MyBatis进阶

MyBatis日志管理

• 日志文件是用于记录系统操作事件的记录文件或文件集合
• 日志保存历史数据是诊断问题以及理解系统活动的重要依据

SLF4j与Logback

演示
添加依赖
pom.xml中

<dependency>
  <groupId>ch.qos.logbackgroupId>
  <artifactId>logback-classicartifactId>
  <version>1.2.3version>
dependency>

添加完成后 控制台出现日志信息

日志自定义
在resources目录下新增logback.xml文件

<configuration>
    <appender name="console" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>[%thread] %d{HH:mm:ss.SSS} %-5level %logger{36} - %msg%npattern>
        encoder>
    appender>
    
    <root level="debug">
        <appender-ref ref="console"/>
    root>
configuration>

再次运行时 日志时间换了位置

动态SQL

• 动态SQL是指根据参数数据动态组织SQL技术

goods.xml中

 <select id="dynamicSQL" parameterType="java.util.Map" resultType="com.mybatis.entity.Goods">
        select * from t_goods
        <where>
          <if test="categoryId != null">
              and category_id = #{categoryId}
          if>
          <if test="currentPrice != null">
              and current_price < #{currentPrice}
          if>
        where>
    select>

MybatisTestor中

/**
* 动态SQL语句
* @throws Exception
*/
@Test
    public void testDynamicSQL() throws Exception {
    SqlSession session = null;
try{
    session = MyBatisUtils.openSession();
    Map param = new HashMap();
    param.put("categoryId", 44);
    param.put("currentPrice", 500);
    //查询条件
    List<Goods> list = session.selectList("goods.dynamicSQL", param);
    for(Goods g:list){
        System.out.println(g.getTitle() + ":" +
                           g.getCategoryId()  + ":" + g.getCurrentPrice());

    }
}catch (Exception e){
    throw e;
}finally {
    MyBatisUtils.closeSession(session);
}
}

运行结果

MyBatis二级缓存

• 一级缓存默认开启，缓存范围SqlSession会话
• 二级缓存手动开启，属于范围Mapper Namespace

SqlSession一级缓存使用率不高
二级缓存被所有SqlSession共享
二级缓存运行规则

• 二级开启后默认所有查询操作均使用缓存
• 写操作commit提交时对该namespace缓存强制清空
• 配置useCache=false可以不用缓存
• 配置flushCache=true代表强制清空缓存

验证一级缓存
测试代码
MybatisTestor.java中

@Test
    public void testLv1Cache() throws Exception{
    SqlSession session = null;
try{
    session = MyBatisUtils.openSession();
    Goods goods = session.selectOne("goods.selectById",1603);
    Goods goods1 = session.selectOne("goods.selectById",1603);
    System.out.println(goods.hashCode()+"--"+goods1.hashCode();
}catch (Exception e){
    throw e;
}finally {
    MyBatisUtils.closeSession(session);
}
}

输出的哈希地址一致

两个session情况

  @Test
    public void testLv1Cache() throws Exception{
        SqlSession session = null;
        try{
            session = MyBatisUtils.openSession();
            Goods goods = session.selectOne("goods.selectById",1603);
            Goods goods1 = session.selectOne("goods.selectById",1603);
            System.out.println(goods.hashCode()+"--"+goods1.hashCode());
        }catch (Exception e){
            throw e;
        }finally {
            MyBatisUtils.closeSession(session);
        }
        try{
            session = MyBatisUtils.openSession();
            Goods goods = session.selectOne("goods.selectById",1603);
            Goods goods1 = session.selectOne("goods.selectById",1603);
            System.out.println(goods.hashCode()+"--"+goods1.hashCode());
        }catch (Exception e){
            throw e;
        }finally {
            MyBatisUtils.closeSession(session);
        }
    }

一级缓存只存在一个session中
执行commit强制清空

 @Test
    public void testLv1Cache() throws Exception{
        SqlSession session = null;
        try{
            session = MyBatisUtils.openSession();
            Goods goods = session.selectOne("goods.selectById",1603);
            session.commit();
            Goods goods1 = session.selectOne("goods.selectById",1603);
            System.out.println(goods.hashCode()+"--"+goods1.hashCode());
        }catch (Exception e){
            throw e;
        }finally {
            MyBatisUtils.closeSession(session);
        }
    }

