创建工具类的思路的分析: 1. 不让别人来创建对象,就用private私有构造方法化,工具类都是静态的类名点调用,声明所欲变量,提供静态代码块.给变量赋值,创建方法
举例:public class MapperFactory{
private MapperFactory(){};
private static SqlSessionFactory factory;
private static ThreadLocal<SqlSession> tl = new ThreadLocal<SqlSession>();

static{InputStream in = null;
try {
//1.读取mybatis主配置文件
in = Resources.getResourceAsStream("SqlMapConfig.xml");
//2.创建构建者对象
SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
//3.使用构建者创建SqlSessionFactory工厂
factory = builder.build(in);
}catch (Exception e){
//打印异常信息到控制台
e.printStackTrace();
//抛出错误提示程序终止执行
throw new ExceptionInInitializerError("初始化SqlSessionFactory失败");
}finally {
//释放流对象
if(in != null){
try{
in.close();
}catch (Exception e){
e.printStackTrace();
try each的位置,