Mybatis-3.0.6如何采用多个配置文件，模块化，降低耦合度

写文章之前，在网上查找了很多办法，要么代码错误，要么跑不动，要么……总之各种原因的报错，因此参考源代码，自己改写了一个类。

之前的项目，总是把项目所有的“typeAlias”放到一个mybatis.xml文件中，所造成的原因很明显，整个项目耦合度非常高。

本人一直很懒，也不想研究解决办法，随着时间的推移，项目越来越庞大，模块越来越多，所以也就静下心来研究下这个问题。

首先，对配置文件进行解耦，将mybatis.xml分成多个文件，我统一在每个模块下，放了一个配置文件，命名为：type-aliases.xml，其xml格式为：

<?xml version="1.0" encoding="UTF-8" ?>
<typeAliases>
<typeAlias alias="example" type="com.laotoumo.example.entity.Example"/>
</typeAliases>

原来的mybatis.xml删除掉，当然，你不愿意删除，也可以保留了，然后修改applicationContext.xml中的配置。

为什么说可以保留，因为如果系统识别到mybatis.xml配置，会自动将其他配置追加进去。

<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="dataSource"/>
<!-- <property name="configLocation" value="classpath:mybatis.xml"/> -->
<property name="typeAliasesLocations" value="classpath:com/laotoumo/**/type-aliases.xml"/>
<property name="mapperLocations" value="classpath:com/laotoumo/**/*-mapper.xml" />
</bean>

接下来是重头戏，源代码改写了，直接在你项目里增加一个类org.mybatis.spring.SqlSessionFactoryBean，本人不太喜欢继承扩展，这个改造方法是在原有基础上增加了一个typeAliasesLocations的配置选项，对其他的没有影响，这个类我当然是从mybatis-spring的源代码里拷贝来的，也是基于这个做的修改，对原有结构没有进行任何改动，也就是说，原来的配置不做任何修改也可以正常运行，所以大家可以放心使用。想偷懒，可以直接拷贝使用，不放心的，可以自己在把代码原理阅读一遍。

/*
*    Copyright 2010-2011 The myBatis Team
*
*    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.mybatis.spring;

import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
import java.io.StringReader;
import java.io.StringWriter;
import java.util.List;
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.executor.ErrorContext;
import org.apache.ibatis.logging.Log;
import org.apache.ibatis.logging.LogFactory;
import org.apache.ibatis.mapping.Environment;
import org.apache.ibatis.plugin.Interceptor;
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.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
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.ConfigurableApplicationContext;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.core.NestedIOException;
import org.springframework.core.io.ClassPathResource;
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;

/**
* {@code FactoryBean} that creates an MyBatis {@code SqlSessionFactory}.
* This is the usual way to set up a shared MyBatis {@code SqlSessionFactory} in a Spring application context;
* the SqlSessionFactory can then be passed to MyBatis-based DAOs via dependency injection.
*
* Either {@code DataSourceTransactionManager} or {@code JtaTransactionManager} can be used for transaction
* demarcation in combination with a {@code SqlSessionFactory}. JTA should be used for transactions
* which span multiple databases or when container managed transactions (CMT) are being used.
*
* @see #setConfigLocation
* @see #setDataSource
* @version $Id: SqlSessionFactoryBean.java 3767 2011-05-25 06:53:43Z eduardo.macarron@gmail.com $
*/
public class SqlSessionFactoryBean implements FactoryBean<SqlSessionFactory>, InitializingBean, ApplicationListener<ApplicationEvent> {

private final Log logger = LogFactory.getLog(getClass());

private Resource configLocation;

private Resource [] typeAliasesLocations;

private Resource[] mapperLocations;

private DataSource dataSource;

private TransactionFactory transactionFactory;

private Properties configurationProperties;

private SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();

private SqlSessionFactory sqlSessionFactory;

private String environment = SqlSessionFactoryBean.class.getSimpleName();

private boolean failFast;

private Interceptor[] plugins;

private TypeHandler[] typeHandlers;

private String typeHandlersPackage;

private Class<?>[] typeAliases;

private String typeAliasesPackage;

public void setTypeAliasesLocations(Resource[] typeAliasesLocations) {
this.typeAliasesLocations = typeAliasesLocations;
}

/**
* Mybatis plugin list.
*
* @since 1.0.1
*
* @param plugins list of plugins
*
*/
public void setPlugins(Interceptor[] plugins) {
this.plugins = plugins;
}

