已出注解方法，移步：http://www.jfinal.com/share/344
（以下因未考虑请求参数问题，实际尚未完成... JFinal 3.2有更好的解决方案参见CacheInterceptor ）
应用场景：当魔板引擎启用setDevMode(true)，而某些页面需要缓存时。（可作为页面静态化使用）
使用方法：在html中利用魔板的自定义指令进行缓存。
#CacheDirective(key, limit) 参数说明：key缓存键名， limit缓存时间（单位：秒）
#CacheDirective(key) 重载， 永久缓存
1. config中配置自定义指令
me.addDirective("cache", new CacheDirective());
或
me.addDirective("cache", new CacheDirective(cacheName));2. html中添加自定义指令#CacheDirective #end：
#cache("testPage", 600)
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>test</title>
</head>
<body>
#(test)
</body>
</html>
#end3. 缓存前后controller中的写法比对：
//未缓存前的写法
public void test() {
setAttr("test", "test test test !!!");
render("test.html");
}
//缓存后的写法
public void test() {
if ( CacheDirective.notExists("testPage") ) {
setAttr("test", "test test test !!!");
}
render("test.html");
}直接上代码CacheDirective.java：
public class CacheDirective extends Directive {
private static String CACHE_NAME = "PAGE_CACHE";
public CacheDirective() {
super();
}
public CacheDirective(String cacheName) {
super();
CacheDirective.CACHE_NAME = cacheName;
}
@Override
public void setExprList(ExprList exprList) {
if ( exprList.length() != 1 || exprList.length() != 2 ) {
throw new ParseException("#cache directive support one/two parameter only", location);
}
super.setExprList(exprList);
}
@Override
public void exec(Env env, Scope scope, Writer writer) {
Object[] objects = exprList.evalExprList(scope);
String key = (String) objects[0];
Integer limit = objects.length > 1 ? (Integer) objects[1] : null;
String content = getCache(key);
if (content == null) {
FastStringWriter fsw = new FastStringWriter();
stat.exec(env, scope, fsw);
content = fsw.toString();
putCache(key, content, limit);
}
write(writer, content);
}
@Override
public boolean hasEnd() {
return true;
}
public static boolean notExists(Object key) {
return null == CacheKit.get(CACHE_NAME, key);
}
private <T> T getCache(Object key) {
return CacheKit.get(CACHE_NAME, key);
}
private void putCache(Object key, Object value, Integer limit) {
if ( limit == null || limit < 0 ) {
limit = 0;
}
Element element = new Element(key, value);
element.setEternal(false);
element.setTimeToIdle(0);//单位：秒；对象空闲时间，指对象在多长时间没有被访问就会失效。只对eternal为false的有效。默认值0，表示一直可以访问
element.setTimeToLive(limit);//单位：秒；对象存活时间，指对象从创建到失效所需要的时间。只对eternal为false的有效。默认值0，表示一直可以访问
getOrAddCache(CACHE_NAME).put(element);
}
private Cache getOrAddCache(String cacheName) {
CacheManager cacheManager = CacheKit.getCacheManager();
Cache cache = cacheManager.getCache(cacheName);
if ( cache == null ) {
cacheManager.addCacheIfAbsent(cacheName);
cache = cacheManager.getCache(cacheName);
}
return cache;
}
}
