245 lines
8.3 KiB
HTML
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245 lines
8.3 KiB
HTML
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<title>关于XORM中Mapper的使用 - XORM</title>
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<h1 id="profile-title">XORM</h1>
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</a>
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<hr class="divider long">
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<p class="bio">
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官方博客<br/>Xorm 是一个简单而强大的Go语言ORM框架
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<a href="/archive.html">归档
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<h3 class="title">
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<a href="/2016/1/4/1-about-mapper.html">关于XORM中Mapper的使用</a>
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</h3>
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</header>
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<aside class="aside clearfix">
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<span class="date">
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<span class="year">2016</span>/
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<span class="month">1</span>/
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<span class="day">4</span>
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<a class="author"></a>
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<a class="tag" href="/tags/go.html">go</a>
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<a class="tag" href="/tags/golang.html">golang</a>
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<a class="tag" href="/tags/xorm.html">xorm</a>
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<a class="tag" href="/tags/orm.html">orm</a>
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<a class="tag" href="/tags/sql.html">sql</a>
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<a class="tag" href="/tags/database.html">database</a>
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</span>
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</aside>
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<section class="brief"><p>XORM中的Mapper是一个接口机制，专门用来在程序名称和数据库名称之间进行转换。XORM库中带有三种Mapper的实现，SnakeMapper, SameMapper 以及 GonicMapper。同时为了方便还提供了CacheMapper, PrefixMapper 以及 SuffixMapper，这几种Mapper可以和前面的组合使用。</p>
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<h1>SnakeMapper</h1>
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<p>SnakeMapper是默认的映射机制，他支持数据库表采用匈牙利命名法，而程序中采用驼峰式命名法。下面是一些常见的映射：</p>
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<table>
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<thead>
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<tr>
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<th>表中名称</th>
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<th>程序名称</th>
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</tr>
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</thead>
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<tbody>
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<tr>
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<td>user_info</td>
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<td>UserInfo</td>
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</tr>
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<tr>
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<td>id</td>
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<td>Id</td>
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</tr>
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</tbody>
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</table>
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<h1>SameMapper</h1>
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<p>SameMapper就是数据库中的命名法和程序中是相同的。那么鉴于在Go中，基本上要求首字母必须大写。所以一般都是表中和程序中均采用驼峰式命名。下面是一些常见的映射：</p>
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<table>
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<thead>
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<tr>
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<th>表中名称</th>
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<th>程序名称</th>
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</tr>
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</thead>
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<tbody>
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<tr>
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<td>UserInfo</td>
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<td>UserInfo</td>
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</tr>
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<tr>
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<td>Id</td>
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<td>Id</td>
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</tr>
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</tbody>
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</table>
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<h1>GonicMapper</h1>
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<p>GonicMapper是在SnakeMapper的基础上增加了特例，对于常见的缩写不新增下划线处理。这个同时也符合golint的规则。下面是一些常见的映射：</p>
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<table>
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<thead>
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<tr>
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<th>表中名称</th>
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<th>程序名称</th>
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</tr>
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</thead>
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<tbody>
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<tr>
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<td>user_info</td>
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<td>UserInfo</td>
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</tr>
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<tr>
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<td>id</td>
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<td>ID</td>
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</tr>
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<tr>
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<td>url</td>
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<td>URL</td>
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</tr>
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</tbody>
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</table>
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<h1>CacheMapper</h1>
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<p>CacheMapper 通过使用一个map来将已经映射过的内容保存起来，下次直接查找即可获得。</p>
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<h1>PrefixMapper</h1>
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<p>PrefixMapper 前缀映射可以组合SnakeMapper, SameMapper或者GonicMapper来在表名或者字段名的映射完成后，再新增一个固定的前缀。比如和SnakeMapper组合：</p>
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<pre><code class="language-Go">engine.SetTableMapper(core.NewPrefixMapper(core.SnakeMapper{}, "tb_"))
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engine.SetColumnMapper(core.SnakeMapper{})
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</code></pre>
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<p>那么对于结构体<code>User</code>，数据库中对应的表名即为<code>tb_user</code>，而表中字段名比如<code>id</code>对应的程序中结构体字段名仍为<code>Id</code>。</p>
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<h1>SuffixMapper</h1>
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<p>SuffixMapper 后缀映射类似与前缀映射，也可以组合SnakeMapper, SameMapper或者GonicMapper来在表名或者字段名的映射完成后，再新增一个固定的前缀。比如和SnakeMapper组合：</p>
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<pre><code class="language-Go">engine.SetTableMapper(core.NewSuffixMapper(core.SnakeMapper{}, "_table"))
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engine.SetColumnMapper(core.SnakeMapper{})
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</code></pre>
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<p>那么对于结构体<code>User</code>，数据库中对应的表名即为<code>user_table</code>，而表中字段名比如<code>id</code>对应的程序中结构体字段名仍为<code>Id</code>。</p>
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<h1>表名和字段名分别映射</h1>
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<p>在前面的例子中也看到了，这种映射可以对表名和字段名采用相同的映射，也可以表名和字段名采用不同的映射方案。</p>
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<ul>
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<li><p>表名和字段名使用相同映射方案</p>
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<pre><code class="language-Go">engine.SetMapper(mapper)
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</code></pre></li>
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<li><p>表名和字段名使用不同的映射方案</p>
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<pre><code class="language-Go">engine.SetTableMapper(mapper1)
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engine.SetColumnMapper(mapper2)
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</code></pre></li>
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</ul>
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<p>最后，关于名称映射更多的方法可以参考XORM文档 <a href="http://gobook.io/read/go-xorm/manual-zh-cn/chapter-02/3.tags.html">使用Table和Tag改变名称映射</a></p>
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</section>
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</div>
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