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。

<mappers>
    <mapper resource="com/dao/MyBookMapper.xml"/>
</mappers>

之前是

<mappers>
    <mapper resource="com.dao.MyBookMapper.xml"/>
</mappers>
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。

<!--导入resource防止资源导出失败-->
<build>
    <resources>
        <resource>
            <directory>src/main/resources</directory>
            <includes>
                <include>**/*.properties</include>
                <include>**/*.xml</include>
            </includes>
            <filtering>true</filtering>
        </resource>
        <resource>
            <directory>src/main/java</directory>
            <includes>
                <include>**/*.properties</include>
                <include>**/*.xml</include>
            </includes>
            <filtering>true</filtering>
        </resource>
    </resources>
</build>

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<Books> selectBooks();
}
3.接口映射文件

<?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.dao.MyBookMapper">


    <select id="selectBooks" resultType="com.books.Books">
        select * from BOOKS
    </select>

</mapper>
4.mybatis的主配置文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<environments default="development">
    <environment id="development">
        <transactionManager type="JDBC"/>
        <dataSource type="POOLED">
            <property name="driver" value="oracle.jdbc.driver.OracleDriver"/>
            <property name="url" value="jdbc:oracle:thin:@localhost:1521:orcl"/>
            <property name="username" value="s"/>
            <property name="password" value="0"/>
        </dataSource>
    </environment>
</environments>
<mappers>
    <mapper resource="com/dao/MyBookMapper.xml"/>
</mappers>
</configuration>
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<Books> 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"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         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">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>mybatis</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13</version>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>

        <dependency>
            <groupId>com.oracle</groupId>
            <artifactId>ojdbc6</artifactId>
            <version>12.1.0.1-atlassian-hosted</version>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.16</version>
        </dependency>

        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.12</version>
        </dependency>
    </dependencies>

    <!--导入resource防止资源导出失败-->
    <build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>
</project>