添加redis来提升天气预报系统的并发访问能力

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1、为什么要使用redis:

1. ​ 及时响应

2. ​ 有效减少服务调用

开发环境：

​ 1、jdk8

​ 2、maven

​ 3、redis4.*

​ 4. apache httpclient

​ 5、 springboot web starter

​ 6、spring boot data starter redis starter

接下来集成redis

上一步我们已经创建了一个单体天气预报系统应用，我们接着用！

2、集成redis

我们要使用redis,则需要导入RedisTemplate,StringRedisTemplate

找到数据访问层，进行redis的缓存操作。

首先判断是否存在缓存，如果存在，直接从缓存取，不存在，就调用服务，并存入缓存

由于service层进行数据访问的方法只有一个，就是

<pre class="md-fences md-end-block" lang="java" contenteditable="false" cid="n39" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">
public WeatherResponse getWeatherData(String uri)</pre>

则我们只需要对该方法进行数据访问的地方进行判断是否有缓存。为了方便显示，我们加入了日志系统slf4j

代码如下：

<pre class="md-fences md-end-block" lang="java" contenteditable="false" cid="n44" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">
private static final Logger logger = LoggerFactory.getLogger(WeatherDataServiceImpl.class);
private static final String WEATHER_URI = "http://wthrcdn.etouch.cn/weather_mini?";
private static final long TIME_OUT = 1800L;
@Autowired
private StringRedisTemplate stringRedisTemplate;
​
public WeatherResponse getWeatherData(String uri){
String key = uri;
String strBody = null;
​
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
WeatherResponse weatherResponse = null;
ValueOperations<String, String> ops = stringRedisTemplate.opsForValue();
// 先查缓存，有缓存直接在缓存中取数据
if(stringRedisTemplate.hasKey(key)){
logger.info("redis has data!");
strBody = ops.get(key);
}else {
// 缓存没有，调用服务，获取数据，并加入缓存
// ResponseEntity<String> respString = restTemplate.getForEntity(uri, String.class);
// ObjectMapper objectMapper = new ObjectMapper();
// objectMapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
// WeatherResponse weatherResponse = null;
logger.info("redis don't have data!");
ResponseEntity<String> respString = restTemplate.getForEntity(uri, String.class);
if (respString.getStatusCodeValue() == 200) {
strBody = respString.getBody();
}
// 将数据写入缓存
ops.set(key, strBody, TIME_OUT, TimeUnit.SECONDS);
​
}
try {
weatherResponse = objectMapper.readValue(strBody,WeatherResponse.class);
System.out.println(weatherResponse);
}catch (Exception e){
// e.printStackTrace();
logger.error("error",e);
}
​
return weatherResponse;
}</pre>

其中参数讲解：

TIME_OUT: redis缓存过期时间

Logger: slf4j日志系统

我们只需要保存序列化为string就行了，所以我们这里采用StringRedisTemplate

这里说一下redistemplate 与stringredistempalte的区别和联系：

RedisTemplate和StringRedisTemplate的区别：

\ 1. 两者的关系是StringRedisTemplate继承RedisTemplate。

\ 2. 两者的数据是不共通的；也就是说StringRedisTemplate只能管理StringRedisTemplate里面的数据， RedisTemplate只能管理RedisTemplate中的数据。

\ 3. SDR默认采用的序列化策略有两种，一种是String的序列化策略，一种是JDK的序列化策略。

​ StringRedisTemplate默认采用的是String的序列化策略，保存的key和value都是采用此策略序列化保存的。

​ RedisTemplate默认采用的是JDK的序列化策略，保存的key和value都是采用此策略序列化保存的。

由于我原来使用RedisTemplate遭遇过各种序列化及乱码问题，虽然他是泛型类，功能更全，但是我选择StringRedisTemplate,自己选择食用！！！

我们这里使用RedisWindowsDestop作为操作redis数据库的软件

传送门：http://www.downza.cn/soft/210734.html

3、启动application

注：如果发现没写入redis数据库的话，请在application上面加上注解@Enablecashing

打开<http://localhost:8080/weather/cityName/杭州

刚开始提示：redis don`t have data !

