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import{_ as t}from"./chunks/ArticleMetadata.EniEqKqn.js";import{_ as k,D as e,o as n,c as r,I as d,w as g,k as p,a as A,R as y,b as D,e as c}from"./chunks/framework.FVQzxbLi.js";import"./chunks/md5.RtphNWHi.js";const C="/assets/202012271125273.hw9ivIgD.jpg",B="/assets/202012271125276.o5XkKSwe.png",o="/assets/202012271126381.e94Tz-ZT.png",F="/assets/202012271127794.HVcSA8_G.png",L=JSON.parse('{"title":"SQL映射文件之增删改元素","description":"","frontmatter":{"title":"SQL映射文件之增删改元素","author":"查尔斯","date":"2020/12/27 23:55","categories":["MyBatis快速入门"],"tags":["MyBatis","ORM框架"]},"headers":[],"relativePath":"courses/mybatis/01-MyBatis基础/05-SQL映射文件之增删改元素.md","filePath":"courses/mybatis/01-MyBatis基础/05-SQL映射文件之增删改元素.md","lastUpdated":1660404656000}'),E={name:"courses/mybatis/01-MyBatis基础/05-SQL映射文件之增删改元素.md"},u=p("h1",{id:"sql映射文件之增删改元素",tabindex:"-1"},[A("SQL映射文件之增删改元素 "),p("a",{class:"header-anchor",href:"#sql映射文件之增删改元素","aria-label":'Permalink to "SQL映射文件之增删改元素"'},"​")],-1),m=y('<h2 id="前言" tabindex="-1">前言 <a class="header-anchor" href="#前言" aria-label="Permalink to &quot;前言&quot;">​</a></h2><p><strong>C：</strong> 在上一篇，笔者带大家对 MyBatis SQL 映射文件的 select 元素、sql 元素进行了学习。本篇，笔者将带你学习 MyBatis SQL 映射文件中的 insert、update、delete元素，这三个可以说是 SQL 映射文件中最为简单的，别愣神，快跟上我。</p><p><img src="'+C+`" alt="202012271125273"></p><h2 id="insert元素" tabindex="-1">insert元素 <a class="header-anchor" href="#insert元素" aria-label="Permalink to &quot;insert元素&quot;">​</a></h2><p><strong>案例需求：新增用户，PeiQi，18，PeiQi@126.com</strong></p><p>首先，在 Mapper 接口中我们添加一个方法。</p><div class="language-java vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">java</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">public</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> interface</span><span style="--shiki-light:#6F42C1;--shiki-dark:#F69D50;"> UserMapper</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> {</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> /**</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> * 添加用户</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> * </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">@param</span><span style="--shiki-light:#E36209;--shiki-dark:#F69D50;"> user</span><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> 用户信息</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> * </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">@return</span><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> 影响行数</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> */</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> int</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;"> insert</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(User </span><span style="--shiki-light:#E36209;--shiki-dark:#F69D50;">user</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">}</span></span></code></pre></div><div class="tip custom-block"><p class="custom-block-title">笔者说</p><p>insert、update、delete 这类操作，本身默认就是返回影响的行数，所以不需要对 resultType 进行指定。在定义这类接口方法的时候设置返回值类型为 int 即可。</p></div><p>然后我们在 SQL 映射文件中再添加一个与该方法对应的查询元素。</p><div class="language-xml vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">xml</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">&lt;!-- int insert(User user); --&gt;</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">&lt;</span><span style="--shiki-light:#22863A;--shiki-dark:#8DDB8C;">insert</span><span style="--shiki-light:#6F42C1;--shiki-dark:#6CB6FF;"> id</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">=</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">&quot;insert&quot;</span><span style="--shiki-light:#6F42C1;--shiki-dark:#6CB6FF;"> parameterType</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">=</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">&quot;User&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">&gt;</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> insert into user (name, age, email) values(#{name}, #{age}, #{email})</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">&lt;/</span><span style="--shiki-light:#22863A;--shiki-dark:#8DDB8C;">insert</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">&gt;</span></span></code></pre></div><p>测试一下：</p><div class="language-java vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">java</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">class</span><span style="--shiki-light:#6F42C1;--shiki-dark:#F69D50;"> TestMyBatis</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> {</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> @</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">Test</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> void</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;"> testInsert</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">() {</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 获取SqlSession对象</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> try</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (SqlSession</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> sqlSession</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> MyBatisUtils.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">openSession</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">()) {</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 获取 Mapper 接口</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> UserMapper</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> userMapper</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> sqlSession.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">getMapper</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(UserMapper.class);</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 执行 SQL</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> User</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> user</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> new</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;"> User</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">();</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> user.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">setName</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">&quot;PeiQi&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> user.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">setAge</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;">18</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> user.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">setEmail</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">&quot;PeiQi@126.com&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> rows</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> userMapper.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">insert</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(user);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> </span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">&quot;影响行数为：&quot;</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> +</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> rows);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> } </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">catch</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (Exception </span><span style="--shiki-light:#E36209;--shiki-dark:#F69D50;">e</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">) {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> e.