blocks|key|877471|text|处理空参数是BIRT的缺点之一。例如，不允许只将dataset参数的默认值保持为空。如果null在运行时实际上被传递到dataset，BIRT会发出巨大的无用堆栈跟踪，这说明不支持.在Oracle方面，NULL和空字符串是等价的，因此我通常使用"“作为默认值，并确保使用这个小助手将从上下文传递的null转换为"”：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|877472|function+nvl_mt(x)+{
++if+(x==null)+{
++++return+"";
++}
++return+x;
}|code-block|syntax|javascript|877473|要了解参数行为不同的原因，请看一下XML源，您可能会发现其中的不同之处。|877474|还请注意，对于每个报表参数，BIRT都有一个默认值存储在.rptdesign中，另一个默认值存储在相应的.rptconfig文件中，该默认值仅在从IDE启动报表时使用。|877475|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Handling null parameters is one of BIRT's weaknesses.
For example, it's not allowed to just keep the default value of a dataset parameter empty.
And if a null is actually passed to a dataset at runtime, BIRT spits out huge useless stack traces telling that this is not supported...
On the Oracle side, NULL and an empty string are equivalent, so I usually use "" as the default value and make sure that a null passed from the context is converted to "" using this little helper:

<pre><code>function nvl_mt(x) {
 if (x==null) {
 return "";
 }
 return x;
}
</code></pre>

To find out why the parameters behave differently, take a look at the XML source, probably you'll find the difference there.

Also note that for each report parameter, BIRT has a default value stored in the .rptdesign and yet another default value stored in the corresponding .rptconfig file, which is only used when starting the report from the IDE.

blocks|key|787792|text|我有几份有类似限制的报告。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|787793|一种解决方案是使用"All“作为默认值，如果SQL像这样，则使用bit。它返回输入的单个值或所有内容(“All”在CONTCTSM1.OPERATOR_ID中不是有效值，因此它始终是空返回。|787794|where+CONTCTSM1.OPERATOR_ID+=+?
or
'All'+=+?|code-block|syntax|javascript|787795|​|787796|📷|atomic|offset|length|787797|787798|换句话说，您可以在SQL和%25中使用like语句作为默认值。|787799|where+UPMCNOTIFICATIONCONTACTSM1.UPMC_ADDRESS+like+?
and+UPMCNOTIFICATIONCONTACTSM1.UPMC_FULL_NAME+like+?|787800|787801|787802|787803|但|style|BOLD|787804|空不显示在外卡搜索。因此，如果数据中确实有Null，则可能希望使用()或sub为null查询|787805|and+(+UPMC_METADATA_DOMAIN+like+?
or+UPMC_METADATA_DOMAIN+is+null+)|787806|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://developer.qcloudimg.com/http-save/yehe-900000/73334f0eb55b078a1c991507e7d288d5.jpg|imageAlt|1|https://developer.qcloudimg.com/http-save/yehe-900000/537355bd1c167d63a29527a948f98ae0.jpg^0|0|0|0|0|0|1|0|0|0|0|0|0|0|1|1|0|0|0|1|0|0|0^^$0|@$1|2|3|4|5|6|7|1G|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1H|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|1I|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|1J|8|@]|9|@]|A|$]]|$1|K|3|L|5|M|7|1K|8|@]|9|@$N|1L|O|1M|1|1N]]|A|$]]|$1|P|3|J|5|6|7|1O|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|1P|8|@]|9|@]|A|$]]|$1|S|3|T|5|F|7|1Q|8|@]|9|@]|A|$G|H]]|$1|U|3|J|5|6|7|1R|8|@]|9|@]|A|$]]|$1|V|3|L|5|M|7|1S|8|@]|9|@$N|1T|O|1U|1|1V]]|A|$]]|$1|W|3|J|5|6|7|1W|8|@]|9|@]|A|$]]|$1|X|3|Y|5|6|7|1X|8|@$N|1Y|O|1Z|Z|10]]|9|@]|A|$]]|$1|11|3|12|5|6|7|20|8|@]|9|@]|A|$]]|$1|13|3|14|5|F|7|21|8|@]|9|@]|A|$G|H]]|$1|15|3|-4|5|6|7|22|8|@]|9|@]|A|$]]]|16|$17|$5|18|19|1A|A|$1B|1C|1D|-4]]|1E|$5|18|19|1A|A|$1B|1F|1D|-4]]]]

I have several reports with similar constraints. 

One solution is to use "All" as the default value, and bit if SQL like this. It returns either the single value entered or everything ('All' is not a valid value in CONTCTSM1.OPERATOR_ID, so it will always be a null return.

<pre><code>where CONTCTSM1.OPERATOR_ID = ?
or
'All' = ?
</code></pre>

<a href="https://i.stack.imgur.com/RpDlx.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/RpDlx.jpg" alt="All"></a>

Alliteratively you can use a like statement in your SQL and % as your default value. 

<pre><code>where UPMCNOTIFICATIONCONTACTSM1.UPMC_ADDRESS like ?
and UPMCNOTIFICATIONCONTACTSM1.UPMC_FULL_NAME like ?
</code></pre>

<a href="https://i.stack.imgur.com/XhLrA.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/XhLrA.jpg" alt="enter image description here"></a>

BUT

Null does not show in wild card searches. So if you really have Null in your data, you may want to a SQL isnull() or a sub is null query

<pre><code>and ( UPMC_METADATA_DOMAIN like ?
or UPMC_METADATA_DOMAIN is null )
</code></pre>

In a BIRT report, there are two String Text Box parameters that look the same on the "Edit Parameter" page, and both are empty in the "Default value" box. However, when I select to run the report, one defaults the "Null Value" selection while the other defaults to an empty string. How can I configure which default is used? Neither parameter is used by the data set as they're just text.

<a href="https://i.stack.imgur.com/bAL9Y.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/bAL9Y.png" alt="String parameters"></a>

How to cause parameter to default to "Null Value" in BIRT Report?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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在BIRT报告中，有两个字符串文本框参数在“编辑参数”页面上看起来是相同的，并且在“默认值”框中都是空的。但是，当我选择运行报表时，一个默认为"Null Value“选择，而另一个默认为空字符串。如何配置所使用的默认值？两个参数都不是数据集使用的，因为它们只是文本。​​

问如何使BIRT报告中的参数默认为“空值”？
EN

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问如何使BIRT报告中的参数默认为“空值”？EN