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>