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">printStackTrace</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">();</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> }</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> }</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">}</span></span></code></pre></div><p><strong>控制台输出：</strong></p><div class="language-sql vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">sql</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">-- 输出的 SQL 语句</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">insert into</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> user (</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">name</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">, age, email) </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">values</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(?, ?, ?)</span></span></code></pre></div><div class="language- vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang"></span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span>影响行数为：1</span></span></code></pre></div><hr><p>输出的结果一如既往的表示成功了，但是当你前往数据库查看时，却并没有新增数据。</p><p><img src="`+B+'" alt="202012271125276"></p><p>仔细看看执行日志吧！相比于查询元素，插入元素执行多了一行日志，大白话理解就是：<strong>JDBC 连接正在回滚事务</strong> 。</p><p><img src="'+o+`" alt="202012271126381"></p><p>这是因为我们在获取 SqlSession 的时候，采用的是开启事务的方式。开启事务对于查询没什么大影响，但是对于增删改，如果你不提交事务，就意味着不会将数据持久化到数据库。</p><p>所以改动一下测试代码吧：</p><div class="language-java vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">java</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">class</span><span style="--shiki-light:#6F42C1;--shiki-dark:#F69D50;"> TestMyBatis</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> @</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">Test</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> void</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;"> testInsert</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">() {</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 获取SqlSession对象</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> try</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (SqlSession</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> sqlSession</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> MyBatisUtils.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">openSession</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">()) {</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 获取 Mapper 接口</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> UserMapper</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> userMapper</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> sqlSession.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">getMapper</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(UserMapper.class);</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 执行 SQL</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> User</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> user</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> new</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;"> User</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">();</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> user.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">setName</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">&quot;PeiQi&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> user.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">setAge</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;">18</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> user.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">setEmail</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">&quot;PeiQi@126.com&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> rows</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> userMapper.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">insert</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(user);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> </span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">&quot;影响行数为：&quot;</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> +</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> rows);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> </span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 提交事务</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> sqlSession.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">commit</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">();</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> } </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">catch</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (Exception </span><span style="--shiki-light:#E36209;--shiki-dark:#F69D50;">e</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">) {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> e.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">printStackTrace</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">();</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> }</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> }</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">}</span></span></code></pre></div><p>这回测试之后就正常了。</p><p><img src="`+F+`" alt="202012271127794"></p><h3 id="获取自增主键值" tabindex="-1">获取自增主键值 <a class="header-anchor" href="#获取自增主键值" aria-label="Permalink to &quot;获取自增主键值&quot;">​</a></h3><p>我们在一些支持自动生成主键的数据库中设置了主键自增，当数据插入之后，我们可能需要用到刚生成的主键值，这时候传统的方法是自己去手动查询一次，而 MyBatis 则是通过在插入元素上添加几个属性就可以解决了。</p><div class="language-xml vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">xml</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">&lt;!-- int insert(User user); --&gt;</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">&lt;!-- </span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> 【useGeneratedKeys:】（仅适用于 insert 和 update）表示要获取自动生成的主键</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> 这会令 MyBatis 使用 JDBC 的 getGeneratedKeys 方法来取出由数据库内部生成的主键</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> （比如：像 MySQL 和 SQL Server 这样的关系型数据库管理系统的自动递增字段），默认值：false。 </span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> 【keyProperty】:（仅适用于 insert 和 update）表示获取到自动生成主键之后应该映射到对象的哪个属性中</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> MyBatis 会使用 getGeneratedKeys 的返回值或 insert 语句的 selectKey 子元素设置它的值，默认值：未设置（unset）。</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> 如果生成列不止一个，可以用逗号分隔多个属性名称。 [1]</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> --&gt;</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">&lt;</span><span style="--shiki-light:#22863A;--shiki-dark:#8DDB8C;">insert</span><span style="--shiki-light:#6F42C1;--shiki-dark:#6CB6FF;"> id</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">=</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">&quot;insert&quot;</span><span style="--shiki-light:#6F42C1;--shiki-dark:#6CB6FF;"> parameterType</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">=</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">&quot;User&quot;</span><span style="--shiki-light:#6F42C1;--shiki-dark:#6CB6FF;"> useGeneratedKeys</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">=</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">&quot;true&quot;</span><span style="--shiki-light:#6F42C1;--shiki-dark:#6CB6FF;"> keyProperty</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">=</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">&quot;id&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">&gt;</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> insert into user (name, age, email) values(#{name}, #{age}, #{email})</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">&lt;/</span><span style="--shiki-light:#22863A;--shiki-dark:#8DDB8C;">insert</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">&gt;</span></span></code></pre></div><p>测试一下：</p><div class="language-java vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">java</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">class</span><span style="--shiki-light:#6F42C1;--shiki-dark:#F69D50;"> TestMyBatis</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> {</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> @</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">Test</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> void</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;"> testInsert</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">() {</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 获取SqlSession对象</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> try</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (SqlSession</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> sqlSession</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> MyBatisUtils.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">openSession</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">()) {</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 获取 Mapper 接口</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> UserMapper</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> userMapper</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> sqlSession.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">getMapper</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(UserMapper.class);</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 执行 SQL</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> User</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> user</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> new</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;"> User</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">();</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> user.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">setName</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">&quot;PeiQi&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> user.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">setAge</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;">18</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> user.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">setEmail</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">&quot;PeiQi@126.com&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">&quot;插入前：&quot;</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> +</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> user);</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> rows</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> userMapper.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">insert</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(user);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">&quot;影响行数为：&quot;</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> +</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> rows);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">&quot;插入后：&quot;</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> +</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> user);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> </span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 提交事务</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> sqlSession.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">commit</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">();</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> } </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">catch</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (Exception </span><span style="--shiki-light:#E36209;--shiki-dark:#F69D50;">e</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">) {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> e.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">printStackTrace</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">();</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> }</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> }</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> </span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">}</span></span></code></pre></div><p><strong>控制台输出：</strong></p><div class="language- vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang"></span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span>插入前：User [id=null, name=PeiQi, age=18, email=PeiQi@126.com]</span></span>
<span class="line"><span>影响行数为：1</span></span>
<span class="line"><span>插入后：User [id=8, name=PeiQi, age=18, email=PeiQi@126.com]</span></span></code></pre></div><h2 id="update元素" tabindex="-1">update元素 <a class="header-anchor" href="#update元素" aria-label="Permalink to &quot;update元素&quot;">​</a></h2><p>再来试试 update 元素。<strong>案例需求：将id为1的用户年龄改为20。</strong></p><p>首先，在 Mapper 接口中我们添加一个方法。</p><div class="language-java vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">java</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">public</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> interface</span><span style="--shiki-light:#6F42C1;--shiki-dark:#F69D50;"> UserMapper</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> {</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> /**</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> * 修改用户</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> * </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">@param</span><span style="--shiki-light:#E36209;--shiki-dark:#F69D50;"> user</span><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> 用户信息</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> * </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">@return</span><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> 影响行数</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> */</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> int</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;"> update</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(User </span><span style="--shiki-light:#E36209;--shiki-dark:#F69D50;">user</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">}</span></span></code></pre></div><p>然后我们在 SQL 映射文件中再添加一个与该方法对应的查询元素。