<pre class="md-fences md-end-block" lang="java" contenteditable="false" cid="n80" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">
2019-08-23 16:42:49.478 INFO 2372 --- [nio-8080-exec-9] t.j.s.s.impl.WeatherDataServiceImpl : redis don't have data!
​
WeatherResponse(status=1000, desc=OK, data=Weather(yesterday=Yesterday(high=高温 35℃, fx=东北风, low=低温 25℃, fl=<![CDATA[3-4级]]>, type=晴, date=22日星期四), city=杭州, forecast=[Forecast(date=23日星期五, high=高温 34℃, low=低温 26℃, fengli=<![CDATA[3-4级]]>, type=小雨, fengxiang=东北风), Forecast(date=24日星期六, high=高温 34℃, low=低温 27℃, fengli=<![CDATA[4-5级]]>, type=小雨, fengxiang=东北风), Forecast(date=25日星期天, high=高温 35℃, low=低温 26℃, fengli=<![CDATA[4-5级]]>, type=小雨, fengxiang=东风), Forecast(date=26日星期一, high=高温 36℃, low=低温 27℃, fengli=<![CDATA[<3级]]>, type=多云, fengxiang=无持续风向), Forecast(date=27日星期二, high=高温 37℃, low=低温 27℃, fengli=<![CDATA[<3级]]>, type=多云, fengxiang=无持续风向)], ganmao=各项气象条件适宜，发生感冒机率较低。但请避免长期处于空调房间中，以防感冒。, wendu=29))
​</pre>

1、将控制台清空，重新刷新页面

显示： redis has data!

<pre class="md-fences md-end-block" lang="json" contenteditable="false" cid="n85" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">
WeatherResponse(status=1000, desc=OK, data=Weather(yesterday=Yesterday(high=高温 35℃, fx=东北风, low=低温 25℃, fl=<![CDATA[3-4级]]>, type=晴, date=22日星期四), city=杭州, forecast=[Forecast(date=23日星期五, high=高温 34℃, low=低温 26℃, fengli=<![CDATA[3-4级]]>, type=小雨, fengxiang=东北风), Forecast(date=24日星期六, high=高温 34℃, low=低温 27℃, fengli=<![CDATA[4-5级]]>, type=小雨, fengxiang=东北风), Forecast(date=25日星期天, high=高温 35℃, low=低温 26℃, fengli=<![CDATA[4-5级]]>, type=小雨, fengxiang=东风), Forecast(date=26日星期一, high=高温 36℃, low=低温 27℃, fengli=<![CDATA[<3级]]>, type=多云, fengxiang=无持续风向), Forecast(date=27日星期二, high=高温 37℃, low=低温 27℃, fengli=<![CDATA[<3级]]>, type=多云, fengxiang=无持续风向)], ganmao=各项气象条件适宜，发生感冒机率较低。但请避免长期处于空调房间中，以防感冒。, wendu=29))</pre>

WeatherResponse(status=1000, desc=OK, data=Weather(yesterday=Yesterday(high=高温 35℃, fx=东北风, low=低温 25℃, fl=<![CDATA[3-4级]]>, type=晴, date=22日星期四), city=杭州, forecast=[Forecast(date=23日星期五, high=高温 34℃, low=低温 26℃, fengli=<![CDATA[3-4级]]>, type=小雨, fengxiang=东北风), Forecast(date=24日星期六, high=高温 34℃, low=低温 27℃, fengli=<![CDATA[4-5级]]>, type=小雨, fengxiang=东北风), Forecast(date=25日星期天, high=高温 35℃, low=低温 26℃, fengli=<![CDATA[4-5级]]>, type=小雨, fengxiang=东风), Forecast(date=26日星期一, high=高温 36℃, low=低温 27℃, fengli=<![CDATA[<3级]]>, type=多云, fengxiang=无持续风向), Forecast(date=27日星期二, high=高温 37℃, low=低温 27℃, fengli=<![CDATA[<3级]]>, type=多云, fengxiang=无持续风向)], ganmao=各项气象条件适宜，发生感冒机率较低。但请避免长期处于空调房间中，以防感冒。, wendu=29))

2、打开rediswindowsdesktop

连接redis数据库，reload一下

发现database0 有杭州的uri信息及天气预报的信息

则大功告成！

4、congratulations！！！！！

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