Mybatis笔记

2019-07-25

一、MyBatis的简单使用

1、maven项目依赖

简单的使用Mybatis只需要引入依赖包便可以了。

<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.4.6</version>
</dependency>

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.47</version>
</dependency>

2、需要配置的文件

1、mybatis的配置文件
2、数据库的连接配置文件
3、数据库和Do的实体映射文件

mybatis配置文件 configuration.xml名字自定。

<configuration>
    <!-- 加载类路径下的属性文件 -->
    <properties resource="jdbc.properties"/>
    <!-- 设置一个默认的连接环境信息 -->
    <environments default="mysql_developer">
        <!-- 连接环境信息，取一个任意唯一的名字 -->
        <environment id="mysql_developer">
            <!-- mybatis使用jdbc事务管理方式 -->
            <transactionManager type="jdbc"/>
            <!-- mybatis使用连接池方式来获取连接 -->
            <dataSource type="pooled">
                <!-- 配置与数据库交互的4个必要属性 -->
                <property name="driver" value="${driverClass}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${name}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>
    <!--将mybatis配置和映射文件关联起来-->
    <mappers>
        <mapper resource="DictionaryMapper.xml"/>
    </mappers>
</configuration>

连接配置文件jdbc.properties
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driverClass=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost/trainee?useSSL=false
name=root
password=root
相关的配置说明:<properties> resource 加载数据库的相关配置。配置文件和简单的jdbc连接的配置一样。
如何将数据库连接配置文件加载入mybatis配置文件。
<dataSource type="pooled">使用连接池的方式。连接配置参数是如何将属性加载入mybatis的配置文件。
dataSource的属性。<property>中的name属性是固定的。需要的是从外部加载进相应的value中。例如
<property name="driver" value="${driverClass}"/>driverClass便是从连接配置文件加载值的。当然也可以手工给他赋值

实体映射文件。该文件是将数据库中的表和java中的pojo类进行映射和配置相关的操作的。

<?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">

<!--
namespace属性是名称空间，必须唯一
可以自定义
-->
<mapper namespace="DictionarySpace">
    <resultMap id="dictionaryMap" type="com.bosssoft.hr.train.chp2.pojo.entity.Dictionary">
        <id property="categoryId" column="category_id"/>
        <result property="name" column="name" />
        <result property="category" column="category" />
        <result property="value" column="value" />
        <result property="remark" column="remark"/>
        <result property="status" column="status"/>
        <result property="orgId" column="org_id"/>
        <result property="createdBy" column="created_by"/>
        <result property="createdTime" column="created_time"/>
        <result property="updatedBy" column="updated_by"/>
        <result property="updatedTime" column="updated_time"/>
        <result property="version" column="version"/>
    </resultMap>

    <!--增-->
    <insert id="insertDictionary" parameterType="com.bosssoft.hr.train.chp2.pojo.entity.Dictionary">
        INSERT INTO t_dictionary (category_id,name,category,value,remark,status,org_id,
                                  created_by,created_time,updated_by,updated_time,version) values
                                  (#{categoryId},#{name},#{category},#{value},#{remark},#{status},#{orgId},
                                   #{createdBy},#{createdTime},#{updatedBy},#{updatedTime},#{version});
    </insert>
    <!--删-->
    <delete id="deleteDictionary" parameterType="long">
        DELETE FROM t_dictionary WHERE category_id = #{id};
    </delete>
    <!--查-->
    <select id="queryDictionary" parameterType="long" resultMap="dictionaryMap">
        SELECT * FROM t_dictionary WHERE category_id = #{id};
    </select>

    <!--改-->
    <update id="updateDictionary" parameterType="com.bosssoft.hr.train.chp2.pojo.entity.Dictionary">
        UPDATE t_dictionary SET name=#{name},category=#{category},value=#{value},remark=#{remark},status=#{status},org_id=#{orgId},
                                created_by=#{createdBy},created_time=#{createdTime},updated_by=#{updatedBy},updated_time=#{updatedTime},version=#{version}
                            WHERE category_id = #{categoryId};
    </update>
</mapper>

