mybatis的环境搭建

àì夳堔傛蜴生んèń 2022-12-31 02:25 219阅读 0赞

# map.xml\`\`文件的约束 #

<?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">

# 核心配置文件的约束 #

<?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">

## 第一步：创建maven工程并且在pro.xml中导入相关的依赖包 ##

<dependencies>
               
             <dependency>
                 <groupId>org.mybatis</groupId>
                 <artifactId>mybatis</artifactId>
                 <version>3.5.2</version>
             </dependency>
                
             <dependency>
                 <groupId>junit</groupId>
                 <artifactId>junit</artifactId>
                 <version>4.12</version>
                 <scope>test</scope>
             </dependency>
          
             <dependency>
                 <groupId>mysql</groupId>
                 <artifactId>mysql-connector-java</artifactId>
                 <version>8.0.18</version>
             </dependency>
         </dependencies>

## 第二步：创建实体类，和接口 ##

package com.zhu.dao;
    
    import com.zhu.pojo.User;
    
    import java.util.List;
    
    public interface IUserDao {
        
    
        List<User> selectAllUser();
    }

package com.zhu.pojo;
    
    public class User {
        
        private int id;
        private String name;
        private String pwd;
    
        public User(){
        }
        public User(int id,String name,String pwd){
        }
    
        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 String getPwd() {
        
            return pwd;
        }
    
        public void setPwd(String pwd) {
        
            this.pwd = pwd;
        }
    
        @Override
        public String toString() {
        
            return "User{" +
                    "id=" + id +
                    ", name='" + name + '\'' +
                    ", pwd='" + pwd + '\'' +
                    '}';
        }
    }

## 第三步：为接口配置对应的配置文件 ##

<?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.zhu.dao.IUserDao">
    
         
        <select id="selectAllUser" resultType="com.zhu.pojo.User">
            select * from mybatis.user
        </select>
    </mapper>

## 第四步：创建一个生成SqlSession对象的工具类 ##

package com.zhu.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 MybatisUtils {
        
          private  static SqlSessionFactory sqlSessionFactory;
        static {
        
            try {
        
            //创建SqlSessionFactory对象
                String resource = "mybatis-config.xml";
                InputStream inputStream = Resources.getResourceAsStream(resource);
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
                
            } catch (IOException e) {
        
                e.printStackTrace();
            }
        }
        public static SqlSession getSqlSession(){
        
        //通过SqlSessionFactory来创建SqlSession对象
            SqlSession sqlSession = sqlSessionFactory.openSession();
            return sqlSession;
        }
    }

## 第五步：配置核心文件 ##

1.配置连接数据库的相关信息  
2.每一个接口相应的配置文件都得在核心配置文件中通过注册

<?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="com.mysql.cj.jdbc.Driver"/>
                    <property name="url" value="jdbc:mysql://localhost:3306"/>
                    <property name="username" value="root"/>
                    <property name="password" value="zhuminghua"/>
                </dataSource>
            </environment>
        </environments>
        <mappers>
        
            <mapper resource="com/zhu/dao/IUserDao.xml"/>
        </mappers>
    </configuration>

# 没有在核心配置文件中注册相应接口的配置文件会报以下错误 #

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NTcyMzAwMw_size_16_color_FFFFFF_t_70_pic_center][]

## 由于maven的约定大于配置，我们可能遇到配置文件无法导出或者生效的问题。解决方案：在pom.xml文件中加入build配置 ##

<build>
            <resources>
                <resource>
                    <directory>src/main/java</directory>
                    <includes>
                        <include>**/*.properties</include>
                        <include>**/*.xml</include>
                    </includes>
                    <filtering>true</filtering>
                </resource>
                <resource>
                    <directory>src/main/resources</directory>
                    <includes>
                        <include>**/*.properties</include>
                        <include>**/*.xml</include>
                    </includes>
                    <filtering>true</filtering>
                </resource>
            </resources>
        </build>

## 没配置build可能出现一下异常： ##

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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NTcyMzAwMw_size_16_color_FFFFFF_t_70_pic_center 1]: /images/20221120/f416287d11e3479d86b849c8e48b3ee9.png