MyBatis的SqlSessionFactory的创建问题

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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：

 

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：

 

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。

 

 

           

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