3、Mybatis加载过程。

基本流程如下：
1、读取configuration.xml -> 加载连接配置jdbc.properties -> 获得连接对象SqlSession

static {
    try {
        Reader reader = Resources.getResourceAsReader("configuration.xml");
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
    } catch (IOException e) {
        logger.error(e.getMessage(),e);
    }
}

返回连接对象

/**
     * 获取SqlSession
     */
    public static SqlSession getSqlSession(){
        //从当前线程中获取SqlSession对象
        SqlSession sqlSession = threadLocal.get();
        //如果SqlSession对象为空
        if(sqlSession == null){
            //在SqlSessionFactory非空的情况下，获取SqlSession对象
            sqlSession = sqlSessionFactory.openSession();

            //将SqlSession对象与当前线程绑定在一起
            threadLocal.set(sqlSession);
        }
        //返回SqlSession对象
        return sqlSession;
    }

2、使用SqlSession对象来调用sql语句,configuration.xml 知道mapper位置 -> mapper命名空间的和sql的id -> 加载语句执行
简单的插入语句的操作

/**
* @param dictionary 待插入的字典
* @return 返回插入结果
* @throws Exception 可能会抛出异常
*/
public boolean insertDictionary(Dictionary dictionary) throws Exception {
    SqlSession sqlSession = MybatisUtil.getSqlSession();
    boolean returnStatus = false;
    try {
        sqlSession.insert("DictionarySpace.insertDictionary",dictionary);
        sqlSession.commit();
        returnStatus = true;
    } catch (Exception e) {
        sqlSession.rollback();
        throw e;
    } finally {
        MybatisUtil.closeSqlSession();
    }
    return returnStatus;
}

4、完整的源代码

1、configration.xml

<?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>
    <!-- 加载类路径下的属性文件 -->
    <properties resource="jdbc.properties"/>
    <!-- 设置一个默认的连接环境信息 -->
    <environments default="mysql_developer">
        <!-- 连接环境信息，取一个任意唯一的名字 -->
        <environment id="mysql_developer">
            <!-- mybatis使用jdbc事务管理方式 -->
            <transactionManager type="jdbc"/>
            <!-- mybatis使用连接池方式来获取连接 -->
            <dataSource type="pooled">
                <!-- 配置与数据库交互的4个必要属性 -->
                <property name="driver" value="${driverClass}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${name}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>
    <!--将mybatis配置和映射文件关联起来-->
    <mappers>
        <mapper resource="DictionaryMapper.xml"/>
    </mappers>
</configuration>

2、DictionaryMapper.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">

<!--
namespace属性是名称空间，必须唯一
可以自定义
-->
<mapper namespace="DictionarySpace">
    <resultMap id="dictionaryMap" type="com.bosssoft.hr.train.chp2.pojo.entity.Dictionary">
        <id property="categoryId" column="category_id"/>
        <result property="name" column="name" />
        <result property="category" column="category" />
        <result property="value" column="value" />
        <result property="remark" column="remark"/>
        <result property="status" column="status"/>
        <result property="orgId" column="org_id"/>
        <result property="createdBy" column="created_by"/>
        <result property="createdTime" column="created_time"/>
        <result property="updatedBy" column="updated_by"/>
        <result property="updatedTime" column="updated_time"/>
        <result property="version" column="version"/>
    </resultMap>

    <!--增-->
    <insert id="insertDictionary" parameterType="com.bosssoft.hr.train.chp2.pojo.entity.Dictionary">
        INSERT INTO t_dictionary (category_id,name,category,value,remark,status,org_id,
                                  created_by,created_time,updated_by,updated_time,version) values
                                  (#{categoryId},#{name},#{category},#{value},#{remark},#{status},#{orgId},
                                   #{createdBy},#{createdTime},#{updatedBy},#{updatedTime},#{version});
    </insert>
    <!--删-->
    <delete id="deleteDictionary" parameterType="long">
        DELETE FROM t_dictionary WHERE category_id = #{id};
    </delete>
    <!--查-->
    <select id="queryDictionary" parameterType="long" resultMap="dictionaryMap">
        SELECT * FROM t_dictionary WHERE category_id = #{id};
    </select>