/**
* Packages to search for type aliases.
*
* @since 1.0.1
*
* @param typeAliasesPackage package to scan for domain objects
*
*/
public void setTypeAliasesPackage(String typeAliasesPackage) {
this.typeAliasesPackage = typeAliasesPackage;
}

/**
* Packages to search for type handlers.
*
* @since 1.0.1
*
* @param typeHandlersPackage package to scan for type handlers
*
*/
public void setTypeHandlersPackage(String typeHandlersPackage) {
this.typeHandlersPackage = typeHandlersPackage;
}

/**
* Set type handlers. They must be annotated with {@code MappedTypes} and optionally with {@code MappedJdbcTypes}
*
* @since 1.0.1
*
* @param typeHandlers Type handler list
*/
public void setTypeHandlers(TypeHandler[] typeHandlers) {
this.typeHandlers = typeHandlers;
}

/**
* List of type aliases to register. They can be annotated with {@code Alias}
*
* @since 1.0.1
*
* @param typeAliases Type aliases list
*/
public void setTypeAliases(Class<?>[] typeAliases) {
this.typeAliases = typeAliases;
}

/**
* If true, a final check is done on Configuration to assure that all mapped
* statements are fully loaded and there is no one still pending to resolve
* includes. Defaults to false.
*
* @since 1.0.1
*
* @param failFast enable failFast
*/
public void setFailFast(boolean failFast) {
this.failFast = failFast;
}

/**
* Set the location of the MyBatis {@code SqlSessionFactory} config file. A typical value is
* "WEB-INF/mybatis-configuration.xml".
*/
public void setConfigLocation(Resource configLocation) {
this.configLocation = configLocation;
}

/**
* Set locations of MyBatis mapper files that are going to be merged into the {@code SqlSessionFactory}
* configuration at runtime.
*
* This is an alternative to specifying "<sqlmapper>" entries in an MyBatis config file.
* This property being based on Spring's resource abstraction also allows for specifying
* resource patterns here: e.g. "classpath*:sqlmap/*-mapper.xml".
*/
public void setMapperLocations(Resource[] mapperLocations) {
this.mapperLocations = mapperLocations;
}

/**
* Set optional properties to be passed into the SqlSession configuration, as alternative to a
* {@code <properties>} tag in the configuration xml file. This will be used to
* resolve placeholders in the config file.
*/
public void setConfigurationProperties(Properties sqlSessionFactoryProperties) {
this.configurationProperties = sqlSessionFactoryProperties;
}

/**
* Set the JDBC {@code DataSource} that this instance should manage transactions for. The {@code DataSource}
* should match the one used by the {@code SqlSessionFactory}: for example, you could specify the same
* JNDI DataSource for both.
*
* A transactional JDBC {@cod
d43e
e Connection} for this {@code DataSource} will be provided to application code
* accessing this {@code DataSource} directly via {@code DataSourceUtils} or {@code DataSourceTransactionManager}.
*
* The {@code DataSource} specified here should be the target {@code DataSource} to manage transactions for, not
* a {@code TransactionAwareDataSourceProxy}. Only data access code may work with
* {@code TransactionAwareDataSourceProxy}, while the transaction manager needs to work on the
* underlying target {@code DataSource}. If there's nevertheless a {@code TransactionAwareDataSourceProxy}
* passed in, it will be unwrapped to extract its target {@code DataSource}.
*
*/
public void setDataSource(DataSource dataSource) {
if (dataSource instanceof TransactionAwareDataSourceProxy) {
// If we got a TransactionAwareDataSourceProxy, we need to perform
// transactions for its underlying target DataSource, else data
// access code won't see properly exposed transactions (i.e.
// transactions for the target DataSource).
this.dataSource = ((TransactionAwareDataSourceProxy) dataSource).getTargetDataSource();
} else {
this.dataSource = dataSource;
}
}

/**
* Sets the {@code SqlSessionFactoryBuilder} to use when creating the {@code SqlSessionFactory}.
*
* This is mainly meant for testing so that mock SqlSessionFactory classes can be injected. By
* default, {@code SqlSessionFactoryBuilder} creates {@code DefaultSqlSessionFactory} instances.
*
*/
public void setSqlSessionFactoryBuilder(SqlSessionFactoryBuilder sqlSessionFactoryBuilder) {
this.sqlSessionFactoryBuilder = sqlSessionFactoryBuilder;
}