</p><div class="language-xml vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">xml</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">&lt;!-- int update(User user); --&gt;</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">&lt;</span><span style="--shiki-light:#22863A;--shiki-dark:#8DDB8C;">update</span><span style="--shiki-light:#6F42C1;--shiki-dark:#6CB6FF;"> id</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">=</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">&quot;update&quot;</span><span style="--shiki-light:#6F42C1;--shiki-dark:#6CB6FF;"> parameterType</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">=</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">&quot;User&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">&gt;</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> update user set age = #{age} where id = #{id}</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">&lt;/</span><span style="--shiki-light:#22863A;--shiki-dark:#8DDB8C;">update</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">&gt;</span></span></code></pre></div><p>测试一下：</p><div class="language-java vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">java</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">class</span><span style="--shiki-light:#6F42C1;--shiki-dark:#F69D50;"> TestMyBatis</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> {</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> @</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">Test</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> void</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;"> testUpdate</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">() {</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 获取SqlSession对象</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> try</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (SqlSession</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> sqlSession</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> MyBatisUtils.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">openSession</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">()) {</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 获取 Mapper 接口</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> UserMapper</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> userMapper</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> sqlSession.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">getMapper</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(UserMapper.class);</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 执行 SQL</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> User</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> user</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> new</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;"> User</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">();</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> user.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">setId</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;">1L</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> user.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">setAge</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;">20</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> rows</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> userMapper.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">update</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(user);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> </span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">&quot;影响行数为：&quot;</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> +</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> rows);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> </span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 提交事务</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> sqlSession.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">commit</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">();</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> } </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">catch</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (Exception </span><span style="--shiki-light:#E36209;--shiki-dark:#F69D50;">e</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">) {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> e.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">printStackTrace</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">();</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> }</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> }</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">}</span></span></code></pre></div><p><strong>控制台输出：</strong></p><div class="language-sql vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">sql</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">-- 输出的 SQL 语句</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">update</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> user </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">set</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> age </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">=</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> ? </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">where</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> id </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">=</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> ?</span></span></code></pre></div><div class="language- vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang"></span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span>影响行数为：1</span></span></code></pre></div><h2 id="delete元素" tabindex="-1">delete元素 <a class="header-anchor" href="#delete元素" aria-label="Permalink to &quot;delete元素&quot;">​</a></h2><p>再来试试 delete 元素。<strong>案例需求：将id为1的用户删除。</strong></p><p>首先，在 Mapper 接口中我们添加一个方法。</p><div class="language-java vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">java</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">public</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> interface</span><span style="--shiki-light:#6F42C1;--shiki-dark:#F69D50;"> UserMapper</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> {</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> /**</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> * 根据ID删除用户</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> * </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">@param</span><span style="--shiki-light:#E36209;--shiki-dark:#F69D50;"> id</span><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> 用户ID</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> * </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">@return</span><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> 影响行数</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> */</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> int</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;"> deleteById</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(@</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">Param</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">&quot;id&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">) Long </span><span style="--shiki-light:#E36209;--shiki-dark:#F69D50;">id</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">}</span></span></code></pre></div><p>然后我们在 SQL 映射文件中再添加一个与该方法对应的查询元素。