开启二级缓存
goods.xml中添加

<cache eviction="LRU" flushInterval="600000" size="512" readOnly="true"/>

验证二级缓存

@Test
    public void testLv2Cache() throws Exception{
    SqlSession session = null;
try{
    session = MyBatisUtils.openSession();
    Goods goods = session.selectOne("goods.selectById",1603);
    System.out.println(goods.hashCode());
}catch (Exception e){
    throw e;
}finally {
    MyBatisUtils.closeSession(session);
}
try{
    session = MyBatisUtils.openSession();
    Goods goods = session.selectOne("goods.selectById",1603);
    System.out.println(goods.hashCode());
}catch (Exception e){
    throw e;
}finally {
    MyBatisUtils.closeSession(session);
}
}

<cache eviction="LRU" flushInterval="600000" size="512" readOnly="true"/>

MyBatis多表级联查询

商品和详情对象关联查询
在entity目录下创建GoodsDetail.java

package com.mybatis.entity;

public class GoodsDetail {
    private Integer gdId;
    private Integer goodsId;
    private String gdPicUrl;

    public Integer getGdId() {
        return gdId;
    }

    public void setGdId(Integer gdId) {
        this.gdId = gdId;
    }

    public Integer getGoodsId() {
        return goodsId;
    }

    public void setGoodsId(Integer goodsId) {
        this.goodsId = goodsId;
    }

    public String getGdPicUrl() {
        return gdPicUrl;
    }

    public void setGdPicUrl(String gdPicUrl) {
        this.gdPicUrl = gdPicUrl;
    }

    public Integer getGdOrder() {
        return gdOrder;
    }

    public void setGdOrder(Integer gdOrder) {
        this.gdOrder = gdOrder;
    }

    private Integer gdOrder;
}

mappers目录下创建goods_detail.xml

DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="goodsDetail">
  <select id="selectByGoodsId" parameterType="Integer"
    resultType="com.mybatis.entity.GoodsDetail">
    select * from t_goods_detail where goods_id = #{value}
  select>
mapper>

在Goods.java中添加一个List

goods.xml中添加

    
    <resultMap id="rmGoods1" type="com.mybatis.entity.Goods">
        
        <id column="goods_id" property="goodsId">id>
        
        <collection property="goodsDetails" select="goodsDetail.selectByGoodsId"
                    column="goods_id"/>
    resultMap>
    <select id="selectOneToMany" resultMap="rmGoods1">
        select * from t_goods limit 0,10
    select>

mybatis-config.xml中添加

<mapper resource="mappers/goods_detail.xml"/>

测试用例：

@Test
    public void testOneToMany() throws Exception {
    SqlSession session = null;
try {
    session = MyBatisUtils.openSession();
    List<Goods> list = session.selectList("goods.selectOneToMany");
    for(Goods goods:list) {
        System.out.println(goods.getTitle() + ":" + goods.getGoodsDetails().size());
    }
} catch (Exception e) {
    throw e;
} finally {
    MyBatisUtils.closeSession(session);
}
}

ManyToOne对象关联查询

在GoodsDetail.java中添加

private Goods goods;

    public Goods getGoods() {
        return goods;
    }

    public void setGoods(Goods goods) {
        this.goods = goods;
    }

在goods_detail.xml中添加描述

 <resultMap id="rmGoodsDetail" type="com.mybatis.entity.GoodsDetail">
        <id column="gd_id" property="gdId"/>
        <result column="goods_id" property="goodsId"/>
        <association property="goods" select="goods.selectById" column="goods_id">association>
    resultMap>
    <select id="selectManyToOne" resultMap="rmGoodsDetail">
        select * from t_goods_detail limit 0,1
    select>

测试用例

/**
* 测试多对一对象关联映射
*/
@Test
    public void testManyToOne() throws Exception {
    SqlSession session = null;
try {
    session = MyBatisUtils.openSession();
    List<GoodsDetail> list = session.selectList("goodsDetail.selectManyToOne");
    for(GoodsDetail gd:list) {
        System.out.println(gd.getGdPicUrl() + ":" + gd.getGoods().getTitle());
    }
} catch (Exception e) {
    throw e;
} finally {
    MyBatisUtils.closeSession(session);
}
}

数据量增到20条后

PageHelper分页插件

分页查询的麻烦事

• 当前页数据查询-select * from tab limit 0,10
• 总记录数查询-select count(*) from tab
• 程序计算总页数、上一页页码、下一页页码

PageHelper使用流程

• maven引入PageHelper与jsqlparser
• mybatis-config.xml增加Plugin配置
• 代码中使用PageHelper.startPage()自动分页