/**
* Set the MyBatis TransactionFactory to use. Default is {@code SpringManagedTransactionFactory}
*
* The default {@code SpringManagedTransactionFactory} should be appropriate for all cases:
* be it Spring transaction management, EJB CMT or plain JTA. If there is no active transaction,
* SqlSession operations will execute SQL statements non-transactionally.
*
* <b>It is strongly recommended to use the default {@code TransactionFactory}.</b> If not used, any
* attempt at getting an SqlSession through Spring's MyBatis framework will throw an exception if
* a transaction is active.
*
* @see SpringManagedTransactionFactory
* @param transactionFactory the MyBatis TransactionFactory
*/
public void setTransactionFactory(TransactionFactory transactionFactory) {
this.transactionFactory = transactionFactory;
}

/**
* <b>NOTE:</b> This class <em>overrides</em> any {@code Environment} you have set in the MyBatis
* config file. This is used only as a placeholder name. The default value is
* {@code SqlSessionFactoryBean.class.getSimpleName()}.
*
* @param environment the environment name
*/
public void setEnvironment(String environment) {
this.environment = environment;
}

/**
* {@inheritDoc}
*/
public void afterPropertiesSet() throws Exception {
Assert.notNull(dataSource, "Property 'dataSource' is required");
Assert.notNull(sqlSessionFactoryBuilder, "Property 'sqlSessionFactoryBuilder' is required");

this.sqlSessionFactory = buildSqlSessionFactory();
}

/**
* Build a {@code SqlSessionFactory} instance.
*
* The default implementation uses the standard MyBatis {@code XMLConfigBuilder} API to build a
* {@code SqlSessionFactory} instance based on an Reader.
*
* @return SqlSessionFactory
* @throws IOException if loading the config file failed
*/
protected SqlSessionFactory buildSqlSessionFactory() throws IOException {

/*修改的代码 END*/

Configuration configuration;
XMLConfigBuilder xmlConfigBuilder = null;

if (this.configLocation != null || this.typeAliasesLocations != null) {
Document document = null;
Element E_typeAliases = null;
if(this.configLocation != null){
SAXReader reader = new SAXReader();
try {
document = reader.read(configLocation.getInputStream());
Element E_configuration = document.getRootElement();
if(E_configuration == null){
E_configuration = DocumentHelper.createElement("configuration");
document.setRootElement(E_configuration);
}
E_typeAliases = E_configuration.element("typeAliases");
if(E_typeAliases == null){
E_typeAliases = E_configuration.addElement("typeAliases");
}
} catch (DocumentException e) {
e.printStackTrace();
}
}else{
document = DocumentHelper.createDocument();
document.addDocType("configuration",
"-//mybatis.org//DTD Config 3.0//EN",
"http://mybatis.org/dtd/mybatis-3-config.dtd");

Element E_configuration = DocumentHelper.createElement("configuration");
document.setRootElement(E_configuration);

E_typeAliases = E_configuration.addElement("typeAliases");
}
if(this.typeAliasesLocations != null){
/*
* 配置文件格式
* <?xml version="1.0" encoding="UTF-8" ?>
* <typeAliases>
* 	<typeAlias alias="example" type="net.jiaxinnuo.example.entity.Example"/>
* </typeAliases>
*/
/*封装配置文件*/
if (!ObjectUtils.isEmpty(this.typeAliasesLocations)) {
for (Resource typeAliasesLocation : this.typeAliasesLocations) {
if (typeAliasesLocation == null) {
continue;
}
InputStream in = typeAliasesLocation.getInputStream();
SAXReader reader = new SAXReader();
try {
Document doc = reader.read(in);
Element E_root = doc.getRootElement();
List<Element> list = E_root.elements();
for(Element e : list){
E_typeAliases.add((Element)e.clone());
}
} catch (DocumentException e) {
e.printStackTrace();
}
}
}
}
Reader reader = null;
{
String confXml = null;
StringWriter writer = new StringWriter();

document.write(writer);
confXml = writer.getBuffer().toString();
writer.close();
writer = null;
reader = new StringReader(confXml);
}
xmlConfigBuilder = new XMLConfigBuilder(reader, null, this.configurationProperties);
configuration = xmlConfigBuilder.getConfiguration();
}else {
if (this.logger.isDebugEnabled()) {
this.logger.debug("Property 'configLocation' not specified, using default MyBatis Configuration");
}
configuration = new Configuration();
}