    <!--改-->
    <update id="updateDictionary" parameterType="com.bosssoft.hr.train.chp2.pojo.entity.Dictionary">
        UPDATE t_dictionary SET name=#{name},category=#{category},value=#{value},remark=#{remark},status=#{status},org_id=#{orgId},
                                created_by=#{createdBy},created_time=#{createdTime},updated_by=#{updatedBy},updated_time=#{updatedTime},version=#{version}
                            WHERE category_id = #{categoryId};
    </update>
</mapper>

3、MybatisUtil.java

package com.bosssoft.hr.train.chp2.util;

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 org.apache.log4j.Logger;

import java.io.IOException;
import java.io.Reader;


/**
 * 工具类
 * @author longquanxiao
 * @date 2019/7/24
 *
 */
public class MybatisUtil {
    /**
     * 本地线程
     */
    private static ThreadLocal<SqlSession> threadLocal = new ThreadLocal<SqlSession>();

    /**
     * SqlSessionFactory 工厂
     */
    private static SqlSessionFactory sqlSessionFactory;

    /**
     * 日志对象
     */
    private static Logger logger = Logger.getLogger(MybatisUtil.class);
    static{
        try {
            Reader reader = Resources.getResourceAsReader("configuration.xml");
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
        } catch (IOException e) {
            logger.error(e.getMessage(),e);
        }
    }
    /**
     * 禁止外界通过new方法创建
     */
    private MybatisUtil(){}

    /**
     * 获取SqlSession
     */
    public static SqlSession getSqlSession(){
        //从当前线程中获取SqlSession对象
        SqlSession sqlSession = threadLocal.get();
        //如果SqlSession对象为空
        if(sqlSession == null){
            //在SqlSessionFactory非空的情况下，获取SqlSession对象
            sqlSession = sqlSessionFactory.openSession();

            //将SqlSession对象与当前线程绑定在一起
            threadLocal.set(sqlSession);
        }
        //返回SqlSession对象
        return sqlSession;
    }
    /**
     * 关闭SqlSession与当前线程分开
     */
    public static void closeSqlSession(){
        //从当前线程中获取SqlSession对象
        SqlSession sqlSession = threadLocal.get();
        //如果SqlSession对象非空
        if(sqlSession != null){
            //关闭SqlSession对象
            sqlSession.close();
            //分开当前线程与SqlSession对象的关系，目的是让GC尽早回收
            threadLocal.remove();
        }
    }
}

4、Dao 的接口类 IDictionaryDao.java

package com.bosssoft.hr.train.chp2.dao;

import com.bosssoft.hr.train.chp2.pojo.entity.Dictionary;

/**
 * 数据字典的接口类
 * @author longquanxiao
 * @date 2019/7/24
 */
public interface IDictionaryDao {

    /**
     * 插入dictionary数据
      * @param dictionary 输入的参数
     * @return 返回执行的结果 true / false
     * @throws Exception 可能会抛出异常
     */
    boolean insertDictionary(Dictionary dictionary) throws Exception;

    /**
     * 更新数据字典
     * @param dictionary 待修改的字典
     * @return 修改的结果 true / false
     * @throws Exception 异常抛出
     */
    boolean updateDictionary(Dictionary dictionary) throws Exception ;


    /**
     * 根据id 获得dictionary
     * @param id 查询的id
     * @return 返回查询的结果
     * @throws Exception 可能会返回异常
     */
    Dictionary queryDictionary(long id) throws Exception;

    /**
     * 根据id删除字典
     * @param id 待删除的id
     * @return 删除结果 true / false
     * @throws Exception 异常抛出
     */
    boolean deleteDictionaryById(long id) throws Exception;
}