在pom.xml中引入插件

<dependency>
  <groupId>com.github.pagehelpergroupId>
  <artifactId>pagehelperartifactId>
  <version>5.1.10version>
dependency>
<dependency>
  <groupId>com.github.jsqlparsergroupId>
  <artifactId>jsqlparserartifactId>
  <version>2.0version>
dependency>

在mybatis-config.xml配置插件

<plugins>
  <plugin interceptor="com.github.pagehelper.PageInterceptor">
            
            <property name="helperDialect" value="mysql"/>
            
            <property name="reasonable" value="true"/>
        plugin>
plugins>

在goods.xml中添加

<select id="selectPage" resultType="com.mybatis.entity.Goods">
  select * from t_goods where current_price < 1000
select>

测试
MybatisTestor.java中

@Test
    public void testSelectPage(){
        SqlSession session=null;
        try{
            session=MyBatisUtils.openSession();
            /*startPage方法会自动将下一次查询进行分页*/
            PageHelper.startPage(2,10);
            Page<Goods> page = (Page) session.selectList("goods.selectPage");
            System.out.println("总页数:"+page.getPages());
            System.out.println("总记录数:"+page.getTotal());
            System.out.println("开始行号:"+page.getStartRow());
            System.out.println("结束行号:"+page.getEndRow());
            System.out.println("当前页码:"+page.getPageNum());
            List<Goods> data = page.getResult();//当前页数据
            for(Goods g:data){
                System.out.println(g.getTitle());
            }
        }catch (Exception e){
            throw e;
        }finally {
            MyBatisUtils.closeSession(session);
        }
    }

不同数据库分页的实现原理
MySQL分页：select * from table limit 10,20;
Oracle：

select t3.* from(
  select t2.*,rownum as row_num from(
  	select * from table order by id asc
    )t2 where rownum<=20
  )t3
where t2.row_num>11

SQL Server 2000:

select top 3 * from table
where
	id not in 
	(select top 15 id from table)

SQL Server 2012+

select * from table order by id
	offset 4 rows fetch next 5 rows only

MyBatis配置C3P0连接池

添加依赖
pom.xml中

<dependency>
  <groupId>com.mchangegroupId>
  <artifactId>c3p0artifactId>
  <version>0.9.5.4version>
dependency>

创建C3P0DataSourceFactory.java

package com.mybatis.datasource;

import com.mchange.v2.c3p0.ComboPooledDataSource;
import org.apache.ibatis.datasource.unpooled.UnpooledDataSourceFactory;

public class C3P0DataSourceFactory extends UnpooledDataSourceFactory {
    public C3P0DataSourceFactory(){
        this.dataSource=new ComboPooledDataSource();
    }
}

修改连接池配置

<dataSource type="com.mybatis.datasource.C3P0DataSourceFactory">
  <property name="driverClass" value="com.mysql.jdbc.Driver"/>
  <property name="jdbcUrl" value="jdbc:mysql://localhost:3306/babytun?useUnicode=true&characterEncoding=UTF-8"/>
  <property name="user" value="root"/>
  <property name="password" value="123456"/>
  <property name="initialPoolSize" value="5"/>
  <property name="maxPoolSize" value="20"/>
  <property name="minPoolSize" value="5"/>
  
dataSource>

MyBatis批处理

批量插入
在goods.xml中编写

<insert id="batchInsert" parameterType="java.util.List">
  INSERT INTO t_goods(title, sub_title, original_cost, current_price, discount, is_free_delivery, category_id)
  VALUES
  <foreach collection="list" item="item" index="index" separator=",">
    (#{item.title},#{item.subTitle}, #{item.originalCost}, #{item.currentPrice}, #{item.discount}, #{item.isFreeDelivery}, #{item.categoryId})
  foreach>
insert>

测试 MybatisTestor.java

@Test
    public void testInsert1() throws Exception {
        SqlSession session = null;
try{
    long st = new Date().getTime();
    session = MyBatisUtils.openSession();
    List list = new ArrayList();
    for(int i = 0 ; i < 10000 ; i++) {
        Goods goods = new Goods();
        goods.setTitle("测试商品");
        goods.setSubTitle("测试子标题");
        goods.setOriginalCost(200f);
        goods.setCurrentPrice(100f);
        goods.setDiscount(0.5f);
        goods.setIsFreeDelivery(1);
        goods.setCategoryId(43);
        //insert()方法返回值代表本次成功插入的记录总数

        session.insert("goods.insert" , goods);
    }

    session.commit();//提交事务数据
    long et = new Date().getTime();
    System.out.println("执行时间:" + (et-st) + "毫秒");
    //            System.out.println(goods.getGoodsId());
}catch (Exception e){
    if(session != null){
        session.rollback();//回滚事务
    }
    throw e;
}finally {
    MyBatisUtils.closeSession(session);
}
}

