idea新建一个Mybatis项目（使用Maven）

墨蓝 2023-07-15 04:54 62阅读 0赞

**新建一个mybatis项目需要首先配置好maven环境**  
具体的mavne问题在我的其他博客中有提到  
思路：搭建环境–>导入Mybatis–>编写代码–>测试  
新建项目：  
1.新建一个普通的maven项目  
2.删除src目录  
3.导入maven依赖  
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<dependencies>
            
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>5.1.45</version>
            </dependency>
            
            <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>
            </dependency>
        </dependencies>

**1.创建一个模块**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mzg5NDc3MQ_size_16_color_FFFFFF_t_70 1]

*  编写mybatis的核心配置文件

<?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="com.mysql.jdbc.Driver"/>
                    <property name="url" value="jdbc:mysql://localhost:3306/essy?useSSL=false&useUnicode=true&characterEncoding=UTF-8;"/>
                    <property name="username" value="1234"/>
                    <property name="password" value="1234"/>
                </dataSource>
            </environment>
        </environments>
    
    </configuration>`

*  编写mybatis的工具类

package com.superman.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;
    
    //sqlSessionFactory工厂模式 sqlSession
    public class MybatisUtil { 
        private static SqlSessionFactory sqlSessionFactory;
        static { 
            try { 
                //使用mybatis的第一步：获取sqlSessionFactory对象，mybatis官网
                String resource = "mybatis-config.xml";
                InputStream inputStream = Resources.getResourceAsStream(resource);
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            } catch (IOException e) { 
                e.printStackTrace();
            }
        }
    
        //有了sqlSessionFactory，我们就可以从中获得sessionSql的实例
        //sqlSession包含了面向数据库执行SQL命令所需的所有方法
    
        public static SqlSession getSqlSession() { 
            SqlSession sqlSession=sqlSessionFactory.openSession();
            return sqlSession;
        }
    
    }

**2.编写代码**

*  实体类

package com.superman.pojo;
    
    //实体类
    public class User { 
        private int id;
        private String username;
        private String birthday;
        private String sex;
        private  String address;
    
        public User() { 
        }
    
        public User(int id, String username, String birthday, String sex, String address) { 
            this.id = id;
            this.username = username;
            this.birthday = birthday;
            this.sex = sex;
            this.address = address;
        }
    
        public int getId() { 
            return id;
        }
    
        public void setId(int id) { 
            this.id = id;
        }
    
        public String getUsername() { 
            return username;
        }
    
        public void setUsername(String username) { 
            this.username = username;
        }
    
        public String getBirthday() { 
            return birthday;
        }
    
        public void setBirthday(String birthday) { 
            this.birthday = birthday;
        }
    
        public String getSex() { 
            return sex;
        }
    
        public void setSex(String sex) { 
            this.sex = sex;
        }
    
        public String getAddress() { 
            return address;
        }
    
        public void setAddress(String address) { 
            this.address = address;
        }
    
        @Override
        public String toString() { 
            return "User{" +
                    "id=" + id +
                    ", username='" + username + '\'' +
                    ", birthday='" + birthday + '\'' +
                    ", sex='" + sex + '\'' +
                    ", address='" + address + '\'' +
                    '}';
        }
    }

*  dao接口

package com.superman.dao;
    
    import com.superman.pojo.User;
    
    import java.util.List;
    
    public interface UserDao { 
        List<User> getUserList();
    }

*  同时配置UserMapper.xml

<?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.superman.dao.UserDao">
        <select id="getUserList" resultType="com.superman.pojo.User">
            select * from eesy.user
        </select>
    </mapper>

**3.测试代码**  
注意点：  
org.apache.ibatis.binding.BindingException: Type interface com.superman.dao.UserDao is not known to the MapperRegistry.  
**MapperRegistry是什么？**  
核心配置文件中注册mappers  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mzg5NDc3MQ_size_16_color_FFFFFF_t_70 2]

package com.superman.dao;
    
    import com.superman.pojo.User;
    import com.superman.utils.MybatisUtil;
    import org.apache.ibatis.session.SqlSession;
    import org.junit.Test;
    
    import java.util.List;
    
    public class UserDaoTest { 
    
        @Test
        public void test() { 
            //第一步：获得sqlsession对象
            SqlSession sqlSession = MybatisUtil.getSqlSession();
            //方式一：执行SQL
            UserDao mapper=sqlSession.getMapper(UserDao.class);
            List<User> userList=mapper.getUserList();
    
            for (User user : userList) { 
                System.out.println(user);
            }
    
        //关闭SqlSession
            sqlSession.close();
        }
    
    }

可能遇到的问题有java不支持发行版本5，在我的另一篇博客中有提到。  
同时还涉及到一个过滤的问题：  
需要在所有的pom.xml文件中增加下面的代码

<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>

总结：  
1.mybatis的工具类  
2.因为工具类需要resources配置文件，所以在resources中写一个配置文件  
3.环境准备完成以后写实体类  
4.写完实体类以后写接口  
5.为接口写一个mapper.xml  
6.写一个test进行测试  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mzg5NDc3MQ_size_16_color_FFFFFF_t_70 3]

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