手动变量增量 [英] manual variable increment

问题描述

我找不到在报告生成过程中创建变量并修改它的方法。

I can't find the way to just create a variable and modify it during report generation.

我已经声明了一个整数变量：

I have declared an integer variable:

<variable name="my_counter" class="java.lang.Integer" calculation="System">
    <initialValueExpression><![CDATA[new Integer(0)]]></initialValueExpression>
</variable>

这似乎有效，我可以毫无问题地打印它的价值。但是我想在报告生成期间增加该值：当XML（报告的数据源）包含某些参数时，我想增加值（my_counter ++）。

That seems to work, and I can print it's value without problems. But I want to increment that value during report generation: when the XML (the datasource for the report) contains certain parameters I want to increase the value (my_counter++).

我想要实现的目标，在伪代码中：

<textField printWhenExpression="$P{BANANAS}!=null"> ($V{my_counter}++)+" The XML contains <bananas>" </textField>
<textField printWhenExpression="$P{APPLES}!=null"> ($V{my_counter}++)+" The XML contains <apples>" </textField>
<textField printWhenExpression="$P{GRAPES}!=null"> ($V{my_counter}++)+" The XML contains <grapes>" </textField>
<textField printWhenExpression="$P{ORANGES}!=null"> ($V{my_counter}++)+" The XML contains <oranges>" </textField>

包含香蕉，苹果和橙子的XML文件的预期结果 be：

1. The XML contains <bananas>
2. The XML contains <apples>
3. The XML contains <oranges>

我试过了，但目前的结果看起来更像是这样的：

I've tried that, but the current result looks more like this:

0. The XML contains <bananas>
0. The XML contains <apples>
0. The XML contains <oranges>

所以似乎变量 my_counter 是没有被修改。为什么？如何修改每个显示的textField的值？

So it seems that the variable my_counter is not being modified. Why? How can I modify it's value for each displayed textField?

推荐答案

您必须使用可变值持有者而不是 java.lang.Integer 表示变量。例如， java.util.concurrent.atomic.AtomicInteger 会做（你不需要原子性，你也可以使用Commons Lang的MutableInt）。

You'll have to use a mutable value holder instead of java.lang.Integer for the variable. java.util.concurrent.atomic.AtomicInteger would do for instance (you don't need atomicity, you can also go with MutableInt from Commons Lang).

一旦将变量声明为AtomicInteger，就可以在表达式中执行 $ V {my_counter} .getAndIncrement（）。

Once you declare your variable as AtomicInteger, you can do $V{my_counter}.getAndIncrement() in your expressions.

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