批量删除
goods.xml

<delete id="batchDelete" parameterType="java.util.List">
        DELETE FROM t_goods WHERE goods_id in
        <foreach collection="list" item="item" index="index" open="(" close=")" separator=",">
            #{item}
        foreach>
    delete>

测试 MybatisTestor.java

@Test
    public void testBatchDelete() throws Exception {
        SqlSession session = null;
try {
    long st = new Date().getTime();
    session = MyBatisUtils.openSession();
    List list = new ArrayList();
    for(int i=1931;i<=11930;i++)
        list.add(i);
    session.delete("goods.batchDelete", list);
    session.commit();//提交事务数据
    long et = new Date().getTime();
    System.out.println("执行时间:" + (et - st) + "毫秒");
    //            System.out.println(goods.getGoodsId());
} catch (Exception e) {
    if (session != null) {
        session.rollback();//回滚事务
    }
    throw e;
} finally {
    MyBatisUtils.closeSession(session);
}
}

Mybatis注解开发方式

MyBatis常用注解

注解	对应XML	说明
@Insert		新增SQL
@Update		更新SQL
@Delete		删除SQL
@Select		查询SQL
@Param	–	参数映射
@Results		结果映射
@Result		字段映射

创建GoodsDAO接口

public interface GoodsDAO {
    @Select("select * from t_goods where current_price between  #{min} and #{max} order by current_price limit 0,#{limt}")
    public List<Goods> selectByPriceRange(@Param("min") Float min ,@Param("max") Float max ,@Param("limt") Integer limt);

    @Insert("INSERT INTO t_goods(title, sub_title, original_cost, current_price, discount, is_free_delivery, category_id) VALUES (#{title} , #{subTitle} , #{originalCost}, #{currentPrice}, #{discount}, #{isFreeDelivery}, #{categoryId})")
    //
    @SelectKey(statement = "select last_insert_id()" , before = false , keyProperty = "goodsId" , resultType = Integer.class)
    public int insert(Goods goods);

    @Select("select * from t_goods")
    //
    @Results({
        //
        @Result(column = "goods_id" ,property = "goodsId" , id = true) ,
        //
        @Result(column = "title" ,property = "title"),
        @Result(column = "current_price" ,property = "currentPrice")
    })
    public List<GoodsDTO> selectAll();
}

mybatis-config.xml中配置

<mappers>
  
  <package name="com.imooc.mybatis.dao"/>
mappers>

测试

//JUNIT单元测试类
public class MyBatisTestor {

    @Test
    public void testSelectByPriceRange() throws Exception {
        SqlSession session = null;
        try{
            session = MyBatisUtils.openSession();
            GoodsDAO goodsDAO = session.getMapper(GoodsDAO.class);
            List<Goods> list = goodsDAO.selectByPriceRange(100f, 500f, 20);
            System.out.println(list.size());
        }catch (Exception e){
            throw e;
        } finally {
            MyBatisUtils.closeSession(session);

        }
    }

    /**
     * 新增数据
     * @throws Exception
     */
    @Test
    public void testInsert() throws Exception {
        SqlSession session = null;
        try{
            session = MyBatisUtils.openSession();
            Goods goods = new Goods();
            goods.setTitle("测试商品");
            goods.setSubTitle("测试子标题");
            goods.setOriginalCost(200f);
            goods.setCurrentPrice(100f);
            goods.setDiscount(0.5f);
            goods.setIsFreeDelivery(1);
            goods.setCategoryId(43);
            GoodsDAO goodsDAO = session.getMapper(GoodsDAO.class);
            //insert()方法返回值代表本次成功插入的记录总数
            int num = goodsDAO.insert(goods);
            session.commit();//提交事务数据
            System.out.println(goods.getGoodsId());
        }catch (Exception e){
            if(session != null){
                session.rollback();//回滚事务
            }
            throw e;
        }finally {
            MyBatisUtils.closeSession(session);
        }
    }

    @Test
    public void testSelectAll() throws Exception {
        SqlSession session = null;
        try{
            session = MyBatisUtils.openSession();
            GoodsDAO goodsDAO = session.getMapper(GoodsDAO.class);
            List<GoodsDTO> list = goodsDAO.selectAll();
            System.out.println(list.size());
        }catch (Exception e){
            throw e;
        } finally {
            MyBatisUtils.closeSession(session);

        }
    }
}