在Play Framework中使用缓存 [英] Using Cache in Play Framework

问题描述

我正在尝试实施测验应用程序.该应用程序用ajax逐一加载问题.当用户单击到下一个问题"按钮时，他/她的答案将保存在缓存中.但是当我调试时，缓存列表始终为空...

I'm trying to implement a quiz application. The application loads the questions with ajax one by one. When a user clicks the 'to next question' button his/her answer is saved in cache. But when I debug, cache list is always null...

此代码创建第一个缓存数组:

This code creates the first cache array:

public static void viewQuiz(@Required String user, @Required String test) {        
        if(validation.hasErrors()) {
            flash.error("Hoop kullanıcı lazım…");
            index();
        } else{
            TestClass selectedTest = TestClass.find("title", test).first();
            List<String> choiceList = new ArrayList<String>();
            session.put("testID", selectedTest.id);
            Cache.set("choices", choiceList, "30mn");
            render();
        }
    }

这段代码试图一一保存答案:

And this code is trying to save the answers one by one:

public static void question(@Required Long id, String answer){
    Long testId = Long.parseLong(session.get("testID"));
    TestClass test = TestClass.findById(testId);
    List<Question> questList = Question.find("test_id", test.id.intValue()).fetch(); 
    Question quest = questList.get(id.intValue());
    if(answer != null){
        List<String> choiceList= Cache.get("choices",List.class);
        choiceList.add(id.intValue(), answer);
        Cache.set("choices", choiceList, "30mn");
    }   
    int count = questList.size()-1; 
    render(quest, count, id);
}

此代码是第二个代码的html视图:

And this code is the html view of the second:

 #{extends 'main.html' /}

#{set title:'question.html' /}

<script type="text/javascript"> 
        var questionId = ${id};
        $('#nextButton').click(function(){
        $('#questionDiv').html('<p><img id = "loaderGif" src="public/images/loading.gif"/></p>');

        $('#questionDiv').load("/test/" + ++questionId);

    });
    $('#endButton').click(function(){
        $('#questionDiv').html('<p><img id = "loaderGif" src="public/images/loading.gif"/></p>');
        $('#questionDiv').load("/result");
    });
 </script> 

<legend>Soru ${id+1}</legend>
<p>&{quest.question}</p>

#{list items:quest.choices, as:'choice'} 
<p><input type="radio" name = "answer" id = "answer" size="30" value="${choice}"/>&{choice}</p>
#{/list}
#{if id < count}
<input id = "nextButton" name="nextButton" type="button" value="İleri"/>
#{/if}
#{else}
<input id = "endButton" name="endButton" type="button" value="Bitti"/>
#{/else}

推荐答案

不要使用缓存来存储"对象.可以将其存储在会话中，也可以创建一个新模型来存储答案.通常，您不能指望缓存会保留您放入的对象.这是缓存，而不是商店.

Don't use the cache to 'store' objects. Either store it in the session or create a new model to store the answers. Generally, you cannot expect the cache to retain the objects you put into; it's a cache, not a store.

引用Play的话！网站: http://www.playframework.org/documentation/1.2.2/cache

To quote from the Play! website: http://www.playframework.org/documentation/1.2.2/cache

重要的是要了解缓存协定是明确的:何时 您将数据放在缓存中，就不能指望数据会保留在那里 永远.实际上，您不应该这样做.缓存速度很快，但值已过期， 并且缓存通常仅存在于内存中(没有持久性 备份).

It is important to understand that the cache contract is clear: when you put data in a cache, you can’t expect that data to remain there forever. In fact you shouldn’t. A cache is fast, but values expire, and the cache generally exists only in memory (without persistent backup).

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