【求助】使用Mybatis时SqlSessionFactory对象总是报空指针

使用Mybatis时SqlSessionFactory对象总是报空指针：

java.lang.NullPointerException: Cannot invoke "org.apache.ibatis.session.SqlSessionFactory.openSession()" because "com.tao.utils.MybatisUtils.sqlSessionFactory" is null

1、Mysql数据库连接是正常的，使用数据库客户端测试过；

2、resources包导入也是正确的：import org.apache.ibatis.io.Resources;

有哪位高手能帮看看呀？就卡在这里没法继续下去了。多谢啦~~~~

==========================================================================================

相关代码如下

客户端测试类代码如下：

import com.tao.pojo.User;
import com.tao.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import java.util.List;

public class UserDaoTest {

    @Test
    public  void  test(){

        //第一步：获取sqlsession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        //第二步： 执行SQL  方式一: getMapper

        UserDao userDao = sqlSession.getMapper(UserDao.class);
        List<User> userList = userDao.getUserList();

        for (User user : userList) {
            System.out.println(user);
        }

        sqlSession.close();

    }


}

实体类代码如下：

package com.tao.pojo;

public class User {
    private int id;
    private String name;
    private int age;

    public User() {
    }

    public User(int id, String name, int age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }


    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }


    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

工具类代码如下：

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.IOException;
import java.io.InputStream;


//mybatis工具类
public class MybatisUtils {

    public static SqlSessionFactory sqlSessionFactory;

    static {
        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        } catch (IOException e) {
            e.printStackTrace();
        }


    }

    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession();

    }



}

UserMapper.xml文件代码如下：

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">



<mapper namespace="com.tao.dao.UserDao">
    <select id="getUserList" resultType="com.tao.pojo.User">
        select * from test01;
    </select>
</mapper>