5、实现类 DictionaryDaoImpl.java

package com.bosssoft.hr.train.chp2.dao.impl;

import com.bosssoft.hr.train.chp2.dao.IDictionaryDao;
import com.bosssoft.hr.train.chp2.pojo.entity.Dictionary;
import com.bosssoft.hr.train.chp2.util.MybatisUtil;
import org.apache.ibatis.session.SqlSession;

/**
 * 接口实现类
 * @author longquanxiao
 * @date 2019/7/24
 */
public class DictionaryDaoImpl implements IDictionaryDao {
    /**
     * @param dictionary 待插入的字典
     * @return 返回插入结果
     * @throws Exception 可能会抛出异常
     */
    public boolean insertDictionary(Dictionary dictionary) throws Exception {
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        boolean returnStatus = false;
        try {
            sqlSession.insert("DictionarySpace.insertDictionary",dictionary);
            sqlSession.commit();
            returnStatus = true;
        } catch (Exception e) {
            sqlSession.rollback();
            throw e;
        } finally {
            MybatisUtil.closeSqlSession();
        }
        return returnStatus;
    }

    /**
     * @param dictionary 待修改的字典
     * @return 修改的结果
     * @throws Exception 可能会抛出异常
     */
    public boolean updateDictionary(Dictionary dictionary) throws Exception {
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        boolean returnStatus = false;
        try{
            sqlSession.update("DictionarySpace.updateDictionary",dictionary);
            sqlSession.commit();
            returnStatus = true;
        }catch (Exception e){
            // 回滚
            sqlSession.rollback();
            throw  e;
        }finally {
            MybatisUtil.closeSqlSession();
        }
        return returnStatus;
    }


    /**
     * @param id 查询的id
     * @return 返回查询的结果，可能为空
     * @throws Exception 异常
     */
    public Dictionary queryDictionary(long id) throws Exception {
        Dictionary returnDictionary = null;
        try {
            SqlSession sqlSession = MybatisUtil.getSqlSession();
            returnDictionary = sqlSession.selectOne("DictionarySpace.queryDictionary",id);
        } catch (Exception e) {
            throw e;
        } finally {
            MybatisUtil.closeSqlSession();
        }
        return returnDictionary;
    }

    /**
     * @param id 待删除的id
     * @return 删除的结果
     * @throws Exception 抛出的异常
     */
    public boolean deleteDictionaryById(long id) throws Exception {
        boolean returnStatus=false;
        SqlSession sqlSession = MybatisUtil.getSqlSession();

        try{
            if(sqlSession != null) {
                sqlSession.delete("DictionarySpace.deleteDictionary", id);
                sqlSession.commit();
                returnStatus = true;
            }
        }catch (Exception e){
            sqlSession.rollback();
            throw e;
        }finally {
            MybatisUtil.closeSqlSession();
        }
        return returnStatus;
    }
}

6、实体类 Dictionary.java

package com.bosssoft.hr.train.chp2.pojo.entity;

import java.util.Date;

/**
 * 数据字典的DO
 * @author longquanxiao
 * @date 2019/7/24
 */
public class Dictionary {
    /**
     * 数据字典ID
     */
    private long categoryId;
    /**
     * 字典名
     */
    private char name;
    /**
     * 字典类型
     */
    private char category;
    /**
     * 字典值
     */
    private char value;
    /**
     * 备注
     */
    private String remark;
    /**
     * 状态位
     */
    private byte status;
    /**
     * 机构ID
     */
    private long orgId;
    /**
     * 创建人
     */
    private long createdBy;
    /**
     * 创建时间
     */
    private Date createdTime;
    /**
     * 修改人
     */
    private long updatedBy;
    /**
     * 修改时间
     */
    private Date updatedTime;
    /**
     * 版本
     */
    private long version;

    /**getter setter**/
}

7、测试类


/**
 * @author longquanxiao
 * @date 2019/7/24
 */
public class DictionaryDaoImplTest extends TestCase {
    /**
     * 日志
     */
    private static Logger logger = Logger.getLogger(DictionaryDaoImplTest.class);

