.SQLException;
import java.util.Properties;
import javax.sql.DataSource;
import org.apache.ibatis.builder.xml.XMLConfigBuilder;
import org.apache.ibatis.builder.xml.XMLMapperBuilder;
import org.apache.ibatis.cache.Cache;
import org.apache.ibatis.executor.ErrorContext;
import org.apache.ibatis.io.VFS;
import org.apache.ibatis.logging.Log;
import org.apache.ibatis.logging.LogFactory;
import org.apache.ibatis.mapping.DatabaseIdProvider;
import org.apache.ibatis.mapping.Environment;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.reflection.factory.ObjectFactory;
import org.apache.ibatis.reflection.wrapper.ObjectWrapperFactory;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.apache.ibatis.transaction.TransactionFactory;
import org.apache.ibatis.type.TypeHandler;
import org.mybatis.spring.transaction.SpringManagedTransactionFactory;
import org.springframework.beans.factory.FactoryBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.core.NestedIOException;
import org.springframework.core.io.Resource;
import org.springframework.jdbc.datasource.TransactionAwareDataSourceProxy;
import org.springframework.util.Assert;
import org.springframework.util.ObjectUtils;
import org.springframework.util.StringUtils;
public class SqlSessionFactoryBean implements FactoryBean<SqlSessionFactory>, InitializingBean, ApplicationListener<ApplicationEvent> {
private static final Log LOGGER = LogFactory.getLog(SqlSessionFactoryBean.class);
private Resource configLocation;
private Configuration configuration;
//注册mapper文件
private Resource[] mapperLocations;
//引入数据源
private DataSource dataSource;
private TransactionFactory transactionFactory;
private Properties configurationProperties;
private SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
//创建sqlsqlSessionFactory
private SqlSessionFactory sqlSessionFactory;
private String environment = SqlSessionFactoryBean.class.getSimpleName();
private boolean failFast;
private Interceptor[] plugins;
private TypeHandler<?>[] typeHandlers;
private String typeHandlersPackage;
private Class<?>[] typeAliases;
//起别名
private String typeAliasesPackage;
private Class<?> typeAliasesSuperType;
private DatabaseIdProvider databaseIdProvider;
private Class<? extends VFS> vfs;
private Cache cache;
private ObjectFactory objectFactory;
private ObjectWrapperFactory objectWrapperFactory;
//提供无参的构造方法
public SqlSessionFactoryBean() {
}
//提供所有成员变量的set方法，用来做set注入
public void setObjectFactory(ObjectFactory objectFactory) {
this.objectFactory = objectFactory;
}
public void setObjectWrapperFactory(ObjectWrapperFactory objectWrapperFactory) {
this.objectWrapperFactory = objectWrapperFactory;
}
public DatabaseIdProvider getDatabaseIdProvider() {
return this.databaseIdProvider;
}
public void setDatabaseIdProvider(DatabaseIdProvider databaseIdProvider) {
this.databaseIdProvider = databaseIdProvider;
}
public Class<? extends VFS> getVfs() {
return this.vfs;
}
public void setVfs(Class<? extends VFS> vfs) {
this.vfs = vfs;
}
public Cache getCache() {
return this.cache;
}
public void setCache(Cache cache) {
this.cache = cache;
}
public void setPlugins(Interceptor[] plugins) {
this.plugins = plugins;
}
public void setTypeAliasesPackage(String typeAliasesPackage) {
this.typeAliasesPackage = typeAliasesPackage;
}
public void setTypeAliasesSuperType(Class<?> typeAliasesSuperType) {
this.typeAliasesSuperType = typeAliasesSuperType;
}
public void setTypeHandlersPackage(String typeHandlersPackage) {
this.typeHandlersPackage = typeHandlersPackage;
}
public void setTypeHandlers(TypeHandler<?>[] typeHandlers) {
this.typeHandlers = typeHandlers;
}
public void setTypeAliases(Class<?>[] typeAliases) {
this.typeAliases = typeAliases;
}
public void setFailFast(boolean failFast) {
this.failFast = failFast;
}
public void setConfigLocation(Resource configLocation) {
this.configLocation = configLocation;
}
public void setConfiguration(Configuration configuration) {
this.configuration = configuration;
}
public void setMapperLocations(Resource[] mapperLocations) {
this.mapperLocations = mapperLocations;
}
public void setConfigurationProperties(Properties sqlSessionFactoryProperties) {
this.configurationProperties = sqlSessionFactoryProperties;
}
public void setDataSource(DataSource dataSource) {
if (dataSource instanceof TransactionAwareDataSourceProxy) {
this.dataSource = ((TransactionAwareDataSourceProxy)dataSource).getTargetDataSource();
} else {
this.dataSource = dataSource;
}
}
public void setSqlSessionFactoryBuilder(SqlSessionFactoryBuilder sqlSessionFactoryBuilder) {
this.sqlSessionFactoryBuilder = sqlSessionFactoryBuilder;
}
public void setTransactionFactory(TransactionFactory transactionFactory) {
this.transactionFactory = transactionFactory;
}
public void setEnvironment(String environment) {
this.environment = environment;
}
public void afterPropertiesSet() throws Exception {
Assert.notNull(this.dataSource, "Property 'dataSource' is required");
Assert.notNull(this.sqlSessionFactoryBuilder, "Property 'sqlSessionFactoryBuilder' is required");
Assert.state(this.configuration == null && this.configLocation == null || this.configuration == null || this.configLocation == null, "Property 'configuration' and 'configLocation' can not specified with together");
this.sqlSessionFactory = this.buildSqlSessionFactory();
}
//核心方法一
protected SqlSessionFactory buildSqlSessionFactory() throws IOException {
XMLConfigBuilder xmlConfigBuilder = null;
Configuration configuration;
if (this.configuration != null) {
configuration = this.configuration;
