如何使用jstl在jsp中获取数据? [英] how to get data in jsp using jstl?

问题描述

目前，我正在使用scriptlet在jsp中获取数据，但现在想使用JSTL，因此我试图将自己的scriptlet代码转换为JSTL.但是对于以下情况，我不知道如何在jstl中获取数据.

Currently I'm getting data in jsp using scriptlet but now want to use JSTL so I'm trying to convert my scriptlet code to JSTL. But for following scenario I don't know how to get data in jstl.

让我通过示例进行解释:

Let me explain by example:

有3个对象

1. 用户(用户名，用户名，密码)
2. Box(box_id，box_name，list_of_boxCat)
3. BoxCat(box_cat_id，box_id，user_id，cat_name)

现在，我需要显示用户拥有的盒子列表.因此，我通过在servlet中触发查询来创建Box对象的列表，并将该列表传递给jsp的request属性，然后在jsp中对其进行访问.在此之前，一切正常.但是现在我必须访问BoxCat对象，该对象没有直接来自Box对象的任何引用.要获得BoxCat对象，我必须将Userid和Box ID结合起来，然后才能获得BoxCat ID.因此，在scriptlet中，我调用我的DAO并通过运行查询获取列表.但是我不知道如何执行此JSTL.有人请帮我怎么做?

Now I need to display list of boxes a user own. So i have created a list of Box objects by firing query in servlet and pass that list in jsp in request attribute then access it in jsp. Until this everything goes fine. But now I have to access BoxCat object which do not have any reference from Box object directly. To get BoxCat object I have to combine Userid and Box id and then I can get BoxCat id. So in scriptlet I call my DAO and get list by running query. But I don't know how to do this JSTL. Anyone please help me on how to do this?

推荐答案

您应该重新设计或映射模型，使其适合您的视图需求.视图是否需要List<BoxCat>作为User的属性，或者需要BoxCat作为Box的属性?如果是这样，那么就这样做，然后更改您的控制器和DAO以预先填充它.

You should redesign or map your model so that it suits whatever your view needs. Does the view need a List<BoxCat> as a property of User or maybe BoxCat as a property of Box? If so, then make that so and change your controller and DAO to fill that beforehand.

否则，使用实体通过其ID(例如Map<Long, Entity>)进行的映射，最终将导致笨拙且可能导致内存效率低下的变通方法.

Otherwise you will end up in clumsy and potentially memory-inefficient workarounds using a mapping of the entities by their ID such as Map<Long, Entity>.

这篇关于如何使用jstl在jsp中获取数据?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！