cnblogs/dcrenl/Springboot 在项目启动时将数据缓存到全局变量.html

<p>有写字典数据不会频繁更新，但是会频繁查询，想要减少数据库链接次数，把内容缓存到项目的全局变量中，提高方法查询速度</p>
<p>&nbsp;</p>
<div class="cnblogs_code">
<pre> 
<span style="color: #0000ff;">import</span><span style="color: #000000;"> javax.annotation.PostConstruct;
</span><span style="color: #0000ff;">import</span><span style="color: #000000;"> javax.annotation.PreDestroy;
</span><span style="color: #0000ff;">import</span><span style="color: #000000;"> java.util.HashMap;
</span><span style="color: #0000ff;">import</span><span style="color: #000000;"> java.util.List;
</span><span style="color: #0000ff;">import</span><span style="color: #000000;"> java.util.Map;
 
@Component
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">class</span><span style="color: #000000;"> CodeCache {
    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> Map&lt;String, TownNameDto&gt; codeMap = <span style="color: #0000ff;">new</span> HashMap&lt;String, TownNameDto&gt;<span style="color: #000000;">();
    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> Map&lt;String, CompanyModel&gt; companyMap = <span style="color: #0000ff;">new</span> HashMap&lt;String, CompanyModel&gt;<span style="color: #000000;">();
 
    @Autowired
    </span><span style="color: #0000ff;">private</span><span style="color: #000000;"> CityDao cityDao;
    @Autowired
    </span><span style="color: #0000ff;">private</span><span style="color: #000000;"> CompanyDao companyDao;
 
 
    @PostConstruct
    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> init() {
        </span><span style="color: #008000;">//</span><span style="color: #008000;">系统启动中。。。加载codeMap</span>
        List&lt;TownNameDto&gt; codeList =<span style="color: #000000;"> cityDao.selectCityNameAndCodeALL();
        </span><span style="color: #0000ff;">for</span><span style="color: #000000;"> (TownNameDto code : codeList) {
            codeMap.put(code.getTownCode() </span>+<span style="color: #000000;"> code.getValue(), code);
        }
        List</span>&lt;CompanyModel&gt; companyModels =<span style="color: #000000;"> companyDao.selectCompanies();
        </span><span style="color: #0000ff;">for</span><span style="color: #000000;"> (CompanyModel company : companyModels) {
            companyMap.put(company.getCode(), company);
        }
 
 
    }
 
    @PreDestroy
    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> destroy() {
        </span><span style="color: #008000;">//</span><span style="color: #008000;">系统运行结束</span>
<span style="color: #000000;">    }
 
    @Scheduled(cron </span>= "0 0 0/2 * * ?"<span style="color: #000000;">)
    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> testOne() {
        </span><span style="color: #008000;">//</span><span style="color: #008000;">每2小时执行一次缓存</span>
<span style="color: #000000;">        init();
    }
 
}</span></pre>
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<p>&nbsp;</p>
<p>使用：</p>
<div class="cnblogs_code">
<pre><span style="color: #008000;">//</span><span style="color: #008000;">从缓存中获取城市；</span>
        Map&lt;String, TownNameDto&gt; cityModelMap =<span style="color: #000000;"> CodeCache.codeMap;
        Map</span>&lt;String, CompanyModel&gt; companyModelMap = CodeCache.companyMap;</pre>
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<p>&nbsp;</p>
<p>转自：https://blog.csdn.net/Alice_qixin/article/details/101547611</p>