    /**
     * 测试插入数据
     */
    public void testInsertDictionary() {
        IDictionaryDao dao = new DictionaryDaoImpl();
        Dictionary insertDictionary = new Dictionary();
        // 设置属性
        insertDictionary.setCategoryId(10);
        insertDictionary.setName('2');
        insertDictionary.setCategory('2');
        insertDictionary.setValue('2');
        insertDictionary.setRemark("test insert");
        byte i = 1;
        insertDictionary.setStatus(i);

        insertDictionary.setOrgId(12);
        insertDictionary.setCreatedBy(1);
        Date iDate = new Date();
        System.out.println(iDate);
        insertDictionary.setCreatedTime(iDate);

        insertDictionary.setUpdatedTime(iDate);
        insertDictionary.setVersion(1);
        //
        try {
            if(dao.insertDictionary(insertDictionary)){
                System.out.println("插入数据成功");
            }else {
                System.out.println("插入数据失败");
            }
        }catch (Exception e){
            logger.error(e.getMessage(),e);
        }
    }

    /**
     * 测试更新数据
     */
    public void testUpdateDictionary() {
        // 先查后改
        IDictionaryDao dao = new DictionaryDaoImpl();
        Dictionary updateDictionary = null;
        try {
            updateDictionary = dao.queryDictionary(1);
            if( updateDictionary != null){
                updateDictionary.setRemark("update");
                Date idate = new Date();
                updateDictionary.setUpdatedTime(idate);
                // 调用更新函数进行更新
                if (dao.updateDictionary(updateDictionary)) {
                    System.out.println("更新成功");
                } else {
                    System.out.println("更新失败");
                }
            }
        } catch (Exception e) {
            logger.error(e.getMessage(),e);
        }
    }

    /**
     * 查询数据
     */
    public void testQueryDictionary() {
        IDictionaryDao dao = new DictionaryDaoImpl();
        Dictionary queryDictionary = null;
        try {
            queryDictionary= dao.queryDictionary(1);
            if (queryDictionary!=null){
                System.out.println("查询数据成功");
                System.out.println("name:"+queryDictionary.getName());
                System.out.println("created_time="+queryDictionary.getCreatedTime());
            }else{
                System.out.println("查询数据失败");
            }
        } catch (Exception e) {
            logger.error(e.getMessage(),e);
        }
    }

    /**
     * 删除数据
     */
    public void testDeleteDictionaryById() {
        IDictionaryDao dao = new DictionaryDaoImpl();
        try {
            // 删除id为10的数据
            if(dao.deleteDictionaryById(10)){
                System.out.println("删除成功");
            }else{
                System.out.println("删除失败");
            }
        }catch (Exception e){
            logger.error(e.getMessage(),e);
        }
    }
}

规范化的测试。使用断言，不用捕获异常。

package com.bosssoft.hr.train.chp2.dao.impl;

import com.bosssoft.hr.train.chp2.dao.IDictionaryDao;
import com.bosssoft.hr.train.chp2.pojo.entity.Dictionary;
import junit.framework.TestCase;

import java.util.Date;


/**
 * @author longquanxiao
 * @date 2019/7/24
 */
public class DictionaryDaoImplTest extends TestCase {
    /**
     * 测试插入数据
     */
    public void testInsertDictionary() throws Exception{
        IDictionaryDao dao = new DictionaryDaoImpl();
        Dictionary insertDictionary = new Dictionary();
        // 设置属性
        insertDictionary.setCategoryId(10);
        insertDictionary.setName('2');
        insertDictionary.setCategory('2');
        insertDictionary.setValue('2');
        insertDictionary.setRemark("test insert");
        byte i = 1;
        insertDictionary.setStatus(i);

        insertDictionary.setOrgId(12);
        insertDictionary.setCreatedBy(1);
        Date iDate = new Date();
        insertDictionary.setCreatedTime(iDate);

        insertDictionary.setUpdatedTime(iDate);
        insertDictionary.setVersion(1);
        assertTrue(dao.insertDictionary(insertDictionary));
    }

