Mybatis分页插件的实例详解

韦家东 發表於 2023-8-24 00:00:00

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<strong>Mybatis分页插件的实例详解</strong></p>
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<strong>1.前言：</strong></p>
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我们知道，在MySQL中，分页的sql是使用limit来做，如果我们自己写sql，那分页肯定是没有任何问题的。但是一旦model多了起来，复杂了起来，我们很自然的想到使用mybatis的逆向工程来生成相应的po和mapper，但是同时也会带来弊端，比如这里的分页问题就不好解决了。</p>
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　　可能有人会说，我可以修改生成的文件，没错，这是可行的，但是一般我们通过逆向工程生成的文件，都不会去动它，所以这个时候，就需要使用分页插件来解决了。</p>
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如果你也在用Mybatis，建议尝试该分页插件，这个一定是最方便使用的分页插件。</p>
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该插件目前支持Oracle,Mysql,MariaDB,SQLite,Hsqldb,PostgreSQL六种数据库分页。</p>
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<strong> 2.使用方法</strong></p>
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第一步：在Mybatis配置xml中配置拦截器插件:</p>
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<code class="xml spaces"> </code><code class="xml plain"><</code><code class="xml keyword">plugin</code> <code class="xml color1">interceptor</code><code class="xml plain">=</code><code class="xml string">"com.github.pagehelper.PageHelper"</code><code class="xml plain">></code>
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<code class="xml spaces">  </code><code class="xml plain"><</code><code class="xml keyword">property</code> <code class="xml color1">name</code><code class="xml plain">=</code><code class="xml string">"dialect"</code> <code class="xml color1">value</code><code class="xml plain">=</code><code class="xml string">"mysql"</code><code class="xml plain">/></code>
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<strong>第二步：在代码中使用</strong></p>
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1、设置分页信息：</p>
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<code class="xml plain">//获取第1页，10条内容，默认查询总数count</code>
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<code class="xml plain">PageHelper.startPage(1, 10);</code>
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<code class="xml spaces"> </code><code class="xml plain">//紧跟着的第一个select方法会被分页</code>
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<code class="xml plain">List<</code><code class="xml keyword">Country</code><code class="xml plain">> list = countryMapper.selectIf(1);</code>
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2、取分页信息</p>
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<code class="xml plain">//分页后，实际返回的结果list类型是Page<</code><code class="xml keyword">E</code><code class="xml plain">>，如果想取出分页信息，需要强制转换为Page<</code><code class="xml keyword">E</code><code class="xml plain">>，</code>
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<code class="xml plain">Page<</code><code class="xml keyword">Country</code><code class="xml plain">> listCountry = (Page<</code><code class="xml keyword">Country</code><code class="xml plain">>)list;</code>
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<code class="xml plain">listCountry.getTotal();</code>
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3、取分页信息的第二种方法</p>
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<code class="xml plain">//获取第1页，10条内容，默认查询总数count</code>
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<code class="xml plain">PageHelper.startPage(1, 10);</code>
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<code class="xml plain">List<</code><code class="xml keyword">Country</code><code class="xml plain">> list = countryMapper.selectAll();</code>
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<code class="xml plain">//用PageInfo对结果进行包装</code>
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<code class="xml plain">PageInfo page = new PageInfo(list);</code>
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<code class="xml plain">//测试PageInfo全部属性</code>
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<code class="xml plain">//PageInfo包含了非常全面的分页属性</code>
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<code class="xml plain">assertEquals(1, page.getPageNum());</code>
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<code class="xml plain">assertEquals(10, page.getPageSize());</code>
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<code class="xml plain">assertEquals(1, page.getStartRow());</code>
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<code class="xml plain">assertEquals(10, page.getEndRow());</code>
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<code class="xml plain">assertEquals(183, page.getTotal());</code>
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<code class="xml plain">assertEquals(19, page.getPages());</code>
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<code class="xml plain">assertEquals(1, page.getFirstPage());</code>
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<code class="xml plain">assertEquals(8, page.getLastPage());</code>
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<code class="xml plain">assertEquals(true, page.isFirstPage());</code>
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<code class="xml plain">assertEquals(false, page.isLastPage());</code>
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<code class="xml plain">assertEquals(false, page.isHasPreviousPage());</code>
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<code class="xml plain">assertEquals(true, page.isHasNextPage());</code>
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<strong> 3.TestPageHelper</strong></p>
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<code class="xml plain">@Test</code>
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<code class="xml plain">public void testPageHelper() {</code>
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<code class="xml spaces"> </code><code class="xml plain">//创建一个spring容器</code>
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<code class="xml spaces"> </code><code class="xml plain">ApplicationContext applicationContext = new ClassPathXmlApplicationContext("classpath:spring/applicationContext-*.xml");</code>
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<code class="xml spaces"> </code><code class="xml plain">//从spring容器中获得Mapper的代理对象</code>
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<code class="xml spaces"> </code><code class="xml plain">TbItemMapper mapper = applicationContext.getBean(TbItemMapper.class);</code>
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<code class="xml spaces"> </code><code class="xml plain">//执行查询，并分页</code>
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<code class="xml spaces"> </code><code class="xml plain">TbItemExample example = new TbItemExample();</code>
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<code class="xml spaces"> </code><code class="xml plain">//分页处理</code>
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<code class="xml spaces"> </code><code class="xml plain">PageHelper.startPage(2, 10);</code>
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<code class="xml spaces"> </code><code class="xml plain">List<</code><code class="xml keyword">TbItem</code><code class="xml plain">> list = mapper.selectByExample(example);</code>
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<code class="xml spaces"> </code><code class="xml plain">//取商品列表</code>
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<code class="xml spaces"> </code><code class="xml plain">for (TbItem tbItem : list) {</code>
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<code class="xml spaces">  </code><code class="xml plain">System.out.println(tbItem.getTitle());</code>
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<code class="xml spaces"> </code><code class="xml plain">}</code>
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<code class="xml spaces"> </code><code class="xml plain">//取分页信息</code>
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<code class="xml spaces"> </code><code class="xml plain">PageInfo<</code><code class="xml keyword">TbItem</code><code class="xml plain">> pageInfo = new PageInfo<>(list);</code>
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<code class="xml spaces"> </code><code class="xml plain">long total = pageInfo.getTotal();</code>
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<code class="xml spaces"> </code><code class="xml plain">System.out.println("共有商品："+ total);</code>
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<code class="xml plain">}</code>
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感谢阅读，希望能帮助到大家，谢谢大家对本站的支持！</p>
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原文链接：http://www.cnblogs.com/ganchuanpu/p/6147911.html</p>

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Mybatis分页插件的实例详解