Struts 2将数据从JSP传递给动作类(Struts 2 passing data from JSP to action class)

Struts 2将数据从JSP传递给动作类(Struts 2 passing data from JSP to action class)

我试图理解别人的Struts 2代码，我遇到了数据传递问题。

我知道在JSP页面上，如果使用<s:textfield name="something" ... />标记，struts2将尝试在动作类中自动调用setSomething(...) 。

我现在看到这种类型的代码：

<s:textfield name="item.name" ... />

而且我想知道，这是怎么回事. （点）工作？ 我在我的动作类中有一个名为setItem()的方法，并且在该方法中设置的对象具有setName()方法，但显然这不起作用。 点和名称之间的点是什么意思，我如何正确地使用它来实例化项目并设置它的名称？

PS：我的动作类中的setItem()中设置的item对象有一个空的args构造函数。

I'm trying to understand somebody's else Struts 2 code and I'm stuck with a data passing problem.

I know that on a JSP page, if you use a <s:textfield name="something" ... /> tag, than struts2 will try to call setSomething(...) automatically in the action class.

I'm now seeing this type of code:

<s:textfield name="item.name" ... />

and I'm wondering, how does this . (dot) work? I have a method called setItem() in my action class, and the object that is being set in that method has a setName() method, but apparently this doesn't work. What does the dot mean between item and name and how do I use it correctly to instantiate the item and set it's name?

PS: The item object that is being set in setItem() in my action class has an empty args constructor.

最满意答案

在OGNL . 是点符号 。

item.name表示getItem().setName(); item.subitem.name表示getItem().getSubitem.setName();

一个问题可能是缺少空args构造函数， 如此处所述 ，但您说这不是您的情况; 然后我打赌“缺少Item吸气剂”。 如果不是，请发布更相关的代码。

The problem is solved. The getItem() actually contained the following code:

public Item getItem() { System.out.println("Trying to get item: " + item.toString()); return item; }

And this gave a nullpointer exception because item was null. Only, this nullpointerexception was NOT THROWN by the struts framework! The code just continued (and failed of course...). When I removed the sysout statement, the code worked.