Java開發(fā)框架spring實現(xiàn)自定義緩存標簽

更新時間：2015年12月14日 16:35:35 作者：txxs

這篇文章主要介紹了Java開發(fā)框架spring實現(xiàn)自定義緩存標簽的詳細代碼，感興趣的小伙伴們可以參考一下

自從spring3.1之后，spring引入了抽象緩存，可以通過在方法上添加@Cacheable等標簽對方法返回的數(shù)據(jù)進行緩存。但是它到底是怎么實現(xiàn)的呢，我們通過一個例子來看一下。首先我們定義一個@MyCacheable

package caching.springaop; 
 
import java.lang.annotation.Retention; 
import java.lang.annotation.RetentionPolicy; 
import java.lang.annotation.Target; 
import java.lang.annotation.ElementType; 
 
/** 
 * 使用@MyCacheable注解方法 
 */ 
@Retention(RetentionPolicy.RUNTIME) 
@Target(ElementType.METHOD) 
public @interface MyCacheable{ 
 
}

然后定義處理MyCacheable的切面

package caching.springaop; 
 
import java.util.HashMap; 
import java.util.Map; 
 
import org.apache.log4j.Logger; 
import org.aspectj.lang.ProceedingJoinPoint; 
import org.aspectj.lang.annotation.Around; 
import org.aspectj.lang.annotation.Aspect; 
import org.aspectj.lang.annotation.Pointcut; 
 
/** 
 * 處理MyCacheable方法的切面 
 */ 
@Aspect 
public class CacheAspect { 
 
  private Logger logger = Logger.getLogger(CacheAspect.class); 
  private Map<String, Object> cache; 
 
  public CacheAspect() { 
    cache = new HashMap<String, Object>(); 
  } 
 
  /** 
   * 所有標注了@Cacheable標簽的方法切入點 
   */ 
  @Pointcut("execution(@MyCacheable * *.*(..))") 
  @SuppressWarnings("unused") 
  private void cache() { 
  } 
 
  @Around("cache()") 
  public Object aroundCachedMethods(ProceedingJoinPoint thisJoinPoint) 
      throws Throwable { 
    logger.debug("Execution of Cacheable method catched"); 
    //產(chǎn)生緩存數(shù)據(jù)的key值，像是這個樣子caching.aspectj.Calculator.sum(Integer=1;Integer=2;) 
    StringBuilder keyBuff = new StringBuilder(); 
    //增加類的名字 
    keyBuff.append(thisJoinPoint.getTarget().getClass().getName()); 
    //加上方法的名字 
    keyBuff.append(".").append(thisJoinPoint.getSignature().getName()); 
    keyBuff.append("("); 
    //循環(huán)出cacheable方法的參數(shù) 
    for (final Object arg : thisJoinPoint.getArgs()) { 
      //增加參數(shù)的類型和值 
      keyBuff.append(arg.getClass().getSimpleName() + "=" + arg + ";"); 
    } 
    keyBuff.append(")"); 
    String key = keyBuff.toString(); 
    logger.debug("Key = " + key); 
    Object result = cache.get(key); 
    if (result == null) { 
      logger.debug("Result not yet cached. Must be calculated..."); 
      result = thisJoinPoint.proceed(); 
      logger.info("Storing calculated value '" + result + "' to cache"); 
      cache.put(key, result); 
    } else { 
      logger.debug("Result '" + result + "' was found in cache"); 
     
    return result; 
  } 
 
}

上述代碼展示了如何處理MyCacheable自定義的標簽，以及默認情況下產(chǎn)生key值的規(guī)則。最后生成的key值大概是這個樣子：caching.aspectj.Calculator.sum(Integer=1;Integer=2;)
下邊這段代碼在方法上添加了MyCacheable標簽

package caching.springaop; 
 
import org.apache.log4j.Logger; 
public class Calculator { 
  private Logger logger = Logger.getLogger(Calculator.class); 
  @MyCacheable 
  public int sum(int a, int b) { 
    logger.info("Calculating " + a + " + " + b); 
    try { 
      //假設(shè)這是代價非常高的計算 
      Thread.sleep(3000); 
    } catch (InterruptedException e) { 
      logger.error("Something went wrong...", e); 
    } 
    return a + b; 
  } 
}

在方法上加了MyCacheable標簽，當key值相同的情況下會直接在緩存中獲取數(shù)據(jù)，如果沒有相同的key值，則會重新計算，因為這里只是一個加和操作，耗時非常的短暫。我們在這里讓其睡眠3秒鐘。
我們在spring-config.xml配置如下：

<?xml version="1.0" encoding="UTF-8"?> 
<beans xmlns="http://www.springframework.org/schema/beans" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
  xmlns:aop="http://www.springframework.org/schema/aop" 
  xsi:schemaLocation="http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.5.xsd 
    http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd"> 
  <aop:aspectj-autoproxy /> 
  <bean class="caching.springaop.CacheAspect" /> 
  <bean id="calc" class="caching.springaop.Calculator" /> 
</beans>

測試類：

package caching.springaop; 
 
import org.apache.log4j.Logger; 
import org.springframework.context.ApplicationContext; 
import org.springframework.context.support.ClassPathXmlApplicationContext; 
 
/** 
 * 使用SpringAOP緩存的簡單例子 
 * @author txxs 
 */ 
public class App { 
 
  private static Logger logger = Logger.getLogger(App.class); 
 
  public static void main(String[] args) { 
    logger.debug("Starting..."); 
    ApplicationContext ctx = new ClassPathXmlApplicationContext("spring-config.xml"); 
    Calculator calc = (Calculator) ctx.getBean("calc"); 
    //計算出來的結(jié)果將會被存儲在cache 
    logger.info("1 + 2 = " + calc.sum(1, 2)); 
    //從緩存中獲取結(jié)果 
    logger.info("1 + 2 = " + calc.sum(1, 2)); 
    logger.debug("Finished!"); 
  } 
 
}

我們看一下運行的結(jié)果：