</p><div class="language-xml vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">xml</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">&lt;!-- int deleteById(@Param(&quot;id&quot;) Long id); --&gt;</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">&lt;</span><span style="--shiki-light:#22863A;--shiki-dark:#8DDB8C;">delete</span><span style="--shiki-light:#6F42C1;--shiki-dark:#6CB6FF;"> id</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">=</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">&quot;deleteById&quot;</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">&gt;</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> delete from user where id = #{id}</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">&lt;/</span><span style="--shiki-light:#22863A;--shiki-dark:#8DDB8C;">delete</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">&gt;</span></span></code></pre></div><p>测试一下：</p><div class="language-java vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">java</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">class</span><span style="--shiki-light:#6F42C1;--shiki-dark:#F69D50;"> TestMyBatis</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> {</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> @</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">Test</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> void</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;"> testDeleteById</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">() {</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 获取SqlSession对象</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> try</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (SqlSession</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> sqlSession</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> MyBatisUtils.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">openSession</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">()) {</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 获取 Mapper 接口</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> UserMapper</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> userMapper</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> sqlSession.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">getMapper</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(UserMapper.class);</span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 执行 SQL</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> int</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> rows</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> =</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> userMapper.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">deleteById</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#005CC5;--shiki-dark:#6CB6FF;">1L</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> </span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> System.out.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">println</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">(</span><span style="--shiki-light:#032F62;--shiki-dark:#96D0FF;">&quot;影响行数为：&quot;</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> +</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> rows);</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> </span></span>
<span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;"> // 提交事务</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> sqlSession.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">commit</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">();</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> } </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">catch</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> (Exception </span><span style="--shiki-light:#E36209;--shiki-dark:#F69D50;">e</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">) {</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> e.</span><span style="--shiki-light:#6F42C1;--shiki-dark:#DCBDFB;">printStackTrace</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">();</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> }</span></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> }</span></span>
<span class="line"></span>
<span class="line"><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;">}</span></span></code></pre></div><p><strong>控制台输出：</strong></p><div class="language-sql vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">sql</span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span style="--shiki-light:#6A737D;--shiki-dark:#768390;">-- 输出的 SQL 语句</span></span>
<span class="line"><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">delete</span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;"> from</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> user </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">where</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> id </span><span style="--shiki-light:#D73A49;--shiki-dark:#F47067;">=</span><span style="--shiki-light:#24292E;--shiki-dark:#ADBAC7;"> ?</span></span></code></pre></div><div class="language- vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang"></span><pre class="shiki shiki-themes github-light github-dark-dimmed vp-code"><code><span class="line"><span>影响行数为：1</span></span></code></pre></div><h2 id="参考文献" tabindex="-1">参考文献 <a class="header-anchor" href="#参考文献" aria-label="Permalink to &quot;参考文献&quot;">​</a></h2><p>[1]MyBatis 官网. XML 映射文件[EB/OL]. <a href="https://mybatis.org/mybatis-3/zh/sqlmap-xml.html" target="_blank" rel="noreferrer">https://mybatis.org/mybatis-3/zh/sqlmap-xml.html</a>. 2020-12-26</p><h2 id="后记" tabindex="-1">后记 <a class="header-anchor" href="#后记" aria-label="Permalink to &quot;后记&quot;">​</a></h2><p>你就看看，它们使用起来简单不？这还能有理由说学不动、学不会吗？</p><div class="info custom-block"><p class="custom-block-title">笔者说</p><p>对于技术的学习，笔者一贯遵循的步骤是：先用最最简单的 demo 让它跑起来，然后学学它的最最常用 API 和 配置让自己能用起来，最后熟练使用的基础上，在空闲时尝试阅读它的源码让自己能够洞彻它的运行机制，部分问题出现的原因，同时借鉴这些技术实现来提升自己的代码高度。</p><p>所以在笔者的文章中，前期基本都是小白文，仅仅穿插很少量的源码研究。当然等小白文更新多了，你们还依然喜欢，后期会不定时专门对部分技术的源码进行解析。</p></div>`,59);function v(s,b,q,S,M,_){const l=t,h=e("ClientOnly");return n(),r("div",null,[u,d(h,null,{default:g(()=>{var i,a;return[(((i=s.$frontmatter)==null?void 0:i.aside)??!0)&&(((a=s.$frontmatter)==null?void 0:a.showArticleMetadata)??!0)?(n(),D(l,{key:0,article:s.$frontmatter},null,8,["article"])):c("",!0)]}),_:1}),m])}const P=k(E,[["render",v]]);export{L as __pageData,P as default};
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