MyBatis的SqlSessionFactory的创建问题

最新推荐文章于 2025-05-11 18:13:19 发布

原创最新推荐文章于 2025-05-11 18:13:19 发布 · 1.5k 阅读

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本文探讨了如何在不使用Spring等框架的情况下，使用Singleton模式来创建和管理MyBatis的SqlSessionFactory。通过一个内部静态类Holder实现延迟加载，确保SqlSessionFactory在整个应用程序中只被初始化一次。详细代码示例展示了Configuration和SqlSessionFactorySingletonHolder类的设计。

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在MyBatis文档中，提到SqlSessionFactory最好在程序中只被创建一次。建议使用Singleton或者Spring、Guice等dependencyinjection框架。

Spring中使用MyBatis完全可以采用Spring-mybatis，无须考虑factory的生命周期。

本文考虑自己实现Singleton机制。选用之前我的Singleton文章中提到的第四种Singleton实现方案，lazyloading模式。

大体思路：

实现一个Holder类，该类是Singleton的，将SqlSessionFactory作为该类的成员变量。Holder类的构造函数只会被调用一次，并且会将SqlSessionFactory实例化。以后每次调用Holder.getFactory()方法就能获得同一个SqlSessionFactory对象。不过由于我还没有找到支持创建时参数的方案，使用另一个Singleton对象Configuration作为依赖。

使用代码如下：

Configuration.getInstance().setXmlPath("com/lifeix/mybatis/xml/dbConfig.xml");

SqlSessionFactorySingletonHolderfactoryHolder = SqlSessionFactorySingletonHolder.getInstance();

SqlSession session =factoryHolder.getFactory().openSession();

Configuration类代码如下：

[java] view plain copy print ?

public class Configuration {
private static class SingletonHolder{
private static final Configuration INSTANCE = new Configuration();
}
public static Configuration getInstance(){
return SingletonHolder.INSTANCE;
}
private Configuration() {
}
@Getter @Setter
private String xmlPath;
}

public class Configuration { private static class SingletonHolder{ private static final Configuration INSTANCE = new Configuration(); } public static Configuration getInstance(){ return SingletonHolder.INSTANCE; } private Configuration() { } @Getter @Setter private String xmlPath;}

SqlSessionFactorySingletonHodler类的代码如下：

[java] view plain copy print ?

import lombok.Getter;
import java.io.IOException;
import java.io.Reader;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class SqlSessionFactorySingletonHolder {
static class InnerHolder{
private static final SqlSessionFactorySingletonHolder INSTANCE;
static {
try {
INSTANCE = new SqlSessionFactorySingletonHolder();
} catch (Exception e) {
throw new ExceptionInInitializerError(e);
}
}
}
public static SqlSessionFactorySingletonHolder getInstance(){
return InnerHolder.INSTANCE;
}
private SqlSessionFactorySingletonHolder() throws Exception {
init();
}
private void init() throws Exception {
log = LoggerFactory.getLogger(getClass());
Reader reader = null;
try {
reader = Resources.getResourceAsReader(Configuration.getInstance().getXmlPath());
factory = new SqlSessionFactoryBuilder().build(reader);
}catch(Exception ex){
log.error(ex.getMessage(),ex);
throw ex;
} finally {
try {
if(reader != null){
reader.close();
}
} catch (IOException ex) {
log.error(ex.getMessage(),ex);
}
}
}
@Getter
private SqlSessionFactory factory;
private Logger log;
}

import lombok.Getter;import java.io.IOException;import java.io.Reader;import org.apache.ibatis.io.Resources;import org.apache.ibatis.session.SqlSessionFactory;import org.apache.ibatis.session.SqlSessionFactoryBuilder;import org.slf4j.Logger;import org.slf4j.LoggerFactory;public class SqlSessionFactorySingletonHolder { static class InnerHolder{ private static final SqlSessionFactorySingletonHolder INSTANCE; static { try { INSTANCE = new SqlSessionFactorySingletonHolder(); } catch (Exception e) { throw new ExceptionInInitializerError(e); } } } public static SqlSessionFactorySingletonHolder getInstance(){ return InnerHolder.INSTANCE; } private SqlSessionFactorySingletonHolder() throws Exception { init(); } private void init() throws Exception { log = LoggerFactory.getLogger(getClass()); Reader reader = null; try { reader = Resources.getResourceAsReader(Configuration.getInstance().getXmlPath()); factory = new SqlSessionFactoryBuilder().build(reader); }catch(Exception ex){ log.error(ex.getMessage(),ex); throw ex; } finally { try { if(reader != null){ reader.close(); } } catch (IOException ex) { log.error(ex.getMessage(),ex); } } } @Getter private SqlSessionFactory factory; private Logger log;}

希望对不使用Spring等框架的人有帮助。