MyBatis创建时SqlSessionFactory空指针异常

概要

测MyBatis配置的时候创建SqlSessionFactory报NullPointerException，具体错误如下：

java.lang.NullPointerException
    at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:84)
    at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:64)
    at com.wanvale.test.MybatisTest.demo(MybatisTest.java:21)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:157)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
    at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
    at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)

Java代码

package com.wanvale.test;

import com.wanvale.dao.IUserDao;
import com.wanvale.domain.User;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import javax.annotation.Resources;
import java.io.InputStream;
import java.util.List;

public class MybatisTest {
    @Test
    public void demo() throws Exception{
        //读取配置文件
        InputStream in= Resources.class.getResourceAsStream("SqlMapConfig.xml");
        //创建SQLSessionFactory工厂
        SqlSessionFactoryBuilder builder=new SqlSessionFactoryBuilder();
        SqlSessionFactory factory=builder.build(in);
        //使用工厂生产SqlSession对象
        SqlSession session=factory.openSession();
        //使用SqlSession创建Dao接口的代理对象
        IUserDao userDao=session.getMapper(IUserDao.class);
        //使用代理对象执行方法
        List<User> users=userDao.findAll();
        for(User user:users){
            System.out.println(user);
        }
        //释放资源
        session.close();
        in.close();
    }

}

解决方法

经查，是Resources的包导错了
问题出在这一行

InputStream in= Resources.class.getResourceAsStream("SqlMapConfig.xml");

导入的包是：import javax.annotation.Resources;
实际上正确的包是：import org.apache.ibatis.io.Resources;

重新导包，去掉Resources后面的.class，正常运行

总结

敲代码的时候手别太快，确认一下包名对不对再按Enter...