    /**
     * 测试更新数据
     */
    public void testUpdateDictionary() throws Exception{
        // 先查后改
        IDictionaryDao dao = new DictionaryDaoImpl();
        Dictionary updateDictionary = null;
        updateDictionary = dao.queryDictionary(1);

        assertNotNull(updateDictionary);
        updateDictionary.setRemark("update");
        Date idate = new Date();
        updateDictionary.setUpdatedTime(idate);
        // 调用更新函数进行更新
        assertTrue(dao.updateDictionary(updateDictionary));
    }

    /**
     * 查询数据
     */
    public void testQueryDictionary() throws Exception{
        IDictionaryDao dao = new DictionaryDaoImpl();
        Dictionary queryDictionary = null;
        queryDictionary= dao.queryDictionary(1);
        assertNotNull(queryDictionary);
    }

    /**
     * 删除数据
     */
    public void testDeleteDictionaryById() throws Exception {
        IDictionaryDao dao = new DictionaryDaoImpl();
        // 删除id为10的数据
        assertTrue(dao.deleteDictionaryById(10));
    }
}

二、SpringBoot 整合Mybatis

1、application.properties配置mybatis

spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/trainee?serverTimezone=GMT%2B8
spring.datasource.username=username
spring.datasource.password=password

2、使用接口来定义一个Dao层

相比于传统的xml的配置文件来映射数据库实体文件。SpirngBoot只需要注解便可以实现java到实体的映射

2.1 常用注解

@Insert()插入语句的注解
例子:

@Insert("INSERT INTO t_dictionary (category_id,name,category,value,remark,status,org_id," +
            "created_by,created_time,updated_by,updated_time,version) values" +
            "(#{categoryId},#{name},#{category},#{value},#{remark},#{status},#{orgId}," +
            "#{createdBy},#{createdTime},#{updatedBy},#{updatedTime},#{version}) ")
int insertDictionary(Dictionary dictionary);

注意#{}使用预编译的字符填充。填充的字符和dictionary中的成员一致。

@Select()查询语句,需要指定返回值类型

@Select("SELECT * FROM t_dictionary")
@Results(id = "dictionaryMap",value = {
        @Result(id = true,column = "category_id",property = "categoryId"),
        @Result(column = "name",property = "name"),
        @Result(column = "category",property = "category"),
        @Result(column = "value",property = "value"),
        @Result(column = "remark",property = "remark"),
        @Result(property="status",column="status"),
        @Result(property="orgId",column="org_id"),
        @Result(property="createdBy",column="created_by"),
        @Result(property="createdTime",column="created_time"),
        @Result(property="updatedBy", column="updated_by"),
        @Result(property="updatedTime", column="updated_time"),
        @Result(property="version" ,column="version")
})
List<Dictionary> queryAll();

@Results是返回值的类型。如果没有定义过的话就要自己定义一个。id是该result的标识符。property是java实体的成员。column是数据库表中的列。

使用上面定义好的Results

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@Select("SELECT * FROM t_dictionary WHERE name=#{name} AND category=#{category} AND status=#{status}")
@ResultMap("dictionaryMap")
List<Dictionary> queryByNameTypeStatus(String name,String category, byte status);

注解中的@ResultMap(id)使用已定义的Results id = dictionaryMap

更新的注解 @Update()

@Update("UPDATE t_dictionary SET name=#{name},category=#{category},value=#{value},remark=#{remark},status=#{status},org_id=#{orgId}," +
            "created_by=#{createdBy},created_time=#{createdTime},updated_by=#{updatedBy},updated_time=#{updatedTime}, version=#{version}" +
            " WHERE category_id = #{categoryId}")
  int updateDictionary(Dictionary dictionary);

删除的注解@Delete()

1 2	@Delete("DELETE FROM t_dictionary WHERE category_id = #{id}") int deleteDictionary(long id);

2.2 启动类中扫描相关的组件

@MapperScan("com.bosssoft.hr.train.chp2.dao")扫描为dao

3、使用Dao来进行访问

/**
 * dao对象
 */
@Resource
private DictionaryDao dictionaryDao;