if (configuration.getVariables() == null) {
configuration.setVariables(this.configurationProperties);
} else if (this.configurationProperties != null) {
configuration.getVariables().putAll(this.configurationProperties);
}
} else if (this.configLocation != null) {
xmlConfigBuilder = new XMLConfigBuilder(this.configLocation.getInputStream(), (String)null, this.configurationProperties);
configuration = xmlConfigBuilder.getConfiguration();
} else {
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("Property 'configuration' or 'configLocation' not specified, using default MyBatis Configuration");
}
configuration = new Configuration();
if (this.configurationProperties != null) {
configuration.setVariables(this.configurationProperties);
}
}
if (this.objectFactory != null) {
configuration.setObjectFactory(this.objectFactory);
}
if (this.objectWrapperFactory != null) {
configuration.setObjectWrapperFactory(this.objectWrapperFactory);
}
if (this.vfs != null) {
configuration.setVfsImpl(this.vfs);
}
String[] typeHandlersPackageArray;
String[] var4;
int var5;
int var6;
String packageToScan;
if (StringUtils.hasLength(this.typeAliasesPackage)) {
typeHandlersPackageArray = StringUtils.tokenizeToStringArray(this.typeAliasesPackage, ",; \t\n");
var4 = typeHandlersPackageArray;
var5 = typeHandlersPackageArray.length;
for(var6 = 0; var6 < var5; ++var6) {
packageToScan = var4[var6];
configuration.getTypeAliasRegistry().registerAliases(packageToScan, this.typeAliasesSuperType == null ? Object.class : this.typeAliasesSuperType);
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("Scanned package: '" + packageToScan + "' for aliases");
}
}
}
int var27;
if (!ObjectUtils.isEmpty(this.typeAliases)) {
Class[] var25 = this.typeAliases;
var27 = var25.length;
for(var5 = 0; var5 < var27; ++var5) {
Class<?> typeAlias = var25[var5];
configuration.getTypeAliasRegistry().registerAlias(typeAlias);
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("Registered type alias: '" + typeAlias + "'");
}
}
}
if (!ObjectUtils.isEmpty(this.plugins)) {
Interceptor[] var26 = this.plugins;
var27 = var26.length;
for(var5 = 0; var5 < var27; ++var5) {
Interceptor plugin = var26[var5];
configuration.addInterceptor(plugin);
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("Registered plugin: '" + plugin + "'");
}
}
}
if (StringUtils.hasLength(this.typeHandlersPackage)) {
typeHandlersPackageArray = StringUtils.tokenizeToStringArray(this.typeHandlersPackage, ",; \t\n");
var4 = typeHandlersPackageArray;
var5 = typeHandlersPackageArray.length;
for(var6 = 0; var6 < var5; ++var6) {
packageToScan = var4[var6];
configuration.getTypeHandlerRegistry().register(packageToScan);
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("Scanned package: '" + packageToScan + "' for type handlers");
}
}
}
if (!ObjectUtils.isEmpty(this.typeHandlers)) {
TypeHandler[] var28 = this.typeHandlers;
var27 = var28.length;
for(var5 = 0; var5 < var27; ++var5) {
TypeHandler<?> typeHandler = var28[var5];
configuration.getTypeHandlerRegistry().register(typeHandler);
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("Registered type handler: '" + typeHandler + "'");
}
}
}
if (this.databaseIdProvider != null) {
try {
configuration.setDatabaseId(this.databaseIdProvider.getDatabaseId(this.dataSource));
} catch (SQLException var24) {
throw new NestedIOException("Failed getting a databaseId", var24);
}
}
if (this.cache != null) {
configuration.addCache(this.cache);
}
if (xmlConfigBuilder != null) {
try {
xmlConfigBuilder.parse();
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("Parsed configuration file: '" + this.configLocation + "'");
}
} catch (Exception var22) {
throw new NestedIOException("Failed to parse config resource: " + this.configLocation, var22);
} finally {
ErrorContext.instance().reset();
}
}
if (this.transactionFactory == null) {
this.transactionFactory = new SpringManagedTransactionFactory();
}
configuration.setEnvironment(new Environment(this.environment, this.transactionFactory, this.dataSource));
if (!ObjectUtils.isEmpty(this.mapperLocations)) {
Resource[] var29 = this.mapperLocations;
var27 = var29.length;
for(var5 = 0; var5 < var27; ++var5) {
Resource mapperLocation = var29[var5];
if (mapperLocation != null) {
try {
XMLMapperBuilder xmlMapperBuilder = new XMLMapperBuilder(mapperLocation.getInputStream(), configuration, mapperLocation.toString(), configuration.getSqlFragments());
xmlMapperBuilder.parse();
} catch (Exception var20) {
throw new NestedIOException("Failed to parse mapping resource: '" + mapperLocation + "'", var20);
} finally {
ErrorContext.instance().reset();
}
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("Parsed mapper file: '" + mapperLocation + "'");
}
}
}
} else if (LOGGER.isDebugEnabled()) {
LOGGER.debug("Property 'mapperLocations' was not specified or no matching resources found");
}
return this.sqlSessionFactoryBuilder.build(configuration);
}
public SqlSessionFactory getObject() throws Exception {
if (this.sqlSessionFactory == null) {
this.afterPropertiesSet();
}
return this.sqlSessionFactory;
}
//核心方法二
public Class<? extends SqlSessionFactory> getObjectType() {
return this.sqlSessionFactory == null ? SqlSessionFactory.class : this.sqlSessionFactory.getClass();
}
//核心方法三
public boolean isSingleton() {
return true;
}
public void onApplicationEvent(ApplicationEvent event) {
if (this.failFast && event instanceof ContextRefreshedEvent) {
this.sqlSessionFactory.getConfiguration().getMappedStatementNames();
}
}
}

