mybatis配置版出现的问题

迈不过友情╰ 2023-07-01 09:58 15阅读 0赞

## mybatis配置版出现的问题 ##

配置文件

<?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>com.xiao</groupId>
        <artifactId>Mybatis-Study</artifactId>
        <packaging>pom</packaging>
        <version>1.0-SNAPSHOT</version>
        <modules>
            <module>mybatis-01</module>
        </modules>
        
        <dependencies>
          
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>5.1.47</version>
            </dependency>
            
            <dependency>
                <groupId>org.mybatis</groupId>
                <artifactId>mybatis</artifactId>
                <version>3.5.1</version>
            </dependency>
            
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>4.12</version>
            </dependency>
        </dependencies>
        
        <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>
                **//这里注意问题，如果不配置格式，那么会报错，UTF-8下文件出现错误，因为是一个大模块下面包含了分的小模块，建议，在小模块的pom.xml文件中也配置**
                <resource>
                    <directory>src/main/resources</directory>
                    <filtering>true</filtering>
                </resource>
            </resources>
            *****<plugins>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-resources-plugin</artifactId>
                    <configuration>
                        <encoding>UTF-8</encoding>
                    </configuration>
                </plugin>
            </plugins>*****
        </build>
    </project>

分包下配置的另一个文件

resources下的配置文件

<?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/mybatis?useSSL=true&useUnicode=true&characterEncoding=utf8"/>
                    <property name="username" value="root"/>
                    <property name="password" value="123456"/>
                </dataSource>
            </environment>
        </environments>
        
        <mappers>
            <mapper resource="com/xiao/dao/UserMapper.xml"/>
        </mappers>
    </configuration>

实体类，配置版的比较麻烦，方法要给齐，如果是注解版的只需要加个注解即可

package com.xiao.pojo;
    /**实体类
     * @outhor liu
     * @dare 2020/1/20 16:23
     */
    public class User {
        
        private int id;
        private String name;
        private String pwd;
        public User(int id, String name, String pwd) {
        
            this.id = id;
            this.name = name;
            this.pwd = pwd;
        }
        public User() {
        
        }
        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 + '\'' +
                    '}';
        }
    }

utils包

package com.xiao.utils;
    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;
    /**工具类 SqlSessionFactory工厂模式对象
     * @outhor liu
     * @dare 2020/1/20 16:09
     */
    public class MybatisUtils {
        
        private static SqlSessionFactory sqlSessionFactory;
        static {
        
            try {
        
                //使用mybatis第一步：获取SqlSessionFactory工厂模式对象
                String resource="mybatis-config.xml";
                InputStream inputStream= Resources.getResourceAsStream(resource);
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            } catch (IOException e) {
        
                e.printStackTrace();
            }
        }
        //既然有了 SqlSessionFactory，顾名思义，我们就可以从中获得 SqlSession 的实例了。
        // SqlSession 完全包含了面向数据库执行 SQL 命令所需的所有方法
        public static SqlSession getSqlSession(){
        
            return sqlSessionFactory.openSession();
        }
    }

mapper接口

package com.xiao.dao;
    import com.xiao.pojo.User;
    import java.util.List;
    /**
     * @outhor liu
     * @dare 2020/1/20 16:25
     */
    public interface UserDao {
        
        List<User> getUserList();
    }

测试类，建议包名和类名对应java包里面的名字

package com.xiao.dao;
    import com.xiao.pojo.User;
    import com.xiao.utils.MybatisUtils;
    import org.apache.ibatis.session.SqlSession;
    import org.junit.Test;
    import java.util.List;
    /**
     * @outhor liu
     * @dare 2020/1/20 16:39
     */
    public class UserDaoTest {
        
        @Test
        public void test(){
        
            //第一步，获得SqlSession对象
            SqlSession sqlSession = MybatisUtils.getSqlSession();
            //第二步，执行sql[方式一：getMapper]
            UserDao mapper = sqlSession.getMapper(UserDao.class);
            List<User> userList = mapper.getUserList();
            for (User user : userList) {
        
                System.out.println(user);
            }
            //关闭SqlSession
            sqlSession.close();
        }
    }

输出的内容

User{
        id=1, name='张三', pwd='123'}
    User{
        id=2, name='李四', pwd='123'}
    User{
        id=3, name='刘啸', pwd='123'}

配置版的比较麻烦的点就是要注意配置的内容不要出错，mybatis的好处就是省略了jdbc的重复书写，全部在xml文件中就可以搞定