mybatis数据示例

待我称王封你为后i 2021-11-10 15:52 237阅读 0赞

### \* 约定在main文件夹下有Java源代码的Java文件夹和放有配置文件的resources文件夹 ###

##### 关于配置文件mybatis.cfg.xml里的示例内容： #####

<?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="UNPOOLED">
                    <property name="url" value="jdbc:mysql://localhost:3306/mybatis"/>
                    <property name="username" value="root"/>
                    <property name="driver" value="com.mysql.jdbc.Driver"/>
                    <property name="password" value="123456"/>
                </dataSource>
            </environment>
        </environments>
        <mappers>
            <mapper resource="org/mybatis/example/BlogMapper.xml"/>
        </mappers>
    </configuration>

##### 关于util包下的MybatisUtil.java里的内容示例： #####

package com.sz.util;
    
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    
    import java.io.IOException;
    import java.io.InputStream;
    
    public class MybatisUtil { 
    
        private static SqlSessionFactory sqlSessionFactory;
    
        static { 
            String resource = "mybatis.cfg.xml";
            InputStream in = null;
    
            try { 
                in = Resources.getResourceAsStream(resource);
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
            } catch (IOException e) { 
                e.printStackTrace();
            }finally { 
                if (in != null){ 
                    try { 
                        in.close();
                    }catch (IOException e){ 
                        e.printStackTrace();
                    }
                }
            }
        }
        
    	public static SqlSession getSession(){ 
            return sqlSessionFactory.openSession();
        }
    
    }

##### 关于pojo包下的Girl.java内容示例 #####

package com.sz.pojo;
    
    import java.util.Date;
    
    public class Girl { 
    
        private Long id;
    
        private String name;
    
        private String flower;
    
        private Date birthday;
    
        public Long getId() { 
            return id;
        }
    
        public void setId(Long id) { 
            this.id = id;
        }
    
        public String getName() { 
            return name;
        }
    
        public void setName(String name) { 
            this.name = name;
        }
    
        public String getFlower() { 
            return flower;
        }
    
        public void setFlower(String flower) { 
            this.flower = flower;
        }
    
        public Date getBirthday() { 
            return birthday;
        }
    
        public void setBirthday(Date birthday) { 
            this.birthday = birthday;
        }
    }

##### 关于mapper包下的GirMapper.java示例 #####

package com.sz.mapper;
    
    import com.sz.pojo.Girl;
    
    public interface GirlMapper { 
    
        int insert(Girl girl);
    
    }

##### 关于配置文件中com.sz.mapper.GirlMapper.xml示例： #####

<?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.sz.mapper.GirlMapper">
    
        <insert id="insert">
            insert into girl (name,flower,birthday) value (#{ name},#{ flower},#{ birthday})
        </insert>
    
    </mapper>

##### 关于测试类示例： #####

package com.sz;
    
    import com.sz.mapper.GirlMapper;
    import com.sz.pojo.Girl;
    import com.sz.util.MybatisUtil;
    import org.apache.ibatis.session.SqlSession;
    import org.junit.Test;
    
    import java.util.Date;
    
    public class Test1 { 
    
        @Test
        public void m1(){ 
    
            SqlSession sqlSession = MybatisUtil.getSession();
    
            GirlMapper mapper = sqlSession.getMapper(GirlMapper.class);
            Girl g = new Girl();
            g.setName("LingXingRu");
            g.setFlower("HuoJianHua");
            g.setBirthday(new Date());
    
            mapper.insert(g);
            sqlSession.commit();
    
            sqlSession.close();
        }
    }

##### 关于mybatis.cfg.xml配置文件中各节点 #####

*  properties节点：resource引用了外部的jdbc.properties文件
 *  外部引用的jdbc.properties文件级别高于properties内部的

*  typeAliases节点：给完整的类名注册一个简写的类名

这样可以在写查询语句时：

<select id="queryById" resultType="com.sz.pojo.Girl">
         select * from girl where id=#{ id};
    </select>
    将“com.sz.pojo.Girl”简写为：“girl”
    而如果使用了package就会将注册的包下的所有类全部注册，默认为简写类名

*  mappers节点：

##### mytabis关于参数问题 #####

*  单个参数问题基本没有问题  
    传入多个参数时可以再mapper接口中申明

Girl queryByNameFlower(@Param("name") String name,@Param("flower") String flower);
    加上@Param("name")即可对name进行申明，进而在sql语句中可以这么写：
    <select id="queryByNameFlower" resultType="com.sz.pojo.Girl">
            select * from girl where name = #{ name} and flower = #{ flower}
    </select>
    否则只能这么写：
    <select id="queryByNameFlower" resultType="com.sz.pojo.Girl">
            select * from girl where name = #{ arg0} and flower = #{ arg1}
    </select>