if (StringUtils.hasLength(this.typeAliasesPackage)) {
String[] typeAliasPackageArray = StringUtils.tokenizeToStringArray(this.typeAliasesPackage,
ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS);
for (String packageToScan : typeAliasPackageArray) {
configuration.getTypeAliasRegistry().registerAliases(packageToScan);
if (this.logger.isDebugEnabled()) {
this.logger.debug("Scanned package: '" + packageToScan + "' for aliases");
}
}
}

if (!ObjectUtils.isEmpty(this.typeAliases)) {
for (Class<?> typeAlias : this.typeAliases) {
configuration.getTypeAliasRegistry().registerAlias(typeAlias);
if (this.logger.isDebugEnabled()) {
this.logger.debug("Registered type alias: '" + typeAlias + "'");
}
}
}

if (!ObjectUtils.isEmpty(this.plugins)) {
for (Interceptor plugin : this.plugins) {
configuration.addInterceptor(plugin);
if (this.logger.isDebugEnabled()) {
this.logger.debug("Registered plugin: '" + plugin + "'");
}
}
}

if (StringUtils.hasLength(this.typeHandlersPackage)) {
String[] typeHandlersPackageArray = StringUtils.tokenizeToStringArray(this.typeHandlersPackage,
ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS);
for (String packageToScan : typeHandlersPackageArray ) {
configuration.getTypeHandlerRegistry().register(packageToScan);
if (this.logger.isDebugEnabled()) {
this.logger.debug("Scanned package: '" + packageToScan + "' for type handlers");
}
}
}

if (!ObjectUtils.isEmpty(this.typeHandlers)) {
for (TypeHandler typeHandler : this.typeHandlers) {
configuration.getTypeHandlerRegistry().register(typeHandler);
if (this.logger.isDebugEnabled()) {
this.logger.debug("Registered type handler: '" + typeHandler + "'");
}
}
}

if (xmlConfigBuilder != null) {
try {
xmlConfigBuilder.parse();

if (this.logger.isDebugEnabled()) {
this.logger.debug("Parsed configuration file: '" + this.configLocation + "'");
}
} catch (Exception ex) {
throw new NestedIOException("Failed to parse config resource: " + this.configLocation, ex);
} finally {
ErrorContext.instance().reset();
}
}

if (this.transactionFactory == null) {
this.transactionFactory = new SpringManagedTransactionFactory(this.dataSource);
}

Environment environment = new Environment(this.environment, this.transactionFactory, this.dataSource);
configuration.setEnvironment(environment);

if (!ObjectUtils.isEmpty(this.mapperLocations)) {
for (Resource mapperLocation : this.mapperLocations) {
if (mapperLocation == null) {
continue;
}

// this block is a workaround for issue http://code.google.com/p/mybatis/issues/detail?id=235 // when running MyBatis 3.0.4. But not always works.
// Not needed in 3.0.5 and above.
String path;
if (mapperLocation instanceof ClassPathResource) {
path = ((ClassPathResource) mapperLocation).getPath();
} else {
path = mapperLocation.toString();
}

try {
XMLMapperBuilder xmlMapperBuilder = new XMLMapperBuilder(mapperLocation.getInputStream(),
configuration, path, configuration.getSqlFragments());
xmlMapperBuilder.parse();
} catch (Exception e) {
throw new NestedIOException("Failed to parse mapping resource: '" + mapperLocation + "'", e);
} finally {
ErrorContext.instance().reset();
}

if (this.logger.isDebugEnabled()) {
this.logger.debug("Parsed mapper file: '" + mapperLocation + "'");
}
}
} else {
if (this.logger.isDebugEnabled()) {
this.logger.debug("Property 'mapperLocations' was not specified or no matching resources found");
}
}

return this.sqlSessionFactoryBuilder.build(configuration);
}

/**
* {@inheritDoc}
*/
public SqlSessionFactory getObject() throws Exception {
if (this.sqlSessionFactory == null) {
afterPropertiesSet();
}

return this.sqlSessionFactory;
}

/**
* {@inheritDoc}
*/
public Class<? extends SqlSessionFactory> getObjectType() {
return this.sqlSessionFactory == null ? SqlSessionFactory.class : this.sqlSessionFactory.getClass();
}

/**
* {@inheritDoc}
*/
public boolean isSingleton() {
return true;
}

/**
* {@inheritDoc}
*/
public void onApplicationEvent(ApplicationEvent event) {
if (failFast && event instanceof ContextRefreshedEvent) {
// fail-fast -> check all statements are completed
this.sqlSessionFactory.getConfiguration().getMappedStatementNames();
}
}

}