mybatis不能find mapper.xml以及全部代码。查询表中所有数据。

这个问题困扰了我很久。

这次总算是搞定了mybatis的配置。

SqlSession session = sqlSessionFactory.openSession();
这个代码一直报错，最后查到是mybitis.xml的配置文件mapper写错了。用/斜杠隔开是对的。

    


之前是

    

这个是错误的。

第二个困扰pom中必须加一下代码，运行程序会自动把

resources

properties

.xml文件自动添加入class的打包文件中。

    
        
            src/main/resources
            
                **/*.properties
                **/*.xml
            
            true
        
        
            src/main/java
            
                **/*.properties
                **/*.xml
            
            true
        
    

下面是全部代码,按照这个可以直接实现功能。前提是数据的自己写，结构下面有。
1.实体类

package com.books;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@AllArgsConstructor
@NoArgsConstructor
@Data
public class Books {
    private int BOOKID;
    private String BOOKNAME;
    private int BOOKCOUTS;
    private String DETAIL;
2.接口就是相当于是以前的DAO

package com.dao;

import com.books.Books;

import java.util.List;

public interface MyBookMapper {

    List selectBooks();
}
3.接口映射文件

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



    
        select * from BOOKS
    


4.mybatis的主配置文件

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


    
        
        
            
            
            
            
        
    


    


5.工具类主要是减少重复代码。

package com.utils;

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;

public class Utils {


    private static SqlSessionFactory sqlSessionFactory ;

    static {
        String in = "mybatis.xml";
        try {
            InputStream inputStream = Resources.getResourceAsStream(in);
            System.out.println("获取到了xml");
            System.out.println("sqlSessionFactory的值是:"+sqlSessionFactory);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);



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

    public static SqlSession getSession(){


        System.out.println("sqlSessionFactory:"+ sqlSessionFactory);
        SqlSession session = sqlSessionFactory.openSession();
        System.out.println("已经获取到了SqlSessionFactory");
       return session;
    }
}

6.测试类

import com.books.Books;
import com.dao.MyBookMapper;
import com.utils.Utils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;


public class MybatisTest {

    @Test
    public void test(){

    SqlSession session = Utils.getSession();
    MyBookMapper mapper = session.getMapper(MyBookMapper.class);
    List list = mapper.selectBooks();
    for(Books books:list){
        System.out.println(books);
    }


    }
}
7.结果

已经获取到了SqlSessionFactory
Books(BOOKID=1, BOOKNAME=dddd, BOOKCOUTS=0, DETAIL=discribe)
Books(BOOKID=2, BOOKNAME=eeee, BOOKCOUTS=0, DETAIL=discribe)
Books(BOOKID=3, BOOKNAME=java, BOOKCOUTS=0, DETAIL=从入门到放弃)
Books(BOOKID=4, BOOKNAME=Oracle, BOOKCOUTS=0, DETAIL=从删库到跑路)
Books(BOOKID=5, BOOKNAME=Linux, BOOKCOUTS=0, DETAIL=从进门到进牢)

下面是数据库结构和pom。

BOOKID Integer,

,BOOKNAME varchar ,

BOOKCOUNT Integer ,

DETAIL varchar.

pom

<?xml version="1.0" encoding="UTF-8"?>
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    4.0.0

    org.example
    mybatis
    1.0-SNAPSHOT

    
        8
        8
    

    
        
            junit
            junit
            4.13
            test
        

        
            org.mybatis
            mybatis
            3.4.5
        

        
            com.oracle
            ojdbc6
            12.1.0.1-atlassian-hosted
        

        
            org.projectlombok
            lombok
            1.18.16
        

        
            log4j
            log4j
            1.2.12
        
    

    
    
        
            
                src/main/resources
                
                    **/*.properties
                    **/*.xml
                
                true
            
            
                src/main/java
                
                    **/*.properties
                    **/*.xml
                
                true