上面的实现类实现比较复杂，喜欢啃源码的同学可以细细品味一下，对于实战开发来讲，我们只需要知道，我们的工作就是直接用，并且进行如下的先关配置即可:

<!--自动创建sqlSessionFactory-->
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
<!--构建sqlSession需要数据源-->
<property name="dataSource" ref="basicDataSource"></property>
<!--起别名   给该包下所有的类起别名，默认别名为该类的类名-->
<property name="typeAliasesPackage" ><value>com.baizhi.entity</value></property>
<!--mapper文件注册-->
<property name="mapperLocations">
<list><!--默认为com.baizhi.mapper包下面以Mapper.xml结尾的文件进行注册-->
<value>com/baizhi/mapper/*Mapper.xml</value>
</list>
</property>
</bean>

在这个配置中，主要完成的任务只有两件：

1.拿到数据源

2.mapper文件的注册

还有就是关于创建dao实现类，MyBatirs也进行了相关的优化封装，我们可以在spring配置文件中直接去配置：

<!--自动创建Dao的实现类对象-->
<bean id="mapperScannerConfiger" class="org.mybatis.spring.mapper.MapperScannerConfigurer">
<!--告知Spring  为com.baizhi.dao包下面的所有接口构建DAO的实现类对象-->
<property name="basePackage">
<value>com.baizhi.dao</value>
</property>
</bean>